Re-evaluation of the inheritance for root-knot nematode resistance in the Upland cotton germplasm line M-120 RNR revealed two epistatic QTLs conferring resistance

Abstract

We report a second major QTL for root-knot nematode resistance in the highly resistant Upland cotton line M-120RNR and show epistasis between two resistant QTLs with different mechanisms conferring resistance. In an earlier study, we identified a major QTL on Chromosome 11 associated with resistance to root-knot nematode in the M-120 RNR Upland cotton line (Gossypium hirsutum L.) of the Auburn 623 RNR source. Herein, we re-evaluated the genetics of the resistance to root-knot nematode in the M-120 RNR × Pima S-6 population by linkage mapping using recently published SSR markers. The QTL analysis detected two regions significantly associated with the resistance phenotype. In addition to the QTL previously identified on Chromosome 11 (qMi-C11), a major QTL was identified on Chromosome 14 (qMi-C14). The resistance locus on qMi-C11 originated from the Clevewilt parent, while the qMi-C14 locus originated from the other resistant parent, Mexico Wild Jack Jones. The qMi-C14 locus had logarithms of odds score of 17 and accounted for 45 % of the total phenotype variation in egg production. It was also associated with galling index, but the percent variation explained was only 6 %, suggesting that the qMi-C11 locus had a much stronger effect on root gall suppression than egg production, while the qMi-C14 locus had a stronger effect on egg production than galling. The results also suggest that the transgressive segregation observed in the development of Auburn 623 RNR was due to the pyramiding of at least two main effect QTLs as well as an additive-by-additive epistatic effects between the two resistant loci. The SSRs markers tightly linked to the qMi-C11 and qMi-C14 loci will greatly facilitate the improvement of RKN resistance in cotton via marker-assisted breeding.

Genetic analysis of Verticillium wilt resistance in a backcross inbred line population and a meta-analysis of quantitative trait loci for disease resistance in cotton

“…Eight QTL hotspots were identified including two each on c7 and c11 (at 0–25 and 20–45 cM regions), and one each on c5 (at 10–35 cM), c14 (at 0–20 cM), c15 (at 40–60 cM), and c19 (at 20–50 cM). Two major RKN resistance genes or QTLs with major effects from Auburn 623RKN and its derived lines, as reported previously [ 13 , 14 ], have been confirmed in the hotspot regions of c11 with 17 QTLs and c14 with 9 QTLs. Of the 75 RKN QTLs identified, 69 (92 %) and 59 (79 %) were located within 14 resistance QTL clusters and the 8 RKN resistance QTL hotspots, respectively (Table 3 ).…”

“…In Upland cotton, high RKN resistance was achieved in Auburn 623RKN through crossing between moderately resistant Clevewilt and Wild Mexico Jack Jones, which was then transferred to other breeding lines [ 11 ]. The resistance was later determined to be controlled by two genes through a classic genetic analysis [ 12 ], and the two genes ( Mi1 or qMi-C11 and Mi2 or qMi-C14 ) were mapped to chromosomes c11 from Clevewilt and c14 from Wild Mexico Jack Jones through a collective research effort [ 13 , 14 ]. In an interspecific recombinant inbred line population of two susceptible parents of Upland and Pima cotton, major QTLs (on c3, c4, c11, c14, c17 and c23) and 19 putative QTLs for RKN responses were reported [ 15 ].…”

Reproduction of Meloidogyne incognita Race 3 on Flue-cured Tobacco Homozygous for Rk1 and/or Rk2 Resistance Genes

“…Two quantitative trait loci (QTLs) recently discovered in cotton each confer only moderate resistance to M. incognita when present alone, but when present together confer near immunity (Guti errez et al, 2010;He et al, 2014;Batista da Silva et al, 2015). Both QTLs reduced nematode egg production, but qMi-C11 reduced galling, while qMi114 did not (He et al, 2014).…”

Role of QTL mapping to circumscribe various diseases in different crops with special emphasis on cotton.

“…These VW resistance QTLs recognized in this study could provide basics for understanding of genetic basis of this disease. These 28 QTLS, 24 hotspots give imperative information for high resolution mapping and MAS [63][64][65].…”