A study on the relationship between latex yield and antecedent environmental data was undertaken for five clones (RRII203, RRII118, RRIM600, RRII105 and GT1) of Hevea brasiliensis (rubber) in Agartala, northeast India, a region in which rubber is not traditionally cultivated. The explained variance for the regression equations based on parameters determined on the day of tapping and up to 3 days prior to it, varied from 72% to 37% during the NWT period and 94-83% during the WT period. Soil moisture storage, 1 and 3 days prior to tapping, was found to be the primary parameter affecting yield for the NWT and WT periods, respectively. It was observed that the clone RRII105, with a comparatively lower yield to that of RRIM600, was more susceptible to daily WD conditions during the non-winter season. RRIM600 and RRII105 being high-yielding clones were also found to be fairly dependent on the AT of the day prior to tapping. The mean lag period correlation of this parameter with yield was also found to be higher during the WT period than during the NWT period. As a whole, the mean lag period based on prior measurements of environmental variables showed optimum correlation with yield at 15-20 days prior to the day of tapping. The study also confirms that varied responses of yield with environmental factors in this non-traditional region of rubber cultivation depend on clonal character.

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(India) to identify the prepotent mother clones suitable for future breeding programmes in this region. Fully matured seeds were collected directly from the trees of the individual clones of Hevea and put on the germination bed. The germinated seeds were planted in two fields 10 days after collection. Growth observations viz. plant height, plant girth, number of whorls and the number of leaves were recorded annually before the start of the test tapping. After that all the seedlings were subjected to 10 test tapping. In 2008-trial the selected plants showed mean test tap yield range from 3.3-6.06 g t-1 10 t-1 in which the maximum yield was recorded in the clone PB 5/51 (6.06 g t-1 10 t-1) and minimum was in RRIM 600 (3.3 g t-1 10 t-1) whereas in 2009-trial the selected plants showed mean test tap yield range from 2.4-5.4 g t-1 10 t-1. The maximum yield in 2009 trial was recorded in RRII 105 (5.4 g t-1 10 t-1) and minimum was in GL 1 (2.4 g t-1 10 t-1). On the basis of the test tap yield the top yielding seedlings were selected and the selected bud-woods are maintained in the field for further breeding evaluation programme.