Genotypic competition in field beans (phaseolus vulgaris L) varieties

Abstract

Beans in Kenya are normally grown by small scale farmers in mixtures for subsistence agriculture. These mixture often comprise landraces or improved cultivars. Farmers do not select the most sui table cultivars for the combination in this system of cultivation. There is also little information available on the effects of competitive interactions on the production of such mixtures. This study was designed to study genotype interactions and hence analyse the effect of competition on the performance of established bean cultivars. It was therefore to identify the varieties best suited to varietal mixture production systems in the peasant farming sector. Four established bean cu l, tivars namely Rosecoco, Canadian Wonder, Red Haricot and Mwezi Moja planted in Kenya were used in this study. The four varieties were used to develop six biblends and each biblend comprised of equal proportion of the component varieties. The biblends and uniblends formed a total of ten treatments which were planted in a randomised compete block design at Kabete, Kakamega and Bukura. Genotype competition analysis was done according to model presented by Federer et al., (1982). (xi) It was evident from the study that there was genotypic interaction in the mixtures studied. Four forms of competition as described by Schutz et al., (1968). namely neutral effects, overcompesation (cooperati ve), undercompesation and compl imentary were observed. Among these interaction forms overcompesation was considered as the most important interaction form as it clearly pointed at yield advantage. Competi tive abil ity of various genotypes showed awider variability over seasons and locations. Ii is therefore recommended that the results from one location or season can not be used in another before it is tested. For Kabete short rains Canadian Wonder and Mwezi Moj a would be considered favourable. For Kabete during the long rains, however none of the mixture combinations for yield was favourable. For long rains at Kakamega, mixture combination of Rosecoco and Red Haricot and Rosecoco and Canadian Wonder combination could be adapted. At Bukura Rosecoco and Red Haricot combination and Rosecoco and Mwezi Moja mixtures may be favourable combinations