Plant parasitic nematodes have long been known to cause extensive crop losses through reduced yields, shortened productive life, or lowered value of produce. The rood knot nematode, Heterodera marioni, is cosmopolitan. It destroys crops and causes economic losses equal to those of any other plant parasitic speies. in 1948 this nematode caused an estimated loss to the carrot raising industry in Iron County, Utah of approximately $15,000. No estimates for the years prior to 1948 are available; however, reports of the county agent (14) for Iron County show that carrot production in the Cedar Valley is decreasing, and is possibly due to this nematode. The importance of the root knot nematode to the carrot industry in the Cedar Valley was Recognized by farmers at harvest time in 1948. Experimental applications of soil fumigants were tried on many farms with varying success in the spring of 1949. (See figure 1 page 2). One of these experimental plots showed spectacular results. When carrots were harvested in the fall those grown in fumigated soil were found to be of the highest quality and were growing in excellent stands; wheras, the carrots grown in unfumigated soil produced poorer stands of poor quality carrots. Before any conclusions as to the practical value of soil fumigants in carrot raising can be reached, additional tests must be conducted in the area. The fact remains that the root knot nematode is present in the area and causes damage to carrots. If carrots, or any other susceptible crops, are to be grown on economical method of controlling this nematode must be found.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2016-10-17T13:10:34Z No. of bitstreams: 1 DissALG.pdf: 1204557 bytes, checksum: 4002ead709914a04a88c0451755956b6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2016-10-17T17:26:28Z (GMT) No. of bitstreams: 1 DissALG.pdf: 1204557 bytes, checksum: 4002ead709914a04a88c0451755956b6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2016-10-17T17:26:58Z (GMT) No. of bitstreams: 1 DissALG.pdf: 1204557 bytes, checksum: 4002ead709914a04a88c0451755956b6 (MD5) / Made available in DSpace on 2016-10-17T17:35:13Z (GMT). No. of bitstreams: 1 DissALG.pdf: 1204557 bytes, checksum: 4002ead709914a04a88c0451755956b6 (MD5) Previous issue date: 2015-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The sugarcane has great economic importance in Brazil. To keep productivity several biotic and abiotic factors can positively or negatively influence. Among them, weeds, nematodes and synergistic action between pesticides to control both can be cited. Thus, the present work aimed at studying possible common weeds in the mechanized harvesting system that can serve as hosts for the root knot nematode: Meloidogyne incognita and / or M. javanica and study the interaction between herbicides and nematicides used in the groove planting of sugarcane. Two experiments were carried in a greenhouse at the Agricultural Sciences Center (CCA-UFSCar), Araras, SP. The first experiment evaluated the host status ten weeds, as follows: Ipomoea triloba (Dammer), Merremia aegyptia (L.) Urban, Luffa aegyptiaca Mill, Euphorbia heterophylla L., Ricinus communis L., Crotalaria spectabilis Roth, Mucuna aterrima ( Piper & Tracy) Holland, Chloris polydactyla (L.) Sw., Digitaria horizontalis Willd., Urochloa decumbens (Stapf) RD Webster and the control (tomato Santa Cruz Kada) when inoculated with M. incognita or M. javanica in a completely randomized design in a factorial 11 x 2, with six repetitions. The plants were inoculated with 2.000 eggs and J2, and there were three plants per plot (6.000 eggs and J2 per pot - repetition). Sixty days after inoculation (DAI) the plants were removed and evaluated according to the reproduction factor (FR), final nematodes population (PF) and reproduction index (IR). In the second experiment the effect of interaction between two nematicides applied in contact with the stalks was evaluated. The nematicides tested were: benfuracarb (5,0 L ha-1) and carbofuran (50 Kg ha-1), and the herbicides applied preemergence of culture were: sulfentrazone (1,6 L p.c. ha-1), diuron + hexazinone (2,5 Kg ha1), saflufenacil (0,14 Kg p.c. ha-1) and amicarbazone (1,5 Kg p.c. ha-1). The experiment was carried in a completely randomized design in a factorial 15 x 5, with four replications in three sugarcane varieties (RB867515, RB975952 and RB975201). The first factor was corresponded to the 15 treatments and the second, to the five evaluation periods. Evaluations of intoxication symptoms were performed at 7, 15, 30, 45 and 60 days after emergence (DAE) of culture. In the last assessment biometric parameters height (cm), leaf area (cm²) and dry biomass of the aerial part (g) were evaluated. Regarding to the host status of weeds, it was found that L. aegyptiaca behaved as host of both nematodes, with FR > 1, higher than the control. The D. horizontalis was classified as host of M. incognita and non-host of M. javanica. C. spectabilis had the lowest FR and PF. R. communis and I. triloba present galls when inoculated with M. incognita, but were not considered host for presenting FR < 1. None of the weeds tested was considered immune, that is, with RF = 0. Regarding the interaction of herbicides and nematicides in all treatments, plants recover 60 DAE, and in treatments with the use of sulfentrazone increase in symptoms of poisoning was observed. As for the biometric parameters evaluated at 60 DAE, there was no statistical difference only in the variety RB867515 for height. In this case, the treatments amicarbazone / benfuracarb and amicarbazone / carbofuran plants were higher than the control and other interactions. / A cana-de-açúcar tem grande importância econômica no Brasil. Para manter sua produtividade diversos fatores bióticos e abióticos podem influenciar positiva ou negativamente. Dentre eles, podem ser citados as plantas daninhas, os nematóides e a interação entre produtos fitossanitários para o controle de ambos. Em função disto, o presente trabalho teve como objetivo estudar possíveis plantas daninhas comuns no sistema colheita mecanizada que possam servir de hospedeiras para os nematóides-das-galhas: Meloidogyne incognita (raça 3) e/ou M. javanica e estudar a interação entre herbicidas e nematicidas usados no plantio da cana-de-açúcar. Foram desenvolvidos dois experimentos em casa-de-vegetação do Centro de Ciências Agrárias (CCA-UFSCar), em Araras, SP. O primeiro experimento avaliou a hospedabilidade de dez plantas daninhas a nematóides, sendo elas: Ipomoea triloba (L.), Merremia aegyptia (L.) Urban, Luffa aegyptiaca Mill., Euphorbia heterophylla L., Ricinus communis L., Crotalaria spectabilis Roth, Mucuna aterrima (Piper & Tracy) Holland, Chloris polydactyla (L.) Sw., Digitaria horizontalis Willd., Urochloa decumbens (Stapf) R. D. Webste e a testemunha (tomateiro Santa Cruz Kada) quando inoculadas com M. incognita (raça 3) ou M. javanica, em delineamento inteiramente casualizado, em esquema fatorial 11 x 2, com seis repetições. As plantas foram inoculadas com 2.000 ovos e juvenis de segundo estádio (J2), sendo que havia três plantas por unidade experimental (6.000 ovos e J2 por vaso – repetição) e 60 dias após a inoculação (DAI) as plantas foram retiradas e avaliadas segundo o fator de reprodução (FR), população final de nematóides (PF) e índice de reprodutividade (IR). No segundo experimento foi avaliado o efeito da interação entre dois nematicidas aplicados em contato com os toletes, sendo eles: benfuracarbe (5,0 L ha-1) e carbofuran (50 Kg ha-1), com os herbicidas aplicados em pré-emergência da cultura: sulfentrazone (1,6 L p.c. ha-1), diuron + hexazinone (2,5 Kg ha-1), saflufenacil (0,14 Kg p.c. ha-1) e amicarbazone (1,5 Kg p.c. ha-1). O experimento foi conduzido em delineamento inteiramente casualizado, com quatro repetições, em três variedades de cana-de-açúcar (RB867515, RB975201 e RB975952). As avaliações de sintomas de intoxicação foram realizadas aos 7, 15, 30, 45 e 60 dias após a emergência (DAE) da cultura. Na última avaliação foram determinados os parâmetros biométricos altura (cm), área foliar (cm²) e biomassa seca da parte aérea (g). Com relação à hospedabilidade das plantas daninhas, foi verificado que L. aegyptiaca comportou-se como hospedeira de ambos os nematóides, com FR > 1, sendo superior a testemunha. A D. horizontalis foi classificada como hospedeira de M. incognita (raça 3) e não-hospedeira de M. javanica. A C. spectabilis apresentou os menores FR e PF. A R. communis e I. triloba apresentaram galhas quando inoculadas com M. incognita (raça 3), mas não foram consideradas hospedeiras por apresentarem FR < 1. Nenhuma das plantas daninhas foi considerada imune, ou seja, com FR = 0. Com relação a interação dos herbicidas e nematicidas, em todos os tratamentos as plantas se recuperaram aos 60 DAE, sendo que nos tratamentos com o uso do herbicida sulfentrazone foi observado os mais elevados sintomas de intoxicação. Quanto aos parâmetros biométricos avaliados aos 60 DAE, houve diferença estatística apenas na variedade RB867515 quanto à altura, nesse caso os tratamentos amicarbazone / benfuracarbe e amicarbazone / carbofuran foram superiores à testemunha e demais interações.

Canola, Brassics napus L. is a relatively new crop in South Africa. Insect pests have not yet been a major problem, but the notorious brassica specialist, diamondback moth (DBM), Plutella xylostella (L.) (Plutellidae) is establishing itself as a serious pest of this crop. DBM is the most important insect pest of plants from the family Brassicaceae throughout the world. It has developed resistance to all chemical pesticides used against it in the field and to toxins of the bacterium Bacillus thuringiensis. The pest status of DBM in South Africa is lower than in other countries with similar climates. However, due to indiscriminate use of pesticides, local populations of DBM are showing signs of resistance. An initial survey has indicated that in addition to DBM, canola is also attacked by aphids, Myzus persicae (Sulzer), Brevicoryne brassicae (L.), Lipaphis e1ysimi (Kaltenbach), (Aphiade), thrips, Thrips tabaci (Lindeman) and other pests mostly brassica specialists. The study was initiated to determine the composition of the community of insects found on canola, the seasonal phenology of DBM populations in canola, and the composition, relative abundance and seasonality of its parasitoids. Monitoring of the insects was carried out at weekly intervals for three years at Rietondale and Bapsfontein in Gauteng province of South Africa. Berlese funnels have been found to be useful in extracting insects from plants, and were used to indicate the presence ofDBM larvae and other insects found on canola. Adults of DBM were monitored with synthetic pheromone traps; larval and pupal populations were monitored by scouting canola plants. Samples of larvae, pupae and parasitoid cocoons were brought into the laboratory. Parasitoids that emerged were identified and their incidence recorded. Monolepta cf bifasciata (Chrysomelidae) and Listroderes costrirostris (Schoener) (Curculionidae) were the most abundant of the coleopteran pests. (DBM) and Heliothis armigera (H.) (Noctuidae) were most abundant lepidopteran pests of Canola. There was a high proportion of first and second instar larvae as indicated by the results of the Berlese funnels as compared to visual scouting in Bapsfontein. From May to August the infestation level of DBM was high, reaching the maximum of 0.25 larvae per plant in June 1996, then declined and remained low for the rest of the season in Rietondale. From September to December for all three years of the study, the population levels Of DBM were high, reaching a maximum of 9.6larvae per plant in September 1997, and remained low from January to August in Bapsfontein. The number of adult moths per trap per week ranged from 0 to 91 in Rietondale, peaking in January 1996 and September 1997. There was no correlation between infestation levels and the pheromone trap catches. In contrast to Rietondale, there was a high correlation between pheromone trap catches and subsequent larval infestations at Bapsfontein. Although DBM infestation levels were generally low, parasitism levels often reached 100% caused by a complex of parasitoids. During the period of study, the following hymenopteran parasitoids were recorded: Cotesia plutellae (Kurdjumov) and Apanteles eriophyes (Nixon), Braconidae), both larval parasitoids, Diadegma mollipla (Holmgren) (Ichneumonidae), and Oomyzus sokolowskii (Kurdjumov) (Eulophidae), larval-pupal parasitoids, Diadromus collaris (Gravenhorst) (Ichneumonidae) pupal parasitoid, and the hyperparasitoids Mesochorus sp. (Ichneumonidae) and Pteromalus sp. (Pteromalidae). Cotesia plutellae was the most abundant parasitoid occurring throughout the year..

This study involves a measure of the variability of descendants from a cross between Ustilago hordei race 7 and race 11, on two varieties of barley, Trebi and Odessa. Components of variability were defined, statistically described and compared. Biometrical analyses uncovered the action of significant additive and non-additive genetic effects. Differential interactions between treatments and varieties revealed the existence of at least one virulence gene. Specific polygenes and the virulence gene were found to produce significant interactions with different environmental conditions. Homogeneity of variance of the genetic components of the F2 from three randomly chosen F1 dikaryotic lines demonstrated the highly homozygous condition of the parental teliospores. Covariance - variance regression analysis was used to study the dominance and epistatic differences between treatment dikaryons. There is evidence for ambidirectional dominance. The number of effective factors operating against the varieties, Trebi and Odessa, were estimated to be between 4-6 and 1-2 respectively. / Science, Faculty of / Botany, Department of / Graduate

Thesis (Ph. D. Agriculture (Plant Protection)) -- University of Limpopo, 2013 / Global withdrawal of synthetic fumigant and non-fumigant nematicides due to their ecounfriendly impacts and high toxicity to non-target organisms, respectively, increased the research and development of alternatives for managing population densities of plantparasitic nematodes, particularly the root-knot (Meloidogyne species) nematodes. Although Meloidogyne species had been managed using genotypes that are resistant to plant-parasitic nematodes in various crops, various challenges negate the available or introgressed nematode resistance. In tomato (Solanum lycopersicum) production, nematode races and instability of nematode resistant genotypes under certain conditions necessitated the continued research and development of alternatives since most of the existing commercial tomato cultivars are highly susceptible to various biological races of Meloidogyne species. The aim of the study was to research and develop appropriate dosages of two phyto- nematicides which could be applied through drip irrigation system in open field tomato production systems, while the specific objectives were to: (1) determine whether a computer-based model could provide nonphytotoxic concentrations to tomato plants using fresh fruits of wild watermelon (Cucumis africanus) and wild cucumber (C. myriocarpus) under greenhouse conditions, (2) determine whether computer-based concentrations from the two plant species when using dried fruits would be less phytotoxic and more suppressive to nematodes, (3) investigate application time intervals for the two products, (4) determine responses of plant growth in tomato and nematode suppression in respect to the derived dosages, and and (5) validate dosages of fermented crude extracts from the two plant species with respect to plant growth of tomato and suppression of nematode numbers. xxxiii Greenhouse, microplot and field studies were set to test the hypotheses intended to achieve the stated objectives, with reliability of measured variables being ensured by using statistical levels of significance (P ≤ 0.05) and coefficients of determination (R2), while validity was ensured by conducting experiments at the same location over two seasons and/or by setting up factorial treatments. Firstly, fermented plant extracts of fresh fruits from C. africanus and C. myriocarpus consistently reduced population densities of Meloidogyne species by 80-92% and 50-90%, respectively. Tomato plants were highly sensitive to the two products as shown by the total degree of sensitivities (Σk) and biological index of 0 and 3, respectively. Also, the mean concentration stimulation range (MCSR) of 11% and 7% concentrations, respectively, attested to this phytotoxicity. Secondly, fermented crude extracts of dried fruits from C. africanus and C. myriocarpus also reduced population densities of Meloidogyne species by 78-97% and 87-97%, respectively. Tomato plants were highly tolerant to the two products in dried form as shown by the total degree of sensitivities (Σk) and biological index of 4 and 3, respectively. The MCSR values for C. africanus and C. myriocarpus dried fruits on tomato were 2.64% and 2.99%, respectively, which for the purpose of this study were individually adjusted to 3%, which translated to 36 L undiluted material/ha of 4 000 tomato plants. In subsequent studies, 3% concentration was used as the standard, along with double strength concentration, namely, 6% concentration. Thirdly, the MCSR values derived in Objective 4, namely 3% and 6% concentration for both Cucumis species using the CARD model were used in the optimisation of application time interval using the innovative concept of weeks (0, 1, 2, 3 and 4) in a 30-day month period. Application time interval for 3% and 6% concentrations of C. africanus fruits was xxxiv optimised at 2.40 and 2.61 weeks in a 30-day month period, respectively, which translated to 18 days [(2.4 weeks/4 weeks) × 30 days] and 20 days [(2.6 weeks/4 weeks) × 30 days], respectively. In contrast, for both concentrations from fermented crude extracts of C. myriocarpus fruits, application time interval was optimised at 16 days for 2.2 and 2.1 weeks, respectively. During optimisation of application frequencies, fermented crude extracts from C. africanus and C. myriocarpus reduced final population densities of M. incognita race 2 by 70-97% and 76-96%, respectively. Fourthly, optimum application intervals (time), allowed computation of dosage, which is a product of concentration and application frequency (dosage = concentration × application frequency). Fifthly, validation of the dosages under open field conditions suggested that 6% × 16-day dosage under crude extracts from C. myriocarpus fruit significantly (P ≤ 0.05) improved growth of tomato plants when compared with those of either 0% (untreated control) or 3% at 16 days. In contrast, dosages of C. africanus fruit at two application frequency had no effect on growth of tomato plants – suggesting that either of the dosages was suitable for use in tomato production since both reduced nematode numbers. During validation, the materials reduced nematode numbers by margins similar to those observed previously under other environments. In conclusion, crude extracts of the two Cucumis species have stimulatory concentrations which have potential similar reductive effects on population densities of Meloidogyne species and could serve as botanical nematicides. However, since plant responses to the two products differed in terms of their respective dosages and active ingredients, it implied that for further improvement of the two, the overriding focus should be on their interaction with the protected plants and nematode numbers. Ideally, future research xxxv should include environmental impact studies, especially on the influence of the products fruit quality of tomato, earthworms, fish and bees.

Soybean cyst nematode (SCN), a major pathogen of soybean worldwide, causes huge losses in soybean production. Various approaches including cloning of genes to combat this devastating disease help to better understand the cellular function and immune responses of plants. Membrane fusion genes are the important regulatory parts of vesicular transport system, which works through packaging of intracellular compounds and delivering them to apoplast or nematode feeding sites to induce an incompatible reaction. The incompatible nature of membrane fusion proteins such as SNAP25, Munc18, Syntaxin, Synaptobrevin, NSF, Synaptotagmin and alpha-SNAP are conserved in eukaryotes and regulate the intracellular function to combat abiotic and biotic stress in plants. Overexpression of these genes in G. max [Williams 82(PI518671)] which is a susceptible cultivar of soybean to nematodes resulted in a reduction of the SCN population providing further insights of molecular and genetic approaches to solve the SCN problems in agriculture.

Hyperparasitism of beneficial parasites of Pieris rapae was studied on Brassica crops in Montgomery County, Virginia. The goal of the study was to determine whether the hyperparasites attacking the larval parasites of P. rapae were capable of eliminating an introduced population of the larval parasite Cotesia rubecula (Marshall) (Hymenoptera: Braconidae). Pieris rapae was found to be active from April to November with possibly six generations per year in this region. It was attacked throughout this period by five generations of the larval parasite Cotesia glomerata (L.) (Hymenoptera: Braconidae). Although P. rapae larvae were twice as numerous on broccoli (var. Premium Crop) than on cabbage (var. Rio Verde), a higher proportion of P. rapae larvae was parasitized by C. glomerata on cabbage, indicating that C. glomerata preferred to forage for P. rapae in cabbage. In spring plantings, up to 36.9% of C. glomerata cocoon masses had been affected by the hyperparasite T. galaetopus (Ratzeburg) (Hymenoptera: (Eulophidae) and 23.3% by the hyperparasite Spiloehaleis torvina Cresson (Hymenoptera: Chalcididae). In the fall, 93.2% and 4.2% of the cocoon masses were affected by T. galaetopus and S. torvina, respectively. Tetrastiehus galaetopus activity was observed from May to November, but it was most active after mid July. Tetrastiehus ga/aetopus had little impact on the gregarious C. glomerata, and even though it could affect >90% of the C. glomerata cocoon masses for extended periods, 500/0 of the cocoons in each mass were unaffected. However, it's high reproductive capacity could adversely affect a solitary host such as C. rubecula. Spilochalcis torvina was observed as early as late May but it was most active during the mid summer months. It's reproductive activity ceased by early October even though hosts were abundant in the month which followed. Four generations were seen between June and October. Spilochalcis torvina's hosts were Cotesia orobenae Forbes (Hymenoptera: Braconidae), C. glomerata, and Plutella xylostella (L.) (Lepidoptera: Plutellidae), but the principal host was C. glomerata. However, the proportion of female S. torvina progenies was <31% from the Cotesia spp. hosts and 70% from P. xylostella hosts. Spilochalcis torvina typically hyperparasitized <4 pupae per Cotesia spp. cocoon mass in the field. In laboratory experiments, S. torvina hyperparasitized an average of <7 C. rubecula pupae daily, and the maximum number hyperparasitized was 12. Due to its apparently low reproductive rate in the laboratory, and its low rate of hyperparasitization on hosts in the field, it is unlikely that S. torvina is a danger to populations of parasites like C. rubecula. / Master of Science

Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Various aspects of the biology and ecology of woolly apple aphid, Eriosoma lanigerum, were investigated, including initial galling damage caused by E. lanigerum to the roots of apple trees, the possible relationship between E. lanigerum and Xiphinema and Pratylenchus nematodes and the effectiveness of Biostart 2000® and Furfural® as possible control agents of E. lanigerum in the orchard. Preliminary root damage by first instar E. lanigerum feeding was characterized by the mechanical injury of endodermis and parenchyma tissues. Damage by second, third and fourth instar E. lanigerum was similar, but the symptoms were more pronounced. Damage caused by adults included a pronounced swelling at infected areas of the root. Cell walls hardened until the root was radially strengthened with sclerenchyma tissue and nonconducting xylem vessels while the cuticle expanded greatly through the growth of corklike cambium tissue. There was no direct relationship between the population dynamics of E. lanigerum and those of Xiphinema and Pratylenchus nematodes. The occurrence of E. lanigerum appeared to be seasonal while P. penetrans and Xiphinema numbers fluctuated erratically. Undamaged root nitrogen levels seemed to correspond with the normal root growth cycle. Nitrogen levels from galled roots were significantly lower than those of undamaged roots, probably due to E. lanigerum feeding. Soils rich in fine sand and clay sustained higher populations of E. lanigerum and Xiphinema than sandy soils. The number of E. lanigerum found in soil samples correlated well with the damage index allocated to the samples. The numbers of Xiphinema found in soil samples also correlated well with the damage index allocated to the samples according to suspected Xiphinema damage symptoms. Both Biostart 2000® and Furfural® were effective as control agents of woolly apple aphid. Furfural'Ï, a chemical waste product of the sugarcane industry, was however not as effective as Biostart 2000®, a product that includes an activator and three bacterial species, Bacillus laterosporus, B. chitinosporus and B. licheniformis. The bacteria in the Biostart 2000® treated pots could replicate themselves under suitable conditions while Furfural® dilutes with each watering. Biostart 2000® is also easier to prepare than Furfural® since the components of Biostart 2000® readily mix to form a paste easily thinned by water, whereas Furfural® is an oily substance that does not easily disperse in water. Root damage was initiated soon after E. lanigerum started feeding, however there was no apparent relationship between E. lanigerum and the nematode species. The most promising, environmentally friendly control measure was Biostart 2000®. / AFRIKAANSE OPSOMMING: Verskeie aspekte van biologie en die ekologie van die appel bloedluis, Eriosoma lanigerum, was ondersoek insluitende aanvanklike galvorming veroorsaak deur E. lanigerum op wortels van appelbome, die moontlike verwantskap tussen E. lanigerum en Xiphinema en Pratylenchus nematodes en die effektiwiteit van Biostart 2000® en Furfural® as moontlike beheeragente van E. lanigerum in die boord. Aanvanklike wortelskade deur eerste ins tar E. lanigerum voeding was gekenmerk deur die meganiese beskadiging van endodermale en parenchiem weefsel. Skade veroorsaak deur tweede, derde en vierde instar E. lanigerum was soortgelyk alhoewel die simptome meer beklemtoond was. Skade deur volwassenes het 'n meer duidelike swelsel by geïnfekteerde wortelareas ingesluit. Selwande het verhard totdat die wortel radiaalsgewys versterk was met skierenchiem weefsel en nie-geleidende xileemvate terwyl die kutikula grootliks toegeneem het deur die groei van kurkagtige kambiumweefsel. Daar was geen direkte verwantskap tussen die bevolkingsdinamika van E. lanigerum en dié van Xiphinema en Pratylenchus nematodes nie. Die voorkoms van E. lanigerum was seisoenaal terwyl P. penetrans en Xiphinema se getalle onvoorspelbaar gefluktueer het. Onbeskadigde wortel stikstofvlakke het ooreengestem met die normale wortel groeisiklus. Stikstof vlakke van galwortels was noemenswaardig laer as dié van onbeskadigde wortels, heel waarskynlik as gevolg van voeding deur E. lanigerum. Grond ryk aan fyn sand en klei het groter bevolkings van E. lanigerum en Xiphinema onderhou as sanderige gronde. Die aantal E. lanigerum in grondmonsters het goed ooreengestem met die skade indeks wat aan die monsters toegeken was. Die aantal Xiphinema in grondmonsters het ook goed ooreengestem met die beskadigingsindeks wat aan die monsters toegeken is weens vermoedelike Xiphinema skade simptome. Beide Biostart 2000® en Furfural® was effektief as beheeragente van die appelbloedluis. Furfural'", 'n afvalproduk van die suikerriet industrie, was egter minder effektief as Biostart 2000®, 'n produk bestaande uit 'n aktiveerder en drie bakterie spesies, Bacillus laterosporus, B. chitinosporus en B. licheniformis. Die bakterië in die Biostart 2000® behandelde potte kon vermeerder onder gunstige toestande terwyl Furfural® na elke besproeiing verdun het. Biostart 2000® is ook makliker om aan te maak as Furfural® aangesien die bestanddele van Biostart 2000® geredelik meng tot 'n wateroplosbare pasta, terwyl Furfural® 'n olierige vloeistofis wat moeilik 'n waterige suspensie vorm. Wortelskade het plaasgevind kort nadat E. lanigerum begin voed het, alhoewel daar geen duidelike verwantskap tussen E. lanigerum en nematode spesies voorgekom het nie. Die mees belowende omgewingsvriendelike beheermaatreël was Biostart 2000®.

Thesis (M. Agricultural Management (Animal Production)) -- University of Limpopo, 2016 / Cultivated potato (Solanum tuberosum L.) cultigens do not have resistant genotypes to root-knot (Meloidogyne species) nematodes. Currently, efforts are underway to introgress nematode resistance in potato breeding programmes, whereas other environment-friendly nematode management strategies are being assessed in various cultigens. Nemafric-BL and Nemarioc-AL phytonematicides have being researched and developed for managing the root-knot nematode whereas Biocult Mycorrhizae are intended to enhance crop productivity through improved absorption of P, which is inherently low in most South African soils. The objectives of the study, therefore, were: (1) to determine the interactive effects of Nemacur (N), Biocult Mycorrhizae (B) and Nemarioc-AL or Nemafric-BL phytonematicide (P) on population densities of M. javanica and growth of potato plants, (2) to investigate the effects of Nemacur (N), Velum (V), Biocult Mycorhizae (B) and Nemarioc-AL or Nemafric-BL phytonematicide (P) on population densities of M. javanica and growth of potato plants. For the microplot experiment, potato cv. ‘Mondial G3’ seeds were sown in 25 cm-diameter plastic pots with 5 000 ml steam-pasteurised river sand and Hygromix-T at 3:1 (v/v) growing mixture in autumn (March-May) 2015. Pots were buried 80% deep into the soil in with 0.5 m inter-row and 0.5 m intra-row spacing. Potato cv. ‘Mondial G3’ seeds were dipped in a mixture of Mancozeb with a wettener for disease management prior to sowing. Appropriate treatments were applied soon after emergence of leaves. Each plant was inoculated by dispensing a mixture of 5 000 eggs and M. javanica J2. Eight treatments, control (N0B0P0), Nemacur (N1B0P0), Biocult (N0B1P0), phytonematicide (N0B0P1), Nemacur × Biocult (N1B1P0), Nemacur × phytonematicide (N1B0P1), Biocult × phytonematicide (N0B1P1) and Nemacur × Biocult × phytonematicide (N1B1P1), were arranged in a randomised complete block xxvi design (RCBD) with 8 replications (n= 64). Under field conditions the study was conducted in summer (October 2015 - January 2016), with 30-cm furrows dug and potato seeds placed in the soil with 30 cm inter-row and 40 cm intra-row spacing. The four treatments, namely, (1) untreated control, (2) Nemacur or Velum (3) Biocult Mycorrhizae and (4) Nemarioc-AL or Nemafric-BL phytonematicide, were arranged in RCBD, replicated three times for the Velum experiment and five times for the Nemacur experiment. At 56 days after inoculation, the second order interaction (N1B1P1) was highly significant (P ≤ 0.01) for eggs in root and total nematodes, contributing 13 and 12% to total treatment variation (TTV) of the two variables, respectively, in the Nemarioc-AL phytonematicide study. Relative to untreated control, the second order interaction (N1B1P1) reduced eggs in root and total nematodes by 42 and 36%, respectively. In both Nemarioc-AL and Nemafric-BL phytonematicide experiments, the combination of phytonematicide and Biocult Mycorrhizae reduced gall rating. Nemacur, Biocult and Nemarioc-AL phytonematicide, the treatment effects were highly significant on eggs, J2 in root and total nematodes, contributing 53, 68 and 57% to TTV of the three variables, respectively. Nemacur, Biocult and Nemafric-BL phytonematicide treatments each was not significant (P ≤ 0.05) for nematodes variables. Both treatments for Nemacur, Biocult and Nemarioc-AL or Nemafric-BL phytonematicides were significant for gall rating, contributing 92 and 70% to TTV of the variable, respectively. In Nemarioc-AL phytonematicide, relative to the untreated control, gall rating was reduced by 48 to 56%, whereas in Nemafric-BL phytonematicide the variable was reduced by 33 to 56%. In the Velum study, Biocult and Nemarioc-AL or Nemafric-BL phytonematicide, the treatment effects in both experiments were highly significant (P ≤ 0.01) on eggs in root, contributing 88% to TTV of the variable. Both treatments from Nemarioc-AL xxvii and Nemafric-BL phytonematicides had no significant effects on all plant variables measured. In microplot, the second order interaction (Nemacur × Biocult × Nemarioc-AL phytonematicide) was highly significant for nematode eggs in root and total nematode. In a three-way matrix, the N1B1P1 interaction had the highest effects on eggs, followed by Biocult alone, then Nemacur alone and then the phytonematicide. The same trend was observed in the three-way matrix for total nematodes. However, in two-way matrix for eggs, Biocult outperformed Nemacur, as was the phytonematicide on J2. In another microplot study, the second order interaction (Nemacur × Biocult × Nemafric-BL phytonematicide) was significant for J2 in soil and roots, with the three-way matrix showing, that Biocult alone had higher effects than the N1B1P1 interaction on J2 in root. A three-way matrix also showed that Nemacur was outperformed by the phytonematicide alone, Biocult alone and the interactions on J2 in soil. In conclusion, Nemarioc-AL and Nemafric-BL phytonematicides could each be used with Biocult Mycorrhizae in the management of population densities of M. javanica in potato production since the impact from Nemacur which is a synthetic nematicide does not have that much difference from that of phytonematicides interacted with Biocult Mycorrhizae. / Agricultural Research Council

Xanthomonas axonopodis pv citri (Xac), uma bactéria gram negativa, é a causadora da doença Cancro Cítrico que ocasiona enormes prejuizo na citricultura brasileira. Com o seqüenciamento do genoma deste patógeno foram encontradas inúmeras sequências codificadores com funções desconhecidas. Assim com a finalidade de estudos funcionais do genoma de Xac, foram gerados mutantes randômicos usando o transposon EZ::TN, que induziu disrupção aleatoria de seus genes com o intuito de avaliar que genes inativados afetam a patogenicidade da bactéria. Para o mapeamento do local de inserção do transposon foi desenvolvida uma metodologia baseada na técnica de PCR touchdown utizando oligonucleotídeos semidegenerados. A confiabilidade deste novo método foi comprovada através do mapeamento por Southem blot de alguns mutantes. Conseguiu-se mapear 90 mutantes randômicos com este método. Os testes de patogenicidade em citros mostraram mutantes com sua patogenicidade afetada observando-se variações nos sintomas da doença. Mutantes interessantes contendo uma ORF hipotética inativada ou tendo uma inserção num espaço intergênico foram achadas, sendo também detectados alguns mutantes com nocaute de genes nos seus plasmídeos pXac33 e pXac66. / Xanthomonas axonopodis pv citri (Xac), a gram-negative bacteria, is the causer of the Citrus Canker disease that produces enormous losses to the brazilian citrus sector. Many coding sequences with unknown functions were found in the genome sequence of this pathogen. Therefore, with the goal of functional studies of Xac\'s genome, random mutants using the EZ::TN transposon, have been generated, which carry aleatory disruptions of their genes, with the aim of evaluating inactived genes that potentially affect bacterial pathogenicity. A method based in the PCR touchdown technique using semidegenerate primers was developed for the mapping of the transposon insertion site. The reliability of this new method was tested by means of mapping some mutants using Southern blot. Ninety random mutants were mapped with this method. The pathogenicity tests in citrus showed mutants with their pathogenicity affected and variations in the disease symptoms were observed. Interesting mutants containing an inactive hypothetical ORF or with an insertion in intergenic regions have been found, and also some mutants with inactivated genes in their plasmids pXac33 and pXac66 were detected.