| A mapping population in the form of recombinant inbred lines (RILs) derived from a cross2174(a PHS tolerant genotype) and Jagger (PHS susceptible) was used for the study. In order to identify the pre-harvest sprouting resistance of the RILs, three traits (spike germination, seed germination and the activity of α-amylase) were investigated. The pre-harvest sprouting resistance of the RILs and the activity of α-amylase were determined in wheat seeds treated with different temperatures and storage durations. QTLs associated with pre-harvest sprouting were also detected in the genome of wheat. The main results were as follows:1. Continuous distributions were observed in spike germination, seed germination and α-amylase activity. A normal distribution was detected in α-amylase activity; however, there was no normal distribution observed in spike germination and seed germination. There were significant differences existed in spike germination, seed germination and the activity of α-amylase in various RILs families. Two-way separation existed in various RILs families. The color of seed coat affected the germination rate of wheat. Generally, compared with red seeds, higher germination percentage was observed in white seeds. There was no correlation between seed color and α-amylase activity because there was no significant difference in the activity of α-amylase between white seeds and red seeds. The germination percentage and the activity of α-amylase was positively correlated, but at a significant probability level only for white wheat. It indicated that it was the activity of α-amylase that mainly controlled the germination percentage of wheat seeds. But it didn’t mean that high germination percentage was caused by high activity of α-amylase, and low germination was caused by low activity of α-amylase. Perhaps there still existed some other factors affecting the germination of wheat seeds.2. The effects of temperature on seed germination were investigated in three treatments. In the first and the second treatments, the seeds were treated with35℃lasting for7d and22℃lasting for7d. In the third treatment, the seeds were treated with4℃lasting for5d and then with22℃lasting for the following7d. The germination in the first treatment was significantly decreased and significantly promoted in the third treatment. Although the germination percentage under high temperatures was significantly decreased, the activity of α-amylase was increased. Under low temperatures, the germination percentage was increased together with the increase of the activity of α-amylase. Compared with red seeds, the germination percentage and the activity of α-amylase were more affected by high temperatures in white seeds. Compared with white seeds, the germination percentage and the activity of α-amylase were more affected by low temperatures in red seeds.3. The effects of maturity and storage duration on germination percentage and a-amylase activity were studied. With the increase of grain maturity degree, the likelihood of pre-harvest sprouting increased. The pre-harvest sprouting percentage at35d after flowering was lower than that at maturity stage, which was inconsistent with previous studies reporting that the seed and pre-harvest sprouting ratio reached the maximum rate at around35d after flowering. There was significant difference in the pre-harvest sprouting percentage of red and white seeds, no matter they were treated at around35d after flowering or at maturity stage. The white seed-coat wheat varieties had weaker sprouting resistance than the red seed-coat wheat varieties. Both white and red seeds showed resistance to pre-harvest sprouting rate. The seed germination rate of parents and families increased with the extension of grain storage duration. The seed germination rate with15d storage was lower, with an average of50%; the germination rate with30d storage was higher, averaged at84%; the germination rate with45d and75d storage was higher, with an average of86%and89%, respectively. The activity of α-amylase increased with the extension of grain storage duration. Compared with white seeds, the storage duration had greater effects on the activity of α-amylase of red seeds. At the same levels of germination time and germination rate, the activity of α-amylase was significantly different among different families. And at the levels of different germination time and similar germination percentage,, the activity of α-amylase was significantly different in different families.4. QTLs associated with pre-harvest sprouting resistance in wheat were mapped, based on the combining analysis of Interval Mapping method and Multiple Interval Mapping (MIM) using Cartographer2.5software of Windows QTL. Spike and seed germination rate, the activity of α-amylase and respective variation degrees in different temperatures, storage time conditions were determined for different phenotypes. Two QTL sites were detected located at2D and3A chromosomes, respectively were QSd-2D.1, QSd-3A.2, accounting for10%-28%of phenotypic variation; the additive effect variations was1.88%to12.66%. Our study indicated that additive effect was the important genetic bases of pre-harvest sprouting which was also subjected to environmental conditions. There was no QTL detected to control the activity of α-amylase. |
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