MSc

The study aimed at evaluating the performance of three clones of rubber viz. RRII 105, RRIM 600 and PB 235 in Ernad taluk of Malappuram district. Ten identical units in each clone were selected and details on girth and yield characters were gathered. The secondary characters such as resistance to diseases, tapping panel dryness, wind damage, yield depression during summer, dry rubber content, colour of latex etc. were studied.
The study was conducted through personal visits and with the help of a pre – tested questionnaire. Some of the details were collected from the Rubber Board Regional Officer, Nilambur and from the records mainted in the Pullengode estate.
The results of the study showed that the over all performance of the clones RRII 105 and RRIM 600 were satisfactory under the prevailing agro – climatic conditions in Malappuram district and in the hilly tract of Pullengode area. Available information from the estate showed that the highest yield was recorded for the clone RRII 105. It showed a fair degree of tolerance to abnormal leaf fall and pink disease than the other clones, but was susceptible to brown bast. The trees are being kept under the low frequency tapping system to control the occurrence of tapping panel dryness. The clone showed the lowest depression in yield of 16.19 per cent during summer. The clone recorded a dry rubber content of 39.65 per cent.
The clone RRIM 600 occupied the second place in the overall performance and yield. The incidence of abnormal leaf fall and pink disease was not so severe. The powdery mildew and brown bast incidence were low. The yield depression during summer was 18.88 per cent. It recorded the highest dry rubber content of 39.75 per cent.
Since the trees of the clone PB 235 were opened only in 1992, the yield pattern is not possible to be explained as it has not reached the stable stage. More data are required for a realistic comparison with the other clones. The susceptibility to abnormal leaf fall and powdery mildew was high. Incidence of pink disease was low. Tapping panel dryness was also not observed, perhaps being in the second year of tapping under low frequency system. The clone had light yellow latex of low dry rubber content of 31.45 per cent.
In general Pullengode estate maintains the clones, RRII 105, RRIM 600 and PB 235 selected for the study under scientific and uniform conditions. The performance of the clones, except the slight variations inherant with each clone in growth, yield, susceptibility and tolerance to disease incidence, is found to be excellent. The clones are suitable for this region under the existing agro – climatic conditions and the recommended cultural practices.