Identification of Molecular Markers Associated with Root‐Knot Nematode Resistance in Upland Cotton

Abstract

Cotton breeding for resistance to root‐knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] is hindered by the lack of convenient and reliable screening methods for resistant plants. The identification of molecular markers closely linked to RKN resistance will facilitate the development of RKN resistant cultivars through marker‐assisted selection (MAS). Our objective was to identify and develop new DNA markers that are associated with RKN resistance in cotton. Using three pairs of near‐isogenic (NIL) resistant (R) and susceptible (S) lines, two AFLP markers, two RAPD markers, and three RGA markers were identified to be polymorphic between the NIL‐R and NIL‐S lines. One RAPD marker was converted into a sequence‐tagged site (STS) marker. In an F2 population of ‘ST 474’ × ‘Auburn 634 RNR’, the two RAPD markers and the STS marker were mapped to the same linkage group containing several markers that were previously reported to be linked with the RKN resistance gene rkn1 on chromosome 11 in ‘Acala NemX’. All these markers were found to be associated with a major RKN resistance gene, presumably Mi2 in the resistant line Auburn 634 RNR, suggesting that rkn1 and Mi2 are either allelic or closely linked. In addition, no susceptible recombinants were found in a resistance screen of 200 F2 plants from the cross Acala NemX × Auburn 634 RNR. The utility of the two RAPD markers and the converted STS marker were evaluated using 23 R and 8 S germplasm lines. The RAPD and STS markers, along with other previously reported markers associated with RKN resistance will be useful in germplasm screening, MAS for RKN resistance, and map‐based cloning for RKN resistance genes.

Identification and genomic location of a reniform nematode (Rotylenchulus reniformis) resistance locus (Ren ari ) introgressed from Gossypium aridum into upland cotton (G. hirsutum)

“…2) that is duplicated on chromosome 11. The region on chromosome 11 that has been identified as the location of root-knot nematode resistant genes rkn1 (Wang et al 2006) and Mi 2 (Niu et al 2007), an RKN resistance QTL (Shen et al 2006), and another putative RKN resistance QTL (Ynturi et al 2006). It is also the location of the LONREN-1 resistance source (Dighe et al 2009) and possibly resistance QTLs for Fusarium wilt ( Fusarium oxysporum ) and Verticillium wilt ( Verticillium dahliae ) (Roberts et al 2009).…”

Cotton Genomics

“…The heavy water use of cotton has drawn attention to molecular dissection of drought tolerance (Saranga et al 2001b(Saranga et al , 2004Zhao et al 2008). Disease resistance has also been a major focus, with published information for Verticillium (Bolek et al 2005;Wang et al 2008;Yang et al 2008), Xanthomonas Rungis et al 2002), Thielaviopsis (Niu et al 2008), and root knot nematode (Shen et al 2006a;Wang et al 2006b;Wang and Roberts 2006;Ynturi et al 2006;Niu et al 2007). Interest in hybrid cottons in some countries has drawn attention to a nuclear restorer of a cytoplasmic male sterility system (Guo et al 1998;Lan et al 1999;Zhang and Stewart 2004;Feng et al 2005;Wang et al 2007b).…”

New Tools and Traits for Cotton Improvement

“…A good example of such a trait in cotton is resistance to the root knot nematode (Meloidogyne incognito) where resistance is quantified by destructive sampling of root galling or egg counts of progeny that must be grown under RKN infested conditions (Zhang . DNA markers have been discovered that are linked to resistance to RKN (Niu et al 2007;Wang et al 2008). In addition to cost savings, MAS is a powerful tool to disrupt negative associations that may cause yield drag from certain resistant genetic sources.…”