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Abstract
The germplasm sources highly resistant to Meloidogyne incognita (Southern root-knot nematode) in Upland cotton (Gossypium hirsutum L) contain the resistance QTLs qMI-C11 and qMi-C14. Previous research documented resistance expressed at two stages of nematode development, and later research documented an epistatic interaction between the two QTLs, both of which suggest the QTLs have different modes of action. Our experiments demonstrated that qMi-C11 reduces the number of galls and egg masses, total egg production, and eggs/egg mass whereas qMi-C14 reduces the number of egg masses, total egg production, and eggs/egg mass without reducing galling. Fusarium oxysporum f. sp. vasinfectum (Fov) interacts with M. incognita resulting in increased Fusarium wilt (FW), therefore, we tested the effect of the nematode resistance QTLs on the severity of FW. A reduction of plant growth and an increase in FW severity was seen on all genotypes regardless of nematode resistance QTLs when coinfected with Fov and M. incognita. FW has been reported more frequently in Georgia in recent years, which suggests that something affecting the disease complex may have changed. In 2015 and 2016, a survey of Georgia cotton fields was conducted. The survey showed that Fov race 1 is still the dominant race, but Fov genotypes not previously reported in Georgia were found. Additionally, many instances of FW in Georgia are due to Fov interacting with Belonolaimus longicaudatus and not M. incognita as previously believed.