Quantifying the growth and development of commercial barley cultivars over two contrasting growing seasons in Western Australia

Abstract

The relationships between growth, development, and grain yield were examined in 3 phenologically different and commercially available barley cultivars over 2 growing seasons with very different weather patterns. Favourable conditions for crop growth in 1994 were followed by intensifying soil moisture stress over the second half of the season. In 1995, unfavourable conditions for crop growth due to saturated soils over the first half of the season were followed by favourable conditions and the growing season was extended by 1 month.

Floral initiation was delayed, and the duration of the vegetative phase extended, when conditions were favourable for initial crop growth, but durations from sowing to anthesis and maturity were advanced when conditions for favourable crop growth were reversed. Differences in seasonal conditions over different portions of the growing seasons were reflected in corresponding differences in growth occurring over those periods. Favourable conditions up to the time of awn appearance in 1994 resulted in higher maximum leaf area indices than in 1995 (5.36 v. 2.59), higher shoot numbers per plant (10.2 v. 5.7), and higher dry mass per m² (710 v. 462 g/m²). Favourable conditions after awn appearance in 1995 resulted in a higher proportional increase in dry mass over the grain development phase than in the previous year (57% v. 42%), higher grain numbers per spike (25 v. 23), greater grain size (41 v. 35 mg), and higher harvest indices (41% v. 38%). Final dry masses and grain yields, averaged over cultivars, did not differ significantly with season.

Cultivars followed the same generalised patterns of growth and development, with opportunistic interactions between differences in the timing of developmental events and transient weather conditions determining the amountof, and rate with which, dry matter accumulated and the manner in which it was partitioned. Of the developmental differences recorded only one, the timing of awn appearance (= heading), was considered a useful selection criterion. The impact of transient and unpredictable variation in seasonal weather has major implications for the interpretation of studies not replicated over seasons and for early generation selection in barley breeding programs. A methodology for minimising the confounding influences involved is proposed.