Quantitative Trait Loci for Resistance Against Fusarium Wilt Based on Three Cotton F2 Populations

Fusarium wilt (FW) is one of the most common cotton diseases in the world. Identification of QTLs conferring resistance to FW is key for the incorporation of resistance genes into elite cultivars. Two intraspecific (cross between Gossypium hirsutum L.) and one interspecific (cross between Gossypium hirsutum L. and Gossypium bardence L.) F2 populations were constructed by using a highly resistant cultivar and crossing it to a susceptible cultivar with 154, 79, and 148 offsprings, respectively. Simple sequence repeats (SSR) were used to screen genomic regions closely linked to FW resistance. The results showed that five QTLs associated with FW resistance were detected in two intraspecific populations using a composite interval mapping method under four different conditions. Four of these loci located on Chr. 2/Chr. 17 neighboring markers JESPR304 or CIR305 which explained 13.1 to 45.9% of the phenotypic effect. Furthermore, JESPR304 and CIR305 were previously testified and found to be tightly linked. It is possible that these four QTLs detected under different conditions were the same resistance QTL/gene. We consider that there is the possibility of a major FW resistant gene in intraspecific populations. In the interspecific mapping populations two QTLs were detected on Chr. 9 and Chr. 12/26 which explained great phenotypic variance of 49.4 and 45.7%. As the location of QTLs for FW resistance among the intraspecific and the interspecfic populations were totally different, it is suggested that there may be different resistance mechanisms between G. bardence L. and G. hursutum L. Thus, the present research provides an opportunity to understand the genetic control of resistance to FW in Gossypium hirsutum and Gossypium bardence and to conduct MAS in breeding programs to develop FW resistant cultivars.