Promising latex timber clones of Hevea brasiliensis evolved by ortet selection

On the basis of systematic screening of large seedling population of mature trees originated from Tjir 1 seeds and planted in 552 ha during 1961 at Plantation Corporation of Kerala, seventy-five elite trees were initially selected for a detailed study. Forty two ortets were finally selected based on yield, girth and yield per unit length of tapping cut, of which, thirty-nine ortets were cloned and evaluated in two small scale trials with one set of 27 clones and another set of 16 clones in a randomized block design with three replications. The check clones were RRII 105 and RRIM 600 in both the trials for comparison. Clonal performance was evaluated till eight years of tapping. The criteria for evaluation were yield, yield components, girth and secondary attributes. Timber yield was estimated at the 15th year of planting in terms of clear bole volume. Significant clonal variation for the traits resulted in selection of promising latex-timber clones and promising timber yielders. Three clones viz. KnO 39, KnO 36, KnO 49 recorded a mean yield of 55.25 g t-1t-1, 53.38 g t-1t-1 and 55.97 g t-1t-1 respectively and they were showing higher yield comparable to that of RRII 105 with 50.54 g t-1t-1. These clones appear to be promising latex-timber clones as they had recorded significantly high bole volume and possess desirable secondary characters also. Seventeen clones were promising timber yielders as evident from the higher clear bole volume. The superiority of ortets with respect to specific traits is discussed in detail with emphasis to three promising selections based on latex and timber yield

Long term yield of rubber and timber in some promising Prang Besar clones in India

Nine Prang Besar clones were evaluated in a large scale trial laid out in 1989 at the Central Experiment Station of the Rubber Research Institute of India. Rubber yield and its attributes including girth, girth increment rate under tapping, summer yield and secondary traits like incidence of pink disease and tapping panel dryness (TPD), were studied along with stability in long term yield in the clones in relation to the high yielding popular clone RRII 105. Long term yield over 14 years was highest in clones PB 280 (70.7 g tree-1 tap-1), PB 312 (70 g tree-1 tap-1) and PB 314 (68.8 g tree-1 tap-1) which were comparable and superior to rest of the clones. PB 311 was the second best yielding clone with 65.5 g tree-1 tap-1 over 14 years of tapping. This clone was the only promising yielder with stability in yield over the years. In terms of summer yield , the clone PB 280, recorded the best performance in all the three panels indicating its capability to produce more latex in the summer months too when the trees undergo stresses from refoliation as well as low moisture and high temperatures. The promising yielders from the present study, clones PB 280, PB 312 and PB 314 showed very low incidence of pink disease in the immature stage with only 1.5 to 1.7 per cent trees affected. The occurrence of TPD after 16 years of tapping was lowest in clone PB 280 (10.7%) and high in PB 314 (26.6 per cent). Estimates of genetic parameters revealed rubber yield and bole volume to be highly heritable traits. Correlations revealed yield per unit girth to have a close relationship with yield over 14 years and summer yield over 11 years. Clone PB 280 has proven to be a high yielding clone with very good secondary attributes like low incidence of pink disease and TPD. Clone PB 312 has proved its merit as a very promising latex timber clone. PB 314, among the best rubber yielding clones with a high yield per unit girth (0.8 g dry rubber cm-1 girth), though prone to TPD, has shown a low incidence of pink disease. The study indicates scope for further upgradation of clones PB 280, PB 312 and PB 314 in the planting recommendations for the traditional rubber growing regions of India

Influence of young and mature budwood plants on growth and tappability of rubber

Healthy buds from four year old young budwood plants, 20 year old mature budwood plants and 20 year old mature trees were collected and bud grafted onto seedling stock of recommended age and size in the ground nursery and the resultant budded stumps were raised in polybags. The plants were subjected to field evaluation during 2006. At the age of seven years, trees raised from young budwood plants recorded mean girth of 45.6 cm,while those from mature budwood plants had mean girth of 42.2 cm and trees raised from buds of mature trees showed significantly inferior girth of 33.7 cm. Trees raised from young budwood plants showed lesser tree to tree variation (CV: 12.76-14.79) coupled with significantly higher percentage of tappability (60.17%). Trees raised from mature budwood plants recorded higher tree to tree variation (CV: 15.47-19.68) with 39 per cent tappability. Plants developed from the tree buds recorded only 11 per cent tappability (CV: 23.11). Present study indicated that trees generated from young budwood plants showed higher tappability with better uniformity in girth than trees raised from mature budwood plants and mature trees

Reaction of the polycross progenies to two major leaf diseases of rubber (Hevea brasiliensis)

A three-year study was undertaken to evaluate the polycross progeny of prepotent clones for their tolerance/susceptibility for abnormal leaf fall (ALF) disease caused by Phytophthora spp. and powdery mildew (PM) disease caused by Oidium heveae at the Central Experiment Station of Rubber Research Institute of India at Chethackal in Ranni. The clones were evaluated during 11th to 13th year after planting. The data obtained were analysed and computed progeny wise and clone wise. The pooled data of three years showed that for ALF disease, the clone P 128 (progeny of AVT 73) was superior over other clones with leaf retention of 76 per cent followed by the clones P 75 (progeny of PB 217) and P 69 (progeny of PB 252) showing leaf retention of 75 per cent. However, the evaluation of the progenies and clones within each progeny against PM disease were not encouraging as lot of variation was observed among the progenies and clones and the disease intensity in general, was very high. The pooled data of three years of assessment on PM disease revealed that the clone P60 evolved from the progeny of RRII 105 and the clones P 54 and P 104 evolved from the progeny of 5/76 showed less than 25 per cent of PDI and thus, were tolerant. The ALF disease tolerant clones P 132, P 69 and P 128 are also reported to be promising in terms of latex and timber yield

Growth and yield of new generation clones of Hevea under the agroclimate of sub-Himalayan West Bengal

Five rubber (Hevea brasiliensis) clones of the RRII 400 series derived from a cross involving RRII 105 and RRIC 100, along with five other popular clones viz. PB 217, RRII 176, RRII 203, RRII 105 and RRIM 600, were evaluated in Jalpaiguri district of sub- Himalayan West Bengal. Growth of clones in the immature and mature phases, rubber yield over seven years of tapping, biomass and timber yield were recorded for assessing the suitability of clones to the region. Clones RRII 429, RRII 417 and RRII 203 were superior in performance in the region compared to the recommended clone RRIM 600. Estimates of genetic parameters revealed comparatively high heritability and scope for improvement of rubber yield by selection