New Hevea germplasm, its introduction and potential

The rationale and the events leading to the 1981 expedition to collect wild Hevea germplasm in Acre, Rondonia and Mato Grosso States of Brazil are described. The expedition members collected a total of 64 736 seeds and 1522 m of budwood from 194 presumably high-yielding ortet mother trees. Of the seeds collected, 50% were retained in Brazil while the balance was distributed to Malaysia (35%) and Ivory Coast (15%) for conservation, evaluation and eventually for re-distribution to other Internaional Rubber Research and Development Board (IRRDB) member countries. Out of 24 030 seeds received in Malaysia, 15 137 germinated and were quarantined for three months. Of these, 14 316 plants were eventually transplanted in the field nursery of the RRIM Experiment Station, Sungai Buloh. In the nursery, observations were made on growth vigour, leaf disease incidence and other morphological traits.

Preliminary assessments reveal considerable variation in the populations from between and within the Brazilian states. Seedling population from Rondonia appears to be more vigorous while those from Acre seem to be more tolerant to certain leaf diseases. Dwarf characteristics were observed on a few plants. In addition, morphological variations in leaf colour, shape, size and number; petiolar and leaflet orientation were noted. Observation of leaf characteristics shows a small proportion of the collected population was from interspecific hybrids or their parental species (e.g. H. guianensis and H. benthamiana); the majority of the population was from H. brasiliensis. The potential of the new Hevea germplasm in the context of production of new clones through breeding and seedlings is discussed. [Authors' abstract].