CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / A necessidade de controlar os fitonematÃides existentes em determinada regiÃo à condiÃÃo bÃsica para se proceder ao seu manejo racional. Igualmente, tem-se a necessidade de proceder a estudos de produtos naturais, pois serà de grande valia como medida de controle alternativo, principalmente na agricultura orgÃnica. Em vista disso, este trabalho se propÃs a estudar a hospedabilidade de plantas ornamentais e medicinais a Meloidogyne incognita raÃa 2 e o controle alternativo com Ãleos essenciais. Para tanto, realizaram-se trÃs ensaios: no primeiro, avaliou-se a hospedabilidade de 20 espÃcies de plantas ornamentais e 10 medicinais a M. incognita raÃa 2; no segundo, avaliaram-se os Ãleos essenciais de seis espÃcies medicinais Cymbopogon winterianus Jowitt., C. citratus (D.C.) Strapf., Eucalyptus terenticornis L., Lippia alba L., L. sidoides Cham. e Ocimum gratissimum L., em sete concentraÃÃes (0; 0,3125; 0,0625; 1,25; 2,5; 5,0 e 10,0 ml.L-1) no controle de M. incognita raÃa 2, in vitro e no terceiro, avaliou-se o potencial nematicida dos Ãleos essenciais de L. sidoides e C. winterianus no controle de M. incognita raÃa 2, em solo com as espÃcies celÃsia (Celosia plicata L.) e tomate (Lycopersicon esculentum Mill). Dos resultados, observaram-se que todas as espÃcies ornamentais, exceto Tagetes patula L., e cinco das medicinais Rosmarinus officinalis L., Mentha arvensis L. var. piperascens Malinv. ex L. H. Bailey, Ocimum bassilicum L., Ocimum gratissimum L., Plectranthus amboinicus (Lour.) Spreng., sÃo hospedeiras de M. incognita raÃa 2. Todos os Ãleos essenciais revelaram-se efetivos na inibiÃÃo da eclosÃo e na mortalidade dos J2 nas concentraÃÃes de 5,0 e 10,0 ml.L-1, contudo, em diluiÃÃes mais elevadas (<1,25 ml.L-1), apenas os Ãleos de L. sidoides e C. winterianus foram eficazes. A reproduÃÃo do nematÃide mostrou-se menos eficiente em tomate que em celÃsia. Os Ãleos essenciais empregados reduziram a taxa reprodutiva do nematÃide das galhas em 83 e 29%, em tomate e celÃsia, respectivamente. Os Ãleos essenciais de L. sidoides e C. winterianus foram mais eficientes em ensaios in vitro, sendo promissores para o controle do fitonematÃide em solo. / The necessity to control the plant parasitic nematodes existing in a given region is basic condition to proceed to their rational management. Also, it has been the necessity studies of natural products as it will be of great value as a measure of alternative control, especially in organic agricultural. In view of this, this work is proposed to study the hospitability of ornamental and medicinal plants to Meloidogyne incognita race 2 and the alternative control with essential oils. For in such a way, become three tests: the first, evaluate the hospitability of 20 species ofornamental and 10 medicinal plants to M. Incognita race 2; in the second, it is evaluated essential oils of six medicinal species Cymbopogon winterianus Jowitt., C. citratus (DC) Strapf., Eucalyptus terenticornis L., Lippia alba L., L. sidoides Cham. and Ocimum gratissimum L., in seven concentrations (0, 0.3125, 0.0625, 1.25, 2.5, 5.0 and 10.0 ml.L-1) in control of M. Incognita race 2, in vitro; and in the third, evaluated the nematicidal potential of essential oils of L. sidoides and C. Winterianus in control of M. Incognita race 2 in soil with the species celosia (Celosia plicata L.)and tomato (Lycopersicon esculentum Mill). Of the results, noted that all ornamental species, except Tagetes patula L., and five of the medical Rosmarinus officinalis L., Mentha arvensis L. Var. Piperascens Malinv. Ex L. H. Bailey, Ocimum bassilicum L., O. gratissimum L., Plectranthus amboinicus (Lour.) Spreng. are hosts of M. Incognita race 2. All essential oils proved to be effective in inhibiting outbreak and the death of J2 at concentrations of 5.0 and 10.0 ml.L-1, however, at higher dilutions (<1.25 ml.L-1)only the oils of L. sidoides and C. winterianus were effective. A reproduction of the nematode proved to be less efficient in tomato that in celÃsia. The essential oils employees reduced the reproductive rate of the knot nematode in 83 and 29% in tomato and celÃsia respectively. The essential oils of L. sidoides and C. winterianus were more efficient in in vitro assays and are promising for the control of plant parasitic nematode in soil.

Made available in DSpace on 2017-07-10T17:36:55Z (GMT). No. of bitstreams: 1 2014_Diss_Rafael_Augusto_Swarowsky.pdf: 1265471 bytes, checksum: b7b6c650055a2ba1f2346656fda7a03d (MD5) Previous issue date: 2014-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Considering the importance of the tomato crop and the high costs of the control of Meloidogyne incognita with resistant cultivar or nematicides, grows the search of new alternatives to control the root-knot disease. The homeopathy may be an alternative way of control, by inducing resistance. This study aimed to evaluate the influence of the homeopathic drug Cina in the number of root galls, eggs and J2 present in the roots of tomato and soil, as well as the growth of tomato plants. The dynamizations used were 12, 24, 50, 100, 200, and 400CH (centesimal hahnemanian dilutions). It was also used the chemical carbofuran, 70% ethanol and water as control treatments. The assay was conducted in pots in greenhouse for the in vivo assay and in laboratory for the in vitro ones. In both assays, homeopathic treatments were diluted with distilled water to 0.1% before application. On the in vivo assay, the homeopathic drug was applied weekly by foliar spray. The first treatments were done three days before pathogen inoculation with approximately 5000 eggs and 500 J2 per pot. The evaluations were made 50 days after transplanting of the tomato seedlings and 44 days after inoculation. The Cina demonstrated effectiveness in stimulating root development, once the results of root volume were higher in homeopathic treatments than in control. Cina 100CH also favored the growth of the stalk diameter of the plants. However, the homeopathic product showed no nematostatic nor nematicide effect / Considerando a importância da cultura do tomateiro e os custos com variedades resistentes e com nematicidas para controle de Meloidogyne incognita, são necessárias alternativas para manejo da doença das galhas radiculares. A homeopatia pode ser uma alternativa de controle, através da indução de resistência de plantas. Este trabalho objetivou avaliar a influência do medicamento homeopático Cina quanto ao número de galhas radiculares, ovos e J2 presentes nas raízes do tomateiro e no solo, bem como variáveis de crescimento das plantas de tomate. As dinamizações usadas foram 12, 24, 50, 100, 200 e 400CH (centesimal hahnemanniana). Também foram utilizados como tratamentos para comparação o nematicida carbofurano, etanol 70% e água. O experimento foi conduzido em vasos dentro de estufa climatizada para ensaio in vivo e em laboratório para o ensaio in vitro. Em ambos os ensaios, os tratamentos homeopáticos foram diluídos em água destilada a 0,1% antes da aplicação. No ensaio in vivo o medicamento homeopático foi aplicado semanalmente por aspersão foliar. A primeira aplicação dos tratamentos foi realizada três dias antes da inoculação, com aproximadamente 5000 ovos e 500 J2 por vaso. As avaliações foram feitas 50 dias após o transplante das mudas de tomate e 44 dias após a inoculação. A Cina demonstrou eficiência em estimular o desenvolvimento radicular, pois os resultados de volume de raiz foram maiores nos tratamentos homeopáticos do que nas testemunhas. Cina a 100CH também favoreceu o crescimento do diâmetro de caule das plantas. Contudo, o medicamento homeopático não demonstrou nenhum efeito nematostático e nem nematicida

Made available in DSpace on 2017-07-10T17:37:37Z (GMT). No. of bitstreams: 1 Francielle_Fiorentin.pdf: 823255 bytes, checksum: f5dcc6af10e39ff6f305e5ceea972339 (MD5) Previous issue date: 2010-06-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Nematóides pertaining to the Meloidogyne kind are among the greatest agents responsible of damage in plants, because of its wide geographic distribution and difficult control. There is a great justification on studies that involve the diversity of fitonematoides, both in the agricultural areas and in areas covered with primary vegetation, where the increase of economic losses caused to the agricultural activity has aroused increasing interest. With the aim to identify populations of Meloidogyne pertaining to legal Reserves in the counties of Cascavel, Terra Roxa and Marechal Cândido Rondon PR, collects were made in five areas pertaining to each county, with the purpose to find plants naturally parasitized. Through identifications based on the technique of perineal configuration and fenotipo enzimatic for esterase, M. incognita and M. javanica were identified for naturally parasitizing the plants in these reserves. The plants that were naturally infected were Emilia sonchifolia, Ipomea triloba, Solanum americanum, tibouchina herbacea and Leonorus sibiricus. In relation to the parasitism of Meloidogyne, plants of 32 species had been collected and analyzed as for the natural occurrence of meloidoginose, as well as its reaction to inoculation with M. incognita 3 race and M. javanica. It was observed that native species like Rollinia mucosa, Cariniana rubra, jaracatiá spinosa, Citharexylum myriantum, Aspidosperma subicanum, Peltophorum dubium and Ruprechtia laxiflora presented natural infection with M. incognita. The plants which did not present symptoms of root-knots in the radicular system had been inoculated with Meloidogyne spp. The analyzed variables were total gall number(IG), J/2 egg number by radicular system (EGGS/RS) and calculus of Reproduction Factor (RF). The ones resistant to M. incognita race 03 were species like tabebuia impetiginosa, Chorisia speciosa, Galipea jasminflora, Machaerum villosum, Ingá laurina, Allophylus edulius, Campomanesia guazummaefolia, Lueha candicans, Archontophoenix alexandre, Shinus terebinthifolha and Pterogyne nitens and species like Psidium cattleianum, Cedrelo fissilis and Eugenia involucrate were immune. In relation to inoculated species with M. javanica, Jacaranda micrantha, tabebuia heptaphylla, Endliicheria paniculata, Cabralea canjerana, Tabebuia crysotricha, Genipa infudiboboliformis, Bastardiopsis densiflora, Eugenia pyriforms, Balfourodendron riedelianum and Patagonula americana revealed to be resistant, and Caesalpinia ferrea was immune. / Os nematóides pertencentes ao gênero Meloidogyne estão entre os maiores agentes causadores de danos em plantas, pois possuem ampla distribuição geográfica e são de difícil controle. Há uma grande justificativa sobre estudos que envolvam a diversidade de fitonematóides, tanto nas áreas agrícolas como em áreas cobertas com vegetação primária, onde o aumento das perdas econômicas causadas à atividade agrícola tem despertado crescente interesse. Com o objetivo de identificar populações de Meloidogyne em reservas legais pertencentes aos municípios de Cascavel, Terra Roxa e Marechal Cândido Rondon PR foram realizadas coletas em cinco áreas pertencentes a cada município, objetivando encontrar plantas parasitadas naturalmente. Através de identificações baseadas na técnica da configuração perineal e fenótipo enzimático para esterase identificou-se populações de M. incognita e M. javanica parasitando naturalmente as plantas nestas reservas. As plantas encontradas naturalmente infectadas foram Emilia sonchifolia, Ipomea triloba, Solanum americanum, Tibouchina herbacea e Leonorus sibiricus. Em relação ao parasitismo de Meloidogyne, mudas de 32 espécies arbóreas foram coletadas e analisadas quanto a ocorrência natural de meloidoginose, bem como sua reação a inoculação com M. incognita raça 03 e M. javanica. As espécies nativas Rollinia mucosa, Cariniana rubra, jaracatiá spinosa, Citharexylum myriantum, Aspidosperma subicanum, Peltophorum dubium e Ruprechtia laxiflora apresentaram infecção natural com M. incognita. As mudas ao qual não apresentavam sintomas de galhas no sistema radicular foram inoculadas com Meloidogyne spp. sendo realizados dois experimentos, um com inoculações com M. incognita raça 03 e outro com inoculações com M. javanica, As variáveis analisadas foram número total de galhas (IG), número de ovos e J/2 por sistema radicular (Ovos/SR) e o cálculo do Fator de Reprodução (FR). Comportaram-se como resistentes à M. incognita raça 03 as espécies Tabebuia impetiginosa, Chorisia speciosa, Galipea jasminflora, Machaerum villosum , Ingá laurina, Allophyllus edulis, Campomanesia guazummaefolia, Luehea candicans, Archontophoenix alexandre, Schinus terebinthifolia e Pterogyne nitens, e as espécies Psidium cattleianum, Cedrelo fissilis e Euginia involucrata mostraram-se imunes. Em relação as espécies inoculadas com M. javanica, Jacaranda micrantha, Tabebuia heptaphylla, Endlicheria paniculata, Cabralea canjerana, Tabebuia crysotrycha, Genipa infudiboliformis, Bastardiopsis densiflora, Eugenia pyriforms, Balfourodendron riedelianum e Patagonula americana mostraram-se resistentes, e Caesalpinia ferrea apresentou-se imune.

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)

Thesis (M.Agric. (Plant Production)) -- University of Limpopo, 2018 / Meloidogyne incognita race 2 is internationally recognised as one of the most aggressive Meloidogyne species and it is also widely distributed in Limpopo Province, where it occurs alone or as mixed populations with other Meloidogyne species. Traditionally, Meloidogyne species had been managed using synthetic chemical nematicides, most of these products had been withdrawn from agro-chemical markets due to their environment-unfriendliness. Following the withdrawal of synthetic chemical nematicides, nematode resistance had been the most preferred strategy for managing high nematode population densities. The availability of nematode resistant genotypes in sweet potato (Ipomoea batatas) would enhance the use of resistance in managing Meloidogyne species and races in Limpopo Province. Generally, should post-infectional nematode resistance be available in the test sweet potato cultivars, the information would be relayed to plant breeders for use as source of introgression in various commercial cultivars where nematode-resistant genotypes do not exist. The objectives of the study, were to determine: (1) Host-status and host-sensitivity in sweet potato cv. ʹBopheloʹ, ʹBosbokʹ and ʹMvuvheloʹ to M. incognita race 2. (2) the existing nematode resistance mechanism in any of the test cultivars that had resistance to M. incognita race 2. For achieving Objective 1, eight treatments namely, 0, 25, 50, 125, 250, 625, 1250 and 3125 eggs and second stage-juveniles (J2) M. incognita race 2 were used under greenhouse trials for each cultivar. To achieve Objective 2, sweet potato plants were inoculated with 100 J2 with four plants harvested every other day for 30 days counting to 15 harvesting times. At 56 days after inoculation, cv. ʹBopheloʹ had reproductive factor (RF) values above unity for M. incognita race 2 and plant growth variables were reduced. Therefore, the cultivar was a susceptible host to M. incognita race 2 and mechanism trial was not conducted for this cultivar. Meloidogyne incognita race 2 failed to reproduce on cultivars ʹBosbokʹ and ʹMvuvheloʹ whereas nematode infection did not affect plant growth and therefore, the two cultivars were resistant to M. incognita race 2. Mechanisms of resistance to M. incognita race 2 on cultivars ʹBosbokʹ and ʹMvuvheloʹ demonstrated significance existence of (1) necrotic spots, (2) poorly developed giant cells, (3) formation of rootlet interferences (4) absence of root galls and (5) non-detectable J2 in roots. All these features suggested the existence of post-infectional nematode resistance in the two cultivars to M. incognita race 2. In conclusion, cultivar ʹBopheloʹ was susceptible to M. incognita race 2, whereas cultivars ʹBosbokʹ and ʹMvuvheloʹ were resistant to M. incognita race 2, with the evidence of post-infectional nematode resistance to the nematode species

Abamectin is a blend of B1a and B1b avermectins that is being used as a seed treatment to control plant-parasitic nematodes on cotton. Data on the toxicity of abamectin and its effectiveness as a seed treatment to control Meloidogyne incognita or Rotylenchulus reniformis on cotton are lacking. The toxicity of abamectin was based on an assay of nematode mobility, LD50 values of 1.56 µg/ml and 32.9 µg/ml were calculated based on 2 hr exposure for M. incognita and R. reniformis, respectively. There was no recovery of either nematode after exposure for 1 hr to its LD50 concentration. Sublethal concentrations greater than 0.39 µg/ml for M. incognita and 8.2 µg/ml for R. reniformis reduced (P = 0.05) infectivity on tomato. In field trials, suppression (P = 0.05) of M. incognita was observed 32 DAP by abamectin seed treatment whereas no suppression of R. reniformis was observed. No suppression of M. incognita was perceived by abamectin seed treatment in microplots. Suppression of M. incognita was observed in microplots by harpinEA and harpingαβ as a seed treatment and foliar spray, respectively. Seed cotton yields were variable for abamectin-treated seed, but numerically positive for harpin-treated cotton. Initial gall formation on developing taproots was suppressed (P = 0.001), and penetration of 5-cm long taproots by M. incognita and R. reniformis was numerically suppressed by abamectin-treated compared to non-treated seed, but infection increased with root development. Using an assay of nematode mobility, the proportion of dead second-stage juveniles (J2) was higher (P = 0.05) following exposure to an excised radicle from abamectin-treated seed than non-treated seed, but lower (P = 0.05) than J2 exposed to the abamectin-treated seed coat. Thus a higher concentration of abamectin remained on the seed coat than emerging radicle. The concentration of abamectin transferred from the seed coat to the developing roots was limited, which contributed to the variability in suppression of plant-parasitic nematodes on cotton.

Abamectin is a blend of B1a and B1b avermectins that is being used as a seed treatment to control plant-parasitic nematodes on cotton. Data on the toxicity of abamectin and its effectiveness as a seed treatment to control Meloidogyne incognita or Rotylenchulus reniformis on cotton are lacking. The toxicity of abamectin was based on an assay of nematode mobility, LD50 values of 1.56 µg/ml and 32.9 µg/ml were calculated based on 2 hr exposure for M. incognita and R. reniformis, respectively. There was no recovery of either nematode after exposure for 1 hr to its LD50 concentration. Sublethal concentrations greater than 0.39 µg/ml for M. incognita and 8.2 µg/ml for R. reniformis reduced (P = 0.05) infectivity on tomato. In field trials, suppression (P = 0.05) of M. incognita was observed 32 DAP by abamectin seed treatment whereas no suppression of R. reniformis was observed. No suppression of M. incognita was perceived by abamectin seed treatment in microplots. Suppression of M. incognita was observed in microplots by harpinEA and harpingαβ as a seed treatment and foliar spray, respectively. Seed cotton yields were variable for abamectin-treated seed, but numerically positive for harpin-treated cotton. Initial gall formation on developing taproots was suppressed (P = 0.001), and penetration of 5-cm long taproots by M. incognita and R. reniformis was numerically suppressed by abamectin-treated compared to non-treated seed, but infection increased with root development. Using an assay of nematode mobility, the proportion of dead second-stage juveniles (J2) was higher (P = 0.05) following exposure to an excised radicle from abamectin-treated seed than non-treated seed, but lower (P = 0.05) than J2 exposed to the abamectin-treated seed coat. Thus a higher concentration of abamectin remained on the seed coat than emerging radicle. The concentration of abamectin transferred from the seed coat to the developing roots was limited, which contributed to the variability in suppression of plant-parasitic nematodes on cotton.

Root-knot disease caused by Meloidogyne spp. is the most important nematode disease of peanut. Even though many management strategies have been applied to control this disease on peanut, resistance is the most recommendable. Marker-assisted selection has been used as a useful tool for screening of resistant individuals in segregating populations. However, it requires many laborious steps. Thus, there is a need for PCR - based markers, which are more practical, rapid, and efficient. In this study, we tried to develop a SCAR marker linked to root-knot nematode resistance locus in peanut based on the RFLP marker R2430E. The entire sequence of R2430E was 2217 bp and contained one putative open reading frame (ORF) of 713 nucleotides. Thirteen primers including 5 forward and 8 reverse primers were synthesized to sequence the entireR2430E. Based on the results of BLAST searches, R2430E appeared to encode an AAA ATPase containing von Willebrand factor type A (VWA) domain from Magnetococcus sp. MC-1 (106 bits). To determine if there is a portion of the R2430E that hybridizes only to a band co-segregating with the resistance locus, we generated 4 probes spanning different parts of the gene. Southern analysis using these probes revealed identical banding patterns for each probe. Therefore, we concluded that there is very limited if any sequence polymorphism between different alleles detected by the R2430E probe. Additionally, this conclusion is supported by the experiment in which we tested 25 primer pairs derived from the R2430E using genomic DNA from both resistance and susceptible genotypes. In this experiment, all primer pairs amplified identical PCR fragments, suggesting again that there is little or no sequence divergence between putative alleles as differentiated by southern blotting. To identify possible single nucleotide polymorphisms (SNPs) between polymorphic R2430E RFLP bands, we cloned several fragments that span the entire R2430E transcribed sequence. Surprisingly, no SNPs were identified in the transcribed region of this gene. We propose that polymorphism detected by this RFLP marker is outside of the R2430E.

M. Tech. Agriculture / This study was conducted to establish whether genetic resistance to root-knot nematode is present in local available Amaranthus-, Spinacea oleracea-, Beta vulgaris-, Daucus carota-, and Capsicum genotypes. Host suitability trials for the relevant vegetable genotypes were conducted in separate greenhouse studies. Different nematode parameters were used to select for root-knot nematode resistance but reproduction factors values (Rf) were used as main criterion.

No description available.