Abstract
Long term performance of four hybrid Hevea clones and ten ortet selections including nine from a high elevation site within the traditional rubber growing tract of Kerala was studied. Significant variability was observed among the hybrids and ortets for all major agronomic traits. Growth of rubber trees was invariably poor in the high altitude region and tappability by the tenth year of planting was less than 50 per cent. The hybrid clones RRII 203 and RRIC 100 showed highest growth vigour with 80 per cent tappability by the 13th year of planting. Among the ortets, P 270 and Iritty 1 recorded the highest tappability of 64 per cent. The ortet P 270 was the best performer with the highest girth at the opening (61 cm), girth increment during immaturity (5.5 cm) on tapping (3.4 cm) and bole volume (0.1 m3). RRII 203 was the highest yielding clone with 56 g tree-1 tap-1 over eight years of tapping. High annual yield (48 g tree-1 tap-1) and lean season yield of P 270 combined with high drc on par with the highest yielding clone RRII 203 indicated the specific adaptability of this ortet to high elevation areas. The ortets P 213 and Iritty 1 and hybrid clone RRIC 100 were the other promising clones exhibiting growth adaptation and high yield potential under high altitude conditions.
Highlights
The traditional rubber growing belt in peninsular India is situated at altitudes up to 300 m MSL
These areas are characterised by high altitude above 450 MSL, heavy South West monsoon with a mean annual rainfall of 4000 mm, very low temperature in January with over-hanging mist favourable for high powdery mildew infestation, which is followed by a dry spell of four months
In India, from the early screening of high yielding mother trees, RRII 5 was a promising ortet for latex and timber yield, and RRII 33 was noted for its tolerance to abnormal leaf fall (Marattukalam et al, 1980)
Summary
The traditional rubber growing belt in peninsular India is situated at altitudes up to 300 m MSL. To formulate a region-specific recommendation of Hevea clones, the traditional belt of South India was further divided into seven regions of which tropical high altitude region of Wayanad and Idukki has been treated separately (Mydin et al, 2017). These areas are characterised by high altitude above 450 MSL, heavy South West monsoon with a mean annual rainfall of 4000 mm, very low temperature in January with over-hanging mist favourable for high powdery mildew infestation, which is followed by a dry spell of four months. The present study is the first step in this direction in Wayanad
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