Patterns of Inheritance of Maturity Characteristics and Pod Fill Period of Tropically Adapted Common Beans, (Phaseolus vulgaris I.) Early x Late Crosses

Abstract

Two early maturing determinate pure lines TMO 101 (PI) and TMO 216 (Pl) were crossed to two late maturing lines A87 (P5) and CIAT 16-1 (P6) in order to study the inheritance pattern on maturity characteristics. Parental lines and F₂ seeds of PI x P5 and P6 were planted in the fieid in a randomized complete block design wIth three replications at the Sokoine University of agriculture farm. Frequency distribution tables for maturity traits were prepared and segregation data tested by the Chi- square test. A continuous distribution for number of days to first flower were observed in F₂ TMO 2I6 x CIAT I6-1 while for cross TMO 101 x A87 it seemed to be skewed on the early side. Results show that more than one gene is involved in controlling days' to first flower especially fqr the 'cross TMO 216 x CIAT 16-1. A satisfactory fit to a 1:2: I segregation ratio of early, intermediate and late flowering plants occurred in both crosses. Results showed that days to first flower (DFF) in both crosses were controlled primarily by additive gene action. Transgressive segregation for lateness occurred in the cross (TMO 216 x CIAT 16-I). The segregation data fitted a 13:3 ratio suggesting segregation of two major genes, dominantfor late maturity. Days to maturity (DM) in the cross TMO 101 x A87 was found to be monogenically controlled with partial dominance for earliness. Transgressive segregation for long reproductive period was observed in the F₂ of cross TMO 216 x CIAT 16-1 indicating some quantitative inheritance for this trait. The segregation data did not fit the expected ratio of 3:1, further suggesting the involvement of many genes with small effects. For both crosses the data shows continuous distribution in pod fill period-2. Pod fill period-2 was found to be inherited quantitatively in the cross TMO 216 x CIAT16-1. The knowledge obtained from this study together with heritability, values obtained from other studies will be valuable in detamining breeding procedures for improvement of maturity characteristics and podflll periods in tropical conditions.

Keywords: Maturity characteristics, common beans, patterns of inheritance

Tanzania J.Agric.Sc. (2006) Vol.7 No.1, 42-49