Cultivar Susceptibility to the Fusarium Wilt Complex and Race Characterization of Fusarium oxysporum f. sp. vasinfectum

Abstract

Fusarium wilt of cotton is a serious fungal disease caused by Fusarium oxysporum f. sp. vasinfectum (FOV) and highly impacted by root-knot nematode (Meloidogyne incognita). Cotton cultivars were tested for resistance to these pathogens and races of FOV were determined. Under high disease pressure in 2010, Phytogen 367 WRF appeared resistant to RKN and FOV. Comparatively, Phytogen 565 WRF was also resistant to FOV but tolerant to RKN supporting high populations of the nematode. In 2011, the lack of rainfall early in the season eliminated disease pressure by RKN and FOV; all varieties tested produced approximately twice as much cotton yield in 2011 than 2010 with timely rainfalls during bloom. In addition, this study identified that FOV from lineage II, III, and IV exist within Alabama fields based on the partial sequence differences in EF-1α, BT, and PHO genes. These lineages correspond to molecularly recognized races 1, 4, and 8. However, pathogenically the Alabama race 4 isolate did not perform as the hyper-virulent race 4 CA strain that produces a Fusarium wilt which can kill cotton without the presence of nematodes.