Screening wheat for boron efficiency

Abstract

Boron deficiency causes grain set failure in wheat (Triticum aestivum), but a wide range of genotypic variation in boron (B) efficiency has been identified. This paper shows how wheat genotypes may be evaluated for B efficiency. Two sets of genotypes were screened in sand culture in Thailand and in the field in Nepal and Thailand. One set of genotypes, identified as Boron Screening Nursery 1992/93 (BSN 92/93), included 32 genotypes plus seven replicates each of the B inefficient cultivar SW41, and the more efficient Sonora 64, as checks. The other set, Thailand Observation Nursery 1995/96 (TON 95/96), included 56 genotypes and 8 replicates each of check cultivars Sonora 64, Insee 1 and the highly efficient Fang 60. Both the BSN 92/93 and TON 95/96 were evaluated in sand culture with two levels of B added to the nutrient solution, 0 and 1 μM (BO and B+). BSN 92/93 was also grown on a low B soil (hot water soluble, HWS, B at 0.1 mg kg-1) in the field in Nepal. Field evaluation of the TON 95/96 in Thailand was conducted on a sandy loam with two levels of B, 0.1 and 0.2 mg HWSB kg-1 (BL and BH). The response of genotypes to B was measured with the Grain Set Index (GSI). A wide range of B efficiency was expressed among the genotypes in both nurseries. An almost 1:1 relationship was found between GSI in BO and GSI in BO expressed as % of the GSI in B+, and similarly between GSI in BL and GSI in BL expressed as % of GSI in BH with field grown TON 95/96, R2 0.95–0.98 (p <0.001). In sand culture with B0, the very inefficient genotypes set only a few grains per ear while grain set in efficient genotypes approached that in B sufficiency. The effect of B deficiency on grain set in the field was less severe, but the average GSI of genotypes in each group correlated closely (R2 0.82–0.90) with their GSI in BO sand culture. It is suggested that by including B efficient and B inefficient checks, and using GSI to measure plant response, wheat genotypes may be evaluated for their B efficiency without any need for a B sufficient control.