The Genetic Source for Boron Tolerance in Barley

Abstract

Responses of barley genotypes to boron (B) were studied in two growing season, 1997/98 and 1998/99. A preliminary screening was conducted in the first season with advanced lines of barley from the Barley Thailand Yield Nurseries 97/98. The barley lines were tested in sand culture containing washed river quartz sand, watered with complete nutrient solution without added B. Boron efficient (Fang 60) and moderately inefficient (SW 41) wheat genotypes were included as checks. Barley genotypes with different levels of B tolerance were selected for further screening in the next season.

            In 1998/99, the selected barley lines and 4 wheat checks (ranging from B inefficient to efficient) were evaluated on a low B soil in a split plot design. The B levels were in main plots in four replications and genotypes were in subplots. Boron levels included nil (BO), 1 kg borax ha^-1 (B1), 10 kg borax ha^-1 (B2) and 2000 kg lime ha^-1, to accentuate B deficiency (BL). Barley genotypes were found to vary in their response to B in terms of number of grains ear^-1, grains spikelet^-1, grain set index (GSI) and grain yield.

            The range of responses found was comparable to that expressed in the wheat checks. In the low B treatments, grain set was severely depressed in many of the barley genotypes but not in BRB 9604 and BRB 9642. These two genotypes of barley appear to be as tolerant to B deficiency as Fang 60, the most B efficient wheat. Such barley genotypes may be expected to avoid B deficiency-induced grain set problem in low B soils in the Northern and Northeastern Thailand. BRB 9604 and BRB 9642 might also be used as sources of B efficiency in breeding programmes.