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The random amplified polymorphic DNA (RAPD) procedure was used to examine the genetic variability among 8 isolates of Trichoderma harzianum, and their ability to antagonize Sclerotium rolfsii using a dual culture assay was correlated with RAPD profiles. Eight oligodeoxynucleotide primers were selected for the RAPD assays, which resulted in 86 bands for 8 isolates of T. harzianum. The data were entered into a binary matrix and a similarity matrix was constructed using the DICE similarity (SD) index. An unweighted pair grouping mathematical averaging (UPGMA) cluster based on SD values was generated using the NTSYS computer program. A mean coefficient of similarity obtained for pairwise comparisons was c. 30% and it showed that the variability among the isolates of T. harzianum was very high. Using the dual culture method in antagonism experiments, the T. harzianum isolates were classified in to antagonism classes. Further, T. harzianum isolates were screened for chitinase and b-1,3-glucanase activity. RAPD was efficient in demonstrating the high intraspecific genetic variation among isolates. The dendrogram did not show the grouping of isolates by their level of antagonism. Relationship among polymorphism existent, the aggressiveness and the origin of isolates were not found.

Alternative agricultural systems, like organic farming, that are less chemical intensive, less exploitative and environment friendly are gaining popularity. Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is an important starchy tuberous vegetable with high nutritive and medicinal values. Since information on the organic farming of tuberous vegetables is scanty, field experiments were conducted in this crop at the Central Tuber Crops Research Institute, India, over a 5-year period. The impact of organic, conventional, traditional and biofertilizer production systems on growth, yield, quality, soil physico-chemical properties and economics were evaluated in elephant foot yam. Our results show that organic farming favoured canopy growth, corm biomass and lowered collar rot disease. Dry matter and starch contents of organic corms were significantly higher than those of conventional corms by 7% and 13%, respectively. Organic corms had 12% higher crude protein and 21% significantly lower oxalate contents. The content of K, Ca and Mg in corms were slightly higher, by 3-7% under organic farming. After 5 years of farming, the organic plots showed significantly higher pH, by 0.77 unit, and higher organic C by 19%. The exchangeable Mg, available Cu, Mn and Fe contents were also significantly higher. Organic management lowered the bulk density by 2.3%, improved the water-holding capacity by 28.4% and the porosity of soil by 16.5%. In short, organic farming proved superior and produced 20% higher yield (57.097 t ha ). The net profit was 28% higher and an additional income of Indian Rs. 47,716 ha −1 was obtained. Thus organic farming was found to be an eco-friendly management strategy in elephant foot yam for sustainable yield of quality tubers and higher profit besides maintaining soil health. Technologies for organic production involving farmyard manure incubated with bioinoculants, green manuring, neem cake, biofertilizers and ash were also standardized.

The corms and leaves of elephant foot yams (Amorphophallus paeoniifolius (Dennst.) Nicolson) are important foods in the local diet in many Asian regions. The crop has high productivity and wide agroecological adaptation and exhibits suitability for the agroforestry system. Although the plant is assumed to reproduce via panmixia, a comprehensive study on the genetic background across regions to enhance wider consumer palatability is still lacking. Here, ten informative microsatellites were analyzed in 29 populations across regions in India, Indonesia and Thailand to understand the genetic diversity, population structure and distribution to improve breeding and conservation programs. The genetic diversity was high among and within regions. Some populations exhibited excess heterozygosity and bottlenecking. Pairwise FST indicated very high genetic differentiation across regions (FST = 0.274), and the Asian population was unlikely to be panmictic. Phylogenetic tree construction grouped the populations according to country of origin with the exception of the Medan population from Indonesia. The current gene flow was apparent within the regions but was restricted among the regions. The present study revealed that Indonesia and Thailand populations could be alternative centers of the gene pool, together with India. Consequently, regional action should be incorporated in genetic conservation and breeding efforts to develop new varieties with global acceptance.

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