Predicting preharvest sprouting susceptibility in barley:: A model based on temperature during grain filling

Preharvest sprouting (PHS) susceptibility in cereals is a consequence of low grain dormancy before harvest. Dormancy loss rate depends on genotype and may also be affected by environmental conditions during seed formation. To establish a quantitative relationship between temperature and MIS susceptibility, a malting barley (Hordeum vulgare L.) cultivar, 'Quilmes Palomar', was sown on different dates over a 3-yr period to obtain a range of thermal conditions during grain filling (soil type: Aerie Argiudoll). The period from pollination to physiological maturity (PM) was adjusted to a thermal time (TT) scale, which was then divided into 50 degreesC-day intervals. Mean temperature within each interval was calculated for the different sowing dates. Grain dormancy was monitored using a germination index (Gl). We sought a linear relationship between temperature during grain filling and GI at some moment after PM. The strongest correlation (P < 0.0001) was obtained between mean temperature values within the TT interval ranging from 300 to 350C-day (T-m300.350) and GI values 12 d after PM (GI(12DAPM)). This indicates that temperature during this sensitivity window, explains variability in dormancy level among years and locations for this cultivar, and may therefore explain differences in PHS susceptibility. A regression model (GI(12DAPM) = 7.14 x (Tm300-350) - 99; r(2) = 0.95, n = 9) was generated for predicting GI values 12 d after PM, and tested on commercial plots. The linear relationship between temperature and GI after PM was confirmed, though the effect of one or more undescribed, environmental factors differing among tested locations was revealed.