"Reaction of soybean cultivars (Glycine max (L.) Merrill) to two races of Meloidogyne enterolobii (Yang & Eisenback, 1983)".
Soybean genotypes, genetic control, resistance, root-knot nematodes.
Soybean (Glycine max (L.) Merril is considered one of the oldest legumes consumed by humanity. Nematodes are one of the most important groups of pathogens in this crop, and those of the genus Meloidogyne are among the most harmful to this crop. Meloidogyne enterolobii, frequent in areas with the presence of guava trees, was recently detected in cotton, characterizing a new race of this species in Brazil. This nematode has the potential to be a problem in soybeans, as it is virulent to several economically important crops with resistance genes to other Meloidogyne species. Several soybean cultivars currently available on the market show resistance to M. javanica and M. incognita, however little is known about the reaction to M. enterolobii. The objective of this study was to evaluate the main soybean cultivars of Embrapa with proven resistance to Meloidogyne spp., studying them regarding the reaction to the two races of M. enterolobii. The assays were carried out in a greenhouse, in a factorial scheme (DIC) with 16 soybean cultivars x two races of M. enterolobii (guava and cotton populations), totaling 32 treatments x eight replications, and evaluated with two repetitions in time. Soybean sowing took place in pots containing 1.7 liters of the soil : sand : bioplant® substrate (1:1:1), previously autoclaved. Each soybean plant was inoculated with 5000 M. enterolobii eggs. After 75 days for the first experiment, and 90 days for the second, the following variables were evaluated: root fresh mass (MFR), gall index (GI), total eggs and juveniles (J2) (PF), number of total eggs and J2/root gram (NOGR) and the reproduction factor (FR). All treatments showed moderate population levels of eggs and J2 of M. enterolobii, and the cotton race accounted for the highest values for the reproduction factor (FR). Meloidogyne enterolobii races reproduced in all soybean genotypes, with or without genetic resistance to Meloidogyne spp., with variations in FRs for some cultivars. Given the importance and prospects for expansion of the soybean crop, the results of this study expand the knowledge on the pathogenicity of M. enterolobii, as well as demonstrating the need for future research in a breeding program for the selection of soybean genotypes with resistance to the nematode, and its population variants. However, studies on races and intraspecific variability of M. enterolobii populations are needed.