Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2016
Publication Date: 6/17/2016
Publication URL: http://handle.nal.usda.gov/10113/5454513
Citation: Wubben, M., Callahan, F.E., Jenkins, J.N., Deng, D.D. 2016. Coupling of MIC-3 overexpression with the chromosome 11 and 14 root-knot nematode (RKN) (Meloidogyne incognita) resistance QTLs provides insights into the regulation of the RKN resistance response in Upland cotton.... Theoretical and Applied Genetics. 129:1759-1767.
Interpretive Summary: Cotton resistance to the root-knot nematode is controlled by two major quantitative trait loci (QTL). These QTLs reside on chromosomes 11 and 14. Previous experiments showed that the MIC-3 gene family in cotton plays a direct role in contributing to this resistance trait mediated by these QTLs. In this study, we combined a MIC-3 overexpression transgene with different combinations of the chromosome 11 and 14 QTLs. Plants having these different combinations of transgene and QTL were infected with RKN and their respective level of resistance determined by measuring RKN eggs per gram of root. The data showed that when MIC-3 overexpression was coupled with the chromosome 14 QTL, RKN resistance was increased versus plants having only the QTL and not the transgene. No improvement of resistance was observed in plants having the chromosome 11 QTL or in plants having both QTLs. These data indicate that MIC-3 expression in non-transgenic RKN-resistant plants is likely controlled by the chromosome 11 QTL.
Technical Abstract: High levels of resistance to root-knot nematode (RKN) (Meloidogyne incognita) in Upland cotton (Gossypium hirsutum) is mediated by two major quantitative trait loci (QTL) located on chromosomes 11 and 14. We had previously determined that MIC-3 expression played a direct role in suppressing RKN egg production, but not nematode-induced galling, in lines having these QTLs. In the current study, the MIC-3 overexpression contruct T-DNA in the single-copy transgenic line 14-7-1 was converted into a co-dominant molecular marker that allowed the marker assisted selection of F2:3 cotton lines, derived from a cross between 14-7-1 and M-240 RNR, having all possible combinations of the chromsome 11 and 14 QTLs with and without the MIC-3 overexpression construct. RKN reproduction (eggs g-1 root) and severity of root galling were assessed. We discovered that addition of MIC-3 overexpression suppressed RKN reproduction in lines lacking both resistance QTLs and in lines having only the chromosome 14 QTL. MIC-3 overexpression did not improve resistance in lines having the single chromosome 11 QTL nor in lines having both resistance QTLs. MIC-3 overexpression did not affect the severity of root galling phenotype regardless of genotype. We conclude that these data strongly suggest that MIC-3 expression in RKN-resistant lines is mediated by the chromosome 11 QTL during the early phase of the resistance response.