Study of the genetic variability of quantitative characters of Pole Beans (Phaseolus vulgaris)

Abstract

A substantial genetic variability forms a good basis for a selection programme to improve the existing varieties. The efficiency of selection mainly depends on genetic variability and heritability. Therefore, a field experiment was carried out at the Horticultural Crops Research & Development Institute, Gannoruwa, to study the genetic variability o f quantitative characters in eight pole beans {Phaseolus vulgaris) varieties. Those considered quantitative characters were Days to 50% flowering, Duration of flowering, Length of inflorescence, Number of buds per inflorescence, Pod length, Pod width, Number of pods per inflorescence and 100 pods weight. The experiment was laid out in a randomized complete block design with three replicates. The important eight characters of pole bean varieties were collected with the use of characterization catalogue on pole beans developed by Plant Genetic Resource Center, Gannoruwa. Then heritability, phenotypic and genotypic coefficient of variation and genotypic and phenotypic correlation coefficient of those yield characters were estimated. The highest broad sense heritability was recorded in days to 50% flowering, length of inflorescence and pod length, indicating high response to selection based on these characters and which can be used for successful selection in a varietal improvement programmes. The highest phenotypic coefficient of variation (PCV) and the highest genotypic coefficient of variation (GCV) were recorded in the length of inflorescence while the lowest genotypic coefficient of variation was recorded for duration of flowering and lowest phenotypic coefficient of variation was recorded for the pod width. Environment effects for characters such as, days to 50% flowering, length of inflorescence, pod length and pod width were low. The reason is that, it’s phenotypic coefficient of variation and genotypic coefficient of variation are nearly similar. Correlation analysis amongst economically important traits revealed that, the phenotypic correlation coefficient was higher than genotypic correlation coefficient, indicating the masking effect of environment. Selection for increasing the 100 pods weight should primarily be based on long pods, as these two characters show significant positive correlation.