Reação de genótipos de soja ao pratylenchus brachyurus
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Data
2014-05-16
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Universidade Federal de Goiás
Resumo
Soybean is the most important crop in Brazil, which is known for being the
second largest producer of the grain. There are several phytosanitary problems that affect
the culture and cause losses in production, including plant nematodes. Pratylenchus
brachyurus is one of the most widespread nematodes in soybean producing areas of Brazil.
The search for genotypes that have resistance to this plant nematode has been widespread,
but there is still disagreement regarding the behavior of several brazilian cultivars.
Evaluation of soybean cultivars in infested areas has not indicated the existence of
materials resistant or tolerant. Thus, this study was to evaluate the reaction to P.
brachyurus of six soybean cultivars and eight F1 populations originated from crosses in
partial diallel arrangement. We also evaluate the behavior of cultivars exposed to different
inoculum concentrations in three planting dates. The first study aimed to evaluate the
reaction of cultivars and F1 populations of the plant nematode P. brachyurus. Experiment
were conducted in naturally infested field conditions to evaluate the cultivars MT/BR51
(Xingu), BRSGO Caiapônia, MSOY 8360RR, BRS 8560RR, Emgopa 313RR and MSOY
7639RR and another in greenhouse conditions, which were evaluated in addition to these
cultivars, the F1 progenies obtained by crossing between the parents of group I (Xingu and
BRSGO Caiapônia) and group II (MSOY 8360RR, BRS 8560RR, Emgopa 313RR and
MSOY 7639RR). In the field experiment all cultivars were susceptible to plant nematode,
except the cultivar Xingu that showed behavior of resistance in the evaluation at 60 days
after planting (DAP) with a RF of 0,80. However, this cultivar enabled the multiplication
of P. brachyurus in the evaluation at 30 DAP. In the greenhouse condition, all parents
behaved as resistant. The diallel analysis revealed the presence of non-additive and
additive effects in controlling resistance. The Xingu cultivar showed the best GCA and
cross between the cultivars Xingu and MSOY 8360 RR was the most promising in
generating progeny with resistance reaction. The second study aimed to evaluate the
reaction of soybean cultivars BRSGO Caiapônia, MT/BR51 (Xingu), MSOY 8360RR,
MSOY 7639RR, BRS 8560RR and Emgopa 313RR, subjected to different inoculums
concentrations in three planting dates. For this, three experiments were conducted under
greenhouse conditions to evaluate the reaction of soybean cultivars under initial inoculum
concentrations of 200, 400 or 600 juveniles and/or adults of P. brachyurus per plant in
three planting dates. The planting date interferes with the infection of P. brachyurus and in
the development of plants. Temperatures recorded in the second planting date, probably
favored the multiplication of the nematode resulting in the lowest root development of
cultivars. In this planting date was observed the highest population density of the
nematode. In the third planting date the average temperature of the environment presented
milder. At this planting date it was noted that all cultivars had lower population densities of
P. brachyurus and resistant behavior (RF<1). There was a trend towards growing the plant
nematode population density increased as the inoculums concentration in the first and
second planting dates. In their results, we can observe the vulnerability of Brazilian
soybean genotypes to P. brachyurus and the existence of variability of the pathogen. More
research is needed to identify genotypes that have resistance to this nematode, as well as
population studies related to the nematode. These studies should take into account the
annual variation of nematode population due to low infectivity observed in dates of
warmer temperatures.
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SILVA, A. C. F. Reação de genótipos de soja ao pratylenchus brachyurus. 2014. 67 f. Tese (Doutorado em Genetica e Melhoramento de Plantas) - Universidade Federal de Goiás, Goiânia, 2014.