Evaluation of Ugandan sorghum accessions for cytoplasm male sterility status and combining ability for hybrid development.

Abstract

In sorghum, a predominantly self-pollinated crop, hybrid seed production relies exclusively on the cytoplasmic-genetic male sterility system. The system of hybrid development requires sorghum breeding programs to develop two breeding groups: a male-parent group (R-line/ fertility-restorer) and a female-parent group (an A/B line, lacking the fertility-restoring gene of the A1 male-sterility system). These have to serve as heterotic groups in sorghum breeding programs. Progressive research has been done on sorghum landraces in Ugandan ranging from breeding for resistance to diseases, to the development of open pollinated varieties. However, little work has been done to determine heterotic groups and identification of good parental lines among sorghum landraces in Uganda. This study was conducted with the objective of: 1) determining existence of potential B and R lines and; 2) determining combining ability for traits of agronomic importance and multiple stress tolerance among elite sorghum landrace accessions in Uganda.

Twenty three parents were chosen from elite germplasm and crossed with an A line (P5907) in the A1 CMS background to produce F1 crosses for testing. At the same time, these twenty three sorghum landrace accessions were planted in three crossing blocks, consisting of three mating groups following North Calorina I (NCI) mating design. Each of the mating groups consisted of one male parent and seven female parents. Twenty F1 crosses were evaluated for traits of agronomic importance and multiple stress tolerance at MUARIK in December 2010 and March 2011. This study revealed that among the Ugandan sorghum landraces, there exist two groups of genotypes that can be classified as maintainer (B) and restorer lines (R) lines based on ability to either restore or maintain an A1 cytoplasmic male sterility. The study also, showed that parent MUC007/144 was general good combiner for yield related characters and tolerant to multiple stress while parent MUC007/167 exhibited good general combining ability for earliness. Thus, Ugandan sorghum landraces offer a valuable resource for developing a breeding system for sorghum hybrids.