Variability in Reproduction of Four Populations of Meloidogyne incognita on Six Cultivars of Cotton

A range of virulence levels was found in four populations of Meloidogyne incognita collected from cotton fields of the Punjab region of Pakistan. The most virulent population was associated with development of larger gall size, larger giant cell formation and improved success of juveniles transitioning into reproducing adults. The most virulent nematode population, MI-78, emanated from cotton cultivar NIAB-78. This cotton cultivar also possessed the greatest level of resistance to the three other nematode populations evaluated in this study. The source of plant resistance was not evident during root penetration by second-stage juveniles (J2), but became apparent as nematode feeding was attempted. Although one other cotton cultivar, CIM-506, could also be designated as showing a level of resistance, none of the other cultivars reduced any nematode stage by more than 75% of that achieved on the best host. These data provide an example of a single cotton cultivar that could have short-term utility in field settings. The data also provide insight for future cotton breeding programs.