|ZHENG, XIUTING - Texas A&M University|
|HOEGENAUER, KEVIN - Texas A&M University|
|Bell, Alois - Al|
|HULSE-KEMP, AMANDA - Texas A&M University|
|NICHOLS, ROBERT - Cotton, Inc|
|STELLY, DAVID - Texas A&M University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2015
Publication Date: 4/8/2016
Citation: Zheng, X., Hoegenauer, K.A., Quintana, J., Bell, A.A., Hulse-Kemp, A.M., Nichols, R.L., Stelly, D.M. 2016. SNP-based MAS in cotton under depressed-recombination for Renlon-flanking recombinants: Results and inferences on wide-cross breeding strategies. Crop Science. 56:1-14.
Interpretive Summary: The reniform nematode (Rotylenchulus reniformis) resistance gene Renlon was transferred to upland cotton (Gossypium hirsutum L.) from the wild African species Gossypium longicalyx. Lines containing the gene reduce nematode reproduction 50%-90%. However, in nematode-infested fields, resistant plants were smaller and less productive than were susceptible sibling plants in early season. In this manuscript, we describe several hypotheses, including "linkage drag and hypersensitivity”. By the previous SNP development efforts between G. longiclayx and G. hirsutum (Gh-Gl SNP), we have identified 85 Renlon-linked SNP markers in the alien region. Meanwhile, we have created a large BC1F1 populations using advanced backcross-inbred lines with previously identified proximal (PCO) or distal recombination (DCO) events near Renlon. By high-resolution mapping of the alien region and identification of the best recombinants without stunting in BC1F1 families using MAS, extremely low recombination rates were observed. Then we compared two breeding strategies using a DCOxPCO intercross population versus a backcross population. We observed recombinants far more frequently among the intercross than the backcross progeny. By comparing the two strategies, we provided a very important approach for increasing the number of recombinants when a breeding project requires interspecific introgression from an alien genome that exhibits reduced recombination. It is likely to be one where nearby flanking recombinants are sought out in early generations, and subsequently recombined, rather than obtained in serial fashion. This breeding strategy will benefit many plant researchers who are involved in interspecific introgression breeding programs.
Technical Abstract: Renlon, a gene from the wild African species, Gossypium longicalyx, confers a high level of resistance against reniform nematode (Rotylenchulus reniformis) when introgressed into Gossypium hirsutum. However, LONREN lines were stunted when grown in fields heavily infested with nematodes during early growth season. Several hypotheses, including "linkage drag" could explain the "stunting". To characterize Renlon chromosomal region, Renlon-linked SNP markers were identified and eighteen SNPs were selected for high-resolution mapping across two different BC1F1 populations using advanced backcross-inbred lines with previously identified proximal (PCO) or distal recombination (DCO) events near Renlon. Extremely low recombination rates were observed. Two of the closest Renlon-linked SNPs were selected for identifying best recombinant without stunting across all BC1F1 families. None of the five recombinants found separated stunting and resistance. To investigate a better approach for recovering recombinants, we compared recombination rates using a DCOxPCO intercross population versus a backcross population. Far more recombinants were observed among the intercross than the backcross progeny. These indicate that if a breeding project requires interspecific introgression that exhibits reduced recombination, the best strategy is likely to be one where nearby flanking recombinants are sought out in early generations, and subsequently recombined, rather than obtained in serial fashion.