Early clonal selection of Hevea brasiliensis based on latex physiological parameters in Cambodia

Since the introduction of new rubber clones from abroad becomes more and more difficult, Cambodian Rubber Research Institute (CRRI) has to consider the possibility to create new clones in Cambodia for improving the rubber yield potential and testing their adaptation to the instability of the environment predicted by climatologists in relation with the climate change. In order to shorten the duration of new clones creation and as hand pollination garden was not developed yet, more than two thousand seeds were collected at random from old seedling trees planted in 1924 in the field 87-A of Sopheak Nika Investment Group Co., Ltd (former Chup rubber plantation) for planting and evaluation in a Seedling Evaluation Trial (SET). All the seeds were germinated and planted in the field with the spacing of 2m x 2m at the CRRI experimental station in 2012, with a total number of 1 230 seedling trees. Early tapping was carried out for 6 months in 2015 in S/2 d3 7d/7. Girth (cm), yield (g.tree-1 and g.tree-1.cm-1) and latex physiological parameters such as sucrose latex content (Suc, mM.l-1), inorganic phosphorus latex content (Pi mM.l-1) and latex DRC (%) have been measured. 20 genotypes showing the best trade-off between girth (cm), early production (g.cm-1.t-1) and latex sucrose content (mM.l-1) have been selected as the 20 most promising clones among the initial seedlings population. These 20 genotypes were characterized with a latex sucrose content increased by more than 40% when compared to the theoretical latex sucrose content deducted from their latex yield, making them candidates for a high latex yield potential, a good response to hormonal stimulation and an improved tolerance to stress. (Resume d'auteur)