Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2006
Publication Date: 12/1/2006
Citation: Ynturi, P., Jenkins, J.N., McCarty Jr., J.C., Gutierrez, O.A., Saha, S. 2006. Association of root-knot nematode resistance genes with simple sequence repeat markers on two chromosomes in cotton. Crop Science. 46:2670-2674. Interpretive Summary: Root-knot nematode is a serious pest of Upland cotton. Excellent sources or resistance have been developed by ARS scientists, but no commercial cultivars have a high level of plant resistance to this nematode. Breeding resistance genes into cultivars is tedious, expensive, and time consuming because the highly resistant plants are usually identified in a segregating population by infesting plants in the greenhouse, growing plants for six weeks, and scoring plants for root galls. Molecular markers should assist in the development of resistant cultivars. We confirmed that two major genes are involved in resistance. We place the location of one gene on chromosome 14 and this gene has both additive and dominance gene effects and one gene is on chromosome 11; this gene has only additive genetic effects. We further determined that BNL SSR marker 3661 is on chromosome 14 and accounts for 21% of the variation in gall index, and BNL SSR marker 1231 is on chromosome 11 and accounts for 11% of the variation in gall index. Together these two markers account for 31% of the variation in gall index. These markers should be helpful in marker assisted selection when breeding for resistance to root-knot nematode.
Technical Abstract: Breeding for root-knot nematode (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood] resistance in cotton (Gossypium hirsutum L.) is hindered by intensive screening procedures for the selection of resistant plants. The identification of DNA markers closely associated with RKN resistance would provide useful tools for marker assisted selection (MAS) in the development of resistant cultivars. The objective of this study was to identify DNA markers associated with RKN resistance and associate the markers with specific chromosomes. Parents and a F2 population from a cross of resistant near isoline (RNIL) % 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). Genotype analysis was conducted on 86 F2 plants with 9 polymorphic SSR markers. Additive dominance model analysis showed that BNL SSR markers 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 dominance genetic effects of 0.61 and 0.50 respectively. BNL 1231 had significant additive genetic effects of 0.51 and no dominance effects. BNL 3661, 3544, and 3645 were linked and deletion analysis with aneuploid stocks revealed that 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 that at least two genes are involved in RKN gall score index in the cross studied.