Chromosome substitution lines (CS-B) revealed the presenceof cryptic beneficial alleles in G. barbadense with potential to increase lint and seedcotton yield in Upland cotton

Sukumar Saha¹, Jixiang Wu² , Johnie N.Jenkins¹, JackC. McCarty¹, and David M. Stelly³

¹United States Department ofAgriculture-Agriculture Research Service, Crop Science Research Laboratory,Mississippi State, Mississippi 39762, ²Departmentof Plant and Soil Sciences, Mississippi State University, Mississippi State,Mississippi 39762, ³Departmentof Soil and Crop Sciences, Texas A&M University, College Station, Texas77843

One of the most promising opportunities to improve thegenetic diversity of Upland cotton is from interspecific germplasmintrogression from the other tetraploid species, including G. barbadense.  Past efforts to utilize other species assources for genetic improvement of cultivated types of G. hirsutum has been hampered by the paucity ofinformation of the beneficial alleles in the other species.  In addition to the many biological andgenetic challenges associated with the interspecific introgression, thepotential value of the wild non-adapted species is often not manifest, due toeffects of differing geneticbackgrounds, e.g., phenotypically antagonistic and deletorious genes. To test for epistatic interactions, which theoretically might havegreater influence when breeding at interspecific levels, we haveevaluated intercrosses among quasi-isogenic backcross chromosome substitution lines (CS-B), eachcarrying a different pair of alien chromosomes.  The results revealedotherwise cryptic beneficial alleles in G. barbadense (3-79) with potential to increase lint andseedcotton yield in Upland cotton (TM-1). The findings underscore the value of alien germplasm as a source of newand valuable genes, including those affecting yield and other complextraits.  More importantly, theygreatly strengthen evidence that epistatic effects are a major contributor tocomplex trait variance.  Thus,breeding methods that capture the value of epistatic interactions should bemore efficient for genetic improvement programs using alien germplasm.  The results demonstrate usefulness ofinterspecific chromosome substitution lines for detecting beneficial alleles in specific alien chromosomesand chromosome arms.  Mostsignificantly, the results underscore the value of interspecificchromosome substitution lines as a means to capture the largely untapped potential wild unadapted speciesfor the genetic improvement of cotton.