Variability in Wild Germplasm of Natural Rubber (Hevea brasiliensis Muell. Arg.)

Para rubber (Hevea brasiliensis), a native of the Amazon forests of South America, is the chief source of natural rubber in the world. With the objective of broadening the original gene pool collected by Sir Henry Wickham in 1876, the International Rubber Research and Development Board (IRRDB) made a large collection of wild germplasm from Acre, Rondonia and Mato Grosso states of Brazil in 1981, which was distributed to various member countries including India for conservation and evaluation. In the present study, variability was assessed in a set of 195 Hevea accessions belonging to the wild gene pool in India, using 22 characterization descriptors and eight quantitative growth characters in the juvenile stage. The Shannon-Weaver diversity indices worked out for each of the 22 qualitative traits indicated a high level of diversity in the collection. The range of variation for quantitative traits viz., plant height (0.43 to 3.16 m), basal diameter (0.81 to 2.52 cm), number of whorls (1.23 to 5.48), inter-node length (4.11 to 45.26 cm), number of leaves (11.44 to 91.26), single leaf area (80.22 to 223.57 cm2), total leaf area (2356.00 to 14660.50 cm2) and leaf area index (0.24 to 1.47), also represented wide variability in the collection. The accessions were ranked for overall performance and top 10% were selected for early growth vigour. The high level of variability observed in this germplasm indicates its potential use in crop improvement programmes and for broadening the genetic base of Hevea.