The effect of size and type of polybags and that of nursery practices on rooting characteristics of polybagged plants of Hevea brasiliensis was studied. Direct seeding in polybags significantly increased the length, girth and dry weight of tap roots. The lateral and feeder roots were more for plants raised by direct seeding. In general, larger polybags had a positive effect on root growth. Retaining the plants in the polybags beyond 10 months after sowing resulted in curling of tap root. It was concluded that polybagged plants raised by direct seeding had better root growth, which helped in their better survival on field planting

Latex foam was prepared from natural rubber and a blend of natural rubber and styrene butadiene rubber using rubber seed oil soap as well as potassium oleate. Evaluation of the properties indicated that the quality of foam obtained using rubber seed oil soap was comparable to that of the foam prepared using potassium oleate and conformed to Bureau of Indian Standards (BIS) specification for latex foam. Rubber seed oil soap was also found to be comparable to potassium oleate as foaming agent in blends of NR and SBR latices for foam production. 

Phylogenetic relationship was studied among three species of rubber available in India, Hevea brasiliensis, H. benthamiana and H. spruceana by employing different molecular marker techniques namely, RAPD, chloroplast DNA (cpDNA) PCR-RFLP and heterologous chloroplast microsatellites. RAPD analysis clearly indicated a high degree of polymor­phism among the three species. Using twenty-five arbitrary primers, a total of 305 bands were amplified in the clones RRII 105 and GT 1 belonging to H. brasiliensis, H. bentbamiana, H spruceana and FX 516, an interspecific hybrid of H. benthamiana and H. brasiliensis, out of which 256 bands were polymorphic. Analysis of the interrelationships among the species clearly revealed that the clones of H. brasiliensis (>50% genetic dissimilarity) are closer to H. benthamiana than to H. spruceana (>70% genetic dissimilarity). Species-specific RAPD markers were identified for each species and their locus specificity was proved through hybridization. RFLP analysis using three hyper variable intergenic spacers, rbcL-ORF106, trnM-rbcL and trnC-trnD could not detect variability. Among different primer­-pairs for heterologous chloroplast microsatellites tested, five could successfully be amplified, of which one (ccmp6) was highly polymorphic and could detect both intra- and inter-species polymorphism to prove the maternal mode of inheritance of the chloroplast genome in Hevea. 

The insecticidal property of rubber seed oil against the cowpea bruchid, Callosobruchus maculatus in stored cowpea was investigated. Rubber seed oil (RSO) was tested at five levels, namely, 2.5, 5, 7.5, 10 and 20 ml/kg cowpea seed (Vigna unguiculata L. Walp.) against C. maculatus. The oil dissolved in petroleum ether was applied on the seed coat. The effectiveness of the RSO was assessed by recording the emergence of adult beetle from the RSO treated seed, percentage seed germination, percentage weight loss and ill effects on quality of seed such as taste and smell. Application of the RSO at 1.92 per cent concentration protected stored cowpea against C. maculatus for a period of five months after application, with no subsequent damage to the viability of the cowpea. Emergence of adult weevils was completely inhibited at this concentration. The germination percentage in all the treatment combinations was not significant. The untreated control recorded the highest per cent germination. 

The availability of soil applied phosphorus (P) to rubber (Hevea brasiliensis) cultivated in Kerala State in India is a major limiting factor as the soils are prone to P fixation due to high content of Fe and AI oxides. Phosphorus fractions and fixation of added P were determined in four major soil series viz., Kanjirapally (Kpl), Thiruvanchoor (Tvr), Kadambanad (Kdb) and Kunnathur (Ktr) representing Central Kerala, where rubber is grown extensively. The relationship of the soil properties with P fractions and P fixation capacity of soil were worked out. The results revealed that total and active P varied and a fairly good P reserve was present in the soil. Iron-P was the dominant P fraction in all the soils and was present in relatively higher amounts in soils of Tvr series. All these soils had appreciable amounts of reductant soluble P (11 to 69 mg/kg) which is regarded as the most difficult fraction to release P. Fixation of added P ranged from 84 to 91 per cent, with a mean value of 86 per cent, indicating a high P retention capacity of these soils. Among the four soil series, the fixation of P in Kpl series (88%) was higher. P fixation had significant positive correlation with clay content, organic carbon, oxalate extractable AI and Fe contents and negatively with Bray II-P 

Rubber (Hevea brasiliensis) is being cultivated in non-conventional areas viz., upland paddy fields, lowlands and coastal sand belts within the traditional region of Kerala, India. These areas differ in soil characteristics and production potential among themselves as well as from the traditional rubber growing slope lands. Present study examines the difference in soil characteristics and yield of rubber plantations raised in these land forms and their relationships besides leaf nutrient content. The texture of soil of upland paddy fields varied from sandy loam to clay while low land soils were sandy clay loam to clay loam. Coastal sandy soils contained higher amount of sand throughout the profile. Moisture content at field capacity (FC), permanent wilting point (PWP) and available water content showed wider variations between land forms. The silt and clay had a significant positive influence on FC and PWP. The study showed that the performance of rubber in upland paddy fields and low lying areas is appreciable with respect to growth (gestation period) and yield. With appropriate agromanagement practices, good growth of rubber was observed in sandy soils also, though conventionally sandy soils are considered unsuitable. Significant difference between group variability in mean yield was observed indicating the difference in production potentials of land forms studied.