Performance de cruzamentos entre genitores tolerantes à ferrugem asiática da soja

Abstract

Performance of crosses among parents with tolerance to soybean rust The Asian soybean rust (FAS) was reported for the first time in Brazil in 2000/2001 and has since caused considerable damage to soybean crops. The use of genetically resistant cultivars is a key component of an integrated program to control this disease. In the researches has been found many difficulties because the fungus Phakopsora pachyrhizi shows great variability in pathogenicity and the small number of sources of resistance that are available has no adaptability to Brazilian environmental conditions. The overall objective of this study was to evaluate the performance of experimental soybean lines derived from crosses among soybean rust tolerant parents, in order to increase the horizontal resistance (tolerance). The experiments were conducted during the crop years 2008-09, 2009-10 and 2010-11, in three experimental stations (Anhumas, Areão and ESALQ), areas belonging to the College of Agriculture "Luiz de Queiroz" and located within the municipality of Piracicaba, State of São Paulo, Brazil. The experiments with progenies in generations F 2:4 , F 2:5 and F 2:6 were designed in augmented block of Federer, with each experiment divided into sets with common checks. In order to estimate the effect of FAS and the level of tolerance of each genotype to FAS, in each location and crop year, there was conducted two experiments with applications of different fungicides: in the first experiment was applied one fungicide for controlling only the soybean late season leaf diseases (DFC), while in the second experiment were applied one fungicides with active principles for controlling DFC as well as FAS. In the experiments with control of DFC and FAS there was tendency of superior means for PG and PCS. The methodology of contrasting the plant reactions to different fungicides was effective for estimating the effect of FAS and the level of tolerance of each genotype to FAS. The pressure of the fungal FAS on progenies ranged among crop years, being highest in 2009-10. The location Anhumas stood out among the rest, enabling high average seed yield (PG) in all evaluated crop years; this environment also proved to be suitable for estimating the rust effect. The parents 1 (USP 04-18032) and 5 (USP 11-38) were those that originated the earliest progenies and parents 3 (USP 97-08135) and 10 (USP 191-104-11) the later progenies. The parents 8 (USP 191-102-03) and 10 (USP 191-104-11) were the main contributors to higher average PG and one hundred seed weight (PSC). However, the parent 4 (BUSP 16-015) exceeded for PG, besides also have presented high value of average combining ability for PG, in average of the three crop years. The cross 7x10 (USP 14-06-20 x USP 191-104-11) stood out by originating the highest number of progenies with superior performance in PG and tolerance to FAS. On the other hand, the parents 1 (USP 04-18 032), 3 (USP 97-08 135), and 9 (USP 191-103-12) have contributed with the smallest number of superior progenies in PG. There was variation amo...

Seleção de linhagens experimentais de soja para tolerância à ferrugem asiática e produtividade

“…Utilizando a estratégia antes relatada (item 2.1.6) de se conduzir dois experimentos vizinhos com diferentes manejos de fungicidas, Araújo et al (2005) e Unfried (2007 obtiveram dados sobre a resistência/tolerância de várias linhagens experimentais de soja do SGAEA; com base nestas avaliações, foram selecionadas as dez linhagens mais tolerantes à ferrugem asiática, as quais foram recombinadas em um dialelo completo 10 x 10, sem recíprocos, gerando 45 cruzamentos biparentais (Tabela 1, Vieira (2009)). O avanço das gerações de endogamia dos cruzamentos foi feito até a geração F 2:3 por Vieira (2009) e as gerações F 2:4 , F 2:5 e F 2:6 foram pesquisadas por Marques (2014).…”