ABSTRACT

Four experiments were carried out in the Green 1-louse and Research Farm of' Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria, between 2005 and 2007, to investigate the relationships between nodulation, yield, and certain other attributes in cowpca, [1 'ig;ui unguiculata (L.) Waip.]. There were two Green 1 louse experiments involving pot-screening of 30 varieties of cowpea for nodulation, and secondly, a hybridization experiment. In the pot- screening experiment, the 30 cowpea accçssions were randomized in a total of 300 each variety being planted in ten pots, and each pot containing one plant. Nodule counts were taken five times at intervals oh two weeks. For each accession. two plants were iakeii out every \\ 0 weeks, washed, and their nodules counted in three categories, namely, Immature, functional. and Dead. Number of functional nodules at flowering was positively correlated with I 00 seed (P<0.05). It was, however, not correlated with grain yield, meaning that nodule number cannot be used as an index for indirectly improving cowpea for grain yield. Nodule number was observed to show dominance. Backcrosses differed as to the nodule parameters studied. indicating the involvement of cytoplasmic factors in the inheritance of nodulation in cowpea. The number of functional nodules reached a peak 4 weeks aller planting. Error variance fur nodule number as very high, indicating that environmental component was the domiriatit contributor to the total variability observed in respect of this character. Significant mid-parent and better-parent hcterosis were obtained !'or number of nodules. indicati ig the existence of' high genetic diversity among the co\\'pea acceSsions studied, denonsirati ug the I'casihi Ii lv of isulati I highly nodulatin; transgressivc segregants from hybrid populations.