VARIATION IN STERILITY AMONG WHEAT (TRITICUM-AESTIVUM L) GENOTYPES INRESPONSE TO BORON DEFICIENCY IN NEPAL

Two field experiments were carried out at the Khairanitar Farm, Nepal during the winter season of 1993 to investigate whether wheat genotype s differ in their sterility response to low soil boron and whether bor on added to soil can correct sterility. A nursery consisting of 41 div erse genotypes from Nepal, India, Bangladesh, Thailand, China, Pakista n and CIMMYT/Mexico were evaluated in a plot where severe sterility ha d been observed in previous years. The second experiment involved six genotypes of known sterility responses to boron grown with or without an application of boron at 1 kg ha(-1). Large differences were observe d among genotypes in terms of number of grain set per ear (range 0.5 t o 30) and sterility (5.5% to 97.5%). About one third of all the genoty pes had <25% sterility and 16 of them suffered >75% sterility. The gen otypes Fang-60, Sonalika, De Mai 6-22, BUC/FLK/MYNA/VL and HDW-234 wer e highly tolerant to boron deficiency with <10% sterility. In sharp co ntrast, genotypes BOW/BUT, SERI/THB, Glennson, SW-41, Yunmai-33 and UH U were highly susceptible and set virtually no grains in the boron def icient plots. Strong responses to boron application were observed and genotypic variations were evident. Boron at 1 kg ha(-1) significantly reduced the number of late ears, increased number of grains per ear an d grain yield in boron-responsive genotypes. Tolerant genotypes were n ot influenced by added boron. Given these striking genetic differences , progress in breeding wheat for B-deficient soils in Nepal should be worthwhile.