Selection of Superior Genotypes at Early Stage of the Rubber (Hevea brasiliensis) Breeding Cycle

Hybridization and selection procedure of Hevea brasiliensis plays an important role in genetic improvement of planting material with a wide range of genetic diversity aim to develop superior Hevea clones. Time is the critical factor of the conventional breeding program, as it needs around 20-25 years to complete a one cycle. Early selection is very important to shorten the Hevea breeding program. However the selections are needed to be strengthen through thorough analysis of all possible yield parameters. This study mainly aimed to precise selection of genetically superior genotype(s) at early stage of the Hevea breeding cycle (first evaluation stage) to reduce the evaluation period of breeding cycle.  Preliminary four outstanding genotypes which were already selected from 2011 hand pollination progeny were taken to the study. Performances were monitored using more yield parameters as girth, bark thickness and bark anatomical parameters such as number of latex vessels per unit area (density), number of latex vessel rows and diameter of latex vessels. Each parameter was analyzed with their yield performance. These parameters analyzed to verify the previous preliminary selections as well to develop the correlation of these parameters with high yield. Regression analysis, cluster analysis and two sample t-test in Minitab 17 version were used to analysis of data. It has observed around 39.3% positive correlation between yield and girth and around 4.6% negative correlation between yield and bark thickness. Strong positive correlations between yield and latex vessels’ density and between yield and number of latex vessel rows were observed with 81.9% and 91.7% respectively. In addition to 57.4% negative correlation was observed between yield and diameter of latex vessels. In the cluster analysis with yield, girth and all the bark anatomical parameters, three clusters showed significant difference. Out of four preliminary selected outstanding genotypes only the 2011HP42 clearly separated from other three genotypes showing higher performances than other three genotypes. All four low yielding genotypes separated in to cluster three showed the poor performances. Results clearly showed that the precise early selections can be done by taking more yield parameters and their correlations will be helpful to develop a yield indexes in future. However, further studies need to be carried out with more number of genotypes to strengthen the precise early selection procedure.