EVALUATION OF HALF-SIB PROGENIES UNDER TWO DIFFERENT AGRO-CLIMATIC REGIONS
Clonal nursery evaluation has emerged as a useful technique to reduce the time span of breeding in Hevea. This paper reports the performance of half-sib progenies from eight parental clones under clonal nursery trials in two different agro-climatic regions namely Padiyoor in North Kerala having dry sub humid conditions and Chethackal in Central Kerala with ideal conditions for rubber. Three important juvenile parameters viz., girth, yield on test incision and yield on test tap were employed for the study. Clones in general showed lower girth and yield in Padiyoor compared to Chethackal, indicative of the effect of climatic stress existing in Padiyoor. Out of the 15 top performing clones at Chethackal, 9 clones were among the top 15 at Padiyoor also. Hence, these clones can be considered stable and may have the potential for cultivation in varied agro-climatic conditions. Half-sib progenies from PB 255, PB 260, GT 1, RRII 203, PB 28/83 and PB 217 maintained superiority in the clonal population of progenies reconfirming the prepotency of the parent clones. Correlation analysis showed that girth from 12th month onwards is highly correlated with girth in subsequent years suggesting that clones with good growth potential can be identified from the very first year itself. Yield on test incision was highly correlated with test tap yield on 24 months at Chethackal and 24 and 48 months at Padiyoor. Girth recorded in plants from 18th month onwards showed significant correlation with yield at Chethackal and Padiyoor except in the final test tap yield at Padiyoor. Yield on test tapping in 24 months was highly correlated positively with final test tap yield (48 months) in both the locations suggesting that test tap yield in 24 months itself can be used for the identification of a potentially high yielding clone.
Keywords: Hevea, clonal nursery, half-sib progeny, test incision, test tapping