Genetic divergence in landraces of pumpkin (Cucurbita moschata Duch. ex. Poir.)

Pumpkin (Cucurbita moschata), a nutritious underutilized cucurbit, exhibits wide variability owing to its monoecious and cross pollination nature. However, no systematic crop improvement research has been attempted in India. Collection of genetic resources and systematic study of the nature and magnitude of genetic divergence would help the breeder in choosing the right type of parents for a hybridization programme. In total 48 local landraces of pumpkin were collected from farmers' fields all over Tamil Nadu and were selfed continuously for five generation to obtain homozygosity. A field experiment on genetic divergence was conducted with the selfed seeds of all the 48 homozygous lines of pumpkin at the Horticultural College and Research Institute, Periyakulam, Theni (District), Tamil Nadu, India during 2012-2014. The experiment was laid out in a randomized block design with three replications. Selfed seeds of all the genotypes were sown in a pit size of 45 cm³ and at a spacing of 2.5×2.5 m. In total eleven biometrical observations were made from randomly selected ten plants from each genotype and the mean values were used for statistical analysis. The results revealed that the highest variation was found in vine length (cm), fruit girth (cm), fruit length (cm) and days to first female flower. On the basis of D² values 48 pumpkin genotypes were grouped into five clusters suggesting the existence of genetic diversity among the genotypes. From the result it was also observed that the genotypes of same origin distributed in different clusters indicates that geographic diversity may not necessarily be related with genetic diversity. The inter-cluster distances in all the cases were larger than intra-cluster distances indicating the presence of a high range of genetic diversity in the experimental materials. The inter-cluster distance ranged from 11.071 to 32.029. It is expected that crossing of lines belonging to high D² values tend to produce high heterosis. The highest inter-cluster distance was observed between clusters III and IV. Hence, the crosses between the lines CM (P) 41 and CM (P) 42 in cluster III and the lines CM (P) 33, CM (P) 34, CM (P) 35, CM (P) 40 and CM (P) 43 in cluster IV would exhibit the highest heterosis and produce new recombinants with desired traits in pumpkin.