Screening of edible soybean varieties for resistance to the root-knot nematode, Meloidogyne incognita, under field conditions

In spite of the economic potential of edible soybean, the crop is attacked by pests and diseases, including the root-knot nematode, Meloidogyne incognita, which is the most troublesome plant-parasitic nematode in the tropics. Field studies were conducted in 2004 and 2005 to assess the reaction of 34 varieties of soybean for resistance to natural infestation of M. incognita. Ten weeks after planting, ten randomly selected plants were observed for root galls and nodules. Plant height, days to 50% flowering, days to maturity, 100 seed weight and yield were also recorded. Root galling varied significantly among soybean varieties. Root galling correlated negatively with number of pods and leaves; however, there was positive correlation between root gall and stem girth when all 34 varieties were considered. Of the 34 varieties, TGM 344, TGM 1784 and TGX 1448-2E were the most resistant with reproduction factors of 0.54, 0.56 and 0.54, respectively. Ten varieties exhibited tolerance, four were hyper-susceptible while the rest were susceptible to root-knot nematode.