The LT50 values and soluble carbohydrate levels in wheat (Triticum aestivum L.) crowns and leaves were monitored throughout autumn and winter in cultivars varying in freezing tolerance and snow mold resistance during 1993/1994 and 1994/1995 in the field at Sapporo, Japan. During the first stage of hardening, from sowing to mid‐November, the pattern of accumulation of mono‐ and disaccharides was similar for all cultivars. During the second stage of cold hardening, from mid‐November to mid‐December, the greatest accumulation of mono‐ and disaccharides, without a corresponding increase in fructan, was observed among the freezing‐tolerant cultivars; and levels of simple saccharides rapidly decreased under snow cover. Conversely, levels of mono‐ and disaccharides in snow mold‐resistant cultivars were less than 70% of those in freezing‐tolerant cultivars before snow cover and maintained low levels throughout winter, while polysaccharide levels in snow mold‐resistant cultivars were about 120% of those in freezing‐tolerant cultivars in December. Sugar metabolism during the winter was examined using 18 cultivars in 1994/1995. LT50 values were correlated to the greatest extent with total mono‐ and disaccharide and fructan content among wheat cultivars excluding snow mold‐resistant cultivars in December. Snow mold‐resistant cultivars tended to metabolize carbohydrates more slowly until the end of the snow cover period. This result suggested that the enzymatic metabolism of the synthesis of sugars and the conversion of fructan to cryoprotective sugars in response to low temperatures, especially subzero ones, might be different between the two contrasting types in resistance to winter stress.

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The effects of increase in ␣-amylase and endo-protease activities during germination on the deterioration of the breadmaking quality of hard wheat were examined using three varieties with different strengths of gluten: VictoriaINTA, Harunoakebono, and Leader. The results are summarized as follows: (1) The degradation of the breadmaking quality of flour damaged in germination differed greatly according to the gluten strength of each variety. VictoriaINTA, which has extra-strong gluten, was more tolerant of the germination damage than the other varieties with strong gluten. (2) The degradation of specific loaf volume, which is caused by lowering the gas retention of the dough, was the result of the softening of the dough that was observed as a decrease in the mixing peak time and the breaking force of the dough. (3) The ␣-amylase and endo-protease activities of flours did not seemed to influence the breadmaking quality, although there was a considerably high correlation between endo-protease activity of whole wheat flour and breadmaking quality. From these results, it would seem that the main reason that flour damaged during germination degrades breadmaking quality is the endo-protease in the wheat grain, which already causes partial gluten decomposition. Accordingly, it might be better to examine the endo-protease activity of whole wheat flour at harvest ripeness in order to estimate the value of breadmaking quality within the hard-wheat breeding system. Keywords: extra-strong variety, breadmaking quality, endo-protease activity, ␣-amylase activity Most Japanese hard wheat used for bread is grown in Hokkaido; however, pre-harvest sprouting often occurs as grain develops due to unfavorable weather. This problem is serious because wheat flour that is damaged during germination has a maximum viscosity (MV) of Amylograph that is below 300 B.U. and is unsuitable for industrial processing. Many studies on germination damage in wheat deal with starch degradation, i.e., MV of Amylograph, Falling number, ␣-amylase activity and the quality of bread (MacGregor & Matsuo, 1972; Meredith & Pomernz, 1985;MacGregor & Dushnicky, 1989). However, the deterioration of breadmaking quality in flour that has been damaged during sprouting cannot always be explained by low MV values (Yamauchi et al., 1998;Sato et al., 1999). Therefore, another practical index to estimate the value of breadmaking quality is required within the hard-wheat breeding system. On the other hand, there is some evidence that the degradation of storage protein also greatly contributes to the loss of breadmaking quality during germination. (Kruger, 1971;Bushuk & Lukow, 1987;Lukow & Bushuk, 1984;Janssen et al., 1996b;Weegels et al.,1996). Studies show that an increase in ␣-amylase and endoprotease activities in wheat may lead to degradation of endosperm starch and protein during germination and may have a deleterious effect on the quality of bread (Kiribuchi & Nakamura, 1973; Preston & Kruger, 1979;Meredith & Pomeranz, 1985;Salomonsson et al., 1989; Sun & Henson,19...

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