Evaluation of Methods Used in Testing Winter Wheat Susceptibility to Preharvest Sprouting¹

Abstract

Rains after wheat (Triticum aestivum L.) is physiologically ripe can cause preharvest sprouting which can lower the baking quality of flour due to de novo synthesis of alpha‐amylase. A fast, repeatable method is needed by plant breeders to screen wheat lines for their susceptibility to preharvest sprouting. In this study, three winter wheat cultivars varying in susceptibility to preharvest sprouting were grown in six different environments within the Pacific Northwest and were used to evaluate four germination and three enzymatic tests that measure sprouting susceptibility. Germination tests were performed with intact spikes and threshed seeds at four temperatures (15, 20, 25, and 30°C). Enzymatic tests were performed using flour milled from seeds that had been germinated at 15°C. The evaluation was based on 15 parameters of sprouting measured in the various tests. For a sprouting parameter to be considered a useful indicator of sprouting susceptibility it had to show significant (P < 0.05) differences in both cultivar and environmental effects at a given germination temperature, and its coefficient of variation had to be low. A germination test using intact spikes rolled in paper towels and one using threshed seeds in petri dishes at 20°C were the only tests that yielded parameters meeting the required criteria. Although disadvantages and advantages are associated with each of the parameters examined, germination tests were better in predicting sprouting susceptibility whereas enzymatic tests were better in quantifying actual sprout damage.

Components of variation, heritabilities and correlations for indices of sprouting tolerance and seed dormancy in Triticum spp.

“…(1989) obtained a significant positive correlation in 7 out of 9 comparisons between tests that measured sprouting of kernels in intact spikes and germination tests performed on threshed spikes . Similarly, Hagemann and Ciha (1984) detected a significant correlation between assays that measured sprouting of kernels in intact spikes and germination tests performed on threshed spikes at temperature treatments of 25'C and 30'C, but not at 15'C or 20'C . A significant positive correlation between values for sprouting of kernels in intact spikes and alpha-amylase activity in the kernels has been reported by Bhatt et al .…”

“…(1989) obtained a significant positive correlation for 7 out of 9 comparisons between assays that measured sprouting of kernels in intact spikes and embryo germination tests . Hagemann and Ciha (1984) reported a significant correlation between tests that measured sprouting of kernels in intact spikes and embryo germination tests performed at higher temperatures but not lower temperatures .…”

“…(1989) . Hagemann & Ciha (1984) obtained a significant correlation between both a germination index (GI) and percent germination (PG) with falling number values on ungerminated seeds, but neither GI nor PG was correlated with alpha-amylase activity in ungerminated seeds . They attributed these apparently anomalous correlations to the absence of de novo synthesis of alpha-amylase enzyme in ungerminated seeds, although endosperm degradation had already occurred by the time the samples were harvested at 11% moisture content .…”

“…(1989), Derera et al . (1977), and Hagemann & Ciha (1984) might be attributable to one or more of the following : (1) * * * Corresponding proportion of genetic ((y) or genotype-year interaction (o2) variance estimate is significantly greater than zero at the 0.05 and 0.01 level of probability, respectively . Sprouting of kernels in wetted spikes may be affected not only by characteristics associated with the morphology and biochemistry of the spike, but also by endogenous inhibitors and SD of the kernel itself (see review by Mares, 1989) .…”

Tolerância à germinação na espiga em cultivares de trigo colhido na maturação fisiológica

“…A condição propícia para simular a precipitação na pré-colheita, provocando a germinação na espiga, foi obtida pelo emprego de um simulador de chuva em uma casa de vegetação. O modelo corresponde a uma versão do simulador usado por OKUYAMA et al (2003), com suporte no modelo obtido por McMASTER & DERERA (1976) e HAGEMANN & CIHA (1984). Para distribuir as espigas em mesas, foram colocados isopores de poliestireno de 6cm de espessura, com perfurações equidistantes 5cm umas das outras, na horizontal e na vertical.…”