Characterisation and Evaluation of an Indigenous Collection of Greater Yam (Dioscorea alata L.)

The germplasm holding of Dioscorea alata L. at National Bureau of Plant Genetic Resources, Regional Station, Thrissur, consisting of 182 accessions collected from different agro-ecological situations of peninsular India was subjected to characterisation and preliminary evaluation during May to January 1999–2001. Data recorded for 43 qualitative and 23 quantitative traits were analysed for frequency distribution, range, mean, standard deviation and coefficient of variation. The results showed wide range of variability in leaf length (9.77–23.83 cm), petiole length (5.43–20.0 cm), bulbillength (0.38–11.95 cm), number of bulbi!s per plant (0.66–268.33), tuber length (10.33–45.0 cm) and tuber yield per plant (0.33–4.40 kg). The bulbi!s produced by different accessions varied from very small amorphous callus-like ones to very large oblong ones. The shape of the tuber and the tuber flesh colour showed maximum range of variability. The graphical representation of variance for 20 different leaf, bulbil and tuber quantitative traits indicated large variability in leaf traits, bulbil production, tuber length and tuber perimeter. Observations on flowering indicated erratic female flowering and non-synchronisation of male and female phases. Studies on correlation between different quantitative traits showed maximum correlation coefficient of 0.9187 between basal wing length and leaf breadth. Path coefficient analysis showed maximum direct effect of 0.8296 of individual tuber weight on yield.