Most cultivated rubber tree (Hevea brasiliensis Willd. ex A. Juss.) clones in India are susceptible to abnormal leaf fall disease (ALF), which is caused by various Phytophthora species and results in yield losses of up to 40%. Because the conventional breeding programs for this perennial tree crop are complex and time consuming, we attempted to find a molecular solution to increase the tolerance of rubber trees to ALF. The expression patterns of the gene coding for the pathogenesis-related beta-1,3-glucanase (beta-glu) enzyme in a tolerant (RRII 105) and a highly susceptible (RRIM 600) clone of rubber tree were examined, following infection with ALF-causing Phytophthora meadii McRae. Infected leaf samples were collected at different times after inoculation, and RNA was extracted and subjected to Northern blot hybridization and reverse transcriptase polymerase chain reaction (RT-PCR). On hybridization with a 1.25 kb beta-glu probe, Northern blots showed a marked increase in beta-glu transcript levels in both clones 48 h after inoculation. However, compared with the susceptible RRIM 600 clone, the tolerant RRII 105 clone had a higher rate of increase and a more prolonged induction, with beta-glu transcript levels remaining high for 4 days after inoculation. In RRIM 600, the mRNA levels decreased significantly 48 h after inoculation. On re-hybridization with an 18S rRNA probe, uniform signals were detected in all the lanes, indicating that an equal amount of total RNA was present in all samples. Similar results were obtained in relative quantitative RT-PCR experiments with the housekeeping actin gene as an internal control. Thus, although induction of the beta-glu gene occurred in both tolerant and susceptible clones, the predominant difference between clones was in the intensity and duration of the response. The tolerance of clone RRII 105 may be associated with the prolonged expression of the gene following infection. The antifungal activity of these hydrolase enzymes makes them rational candidates for overexpression by genetic transformation to produce disease resistant crops.

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The study on characterization of ecotypes of banana (Musa AAB Plantain subgroup) was undertaken in the Department of Pomology and Floriculture, College of Agriculture, Vellayani during April 2016-May 2017 with the objective to characterize the various ecotypes of plantain with respect to clonal characteristics and yield potential. The study revealed that considerable variability existed between the different ecotypes of plantain. The ecotypes varied significantly with respect to all the clonal characters studied, except the number of ridges. Mettupalayam Nendran produced the highest yield but it had long duration. Zanzibar and Big Ebanga were superior in terms of finger characteristics.PSI (Pedicel Strength Index) was the highest in Mettupalayam Nendran (3.17) which was significantly higher than all other clones. The genotypes having high yield like Mettupalayam Nendran, Myndoli etc can be used in further crop improvement programmes to develop high yielding Nendran types.

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