825 ISBN: 978-93-5067-867-1 Systematics, Biotechnology and Bioprospecting GENETIC TOLERANCE OF WHEAT (TRITICUM AESTIVUM L. EM. THELL) UNDER BORON-DEFICIENT SOIL K. K. Sarkar, Sujaya Das (Dewanjee), S. Mukherjee and T. S. Ghimiray Abstract The major constraint against successful wheat cultivation in terai zone of West Bengal had been identified as the deficiency of boron. The deficiency of the micronutrient had been implicated as a causal factor of reduction in floret fertility along with the sharp decline in crop production. Identification oflines bearing genetic resistance to boron deficiency and their inclusion in cultivation may be considered as the best solution to this problem. To achieve the success in this direction the present investigation was carried out for the evaluation oftwenty five genotype of wheat, collected from different sources. Amongst the genotypes of wheat Sonara 64, Fang 60 and Sonalika were found to be the highly tolerant on the basis of traits like number of tillers per plant, length of spikes, number of spikelets per spike, number of seeds per spike, test weight and yield per plant. Number of spikelets per spike, number of grain per spike and yield per plant were found to be most effective for the selection of resistant lines. Genetic nature of resistance was estimated following 8 x 8 diallel experiment and tolerance was found to be polygenically controlled with the influence of additive as well as non additive gene actions. Sonalika was found as the best general combiner for a number oftraits followed by Fang 60 and Sonara 64 Key words: Triticum aestivum, Genotypes, Boron deficiency, Diallel analysis. Introduction Wheat (Triticum aestivum L.) is an important cereal crop ofIndia occupying 52.8% of its total rabi-crop grown areas and one tenth of the total global production of wheat comes from India. It is also predicted that on the basis of increasing per hectare production the total production can be raised to 109 metric tonnes from its present level of 68.7 metric tonnes (Nagarajan, 1996). It is unfortunate that maintenance of such dynamic change in some parts of West Bengal like its terai zone may not be realized because yield potentiality of wheat varieties is substantially low due to the deficiency of boron in its soil and the micronutrient has proved its importance towards grain setting and as the result of the total yield in wheat (MandaI and Ghosal, 1985; Mitra and Jana, 1991). The estimated boron concentration in terai zone was found below 0.50 ppm, the critical level for maintenance of plantgrowth and seed development in wheat (Das, 2007). Although yield of wheat can be maintained by supplementation of boron, however, it is prudent to develop resistant genotypes against the deficiency as it is the cheapest and best method to fight against such problem. In the present investigation twenty five genotypes were evaluated for identification of resistant genotypes and estimation of gene action against resistance was done following 8 x 8 diallel experiment with an aim to propose breeding strategies for the development ofhigh yielding resistant lines suitable for cultivation in terai zone of West Bengal. Materials and Methods Twenty five genotypes of wheat (Triticum aestivum L.) collected from different sources (Table 1) were evaluated for identification of resistant genotypes following Randomized Block Design with three replications in boron deficient and boron-supplemented condition separately at experimental farm of UVKV, Pundibari, maintaining 30 cm and 10 cm distance between row to row and plant to plant respectively. Recommended dose of nitrogen, phosphorus and potassium were applied and normal intercultural operations were followed. Evaluation of the genotypes were made on the basis of the traits like number of tillers per plant, length of spike, number of spikelets per spike number of grains per spike, 250 grain weight and yield per plant and these are presented in table 2. Estimation of genetic nature of resistance was made following 8 x 8 diallel experiment in the following years where the eight parents showed differential response to boron deficiency and