新疆冬小麦地方品种高分子量麦谷蛋白亚基的地理分布及其新发现亚基的特性

[目的]和方法]为了揭示新疆小麦地方品种高分子量谷蛋白亚基( HMW - GS)的遗传多样性,对新疆北部地区(北疆)、东部地区(东疆)和南部地区(南疆)小麦地方品种HMW - GS的分布进行了研究.[结果]研究表明:新疆小麦地方品种HMW - GS等位变异的分布与其地理来源具有密切关系,除Glu - B1位点外,Glu -A1和Glu - D1位点等位变异在北部地区、东部地区和南部地区的分布频率存在显著差异.在Glu - A1位点,Glu - A1c编码的亚基出现的频率最高,其次是Glu - A1b编码的2*亚基;但在北部地区,几乎所有品种都含有Glu -A1c编码的亚基,仅有1个品种含有Glu-A1b编码的2*亚基.在Glu - B1位点,新疆大多数小麦地方品种含有Glu -B1b编码的7+8亚基.在Glu - D1位点,新发现的等位基因Glu -D1bp(t)编码的2.6亚基在东疆和南疆出现的频率较高,但在北疆出现的频率最低,分别为91;(东疆),61;(南疆),19;(北疆);等位基因Glu - D1bp(t)在南疆冬小麦地方品种中普遍存在.然而,北疆是以等位基因Glu - D1a编码的2+12亚基为主,其频率为83;.关于Glu - D1bp(t)的起源,推测可能是在南疆地区自然突变产生,然而由于南疆和东疆荒漠化造成的地理阻碍使其向北疆传播的概率较低,同时抑制了该基因向东亚地区的迁移.[结论]基于DNA序列的氨基酸序列比对,发现Glu -D1bp(t)编码的2.6亚基与Glu - D1al编码的2.2*亚基非常相似.     

Root development across a chronosequence in a Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don) plantation

We investigated the biomass, vertical distribution, and specific root length (SRL) of fine and small roots in a chronosequence of Japanese cedar (Cryptomeria japonica D. Don) plantations in Nara Prefecture, central Japan. Roots were collected from soil blocks up to 50 cm in depth in five plantations of differing age: 4, 15, 30, 41, and 88 years old. Fine-root biomass reached a maximum (639 g m₋₂) in the 15-year-old stand before canopy closure, decreased in the 30-year-old stand (422 g m₋₂), and thereafter was stable. Except in the 30-year-old stand, fine-root biomass increased in deeper soil layers as stand age increased, and the depth at which the cumulative biomass of fine roots reached 90% exhibited a good allometric relationship with mean stem diameter. Both root-length density (root length per unit soil volume) and SRL decreased with soil depth in all stands, indicating that plants mainly acquire water and nutrients from shallow soils. The highest SRL was observed in the 4-year-old stand, but the relationship between SRL and stand age was unclear in older stands. The SRL in surface soils seemed to decrease with increases in root-length density, suggesting that branching of the fine-root system during development is related to density-dependent processes rather than age.     

Specific Glu‐D1ƒ Allele Frequency of Japanese Common Wheat Compared with Distribution of Glu‐1 Alleles in Chinese Wheat

The quality of wheat (Triticum aestivum L.) grain favored in breadmaking is strongly affected by components of seed storage protein, particularly high molecular weight glutenin subunits (HMW‐GS). The HMW‐GS 2.2 controlled by the Glu‐D1ƒ allele is frequently found in Japanese cultivars and landraces. In the investigation into the factors affecting the distribution of the allele, the available data on HMW‐GS of common wheats from Japan were analyzed and compared with the data for intensity of winter habit and wheat flour hardness. We show that the main factors affecting the Glu‐D1ƒ allele frequency in Japanese wheat were the intensity of natural selection for winter habit and artificial selection for flour hardness. According to a study of the worldwide distribution of Glu‐1 alleles, the Glu‐D1ƒ allele is rare. However, Glu‐D1ƒ allele was the most common Japanese wheat seed storage protein allele. It is well known that Chinese wheat contributed to Japanese landraces, and Japanese landraces contributed to modern cultivars from Japan. However, common Japanese and Chinese wheats differ in the frequencies of Glu‐D1ƒ allele. These results may be explained either by the founder effect or by a selective bottleneck in Japanese common wheat genetic resources.