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United States Department of Agriculture

Agricultural Research Service

Research Project: HOST PLANT RESISTANCE AND OTHER MANAGEMENT STRATEGIES FOR NEMATODES IN COTTON AND PEANUT

Location: Crop Protection and Management Research

Title: 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

Authors
item He, Yajun -
item Kumar, Pawan -
item Shen, Xinlian -
item Davis, Richard
item Becelaere, Guillermo -
item May, O -
item Nichols, Robert -
item Chee, Peng -

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2014
Publication Date: June 1, 2014
Citation: He, Y., Kumar, P., Shen, X., Davis, R.F., Becelaere, G.V., May, O.L., Nichols, R.L., Chee, P.W. 2014. 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. Journal of Theoretical and Applied Genetics. 127:1343-1351.

Interpretive Summary: In a previous study, we identified a genetic region (a QTL) on Chromosome 11 that is associated with resistance to the root-knot nematode in Upland cotton (Gossypium hirsutum L.). We used the germplasm line M-120 RNR, which derives nematode resistance from the Auburn 623 RNR source. Auburn 623 RNR was created by crossing two moderately-resistant cotton lines, Clevewilt and Wild Mexican Jack Jones. Recent studies have indicated that more than one major QTL was present in this resistance source. In the present study, we re-evaluated the genetics of resistance to root-knot nematode with that source of resistance by applying genome wide association analysis using recently published genetic markers. Our new analysis detected two regions significantly associated with resistance. In addition to the QTL previously identified on Chromosome 11 (qMi-C11), a major QTL also was identified on Chromosome 14. We showed that the resistance QTL on Chromosome 11 originated from the Clevewilt parent, whereas the locus on Chromosome 14 originated from the other resistant parent, Wild Mexican Jack Jones. The locus on Chromosome 14 (qMi-C14) accounted for 45% of the total variation in egg production. The qMi-C14 locus was also associated with root galling, 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 two moderately resistant QTLs as well as an epistatic interaction between the two resistance loci, which means that the effect of one gene depends on the presence of the other gene. The markers we identified that are tightly linked to the qMi-C11 and qMi-C14 loci will greatly facilitate the improvement of RKN resistance in cotton via marker-assisted breeding.

Technical Abstract: In our earlier study, by using the bulk segregant approach, 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. Recent studies have indicated that more than one major QTL was present in this resistance source. In this study, we re-evaluated the genetics of the resistance to root-knot nematode in the M-120 RNR x Pima S-6 population by applying genome wide association analysis 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 in the interval flanked by SSR markers CIR381 and CGR5668. The resistance locus on Chromosome 11 originated from the Clevewilt parent, while the locus on Chromosome 14 originated from the other resistant parent, Wild Mexican Jack Jones. The locus on Chromosome 14 (qMi-C14) had a LOD score of 17 and accounted for 45% of the total phenotype variation in egg production. The qMi-C14 locus 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 two moderately resistant QTLs as well as an epistatic interaction between the two resistance 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.

Last Modified: 12/18/2014
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