Combining Ability of Cowpea (Vigna unguiculata (L) Walp) Genotypes for Resistance to Cowpea Bacterial Blight in Uganda

Abstract

The low productivity of cowpea is partly attributed to a number of constraints including diseases such as cowpea bacterial blight (CoBB). Cowpea bacterial blight has the capacity to cause up to 92% yield loss under severe infections. The objective of this study was to determine the combining ability for resistance to CoBB among cowpea genotypes in Uganda. Nine selected parents were crossed to produce 63 progenies. F1 progenies were evaluated and data gathered included days to 50% flowering, CoBB disease scores and grain yield. The mean squares for rAUDPC due to GCA and SCA effects were significant (P≤0.001) and non-significant respectively. The broad sense coefficient of genetic determination (BCGD) and narrow sense coefficient of genetic determination (NCGD) were 44.3% and 29.1% respectively for rAUDPC. Parents WC 26 (-0.023) and NE 31 (-0.035) had highly significant negative GCA effects for rAUDPC and were therefore good general combiners for this trait. Crosses SECOW 3B x ACC 26 X SECOW 1T and WC 26 x NE 32 had negative significant SCA effect for rAUDPC with a values of -0.073 and -0.06, respectively while Crosses ACC 26 x SECOW 1T x NE 40 (-0.07) and NE 40 x WC 26 (-0.06) had significant negative reciprocal effects for rAUDPC. This study revealed that genetic inheritance for cowpea bacterial blight was controlled predominantly by additive gene effects. Parents WC 26 and NE 31 identified as good general combiners for resistance to CoBB could be utilized as sources of resistance while Crosses SECOW 3B x ACC 26 X SECOW 1T, WC 26 x NE 32, ACC 26 X SECOW 1T x NE 40 and NE 40 x WC 26 that were the best specific combiners for resistance to CoBB could be put under further evaluation as potential varieties.