Phenological Variability: Effect on Determination of Leaf Water Loss in Wheat

Abstract

Low rate of water loss (RWL) from excised leaves has been suggested for screening wheat (Triticum spp.) genotypes for adaptation to dry growing conditions. Large‐scale RWL screening of phenologically diverse genotypes could be difficult, because RWL is known to vary within genotypes with leaf age and insertion level. To evaluate the effect of phenological diversity on measurement of RWL, 10 durum wheat (T. turgidum L. var. durum) genotypes were grown for 3 yr (1988‐1990), each with three planting dates, on an Aridic Haploboroll at Swift Current, SK, Canada. Heading dates of the genotypes varied by an average of 7 d; across seeding dates, the heading date range was 19 to 32 d. Leaves were sampled from the three seeding dates for RWL determination at various growth stages. Genotype seeding date interactions were significant (P < 0.01) in many cases, but significant (P = 0.05) changes in genotype rank order occurred for only one sampling date in 1989, and for three dates in 1990. Similarly, there were significant (P < 0.01) genotype × sampling day interactions within seeding dates and some significant (P = 0.05) changes in genotype rank order. In most cases the rank changes were comparisons in which some genotypes had passed the heading stage and others had not. It appears that RWL screening of phenologically diverse genotypes is possible with low risk of genotype growth stage interactions, provided that sampling is completed before any genotypes reach the heading stage of growth.