Association of root-knot nematode resistance genes with simple sequence repeat markers on two chromosomes in cotton

Breeding for root-knot nematode (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood] resistance in cotton (Gossypium hirsutum L.) is hindered by intensive screening procedures. Identification of DNA markers associated with RKN resistance would provide tools for marker-assisted selection (MAS). The objective of this study was to identify DNA markers associated with RKN resistance and associate these with chromosomes. Parents and an FZ population from a cross of resistant near isoline (RNIL) X susceptible near isoline (SNIL) were grown in a greenhouse, inoculated with RKN eggs, and scored for gall index, followed by genotyping with simple sequence repeats (SSRs). The source of the resistance was from the Auburn 634 line. Genotype analysis was conducted on 86 FZ plants with nine polymorphic SSR markers. Additive dominance model analysis showed that Brookhaven National Laboratory (BNL) SSR markers BNL 3661, 3644, 3545, and 1231 accounted for 21,19,12, and 11% of the variation in gall index, respectively. BNL 3661 and 1231 together accounted for 31% of the variation in gall index. BNL 3661 had significant additive and dominant genetic effects of 0.61 and 0.50, respectively. BNL 1231 had significant additive genetic effects of 0.51 and no dominant effects. BNL 3661, 3544, and 3645 were linked and these markers were located on the short arm of chromosome 14. BNL 1231 is located on the long arm of chromosome 11. The association of two different chromosomes with RKN resistance suggests at least two genes are involved in RKN gall score in the cross studied.