Egg Mass Index Research Articles

Pathological Interrelations of Soil-Borne Diseases in Cucurbits Caused by Fusarium Species and Meloidogyne incognita.

Pathological interrelations of two soil-borne diseases in cucurbits (watermelon, oriental melon, shintosa and cucumber) caused by Fusarium isolates (FI) and the root-knot nematode (RKN), Meloidogyne incognita were characterized by the fusarium disease severity index (DI), RKN gall index (GI) and eggmass index (EI) in inoculation tests using FI and RKN. Virulence of FI as determined by DI at 4 weeks after inoculation was mostly in the higher order of Fusarium proliferatum F6, F5 and Fusarium oxysporum f. sp. melonis or Fusarium oxysporum f. sp. niveum with no significant differential interactions among the cucurbits and RKN co-infection. Significant increases of DI due to RKN coinfection were noticed in watermelon and oriental melon infected with F. proliferatum isolates, suggesting the DI increase due to RKN coinfection may depend upon the virulence of FI relative to aggressiveness of RKN on the cucurbits. For the coinfection of FI and RKN, GI and EI were mostly reduced logarithmically with the increase of DI, largely more in EI than GI, in all cucurbits except for shintosa. Microscopic examination of the root tissues showed histopathological features characteristic to infection types; formation of fungal hyphae and/or spores and plant defense structures (tyloses and mucilage) in variable degrees and formation of giant cells at variable developmental stages and with variable cytoplasmic depletion or degeneration which were visualized in relations with the values of DI, GI and EI. These findings will be helpful to develop control strategies of the soil-borne disease complex based on their pathological characteristics.

Wild Coffea arabica resistant to Meloidogyne paranaensis and genetic parameters for resistance

Arabica coffee production is based on highly productive cultivars; however, these cultivars are susceptible to infestation by several biotic agents, including root-knot nematodes. Collections of wild Coffea arabica germplasm represent an important source of genetic variability for resistant cultivar development. In this study, 1046 plants derived from 71 wild coffee trees were evaluated with respect to Meloidogyne paranaensis resistance. In addition to information on plants reactions, we also evaluated the genetic parameters related to resistance. Progenies from the five most promising plants were also evaluated regarding resistance to M. incognita and M. exigua. The yield potential of selected plants was estimated through analysis of data for fruits harvested in 4 different years. Forty-seven plants were considered resistant based on reproduction factor values. The estimated heritability was high for all analyzed variables leading to substantial selection gain, mainly at the progeny mean level. On the basis of heritabilities and genetic correlations, we conclude that selection could be performed based on values of the gall and egg mass index. However, higher genetic gain could be obtained based on nematode count variables. A second experiment confirmed the reactions of the selected five plants to M. paranaensis, and multiple resistance was detected in three of them. The resistant accessions also have yield potential.

Resistance to root-knot nematodes on passion fruit genotypes in Brazil

With the expansion of passion fruit cultivation in Brazil, phytosanitary problems have increased, among them, the occurrence of root-knot nematodes. This research aimed to study the response of passion fruit genotypes to Meloidogyne incognita, M. javanica and M. enterolobii in addition to evaluating the life cycle of M. enterolobii in the passion fruit genotype ‘FB 200’. The genotype response was carried out in a greenhouse. Each pot’s soil was inoculated with 5000 eggs. Gall index, egg mass index and nematode reproduction factors were evaluated at 120 days after inoculation. All genotypes studied were resistant to M. incognita, M. javanica and M. enterolobii, except ‘Roxinho do Kenia’, which was susceptible to the three nematode species. The life cycle of M. enterolobii in “FB 200” passion fruit was studied in a growth chamber at 26 °C with a photoperiod of 12 h. Seven days after transplantation, each plant was inoculated with approximately 400 second-stage juveniles. Evaluations were done at 7, 14, 21, 28, 35, 42 and 49 days post inoculation. The nematode did not complete its life cycle.

<b>Inheritance of resistance to <i>Meloidogyne incognita</i> race 3 in cotton accession TX 25

Cotton producers worldwide suffer with the losses caused by the presence of phytonematodes. The aim of the present study was to investigate the inheritance of resistance to Meloidogyne incognita race 3 in Gossypium hirsutum variety punctatum accession TX 25. Accessions of Gossypium sp. were obtained from the germplasm bank of Embrapa Cotton. Two experiments were performed in two consecutive years. In the first experiment, a susceptible parental line, FiberMax 966, a resistant parental line, TX 25, and their F 1 , F 2 and backcross generations were tested. In the second experiment, parental lines FiberMax 966 and TX 25, their F 2 generation, and genotypes M315 (resistant), LA887 and DeltaOpal (moderately resistant) were tested. In both experiments, plants were inoculated with 2000 eggs and J2 of M. incognita race 3. The gall index, egg mass index and reproduction factor were evaluated 120 days following inoculation. In the first experiment, plants from the F 1 and backcross generations were susceptible. Plants from the F 2 generation presented a 3:1 resistant-to-susceptible ratio in the two experiments, indicating oligogenic resistance.

Evaluation of Pochonia chlamydosporia and Purpureocillium lilacinum for Suppression of Meloidogyne enterolobii on Tomato and Banana.

Meloidogyne enterolobii is one of the most important root-knot nematode in tropical regions, due to its ability to overcome resistance mechanisms of a number of host plants. The lack of new and safe active ingredients against this nematode has restricted control alternatives for growers. Egg-parasitic fungi have been considered as potential candidates for the development of bionematicides. In tissue culture plates, Pochonia chlamydosporia (var. catenulata and chlamydosporia) and Purpureocillium lilacinum strains were screened for their ability to infect eggs of the root-knot nematode M. enterolobii on water-agar surfaces. Reduction in the hatching of J2 varied from 13% to 84%, depending on strain. The more efficacious strains reduced hatchability of J2 by 57% to 84% when compared to untreated eggs, but average reductions were only 37% to 55% when the same strains were applied to egg masses. Combinations of fungal isolates (one of each species) did not increase the control efficacy in vitro. In experiments in which 10,000 nematode eggs were inoculated per plant, reductions in the number of eggs after 12 months were seen in three of four treatments in banana plants, reaching 34% for P. chlamydosporia var. catenulata. No significant reductions were seen in tomato plants after 3 mon. In another experiment with tomato plants using either P. chlamydosporia var. catenulata or P. lilacinum, the number of eggs was reduced by 34% and 44%, respectively, when initial infestation level was low (500 nematode eggs per plant), but tested strains were not effective under a moderate infestation level (5,000 eggs per plant). Under all infestation levels tested in this work, gall and egg mass indexes (MI) did not differ from the untreated controls, bringing concerns related to the practical adoption of this control strategy by farmers. In our opinion, if the fungi P. chlamydosporia and P. lilacinum are to be used as biocontrol tools toward M. entorolobii, they should focus on agricultural settings with low soil infestation levels and within an IPM approach.

Oat, Wheat, and Sorghum Genotype Reactions to Meloidogyne incognita and Meloidogyne javanica

Meloidogyne spp. are the most economically important species of plant-pathogenic nematodes. Plant resistance and crop rotation are the main nematode management methods. Thus, the objective was to evaluate the resistance of seven wheat genotypes, five oat genotypes, ten sorghum hybrids, and three sorghum-sudangrass genotypes to Meloidogyne incognita and Meloidogyne javanica. The crops were sowed in pots with an autoclaved substrate. A single plant/pot was left after thinning. The soil was infested with 5,000 eggs of the studied nematodes. Tomato (cv. Rutgers) plants were used as the standard for nematode susceptibility. The evaluations were conducted 60 d after inoculation. Gall and egg-mass indexes were obtained according to a 0-5 scale. Plants with a reproduction factor higher than 1.0 were classified as susceptible (S) and lower than 1.0 as resistant (R). Wheat and oat genotypes did not allow M. incognita and M. javanica reproduction, proving resistance to these organisms. Sorghum genotypes had different reactions to M. incognita and M. javanica. The tomato (cv. Rutgers) plants demonstrated the viability of the nematode inoculum for the three crops. The wheat and oat genotypes and the sorghum hybrids 'BRS-610', 'BRS-800', and '307.343' can be used in crop rotation systems for M. incognita and M. javanica management.

Endophytic Bacillus cereus Effectively Controls Meloidogyne incognita on Tomato Plants Through Rapid Rhizosphere Occupation and Repellent Action.

Root-knot nematodes (Meloidogyne spp.), which cause severe global agricultural losses, can establish a special niche in the root vascular cylinder of crops, making them difficult to control. Endophytic bacteria have great potential as biocontrol organisms against Meloidogyne incognita. Three endophytic bacteria were isolated from plant tissues and showed high nematicidal activity against M. incognita second-stage juveniles (J2) in vitro. The gyrB gene sequence amplification results indicated that the three isolates were Bacillus cereus BCM2, B. cereus SZ5, and B. altitudinis CCM7. The isolates colonized tomato roots rapidly and stably during the colonization dynamic experiment. Three pot experiments were designed to determine the potential of three endophytic bacterial isolates on control of root-knot nematodes. The results showed that the preinoculated B. cereus BCM2 experiment significantly reduced gall and egg mass indexes. The inhibition ratio of gall and egg mass was up to 81.2 and 75.6% on tomato roots and significantly enhanced shoot length and fresh weight. The other two experiments with inoculated endophytic bacteria and M. incognita at the same time or after morbidity had lower inhibition ratios compared with the preinoculated endophytic bacteria experiment. The confocal laser-scanning microscopy method was used to further study the possible mechanism of endophytic bacteria in the biocontrol process. The results showed the localization pattern of the endophytic bacteria B. cereus BCM2-(str')-pBCgfp-1 in tomato root tissues. Root tissue colonized by endophytic bacteria repelled M. incognita J2 infection compared with the untreated control in a repellence experiment. We isolated an endophytic B. cereus strain that stably colonized tomato and controlled M. incognita effectively. This strain has potential for plant growth promotion, successful ecological niche occupation, and M. incognita J2 repellent action induction. It plays an important role in endophytic bacteria against root-knot nematodes.

Histopathology of roots of three tomato cultivars infected with two separate isolates of the false root-knot nematode Nacobbus aberrans

The plant-parasitic nematode Nacobbus aberrans attacks weeds and cultivated plants, causing drastic crop yield losses. Several tomato cultivars, such as Superman and Mykonos, are produced by Seminis® as nematode resistant and are widely used in Argentina; their specific resistance response to different nematode species, however, is still unknown. In this study we explored the response of tomato cultivars to the infection of N. aberrans isolates, and determined the host status by performing histological analyses and estimating egg mass index (EMI). Two Argentina isolates (from Lules-Tucuman and Rio Cuarto-Cordoba) were tested separately in plants of Superman, Mykonos and Platense cultivars. Plants were maintained in a greenhouse for 90 days; then EMI was estimated in root systems and the material was processed to prepare histological slides and for histochemical test. Infected roots exhibited galls with females and a syncytium (feeding site) developed inside them. The vascular tissues were disorganized and displaced to the periphery; xylem percentage was lower than that in the control plants. All the cultivars were susceptible and developed a close plant-parasite relationship, with Mykonos and Platense cultivars infected with the Lules isolate being the most highly affected, as indicated by their highest EMI values. Superman was the least susceptible cultivar, as evidenced by its lowest EMI values, the amount of starch observed, the presence of thickened cell walls around the nematode and the egg mass, and the low percentage of gall occupied by syncytium.

Comparative Efficacy of Different Approaches to Manage Meloidogyne Incognita onGreen Beans

Comparative Efficacy of Different Approaches to Manage Meloidogyne Incognita on Green Beans A greenhouse study was conducted to compare the relative efficacy of different approaches to manageMeloidogyne incognita on green beans. These approaches included: chemical (fumigant, nonfumigant, seed dressing, and seed dip), biological (the egg-parasitic fungus, Paecilomyces lilacinus, and the mycorrhyzal fungus Glomus sp.), physical (soil solarization), and cultural practices (chicken litter, and urea). In total, nine different control materials and methods of applications were compared. Two important parameters were considered: plant response (plant growth and root galling), and nematode reproduction (production of eggs and the reproduction factor Rf). Results showed that the organic fertilizer, chicken litter, has severely affected the growth or survival of the seedlings. Therefore, this treatment was removed from the evaluation test. All other treatments were found to be effective against the nematode, but with different levels of efficacy. The eight treatments decreased (38.9-99.8%) root galling, increased plant growth and suppressed nematode reproduction. Based on three important criteria, namely: gall index (GI), egg mass index (EMI), and reproduction factor (RF), the tested materials and methods were categorized into three groups according to their relative control efficacy under our test conditions. These three groups were: 1) the relatively high effective group (GI=1.0-1.4, Rf=0.07-0.01) included: the fumigant dazomet, the non-fumigant fenamiphos, soil solarization, and seed-dip with fenamiphos; 2) the relatively moderate effective group (GI=3.4-4.0, Rf=0.24-0.60) included: seed dressing with fenamiphos, and urea; and 3) the relatively less effective group (GI=5.0, Rf=32.2-37.2) included: Paecilomyces lilacinus and Glomus sp....

Comparative efficacy of different approaches to managing Meloidogyne incognita on green bean.

A greenhouse study was conducted to compare the relative efficacy of different approaches to managing Meloidogyne incognita on green bean. These approaches included chemical (fumigant, non-fumigant, seed dressing, and seed dip), biological (the egg-parasitic fungus, Paecilomyces lilacinus and the mycorrhizal fungus Glomus sp.), physical (soil solarization), and cultural (chicken litter and urea) methods. Accordingly, nine different control materials and application methods plus nematode-infected and non-infected controls were compared. Two important parameters were considered: plant response (plant growth and root galling) and nematode reproduction (production of eggs and the reproduction factor Rf). The results showed that the use of chicken litter as an organic fertilizer severely affected the growth and survival of the plants. Therefore, this treatment was removed from the evaluation test. All of the other eight treatments were found to be effective against nematode reproduction, but with different levels of efficacy. The eight treatments decreased (38.9–99.8%) root galling, increased plant growth and suppressed nematode reproduction. Based on three important criteria, namely, gall index (GI), egg mass index (EMI), and nematode reproduction factor (RF), the tested materials and methods were categorized into three groups according to their relative control efficacy under the applied test conditions. The three groups were as follows: (1) the relatively high effective group (GI = 1.0–1.4, Rf = 0.07–0.01), which included the fumigant dazomet, the non-fumigant fenamiphos, soil solarization, and seed dip with fenamiphos; (2) the relatively moderate effective group (GI = 3.4–4.0, Rf = 0.24–0.60), which included seed dressing with fenamiphos and urea; and (3) the relatively less effective group (GI = 5.0, Rf = 32.2–37.2), which included P. lilacinus and Glomus sp.

Survey and Identification of Root-Knot Nematodes Associated with Brinjal Crops in Fatehabad, Agra

A survey was conducted over a period of one and half year to estimate the occurrence of root-knot nematode disease on brinjal crops in five selected localities in and around Fatehabad, Agra. Our survey indicates that brinjal crops grown in the selected localities were heavily infested with root-knot nematodes. Highest frequency of disease occurrence in which almost all the roots have knot-like appearance (>85%) was reported from Firozabad Road area. Other localities were also having the significant infestations and these were reported as 80%, 78%, 65%,62% respectively. To access the damage caused by root-knot nematodes in brinjal crop, Meloidogyne gall index and its egg-mass index were calculated and these were found in the range of 2-5. An increased gall index and egg-mass index point to heavy infection on selected crops. Sampled crop showed the significant presence of Meloidogyne javanica. However, there were other species of root-knot nematode as mixed population was also reported. Other species of the root-knot nematodes which were reported in this survey was M. incognita. This survey indicates that the M. javanica is a frequently occurring population in brinjal field infested with root-knot disease.

Effectiveness of salicylic acid, Pseudomonas fluorescens CHA0 and Trichoderma viride to control Meloidogyne incognita race 2 on different tomato cultivars

Summary The effects of salicylic acid (SA), Trichoderma viride and Pseudomonas fluorescens CHA0 were studied on the root-knot nematode Meloidogyne incognita race 2 in resistant and susceptible tomato cultivars (Gina VF, Falat CH, Falat 111, Karoon) during 2012-2013. Four-leaf tomato seedlings were used, grown in pots containing 1000 g of sterilized soil; each seedling receiving 20 ml of T. viride suspension containing 1×106 spores, 30 ml of P. fluorescens CHA0 with 109 cfu/ml, 5mM of salicylic acid and 2000 second stage nematode juveniles. Parameters relevant to nematode population and plant growth were evaluated. The biocontrol agents and salicylic acid were effective in nematode control in combined and single treatments. High reductions in root galling and egg mass indices were observed with combination of SA and biocontrol agents. The greatest increase in plant growth was obtained when cv. Falat CH was treated with SA followed by P. fluorescens CHA0 and T. viride. The highest number of galls was recorded in cv. Karoon, followed by cvs. Falat 111, Gina VF and Falat CH. Pseudomonas fluorescens CHA0 provoked the highest increase in fresh and dry root weight, fresh and dry shoot weight and plant length in all free nematode treatments. The results indicated that chemical inducer (salicylic acid), in combination with biocontrol agents (T. viride and P. fluorescens CHA0), stimulated and eventually increased plant growth.

Response of Malpighia emarginata active germplasm bank accessions to Meloidogyne enterolobii parasitism.

Malpighia emarginata is cultivated in almost all Brazil and is considered an important agricultural crop. The root-knot nematode Meloidogyne enterolobii has been described as a major threat to this crop, causing great production losses. Due to the scarcity of information about the severity of this parasite in M. emarginata plants in Brazil, this study investigated M. enterolobii resistance of ten M. emarginata genotypes from the active germplasm bank of Universidade Federal Rural de Pernambuco. The experiment was conducted adopting a completely randomized design in a factorial arrangement of 11 x 2 x 5, where M. emarginata cuttings were inoculated with 10,000 eggs in a greenhouse. After 150 days, plants were evaluated for the following parameters: gall index, egg mass index, number of eggs per root system, number of eggs per gram of root, and reproduction factor. The accessions showed different responses depending on host x pathogen interaction, from susceptibility to moderate tolerance. Accessions 027-CMF and 031-CMF were considered tolerant to the nematode and could be of great value in new breeding programs for resistance to M. enterolobii infection.

Controle alternativo de nematoide das galhas (Meloidogyne incognita) raça 2, com óleos essenciais em solo

A ação de produtos naturais sobre fitopatógenos tem sido investigada visando-se avaliar sua eficácia no controle alternativo de doenças, principalmente na agricultura orgânica. O objetivo desse trabalho foi avaliar o efeito dos óleos essenciais de alecrim pimenta (Lippia sidoides) e capim citronela (Cymbopogonwinterianus) no controle de Meloidogyne incognita raça 2, em tomate (Solanumlycopersicum) e celósia (Celosia plicata). Para tanto, conduziu-se ensaio em esquema fatorial 6 x 2, com cinco repetições. O ensaio foi realizado em casa de vegetação do Setor de Fitossanidade do Departamento de Fitotecnia/CCA/UFC, no período de abril a junho de 2007. As mudas utilizadas neste ensaio foram transplantadas para vasos plástico contendo 2 kg de solo estéril, nos quais, 24 horas após o transplantio, foram inoculados com 4.000 ovos/J2 de M. incognita, raça 2, exceto as testemunhas negativas. Em 50% do número de vasos, aplicou-se, logo em seguida, 100 ml das soluções de cada óleo essencial em cada vaso na concentração de 2,5 ml L-1. Esperaram-se mais 48 horas para aplicação da mesma quantidade nos vasos restantes. Este volume corresponde a 60% da capacidade de campo desse substrato, que foi previamente calculada. A avaliação final do ensaio deu-se aos 45 dias após a inoculação. Analisou-se em relação ao nematoide: número de galhas (NG), número de ovos (NO), índice de massas de ovos (IMO), fator de reprodução (FR), redução no fator de reprodução (RFR). Quanto ao desenvolvimento das plantas mensurou-se: altura da planta, massa fresca e seca da parte aérea e massa fresca do sistema radicular. Verificou-se que a reprodução do nematoide, mostrou-se menos eficiente em tomate. Os óleos essenciais empregados reduziram a taxa reprodutiva do nematoide em 83 e 29%, em tomate e celósia, respectivamente. As épocas de aplicação dos óleos essenciais diferiram quanto à reprodução do nematoide, para número de galhas e fator de reprodução.

Reproduction of Meloidogyne enterolobii in lettuce cultivars of the American group

Lettuce is the main vegetable cultivated in Brazil, in volume and in marketed value. There are ranges of diseases which may affect lettuce crops, including those caused by root-knot nematodes (Meloidogyne spp.). We evaluated the reproductive potential of Meloidogyne enterolobii in 22 lettuce cultivars. The plants were inoculated with 5,000 eggs and eventuals second stage juveniles of nematode per pot, two days after the transplanting. 'Rutgers' tomato was used as standard for inoculum viability of M. enterolobii. We evaluated, 60 days after inoculation, the gall index, egg mass index and reproduction factor (RF). The 'Ithaca', 'Raider Plus', 'RS-1397', 'L-104', 'Challenge', 'IP-11', 'Classic', 'Salinas 88', 'Vanguard 75', 'Calona' and 'Desert Queen' were resistant to M. enterolobii with RF varying from 0.22 to 0.9, and the cultivars Lady Winterset, Robinson, Sonoma, Raider, Lucy Brown, Bnondaga, Summer Time, Taina, Sundevil and L-109 were susceptible to this nematode, with RF ranging from 1.06 to 5.73.

Root-knot Nematode Resistance, Yield, and Fruit Quality of Specialty Melons Grafted onto Cucumis metulifer

Interest in specialty melons (Cucumis melo) with distinctive fruit characteristics has grown in the United States in recent years. However, disease management remains a major challenge in specialty melon production. In this study, grafting experiments were conducted to determine the effectiveness of using Cucumis metulifer, a species known for its genetic resistance to root-knot nematodes (RKNs; Meloidogyne spp.), as a potential rootstock for managing RKNs in susceptible specialty melon cultivars. In the greenhouse experiment, honeydew melon ‘Honey Yellow’ was grafted onto C. metulifer and inoculated with M. incognita race 1. The grafted plants exhibited significantly lower gall and egg mass indices and fewer eggs compared with non- and self-grafted ‘Honey Yellow’. Cucumis metulifer was further tested as a rootstock in conventional and organic field trials using honeydew melon ‘Honey Yellow’ and galia melon ‘Arava’ as scions. ‘Honey Yellow’ and ‘Arava’ grafted onto C. metulifer exhibited significantly lower galling and reduced RKN population densities in the organic field; however, total and marketable fruit yields were not significantly different from non- and self-grafted plants. Although the improvement of RKN resistance did not translate into yield enhancements, incorporating grafted specialty melons with C. metulifer rootstock into double-cropping systems with RKN-susceptible vegetables may benefit the overall crop production by reducing RKN population densities in the soil. At the conventional field site, which was not infested with RKNs, ‘Honey Yellow’ grafted onto C. metulifer rootstock had a significantly lower total fruit yield than non-grafted ‘Honey Yellow’ plants; however, fruit yields were similar for ‘Arava’ grafted onto C. metulifer rootstock and non-grafted ‘Arava’ plants. Although no significant impacts on the fruit quality attributes of ‘Honey Yellow’ were observed, grafting onto C. metulifer decreased the flesh firmness of ‘Arava’ in both field trials and resulted in a reduction in total soluble solids content under conventional production. In summary, grafting RKN-susceptible melons onto C. metulifer rootstock offers promise for growing these specialty melons; however, more studies are needed to elucidate the scion–rootstock interaction effect on fruit yield and quality.

Reação de aceroleira (Malpighia emarginata D.C.) à Meloidogyne enterolobii

O Brasil é o maior produtor, consumidor e exportador de acerola (Malpighia emarginata D.C.) do mundo. Por conter altos teores de vitamina C, tornou-se uma fruta altamente requisitada no mercado mundial para o preparo de sucos e no consumo in natura. Nos últimos anos, as lavouras desta fruta vêm apresentando um decréscimo nas produções em razäo da ocorrência de nematoides de galhas (Meloidogyne spp.), um dos principais problemas que afetam a cultura. O objetivo deste trabalho foi avaliar a resistência de genótipos de aceroleira frente à Meloidogyne enterolobii. O experimento foi conduzido em casa de vegetação do Departamento de Proteção Vegetal, da Faculdade de Ciências Agronômicas/UNESP - Câmpus de Botucatu (SP). Foram utilizados cinco clones: Cereja-Brs-236; Fruta Cor- Brs-238; Roxinha-Brs-237; Mirandópolis; Japi, e três variedades: Okinawa; Olivier e Waldy-CATI. Cada planta foi inoculada com 2.500 ovos e eventuais juvenis de segundo estádio (Pi) de M. enterolobii. Após 60 dias, a parte área de cada planta foi descartada, e o sistema radicular lavado, submetido à coloração com floxina-B e examinado para a obtenção dos índices de galhas (IG) e massa de ovos (IMO), e processados pelo método de trituração em liquidificador, peneiramento e centrifugação com sacarose para a obtenção do número total de ovos (Pf), que foi utilizado para o cálculo do fator de reprodução (Pf/Pi). Todos os clones e as variedades foram considerados suscetíveis à Meloidogyne enterolobii apresentando os fatores de reprodução variando de 4,1 a 18,3.

Root-Knot Nematode (Meloidogyne Species) Distribution in Some Tomato Fields in Makurdi

Studies were conducted to assess the distribution of root-knot nematode in some tomato fields in Makurdi from October 2010 to January 2011. Tomato plants were surveyed for infection based on symptoms such as stunted growth, yellowing of leaves and wilting in farmers' farm for determining disease incidence. Number of knots (NK) and root knot index (RKI) was used for disease severity. Disease plant Samples were collected and taken to the laboratory for extraction. Perineal patterns were prepared and examined under the microscope and species identified using appropriate keys. The result shows incidence range from 20%-60% in October, 2010 and 20%-80% January, 2011 while the severity of the disease ranged from 1-3 in October, 2010 and 1-4 in January, 2011. Significant differences (P=0.05) in the study areas. Egg Mass Index (EMI) and Gall Index (GI) ranged from 1.0 - 4.0. Meloidogyne incognita and M. javanica were identified to be the causes of infection. It is suggested that control methods should be applied in the nematode management in farmers fields

First report of pathogenicity of entomopathogenic nematodes of the genus Heterorhabditis on partially engorged females of Dermacentor nitens (Acari: Ixodidae)

The aim of this study was to evaluate the effect of different concentrations of the entomopathogenic nematodes (EPNs) Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 on the reproductive biology of partially engorged females of Dermacentor nitens. Four groups were formed, with each group containing 10 females and exposed to concentrations of 0, 75, 300, and 1200 nematodes for each female. This procedure was performed separately for each nematode. The following biological parameters were evaluated: egg mass weight, egg production index, hatching percentage, and percentage of control. H. bacteriophora HP88 at the two highest concentrations (300 and 1200 EPNs/female) caused a reduction (p<0.05) on the egg mass and egg production index. Was noted a significant reduction (p<0.05) in the percentage of hatched in all the treated groups. For H. indica LPP1, all treatments resulted in decreased (p<0.05) values for all the parameters. The percentages of controls obtained at concentrations of 75, 300, and 1200 EPNs/female were 56.3, 89.3, and 98.8 and 77.5, 77.1, and 95.9 for H. bacteriophora HP88 and H. indica LPP1, respectively. Therefore, it is concluded that these nematodes showed pathogenicity toward partially engorged females of D. nitens, thereby negatively affecting the reproductive biology of this tick.

Reproduction of root knot nematode (&lt;/i&gt;Meloidogyne incognita&lt;i&gt;) on Bt cotton expressing Cry1Ac and Cry2Ab2 protein

Objective: The sedentary endoparasite Meloidogyne incognita is an important plant parasitic nematode that infects cotton causing significant yield losses. The objective of this study was to evaluate reproduction of M. incognita in Bt cotton (06Z604D), isoline (99M03) and HART 89M (local non-Bt cotton cultivar) under greenhouse conditions. Methods and results: Plant height, number of squares/bolls, fresh shoot and root weight were determined before root knot nematode (RKN) screening at 90 and 180 days after planting (DAP). Galling severity, egg mass index, number of juveniles and the presence of Bt protein in roots and soil were also determined. The ELISA detected Bt protein in soil and roots of Bt cotton but not in HART 89M and isoline plant tissues and soil. Reaction of Bt cotton and isoline to M. incognita was different with the transgenic cotton being more susceptible to RKN. HART 89M was more resistant to RKN infection compared with the isoline. Conclusion and application of findings: The study has demonstrated that Bt cotton (06Z604D) is susceptible to M. Incognita . The results indicate the importance of integrating nematode management practices such as the use of organic amendments and nematicides with other cultural practices in future Kenyan Bt cotton agroecosystems.