Evidence of a unique inter-allelic epistatic interaction for seed coat color in pigeonpea [Cajanus cajan (L.) Millspaugh]

Abstract

For enhancing productivity and profitability of pigeonpea (Cajanus cajan (L.) Millsp.) a hybrid breeding technology based on a cytoplasmic nuclear male-sterility (CMS) system was developed at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Among the elite hybrids 'ICPH 2671' was most out-standing with 30-35% yield advantage over local varieties. Despite its commercial release in 2010, this hybrid could not attract many growers due to its less preferred seed color. Both the parents (ICPA 2043 and ICPR 2671) of this hybrid and their crossed seeds had Greyed-orange [code no *: 167B/C (* The standard identification numbers of Royal Horticultural Society)] color. However, the commercial seeds produced on the hybrid plants surprisingly have Greyed-purple (code no: 183C) color that fetches relatively less profits. To understand the genetics of this phenomenon a cross combination was studied for seed color in F 1, F 2, and B 1C 1F 1 generations. The data suggested that three independent dominant genes controlled the expression of seed coat color. The observations further suggested the presence of two dominant genes (Brsd 1 and Brsd 2) in the male-sterile line 'ICPA 2043', 'ICPR 2671' and another dominant gene (Brsd 3) in the restorer line. In the hybrid plants genes Brsd 1 and Brsd 2 act in complementation with the third gene Brsd 3, this also acts as a modifier. The presence of Brsd 3 gene in a genotype together with Brsd 1 and/or Brsd 2 produces a strong inter-allelic epistatic interactions resulting in the Greyed-purple (183C) seed color. It was further postulated that the genetic constitution of 'ICPA 2043' is Brsd 1Brsd 1Brsd 2Brsd 2brsd 3brsd 3, while the genotype of the restorer line 'ICPR 2671' is brsd 1brsd 1brsd 2brsd 2Brsd 3Brsd 3. © 2012 The Author(s).