|Bell, Alois - Al|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/4/2005
Publication Date: 3/2/2005
Citation: Dighe, N.D., Stelly, D.M., Menz, M., Robinson, A.F., Bell, A.A., Bridges, A. 2005. Reniform nematode resistance - Cytogenetics of Gossypium longicalyx introgression products [abstract]. In: Proceedings of the Beltwide Cotton Conferences, January 4-7, 2005, New Orleans, Louisiana. 2005 CDROM.
Technical Abstract: The reniform nematode is recognized as a significant problem for US cotton producers. Severity and acreage of damage have been increasing. Although no commercial upland cotton cultivar has high resistance to the reniform nematode, the wild African 13-chromosome species G. longicalyx related to cotton is immune to this pest. Intensive wide-cross breeding efforts at the USDA, College Station yielded two tri-species hybrids that involve G. longicalyx and G. hirsutum, but differ in the third parent – either G. armourianum or G. herbaceum, respectively. The genomic compositions of these two hybrids, ADFD and ADAF, respectively, suggested that chromosomal abnormalities would abound in early backcross generations, and that interpretation of segregation ratios for resistance/susceptibility to nematodes would be error-prone if unaided by cytogenetic analyses. We report here on chromosome numbers and meiotic metaphase I configurations that were assessed for most of the BC1F1, BC2F1, BC1S1, BC3F1, BC4F1 and BC5F1 plants. Cytological information obtained from these populations revealed a progression toward 100% 52-chromosome individuals and increasing frequencies of resistant plants that form 26 bivalents at metaphase I. At advanced generations, the genetic control seems to be pollen-transmissible and relatively simple. Recombination is occurring between the F-genome and the A-genome of G. hirsutum (AD-genome). Highly resistant plants with normal or nearly normal chromosomal constitution have been selected, and progress to date indicates that this approach is likely to culminate in successful introgression of high levels of reniform nematode resistance into elite upland cotton types of G. hirsutum. Because screening for reniform nematode resistance is a time-consuming and a laborious process, we have initiated efforts to identify molecular markers closely linked to the gene(s) conferring resistance to the reniform nematode. A goal of this effort will be to enable indirect screening for the resistance gene, which will expedite and facilitate screening for resistance, i.e., enable marker-assisted selections (MAS). Initial efforts have been aimed at identifying AFLP markers linked to the reniform nematode resistance gene locus in the 12 most resistant and 12 most susceptible BC2 plants from a population of 186 classified plants. So far, three potential markers have been identified; however, the results are yet to be tested on the reniform nematode screened BC2 population. In addition to their host institutions, the authors would like to acknowledge the support of cotton Incorporated.