|Bell, Alois - Al|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2009
Publication Date: 7/1/2009
Citation: Dighe, N.D., Robinson, A.F., Bell, A.A., Menz, M.A., Cantrell, R.G., Stelly, D.M. 2009. Linkage mapping of Gossypium longicalyx resistance to reniform nematode during introgression into cotton Gossypium hirsutum. Crop Science. 49:1151-1164. Interpretive Summary: The reniform nematode is a serious pest of cotton causing losses of nearly ten percent of the potential crop in some states. None of the commercial varieties have appreciable resistance to the nematode, but a breeding line that is immune to the nematode has been developed by the authors of the paper, and two germplasm lines have been released to the public. Most commercial breeders however, do not have facilities or expertise to screen against the nematode. Thus, an alternate method is needed to quickly and accurately identify plants carrying resistance. In this paper, the authors report several molecular markers that can be used to identify resistant plants with greater than 98 percent accuracy. Of these, two markers have been identified that are 100 percent accurate in identifying resistant plants. This technology should facilitate development of reniform resistance in commercial cotton.
Technical Abstract: The reniform nematode (Rotylenchulus reniformis Linford and Oliveira) poses significant problems for US cultivated Upland cottons (Gossypium hirsutum L., 2n=52), all of which lack high resistance. The African species G. longicalyx (Hutch. and Lee), however, is extremely resistant. We used three progressively larger panels to map the governing locus during extensive backcross breeding to transfer the resistance to Upland cotton. Widely spaced SSR marker loci from all A-subgenome linkage groups were first screened against parents for polymorphism. Polymorphic SSRs were then screened against the second panel, with 12 resistant and 12 susceptible segregates. Strong associations were detected between the resistance and two chromosome-11 SSRs BNL1066_156 and BNL836_215. Tests with homeologous SSR primers revealed that SSR BNL3279_114 is also linked with the resistance. A G. longicalyx allele conferring green fuzz, dubbed Fzglon, also cosegrated with the resistance in most instances. A third panel extended analysis to nearly 1,000 individuals. To obviate the need for progeny testing of putatively resistant types, we created a “susceptible-based map” exclusively from 374 susceptible backcross hybrids (BC2-BC8) and 16 susceptible self progeny (BC1-BC6). SSRs BNL3279_114, BNL1066_156, and BNL836_215 mapped to one side of the resistance locus, just 0.8, 0.8, and 1.4 cM away, respectively, whereas the green fuzz marker, Fzglon, mapped to the opposite side, just 2.8 cM away.