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Brasília, Brazil

Inomoto M.M.,University of Sao Paulo | Asmus G.L.,Laboratorio Of Nematologia
Plant Disease | Year: 2010

Taking into account that information about the host status of cover crops for Pratylenchus brachyurus is scarce or contradictory, this study was undertaken to assess the host status of selected graminaceous cover crops by estimating nematode reproduction and their ability to decrease the nematode density in glasshouse conditions. Furthermore, the reproductive fitness of three P. brachyurus populations was assessed for Brachiaria grasses. Silage and forage sorghum proved to be good hosts for P. brachyurus; consequently, they should be avoided in fields infested with this lesion nematode, mainly before susceptible crop such as soybean, common bean, cowpea, and cotton. Dictyoneura grass, the pearl millet cv. ADR 300, and black oat were poor hosts for P. brachyurus but may increase densities of this nematode over time. Consequently, these cover crops might be used in infested fields for only short periods, because they could increase the P. brachyurus population density slowly but progressively. © 2010 The American Phytopathological Society.

Robaina R.R.,UENF | Marinho C.S.,Laboratorio Of Fitotecnia | de Souza R.M.,Laboratorio Of Nematologia | Campos G.S.,State University of Norte Fluminense
Revista Brasileira de Fruticultura | Year: 2012

Previous screenings have found resistance to M. enterolobii in cattley guava (Psidium cattleyanum sabine) genotypes, but not in guava (P. guajava). This study aimed to evaluate inarching between the guavas 'Paluma' and cattley as a mean to obtain nematode-resistant guava plants. Eighty 'Paluma' plantlets were produced from stem cuttings and cultivated in 5L pots (one plant per pot) until they reached a stem diameter of about 8 mm at 10 cm from the collar. Cattley guavas were obtained from true seeds of the accessions 115, 116 and 117. When all the plants reached a stem minimum diameter for inarching, two cattley guava seedlings were transplanted to each of the 5L pots, into holes of about 280 cm3 dig on each side of the 'Paluma' plants. For inarching, a cut was made in the 'Paluma' stem, and one of the cattley guava or 'Paluma' seedling was inserted under the bark. The other side plant remained as a blank control. Every 20 days the following variables were evaluated: fusion of tissues between the grafted plants and growth of the plants ́ stem diameter. successful inarching, as measured by initial connection between vascular tissues and survival of the plants, occurred more often between 'Paluma' plants than between 'Paluma' and cattle guava. Nonetheless, in the long term the plants often failed to develop functional vascular connection, since removing the root system of 'Paluma' plants resulted in their death, since root system of the cattley guavas were unable to sustain their nutrition. in conclusion, more study is needed to develop inarching as a method to produce guava rootstocks.

Freitas V.M.,Laboratorio Of Nematologia | Freitas V.M.,University of Brasilia | Correa V.R.,Laboratorio Of Nematologia | Correa V.R.,University of Brasilia | And 8 more authors.
Plant Pathology | Year: 2014

Meloidogyne enterolobii has been reported in some states of Brazil and other countries causing severe damage on commercial guava (Psidium guajava). The use of resistant varieties is the most effective way to manage nematode parasitism. This study screened 51 accessions of Psidium spp. selected from the Psidium Germplasm Collection (Embrapa) to look for resistance against M. enterolobii. Six months after inoculation, nematode reproduction factor (RF) was used to assess resistance. The following species were resistant to M. enterolobii: P. cattleianum (yellow guava), P. friedrichsthalianum (Costa Rican guava), Acca sellowiana (feijoa) and P. rufum (purple guava). All 43 wild accessions of P. guajava were susceptible, as well as three accessions of P. guineense (Brazilian guava), one of P. acutangulum (pear guava) and the susceptible control P. guajava cv. Paluma. When used as rootstocks under greenhouse conditions, P. cattleianum and P. friedrichsthalianum were compatible with cv. Paluma; however, in greenhouse and field conditions only 50% of both scions survived. No apparent hypersensitive response (HR) was seen in the resistant guava P. cattleianum and P. friedrichsthalianum. Juveniles were able to develop normal feeding sites similar to those in susceptible roots 6-13 days after inoculation (dai). From 27 to 32 dai, giant cell deterioration was observed and nematodes showed arrested development. The majority of nematodes failed to reach maturity and did not begin laying eggs in resistant roots. These results suggested that the induction of resistance is relatively late in this pathosystem. © 2013 British Society for Plant Pathology.

Lima E.A.,University of Brasilia | Furlanetto C.,University of Brasilia | Nicole M.,IRD Montpellier | Gomes A.C.M.M.,Laboratorio Of Nematologia | And 6 more authors.
Phytopathology | Year: 2015

Root-knot nematodes (RKN), Meloidogyne spp., have major economic impact on coffee production in Central and South America. Genetic control of RKN constitutes an essential part for integrated pest management strategy. The objective of this study was to evaluate the resistance of Coffea canephora genotypes (clones) to Meloidogyne spp. Sensitive and drought-tolerant coffee genotypes were used to infer their resistance using nematode reproduction factor and histopathology. Eight clonal genotypes were highly resistant to M. paranaensis. 'Clone 14' (drought-tolerant) and 'ESN2010-04' were the only genotypes highly resistant and moderately resistant, respectively, to both M. incognita races 3 and 1. Several clones were highly resistant to both avirulent and virulent M. exigua. Clone 14 and ESN2010-04 showed multiple resistance to major RKNs tested. Roots of 'clone 14' (resistant) and 'clone 22' (susceptible) were histologically studied against infection by M. incognita race 3 and M. paranaensis. Reduction of juvenile (J2) penetration in clone 14 was first seen at 2 to 6 days after inoculation (DAI). Apparent early hypersensitive reaction (HR) was seen in root cortex between 4 and 6 DAI, which led to cell death and prevention of some nematode development. At 12 to 20 DAI, giant cells formed in the vascular cylinder, besides normal development into J3/J4. From 32 to 45 DAI, giant cells were completely degenerated. Late, intense HR and cell death were frequently observed around young females and giant cells reported for the first time in coffee pathosystem. These results provide rational bases for future studies, including prospection, characterization, and expression profiling of genomic loci involved in both drought tolerance and resistance to multiple RKN species. © 2015 The American Phytopathological Society.

Mota F.C.,Laboratorio Of Nematologia | Mota F.C.,University of Brasilia | Alves G.C.S.,Federal University of Goais | Giband M.,Nucleo Cerrado da Embrapa Algodao | And 10 more authors.
Plant Pathology | Year: 2013

Accessions of Gossypium spp., some of them never previously tested, were evaluated for resistance to a local isolate of Meloidogyne incognita race 3 in greenhouse experiments. Nematode infection was characterized based on the galling and egg mass indexes and the reproduction factors (RF). Root-knot nematode reproduction among the newly tested accessions varied from highly susceptible (AS0188, AS0189) to moderately resistant (MT123 no. 3), and some accessions showed highly reduced nematode reproduction (CIR1343, CIR1348, Fai Mui). Histological observations of two resistant accessions (G. barbadense CIR1348 and G. hirsutum TX-25, respectively) showed that resistance occurs through a two-stage mechanism in the first accession and through a single-stage mechanism in the second. Parasitism is blocked early after second-stage juvenile (J2) penetration or during its initial tissue migration (CIR1348) and the development of later-stage juveniles into female adults is suppressed at a later stage (TX-25 and CIR1348). Fluorescence and bright light microscopy showed that root cells surrounding nematodes exhibit a hypersensitivity-like reaction, with the accumulation of presumably phenolic compounds and the presence of necrotic cells that limit the development of nematodes and the formation of giant cells. Underdeveloped giant cells with degenerated cytoplasmic content were found in small numbers in CIR1348 and in large numbers in TX-25, along with deformed nematodes. The full characterization of the defence mechanisms of novel sources of resistance to the root-knot nematode in cotton constitutes a first step towards their use in crop improvement. © 2012 British Society for Plant Pathology.

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