Reaction of soybean cultivars to two races of Meloidogyne enterolobii and their aggressiveness under plastic house conditions

Summary Limited information is available regarding the susceptibility or resistance of soybean cultivars to Meloidogyne enterolobii. Recently, a new race of this species was detected in Brazil parasitising cotton and soybean. This nematode has the potential to pose a problem in both of these crops, since it is pathogenic and virulent to several economically important plants that have resistance genes to other Meloidogyne species. The aim of this study was to assess the responses of EMBRAPA’s main soybean cultivars with confirmed resistance to M. incognita and M. javanica to the two races of M. enterolobii detected in Brazil. Additionally, this study aimed to characterise the aggressiveness of these nematode races. The experiments were conducted in a plastic house, in a factorial scheme with 16 soybean cultivars × two M. enterolobii races (guava and cotton), totalling 32 treatments × eight replications, and evaluated with two replications over time. Soybean sowing took place in pots containing 1.7 l of a mixture of soil, sand and Bioplant® substrate (1:1:1), previously autoclaved. Each soybean plant was inoculated with 5000 eggs of M. enterolobii. After 75 days for the first experiment, and 90 days for the second, the following variables were evaluated: gall index (GI), egg mass index (EMI), total number of eggs per g root (NEGR) and the reproduction factor (RF). Both races of M. enterolobii showed reproductive ability in all soybean genotypes (with or without known genetic resistance), albeit with moderate to low values in comparison to their reproduction on tomato plants. The race from cotton was considered statistically more aggressive than the guava population on soybean cultivars. Only ‘BRS 7180 IPRO’ was moderately resistant to both races in both experiments. In view of the importance and prospects for expansion of the soybean crop, the findings of this study contribute to a better understanding of the resistance and aggressiveness exhibited by the two races of M. enterolobii, Moreover, the study highlights the significant challenge that lies ahead in developing breeding programmes to select soybean genotypes with multiple resistance to Meloidogyne spp.