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Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Plant-parasitic nematodes, consisting of a wide range of species, can cause severe economic losses in most agricultural food crops. Meloidogyne spp. (root-knot nematodes), Criconemoides xenoplax (ring nematode), Xiphinema index (dagger nematode) and Pratylenchus spp. (lesion nematodes) are some of the economically important plant-parasitic nematodes that pose a threat to viticulture and other perennial crops in South Africa. Worldwide there is ever-increasing pressure on pre-plant synthetic soil fumigants and post-plant nematicides. For sustainable nematode management, it is important to have a holistic approach; taking into consideration cultural, biological and chemical options as part of an integrated management approach. Biofumigation has the potential to fit into such an integrated management system and previous research indicates the positive response on soil-borne diseases, nematodes and weeds. Biofumigation occurs where certain plant species, containing glucosinolates (GSL) in the vacuole of the plant cells, come into contact (after cell maceration), with the enzyme myrosinase (MYR) situated in the cytoplasm of the cell, to form active compounds such as isothiocyanate (ITC). When this green manure is applied to infested soil, the ITC has the potential to have a direct suppressive effect on the soil-borne pathogens and there is also an indirect effect that can be expected after green manure soil amendment, because microbial activity is enhanced in the soil. Brassicas are known to possess GSL and MYR in their cells and thus have the potential to be utilized as biofumigation crops. There are, however, differences in the potential within the Brassicaceae family, based on different types and concentrations of GSL present in the different species. To ensure effective biofumigation it is important to use the correct brassica species and have a good understanding of the factors that have a positive impact on the biofumigation action. Laboratory bioassays were done to determine the potential of different cover crops to suppress Meloidogyne javanica and C. xenoplax, when applied as a green manure. The cover crops used for the bioassays included Oats (Avena sativa cv. Pallinup), White mustard (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) and Nemat (Eruca sativa cv. Nemat). The plant material was cut into small pieces and mixed with sterilised soil inoculated with either M. javanica or C. xenoplax. Results from the bioassays showed a significant suppression of M. javanica by the three biofumigation species: White mustard, Caliente 199 and Nemat. These results supported previous research, indicating the nematode suppressing effect due to the biofumigation action of certain brassica crops. Canola did not have the same suppressing impact on the M. javanica and gave comparable results to the control, indicating that Canola is not a good biofumigation crop for M. javanica suppression. In terms of biofumigation effect oats did not differ significantly from the control or the three brassicas: White mustard, Caliente 199 and Nemat. In the bioassays done for C. xenoplax no significant differences were found between the green manure treatments and the control. These results indicate that the different crops tested, including the three well known biofumigation crops, did not suppress the C. xenoplax at the applied biomass concentrations used in the bioassay. Crops can also be classified according to their host status for certain plant parasitic nematodes. Crop host trials were conducted to determine the crop host status of the five different cover crops, to M. javanica and C. xenoplax. The crops were planted in sterilised soil, inoculated with the latter plant-parasitic nematodes and left for 60 days, after which, a root gall index analysis was done for M. javanica and for 85 or 92 days after which C. xenoplax was extracted from the soil. All the crops evaluated had a significantly lower root gall index for M. javanica than the control. Nemat and Oats was classified as poor hosts for M. javanica. A visual inspection of the root systems of all the crops was performed to determine whether M. javanica managed to complete its lifecycle in the different root systems. On all root systems, M. javanica managed to form root galls and produce egg masses, from which (J2) juveniles emerged. This indicates that M. javanica did complete its lifecycle in the different root systems of the crops evaluated and that all the cover crops acted as hosts. The expression of the gall symptoms were, however, less severe on Nemat and Oats, compared to the others. In the C. xenoplax crop host trials, all except the Nemat treatment showed a significant difference, compared to the Tomato treatment, with lower C. xenoplax numbers being present in the other crops. The nematode numbers in the different crops, compared well with the control (only inoculated soil), indicating that the crops did not stimulate the reproduction of C. xenoplax. Canola had the lowest numbers of C. xenoplax present after the growing cycle and Caliente 199 also showed a declining trend. In South Africa, the use of annual cover crops in vineyards is an established soil cultivation practice. In a field study, Oats, White mustard, Canola, Caliente 199 and Nemat were established in a vineyard as cover crops for three growing seasons (2009/10, 2010/11, 2011/12), and evaluated for their biofumigation impact, as well as their host impact on the suppression of certain economically important plant-parasitic nematodes. Two cover crop management practices, namely mechanical incorporation (MC) into the top soil and chemical removal of the cover crop (CC) were applied to the different cover crops. Nematode samples were taken in the work row and in the vine row at different times to determine the nematode status. These periods were April/May, before planting the cover crops, as well as 0, 15, 30 and 60 days after the management practices were performed. The crop biomass, measured as dry matter production (DMP) in tons/ha, differed significantly between the different crops, but also showed substantial increases during the three cover crop growing seasons for most crops. During the three consecutive seasons, Canola (CC) and Caliente 199 (CC) showed a constant reduction in the C. xenoplax population in the vine row based on the 60 day analysis. This trend was also observed for the total plant-parasitic nematode population in the vine row for the three seasons, based on 60 day analysis. The same trend took place during the three-year trial period for all the different sampling periods (0, 15, 30 and 60 days). The results can be attributed to the host status of these crops and not primarily because of the biofumigation effect. Both the Canola (CC) and the Caliente (CC) had a substantial increase in DMP during the three growing seasons that might have played a role in this trend. White mustard (CC and MC) showed a significant increase in the C. xenoplax population in the vine row, over the three year period, based on the 60 day analysis. The same trend was found Nemat (CC) and weeds and nematicide (CC) measured at the same period. A positive result from the Meloidogyne sp. analysis was that there was no significant increase in the Meloidogyne sp. in the vine row during the three growing seasons based on the 60 day analysis. This trend was seen in all the different treatments. The results from this study opens the possibility to apply these cover crops as part of a crop rotation programme without expecting an increase in the Meloidogyne sp. population to occur in the vine row through time. / AFRIKAANSE OPSOMMING: Plantparasitiese nematodes, wat bestaan uit 'n wye verskeidenheid van spesies, kan lei tot ernstige ekonomiese verliese in die meeste landbou gewasse. Meloidogyne spp. (knopwortel nematode), Criconemoides xenoplax (ring nematode), Xiphinema index (dolk nematode) en Pratylenchus spp. (letsel nematode) is van dié belangrikste plantparasitiese nematodes wat 'n bedreiging inhou vir wingerd en ander meerjarige gewasse in Suid-Afrika. Wêreldwyd is daar tans toenemende druk op die uitfasering van voor-plant chemiese grondberoking middels en so ook op nauitplant nematisiede. Vir volhoubare nematode bestuur, is dit belangrik om 'n holistiese benadering te volg, in ag genome kulturele, biologiese en chemiese maatreëls as deel van 'n geïntegreerde benadering. Bioberoking het die potensiaal om deel uit te maak van so 'n geïntegreerde benadering en baie vorige navorsing bevestig hierdie positiewe reaksie, in terme van onderdrukking, wat bioberoking op grond-gedraagde siektes, nematodes en onkruid kan hê. Bioberoking kan beskryf word as die reaksie, wat plaasvind wanneer glukosinolaat (GSL), wat teenwoordig is in die vakuool van die plantselle, in kontak kom met die ensiem mirosinase (MYR), nadat selbreking plaasgevind het en die aktiewe verbinding isothiosianaat (ITC) en ander sekondêre metaboliete gevorm word. Wanneer hierdie groen plantmateriaal in die grond ingewerk word, kan ʼn direkte onderdrukkings effek, as gevolg van die ITC, asook ʼn indirekte onderdrukkings effek as gevolg van die stimulasie van mikrobe aktiwiteit, verwag word. Brassica gewasse is bekend daarvoor dat daar GSL en MYR in die plantselle teenwoordig is en hulle besit dus die potensiaal om ITC te vorm. Daar is egter verskille in hierdie potensiaal binne die Brassicaceae familie, wat gebaseer is op verskillende tipes en konsentrasies GSL. Die keuse van ʼn brassica spesie is dus belangrik, tesame met ʼn verskeidenheid van ander faktore, om optimale bioberoking te verseker. Laboratorium biotoetse is gedoen om die bioberokings effek van verskillende dekgewasse op Meloidogyne javanica en C. xenoplax, wanneer dit aangewend word as groenbemesting, te bevestig. Die dekgewasse wat gebruik is sluit in: Hawer (Avena sativa cv. Pallinup), Wit mosterd (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) en Nemat (Eruca sativa cv. Nemat). Die plantmateriaal is fyn opgesny en ingewerk in gesteriliseerde grond wat met onderskeidelik M. javanica en C. xenoplax geïnokuleer is. Resultate van die biotoetse vir M. javanica toon dat die drie gewasse; Wit mosterd, Caliente 199 en Nemat, wat alombekend is vir hul bioberoking potensiaal, ʼn betekenisvolle onderdrukkings op M. javanica tot gevolg gehad het. Hierdie biotoetse ondersteun vorige navorsing, waar effektiewe onderdrukking van sekere Meloidogyne spesies as gevolg van bioberoking verkry is. Die resultate dui ook aan dat Canola nie ʼn goeie opsie is vir effektiewe bioberoking om M. javanica onderdrukking te verkry nie. Die Hawer behandeling het nie betekenisvol van die kontrole of van die ander bioberokings gewasse verskil nie. Daar is geen betekenisvolle verskille verkry tussen die kontrole en die ander gewasse tydens die C. xenoplax biotoetse nie. Die resultate dui aan dat die dekgewasse, insluitende die drie bekende bioberokings gewasse, nie C. xenoplax onderdruk teen die toegediende biomassa konsentrasies nie. Gewasse kan ook geklassifiseer word op grond van hul gasheer status vir sekere nematode. Gasheer toetse is gedoen om die gasheer status van die verskillende dekgewasse vir M. javanica en C. xenoplax te bepaal. Dieselfde vyf verskillende dekgewasse is geplant in grond, wat vooraf onderskeidelik met M. javanica en C. xenoplax geïnokuleer is. Plante is gelos om vir `n spesifieke periode te groei waarna ʼn galindeks evaluasie is gedoen om die gasheer status vir M. javanica te bepaal en ʼn nematode ontleding gedoen is om die gasheer status vir C. xenoplax te bepaal. In die M. javanica gasheer toetse was die galindeks van al die gewasse betekenisvol laer as die kontrole. Nemat kan geklassifiseer word as ʼn swak gasheer vir M. javanica en het betekenisvol minder galle as al die ander gewasse, behalwe die Hawer, waarvan dit nie betekenisvol verskil het nie. Nemat pas dus goed in ʼn dekgewas program waar die doel is om die M. javanica populasie te onderdruk tydens die groei van die gewas. ʼn Visuele inspeksie van die wortelstelsels is ook gedoen ten einde te bepaal of die lewensiklus van M. javanica voltooi is. Wortelgalle en eiersakkies was teenwoordig in die wortels van al die verskillende gewasse en larwes het uit die eiers uitgebroei. Dit dui aan dat M. javanica daarin geslaag het om sy lewenssiklus op al die dekgewasse suksesvol te voltooi. Daar was aansienlik minder eiersakke by Nemat en Hawer; wat hul swak gasheer status bevestig. In die biotoetse vir die gasheerstatus van C. xenoplax het al die gewasse, behalwe Nemat, betekenisvol laer C. xenoplax getalle, in vergelyking met die Tamatie behandeling, tot gevolg gehad. Die nematode getalle was soortgelyk aan die kontrole (slegs geïnokuleerde grond), waar geen gewas in medium geplant is nie, en dui dus aan dat die getalle op die verskillende gewasse nie vermeerder het nie. Die Canola behandeling het die laagste C. xenoplax getalle gehad, gevolg deur Caliente 199. Hierdie gewasse toon dus die meeste potensiaal om aangewend te word in 'n rotasie stelsel of dekgewas program, waar die doel is om die C. xenoplax populasie te onderdruk. In Suid-Afrika is die aanwending van spesifieke eenjarige gewasse, as dekgewasse in wingerde, reeds ʼn standaard praktyk met verskeie voordele. In veldproewe oor ʼn tydperk van drie jaar (2009/10, 2010/11, 2011/12) is Hawer, Wit mosterd, Canola, Caliente 199 en Nemat aangeplant as dekgewasse in ʼn wingerd proefperseel. Die doel van die veldproewe was om die effek van dekgewasse op die plantparasitiese nematodes, wanneer dit aangewend word as bioberokings gewasse, te bepaal. Die gasheer status van die gewasse is ook ondersoek om te bepaal wat die effek sal wees op die nematode getalle. Twee dekgewas bestuurspraktyke is toegepas; meganiese inwerk van die dekgewasse in die bogrond (MC) en chemiese beheer van die dekgewasse (CC) en nematode monsters is op verskillende tye in die werksry en in die wingerdry geneem. Hierdie periodes sluit in April/Mei, voor die vestiging van die dekgewasse en 0, 15, 30 en 60 dae nadat die bestuurspraktyk toegepas is. Die dekgewas se biomassa produksie is, op grond van die droë massa produksie (DMP), in ton/ha gemeet, wat betekenisvol verskil het vir die verskillende dekgewas. Daar het ook `n duidelike toename in DMP plaasgevind oor die drie seisoene vir meeste gewasse. Gedurende die drie jaar periode het die Canola (CC) en Caliente 199 behandelings, gemeet 60 dae na die bestuurspraktyk, ʼn konstante afname getoon in die C. xenoplax in die wingerd ry. Dieselfde tendens het ook voorgekom gedurende hierdie periode in die totale plantparasitiese nematodes teenwoordig in die wingerd ry. Daar is ook ʼn geleidelike afnemende tendens in die C. xenoplax in die wingerd ry, oor die verskillende periodes 0, 15, 30 en 60 dae vir die drie opeenvolgende seisoene, waargeneem. Hierdie resultate kan primêr toegeskryf word aan die gasheer status van die dekgewasse, wat in die gasheer proewe as swak gashere vir C. xenoplax aangetoon is. Nog ʼn faktor wat hier ʼn rol speel is die feit dat beide die Canola (CC) en die Caliente 199 (CC) ʼn toename in DMP van meer as 2 ton, gedurende die drie jaar periode, gehad het; wat op sigself ook ʼn bydraende rol kon speel. Wit mosterd (CC en MC) het oor die drie seisoene ʼn betekenisvolle verhoging in die C. xenoplax populasie tot gevolg gehad, gebaseer op die 60 dae ontleding. Dieselfde tendens is ook opgemerk vir die ander behandelings, onder andere Nemat (CC) en die onkruid en aalwurmdoder (CC) behandeling. ʼn Baie positiewe resultaat na afloop van die drie seisoene is die feit dat daar nie ʼn betekenisvolle verhoging in die Meloidogyne sp. populasie in die wingerdry, op grond van die 60 dae onledings, plaasgevind het nie. Dit was ook die geval vir al die ander behandelings. Hierdie resultate ondersteun die moontlikheid om hierdie bioberokings gewasse deel te maak van ʼn geïntegreerde dekgewas benadering, sonder om in die proses die Meloidogyne sp. in die wingerd ry te verhoog.

Entomopathogenic nematodes (EPNs) in the families Heterorhabditidae and Steinernematidae, and their bacterial symbionts, have been studied intensively because of their role as natural mortality factor for soil-dwelling arthropods, and their potential as biological control agents for belowground insect pests. Moreover, EPN are recognized as key players in regulating soil food webs and triggering trophic cascades. However, most studies of interactions with EPN have been conducted under laboratory setting and simplified conditions, without consider the dynamic of the EPN and their interactions with other soil components in a wider context. In this respect, knowledge of the effect that other soil organisms or human induced factor may have on EPN dynamic and life cycle in the soil may contribute to improve tactics for their implementation and success as natural regulators of herbivores. The present investigation focused on the interactions of EPN with a selection of insecticides, and biotic (saprobic fungus and plant parasitic nematodes) elements that may be present in the soil, and may potentially interact with EPN. Specifically, I investigated how these factors may affect the life cycle (host search behavior, virulence and reproduction) of EPN. Appendix A shows the effect that a group of selected synthetic and biological insecticides have on EPN virulence and reproduction. The results obtained from this study revealed that most combinations of EPN and insecticides under study increased the mortality of the insect host. However, it was also found that some of these combinations reduced the nematode progeny production and emergence of IJs from the insect cadaver. In contrast in Appendix B, when examining the effect of the saprobic fungus Fusarium oxysporum in the life cycle of the EPN Heterorhabditis sonorensis, it was found that this fungus negatively affected the virulence and reproduction of the EPN in the insect host. In the third study of this dissertation (Appendix C) the interactions studied considered the effect of two EPN on an organism of a different trophic guild, the plant parasitic nematode Tylenchulus semipenetrans. This plant parasitic nematode causes serious diseases in citrus plants by infecting their roots and defoliating their branches. Previous studies have shown that some EPN species may negatively affect the life cycle of plant parasitic nematodes by reducing the damage produced by this plant parasite. Results from this study confirm the antagonistic effect between the selected EPN and the citrus nematode. Specifically, it was found that the presence in the soil of both EPN reduced the survival of infective juveniles of the citrus nematode and their penetration to the root. Moreover, the presence of EPN had an antagonistic effect in the production of eggs of T. semipenetrans females.

Objetivando melhor conhecimento a respeito dos nematóides encontrados associados a fruteiras de clima subtropical e temperado, coletaram-se 149 amostras de solo da rizosfera e de raízes de amoreira-preta, caquizeiro, framboeseira, macieira, marmeleiro, nespereira, nogueira-macadâmia, oliveira, pereira, pessegueiro e umezeiro em áreas de produção do Estado de São Paulo e em uma localidade de Minas Gerais. Como resultado desse levantamento, identificaram-se 11 gêneros e as espécies relacionadas a seguir: Aorolaimus nigeriensis, Discocriconemella degrissei, Helicotylenchus dihystera, H. erythrinae, H. microcephalus, H. pseudorobustus, Helicotylenchus spp., Hemicycliophora poranga, Meloidogyne hapla, M. incognita, M. javanica, Mesocriconema onoense, M. ornata, M. sphaerocephalum, M. xenoplax, Mesocriconema spp., Pratylenchus brachyurus, P. zeae, Rotylenchulus reniformis, Scutellonema brachyurus, Tylenchulus semipenetrans, Xiphinema brevicollum, X. elongatum, X. krugi, X. setariae, X. surinamense e Xiphinema spp.. Os três gêneros mais freqüentes foram Helicotylenchus, Mesocriconema e Xiphinema, presentes em 60,4; 55,0 e 30,2 % das amostras, respectivamente; as espécies mais comuns foram H. dihystera e M. xenoplax, ocorrendo em 49 e 38,3 % das amostras. Contudo, apenas M. incognita e M. javanica estavam associados a danos em pessegueiros cujos porta-enxertos não tinham resistência genética. Em casa de vegetação, avaliaram-se as reações de genótipos das citadas fruteiras, mais goiabeira, frente aos nematóides de galhas Meloidogyne incognita raça 2 e M. javanica. As plantas, individualmente inoculadas com 5000 ovos de cada espécie de nematóide, foram conduzidas em recipientes plásticos durante 120 dias. A caracterização das reações baseou-se na capacidade reprodutiva dos parasitos, determinando-se os índices de massas de ovos e de galhas, bem como os números de nematóides por sistema radicular e por grama de raízes. Apenas a cultivar GF-677 de Prunus persica x P. dulcis comportou-se como suscetível, possibilitando desenvolvimento e multiplicação dos dois nematóides. Os demais genótipos avaliados foram hospedeiros desfavoráveis ao desenvolvimento dos nematóides, sendo considerados resistentes, embora vários deles tivessem proporcionado restritas taxas de reprodução dos parasitos. Estudou-se ainda, também sob condição de casa de vegetação, a patogenicidade de M. incognita raça 2 em caquizeiro 'Kyoto', verificando-se correlação negativa entre os níveis populacionais iniciais utilizados (0, 160, 800, 4 000, 20 000 e 100 000 ovos por parcela) e a altura e a massa seca de raízes das plantas, após seis meses da inoculação. Tendo em vista que a intensa formação de galhas radiculares observada e o efeito negativo sobre os dois parâmetros de crescimento das plantas mostraram-se associados a taxas de reprodução muito baixas do parasito, considerou-se que a reação ocorrida foi de intolerância. / In order to achieve a better knowledge on the nematodes found associated with subtropical and temperate fruits, a total amount of 149 soil and root samples were collected from within apple, blackberry, japanese apricot, loquat, macadamia, olive, peach, pear, persimmon, quince and raspberry orchards located in the states of São Paulo and Minas Gerais, Southeastern Brazil. From this survey, a number of species belonging to eleven genera were identified, namely Aorolaimus nigeriensis, Discocriconemella degrissei, Helicotylenchus dihystera, H. erythrinae, H. microcephalus, H. pseudorobustus, Helicotylenchus spp., Hemicycliophora poranga, Meloidogyne hapla, M. incognita, M. javanica, Mesocriconema onoense, M. ornata, M. sphaerocephalum, M. xenoplax, Mesocriconema spp., Pratylenchus brachyurus, P. zeae, Rotylenchulus reniformis, Scutellonema brachyurus, Tylenchulus semipenetrans, Xiphinema brevicollum, X. elongatum, X. krugi, X. setariae, X. surinamense and Xiphinema spp. The most frequent genera were Helicotylenchus, Mesocriconema and Xiphinema, which occurred in 60.4, 54.4 and 30.2 % of the samples, respectively; the two most common species found were Helicotylenchus dihystera and Mesocriconema xenoplax, detected in 49.0 and 38.8 % of the samples, respectively. However, only Meloidogyne incognita and M. javanica could be associated with peach trees that were stunted or showed general symptoms of decline; in these cases, the rootstocks did not have genetic resistance to root-knot nematodes. The host suitability of several genotypes of the mentioned fruit species, plus guava, were evaluated in relation to Meloidogyne incognita race 2 and M. javanica under greenhouse conditions. The plants were individually inoculated with 5,000 nematode eggs and kept to grow in plastic bags for four months. Nematode reproductive rate was determined with basis on gall index, egg mass index and numbers of nematodes per root system and per gram of roots. Only the cultivar GF-677 of Prunus persica x P. dulcis was susceptible to both nematode species. All other genotypes were poor/resistant hosts, even that some allowed the parasites to reproduce at low rates. The pathogenicity of Meloidogyne incognita race 2 to persimmon cv. Kyoto was also studied under greenhouse conditions. After six months of the inoculation with increasing nematode population levels - 0; 160; 800; 4,000; 20,000; and 100,000 eggs/plant - a negative correlation with plant height and top dry weight values was obtained. As an intense root galling was associated with low nematode reproductive rates and some depressive effects on the plant growth, the reaction was rated as being of intolerance.

Thesis (MSc. Agriculture (Horticulture)) -- University of Limpopo, 2018 / The production of tomato (Solanum lycopersicum L.) plants had been crucial in various parts of the world since tomato fruit contribute widely to human health. However, most tomato cultivars had been shown to be highly susceptible to plant-parasitic nematodes, especially the root-knot (Meloidogyne species) nematodes. Two cucurbitacin-containing phytonematicides, namely, Nemarioc-AL and Nemafric-BL phytonematicides, manufactured from fruits of Cucumis species, are being researched and developed in South Africa as an alternative for management of Meloidogyne species. Most trials on tomato plants and cucurbitacin-containing phytonematicides had been under greenhouse conditions, with limited information on their interactive effects under microplot and field conditions. The objectives of this study were: (1) to determine the interactive effects of Nemarioc-AL and Nemafric-BL phytonematicides on growth and accumulation of nutrient elements in leaf tissues of tomato plants under microplot conditions and (2) to investigate the interactive effects of Nemarioc-AL and Nemafric-BL phytonematicides on growth and accumulation of nutrient elements in leaf tissues of tomato plants under field conditions. In the microplot study, uniform four-week-old tomato cv. 'HTX 14' seedlings were transplanted in 4 L plastic bags containing loam soil and Hygromix-T at the 3:1 ratio (v/v). Plastic bags were inserted into holes at 0.50 m inter-row spacing and 0.60 m intra-row spacing. The 2 x 2 factorial trial, with the first and second factors being Nemarioc-AL and Nemafric-BL phytonematicides, respectively, each at two levels. The four treatments, namely, AL0BL0, AL0AL1, BL0BL1 and AL1BL1, were arranged in a randomised complete block design. Treatments were xxiv applied seven days after transplanting and repeated weekly until harvest. Under field conditions, uniform four-week-old tomato cv. 'HTX 14' seedlings were transplanted into the field at 0.50 m inter-row spacing and 0.60 m intra-row spacing. Treatments, experimental designs and application interval were as those under microplot conditions. At 60 days after the treatments, seedlings AL × BL interaction was not significant on all plant variables in Experiment 1 under microplot conditions, whereas in Experiment 2 the interaction was highly significant (P ≤ 0.01) on dry shoot mass, contributing 72% in total treatment variation (TTV) of the variable. Relative to untreated control, the two-way matrix showed that the interaction reduced dry shoot mass by 8%. Nemarioc-AL phytonematicide had a significant (P ≤ 0.05) effect on stem diameter in Experiment 1 under field conditions, whereas Nemafric-BL phytonematicide had significant effects on plant height in Experiment 2, contributing 39 and 56% in TTV of the respective variables. Relative to untreated control, Nemarioc-AL phytonematicide increased stem diameter by 4%, whereas Nemafric-BL phytonematicide increased plant height by 2%. The interaction was also significant (P ≤ 0.05) on Na and S and highly significant (P ≤ 0.01) on Zn, contributing 76, 26 and 6%, respectively, in TTV of the respective variables in Experiment 1 under field conditions. Using a two-way matrix, the interaction increased Na and S by 12 and 41%, respectively, but reduced Zn by 52%. In Experiment 2, the interaction was highly significant (P ≤ 0.01) on P alone, contributing 16% in TTV of the variable, with the interaction reducing P by 76%. Nemarioc-AL phytonematicide had significant effects (P ≤ 0.05) on Ca and highly significant effects (P ≤ 0.01) on S, contributing 31 and 58% in TTV of the respective variables in Experiment 1. Relative to untreated control, Nemarioc-AL phytonematicide increased P by 39%. In xxv Experiment 2, Nemarioc-AL phytonematicide had significant effects on Ca and highly significant effects (P ≤ 0.01) on S, contributing 66 and 49% in TTV of the respective variables. Relative to untreated control, Nemarioc-AL phytonematicide reduced Ca by 19% and S by 36%, respectively. Nemafric-BL phytonematicide had a significant effect (P ≤ 0.05) on P, contributing 33% in TTV of the variable in Experiment 1. Relative to untreated control, Nemafric-BL phytonematicide increased P by 41%. In Experiment 2, Nemafric-BL phytonematicide had significant effects (P ≤ 0.05) on S, contributing 40% in TTV of the variable. Relative to untreated control, Nemafric-BL phytonematicide reduced S by 33%. At 74 days after initiating the treatments under field conditions, the interaction of Nemarioc-AL and Nemafric-BL phytonematicides were not significant for plant height, stem diameter, fresh fruit and dry shoot mass in both experiments. Nemarioc-AL phytonematicide was also not significant in all plant variables in both experiments. Effects of Nemafric-BL phytonematicide were highly significant on dry shoot mass in Experiment 1 and stem diameter in Experiment 2, contributing 60 and 67% in TTV of the respective variables. Relative to untreated control, Nemafric-BL phytonematicide reduced dry shoot mass by 28% and increased stem diameter by 11% in Experiment 1 and Experiment 2, respectively. The AL × BL interaction had significant effects (P ≤ 0.05) on P, contributing 57% in TTV of the variable in Experiment 1. Relative to untreated control, the interaction increased P by 12%. In Experiment 2, the interaction had significant effects (P ≤ 0.05) on K, Mg, S and Mn, contributing 78, 65, 74 and 68% in TTV of the respective variables. Using a two-way matrix, relative to untreated control, the interaction increased K by 8%, but reduced Mg, Mn and S by 14, 82 and 1%, respectively. Nemarioc-AL phytonematicide was not significant in both the xxvi experiments, whereas Nemafric-BL phytonematicide had significant effects on Mg in Experiment 1, contributing 68% in TTV of the variable. Relative to untreated control, Nemafric-BL phytonematicide increased Mg by 15%. In conclusion, the interaction of Nemarioc-AL and Nemafric-BL phytonematicides were not compatible with each other as they had undesirable effects on growth of tomato plants and accumulation of most essential nutrient elements in leaf tissues of this plant. / National Research Foundation (NRF)

Objetivando melhor conhecimento a respeito dos nematóides encontrados associados a fruteiras de clima subtropical e temperado, coletaram-se 149 amostras de solo da rizosfera e de raízes de amoreira-preta, caquizeiro, framboeseira, macieira, marmeleiro, nespereira, nogueira-macadâmia, oliveira, pereira, pessegueiro e umezeiro em áreas de produção do Estado de São Paulo e em uma localidade de Minas Gerais. Como resultado desse levantamento, identificaram-se 11 gêneros e as espécies relacionadas a seguir: Aorolaimus nigeriensis, Discocriconemella degrissei, Helicotylenchus dihystera, H. erythrinae, H. microcephalus, H. pseudorobustus, Helicotylenchus spp., Hemicycliophora poranga, Meloidogyne hapla, M. incognita, M. javanica, Mesocriconema onoense, M. ornata, M. sphaerocephalum, M. xenoplax, Mesocriconema spp., Pratylenchus brachyurus, P. zeae, Rotylenchulus reniformis, Scutellonema brachyurus, Tylenchulus semipenetrans, Xiphinema brevicollum, X. elongatum, X. krugi, X. setariae, X. surinamense e Xiphinema spp.. Os três gêneros mais freqüentes foram Helicotylenchus, Mesocriconema e Xiphinema, presentes em 60,4; 55,0 e 30,2 % das amostras, respectivamente; as espécies mais comuns foram H. dihystera e M. xenoplax, ocorrendo em 49 e 38,3 % das amostras. Contudo, apenas M. incognita e M. javanica estavam associados a danos em pessegueiros cujos porta-enxertos não tinham resistência genética. Em casa de vegetação, avaliaram-se as reações de genótipos das citadas fruteiras, mais goiabeira, frente aos nematóides de galhas Meloidogyne incognita raça 2 e M. javanica. As plantas, individualmente inoculadas com 5000 ovos de cada espécie de nematóide, foram conduzidas em recipientes plásticos durante 120 dias. A caracterização das reações baseou-se na capacidade reprodutiva dos parasitos, determinando-se os índices de massas de ovos e de galhas, bem como os números de nematóides por sistema radicular e por grama de raízes. Apenas a cultivar GF-677 de Prunus persica x P. dulcis comportou-se como suscetível, possibilitando desenvolvimento e multiplicação dos dois nematóides. Os demais genótipos avaliados foram hospedeiros desfavoráveis ao desenvolvimento dos nematóides, sendo considerados resistentes, embora vários deles tivessem proporcionado restritas taxas de reprodução dos parasitos. Estudou-se ainda, também sob condição de casa de vegetação, a patogenicidade de M. incognita raça 2 em caquizeiro 'Kyoto', verificando-se correlação negativa entre os níveis populacionais iniciais utilizados (0, 160, 800, 4 000, 20 000 e 100 000 ovos por parcela) e a altura e a massa seca de raízes das plantas, após seis meses da inoculação. Tendo em vista que a intensa formação de galhas radiculares observada e o efeito negativo sobre os dois parâmetros de crescimento das plantas mostraram-se associados a taxas de reprodução muito baixas do parasito, considerou-se que a reação ocorrida foi de intolerância. / In order to achieve a better knowledge on the nematodes found associated with subtropical and temperate fruits, a total amount of 149 soil and root samples were collected from within apple, blackberry, japanese apricot, loquat, macadamia, olive, peach, pear, persimmon, quince and raspberry orchards located in the states of São Paulo and Minas Gerais, Southeastern Brazil. From this survey, a number of species belonging to eleven genera were identified, namely Aorolaimus nigeriensis, Discocriconemella degrissei, Helicotylenchus dihystera, H. erythrinae, H. microcephalus, H. pseudorobustus, Helicotylenchus spp., Hemicycliophora poranga, Meloidogyne hapla, M. incognita, M. javanica, Mesocriconema onoense, M. ornata, M. sphaerocephalum, M. xenoplax, Mesocriconema spp., Pratylenchus brachyurus, P. zeae, Rotylenchulus reniformis, Scutellonema brachyurus, Tylenchulus semipenetrans, Xiphinema brevicollum, X. elongatum, X. krugi, X. setariae, X. surinamense and Xiphinema spp. The most frequent genera were Helicotylenchus, Mesocriconema and Xiphinema, which occurred in 60.4, 54.4 and 30.2 % of the samples, respectively; the two most common species found were Helicotylenchus dihystera and Mesocriconema xenoplax, detected in 49.0 and 38.8 % of the samples, respectively. However, only Meloidogyne incognita and M. javanica could be associated with peach trees that were stunted or showed general symptoms of decline; in these cases, the rootstocks did not have genetic resistance to root-knot nematodes. The host suitability of several genotypes of the mentioned fruit species, plus guava, were evaluated in relation to Meloidogyne incognita race 2 and M. javanica under greenhouse conditions. The plants were individually inoculated with 5,000 nematode eggs and kept to grow in plastic bags for four months. Nematode reproductive rate was determined with basis on gall index, egg mass index and numbers of nematodes per root system and per gram of roots. Only the cultivar GF-677 of Prunus persica x P. dulcis was susceptible to both nematode species. All other genotypes were poor/resistant hosts, even that some allowed the parasites to reproduce at low rates. The pathogenicity of Meloidogyne incognita race 2 to persimmon cv. Kyoto was also studied under greenhouse conditions. After six months of the inoculation with increasing nematode population levels – 0; 160; 800; 4,000; 20,000; and 100,000 eggs/plant – a negative correlation with plant height and top dry weight values was obtained. As an intense root galling was associated with low nematode reproductive rates and some depressive effects on the plant growth, the reaction was rated as being of intolerance.

Les interventions humaines de plus en plus fréquentes et persistantes dans les écosystèmes d'une part, et l'intensification des systèmes de cultures d'autre part qui s'accompagne pour partie de méthodes radicales pour combattre les bio-agresseurs des cultures, nous posent de multiples questions au sujet des risques écologiques liés aux changements des milieux, dont les perturbations induites sur les communautés d'organismes vivants. Les nématodes phytoparasites (NPP), vers ronds microscopiques telluriques qui occasionnent des pertes de production végétale importantes, sont partout présents en communautés. Ces nématodes répondent rapidement aux forçages extérieurs (e.g. anthropiques et environnementaux) par des modifications de la structure de leurs communautés. Par ce travail de thèse, nous cherchons à mieux comprendre l'effet des facteurs impliqués dans l'assemblage des espèces de NPP en communautés associées à l'olivier méditerranéen et à déterminer la réponse de ces communautés aux forçages imposés par la domestication de l'olivier, par l'intensification de sa culture et par différents facteurs environnementaux. L'étude a été réalisée au Maroc dans toutes les régions oléicoles (vergers traditionnels à faible densité et vergers à haute-densité), dans les zones refuge d'olivier sauvage (oléastre) et sur olivier féral. Les facteurs pédoclimatiques qui caractérisent les sites d'échantillonnage ont également été pris en considération. L'analyse de la nématofaune a révélé d'une grande diversité spécifique, de nombreuses espèces étant décrites pour la première fois sur olivier, et une nouvelle espèce (Meloidogyne spartelensis) ayant été découverte. La diversité, la composition taxonomique, trophique et fonctionnelle, la dominance des taxons, les patrons de communautés sont fortement affectés par les différents forçages pris en compte. Le gradient d'anthropisation croissante (sauvage vs féral vs cultivé traditionnel vs cultivé haute-densité) est la variable qui impacte le plus la diversité par réduction de la richesse spécifique et l'augmentation de l'abondance en NPP. L'étude a également porté une attention particulière sur la diversité des nématodes à galles des racines du genre Meloidogyne, un des principaux ravageurs de l'olivier. Elle a indiqué la dispersion de M. javanica dans les vergers et sur olivier féral, alors que d'autres espèces (M. arenaria, M. hapla et M. spartelensis) sont confinées dans les zones refuge des oléastres. Afin d'analyser la diversité génétique, des marqueurs morphologiques et moléculaires ont dévoilé d'une diversité importante entre et au sein des différentes populations de Meloidogyne. Les études diligentées dans le cadre de cette thèse confirment que la diversité et la structure des communautés de NPP pourraient être des indicateurs pertinents pour évaluer la santé des sols dans les agro et écosystèmes, en corrélant diversité et pathogénicité des communautés. Elles soulignent donc l'importance de la diversité parasitaire comme variable prioritaire à prendre en compte pour inspirer des stratégies de gestion des parasites basées sur le concept de résilience de la diversité (même s'il s'agit de parasites), pour une gestion durable des communautés de NPP et la préservation des milieux. / Human activities increasingly frequent and persistent in ecosystems on one hand, and cropping system intensification on the other hand partly with radical methods to control pests and diseases of crops, raise questions about the ecological risks related to biotop changes, including disturbances of living organism communities. Plant-parasitic nematodes (PPN), microscopic round soil-borne worms that cause significant losses of crop production, are everywhere present in communities. They respond quickly to external forces (e.g. human and environmental) by changing the structure of their communities. In this thesis, we seek to better understand the effect of the factors involved in the assemblage of PPN species in communities associated with the Mediterranean olive tree and to determine the response of these communities to forces imposed by olive domestication, by crop intensification and by various environmental factors. The study was conducted in all olive-growing regions in Morocco (traditional low density and high density orchards), in refugia areas for wild olive (oleaster) and on feral olive trees. The soil and climatic factors that characterize the sampling sites were also considered. The analysis of the nematofauna revealed a wide species diversity, many species being described for the first time on olive tree, and a new species (Meloidogyne spartelensis) have been discovered. The diversity, the species / trophic / functional structure of the communities, the dominance of the taxa, and the community patterns are strongly affected by the various forces considered. The increasing anthropogenic gradient (wild vs feral vs traditional cultivation vs high-density cultivation) is the variable that mostly impacts the diversity by reducing the species richness and increasing the abundance of PPN. A particular attention was attributed in this study to the diversity of root-knot nematodes Meloidogyne, a major pest of the olive tree. It revealed that M. javanica is widespread in orchards and olive feral, while other species (M. arenaria, M. hapla and M. spartelensis) are confined in oleaster refuge areas. In order to analyse the genetic diversity, morphological and molecular markers have revealed a significant diversity between and within different Meloidogyne populations. These thesis studies confirm that both the diversity and the structure of the PPN communities could be relevant indicators to assess soil health in agro and ecosystems, by correlating diversity and pathogenicity of communities. They therefore emphasize the importance of parasite diversity as a main variable to consider for inspiring pest control strategies based on the concept of diversity resilience (even if it concerns parasites) for sustainable management of PPN communities and for environment preservation.