在异源多倍体形成的早期，DNA序列和基因的表达迅速发生了改变。以异源六倍体小麦为例，比较了四倍体小麦与节节麦合成六倍体小麦前后，位于普通小麦D染色体组不同染色体臂上的特异性引物揭示的微卫星位点变化特点。结果表明，从四倍体小麦与节节麦杂交，将A，B与D染色体组结合在一起并加倍得到AABBDD的六倍体小麦这一“剧烈事件”中：（ⅰ）微卫星的侧翼序列发生了变化，导致出现了供体物种没有的新带纹或供体物种的带纹消失，其中，供体物种的带纹消失是主要的。（ⅱ）供体物种的带纹消失不是随机的，而是四倍体小麦消失频率远高于节节麦的频率，即发生在A，B染色体组的消失频率比发生在D染色体组的频率高得多。（ⅲ）微卫星侧翼序列的变化在多倍化的早期（F1代或S1代）就开始发生。由此看来，微卫星两边的侧翼区域在多倍化过程中很活跃，是容易发生变化的区域。微卫星的生物学功能可能与多倍体进化过程有关，微卫星两边的侧翼区域在多倍化过程的早期迅速发生有方向性的改变可能有利于新形成异源多倍体的迅速进化，从而使不同染色体组在遗传上迅速达到协调。

Highly fertile F hybrids were made between Triticum turgidum L. ssp. turgidum (2n = 28, AABB) and Aegilops tauschii Coss. (2n = 14, DD) without embryo rescue and hormone treatment. The F1 plants had an average seed set of 25%. Approximately 96% of the F2 seeds were able to germinate normally and about 67% of the F2 plants were spontaneous amphidiploid (2n = 42,AABBDD). Cytological analysis of male gametogenesis ofthe F1 plants showed that meiotic restitution is responsible for the high fertility. A mitosis-like meiosis led to meiotic restitution at either of the two meiotic divisions resulting in unreduced gametes. Test crosses of the T. t. turgidum–Ae. tauschii amphidiploid with Ae.variabilis and rye suggested that the mitosis-like meiosis is controlled by one or more nuclear genes that continue to function in derived lines. This discovery indicates a potential application of such genes in producing double haploids.

Chromosomal locations of crossability genes in tetraploid wheat Ailanmai with high crossability native to Jianyang of Sichuan province, China, was determined by aneuploid analysis employing the D-genome chromosome substitution lines of Langdon durum wheat and monosomic lines of common wheat, Abbondanza. High crossability of Ailanmai was attributed to recessive crossability alleles on chromosomes 1A, 6A and 7A. The effects of chromosomes 7A and 1A were stronger than chromosome 6A. These results indicated that high crossability in Chinese tetraploid wheat cv. Ailanmai and Chinese hexaploid wheat is controlled by different genetic systems.

We crossed the 14 D-genorne disomic substitutions of durum wheat cv. Langdon with an inbred rye and obtained a large variation in crossability percentages in the 1995-1996 and 1996-1997 growing seasons. The results showed that chromosomes 2A, 2B, 3B and 5B of Langdon carry crossability genes, while chromosomes 4B, 5A, 6A and 7A are involved in a suppressing effect on crossability with rye. Of which, chromosomes 2B and 3B showed a stronger effect on crossability than chromosome 5B, and chromosomes 4B and 7A showed a stronger effect than chromosome 5A. Thus, it was indicated that the tetraploid wheat cv. Langdon has a different kr system regulating crossability with rye in comparison with that of hexaploid common wheat.

It was suggested that the rapid changes of DNA sequence and gene expression oc-curred at the early stages of allopolyploid formation. In this study, we revealed the microsatellite (SSR) differences between newly formed allopolyploids and their donor parents by using 21 primer sets specific for D genome of wheat. It was indicated that rapid changes had occurred in the "shock" process of the allopolyploid formation between tetraploid wheat and Aegilops tauschii. The changes of SSR flanking sequence resulted in appearance of novel bands or disappearance of parental bands. The disappearance of the parental bands showed much higher frequencies in comparison with that of appearance of novel bands. Disappearance of the parental bands was not random. The frequency of disappearance in tetraploid wheat was much higher than in Ae. tauschii, i.e. the disappearance frequency in AABB genome was much higher than in D genome. Changes of SSR flanking sequence occurred at the early stage of F1 hybrid or just after chro-mosome doubling. From the above results, it can be inferred that SSR flanking sequence region was very active and was amenable to change in the process of polyploidization. This suggested that SSR flanking sequence probably had special biological function at the early stage of ploy-ploidization. The rapid and directional changes at the early stage of polyploidization might con-tribute to the rapid evolution of the newly formed allopolyploid and allow the divergent genomes to act in harmony.

An artificial amphiploid 'RSP' (2n=42, AABBDD) between tetraploid landrace Ailanmai (Triticum turgidum L., 2=28, AABB) and Aegilops tauschii (DD, 2n=14) expressed high tolerance to preharvest sprouting which derived from Aegilops tauschii. To determine the inheritance of sprouting tolerance in 'RSP', it was crossed with six cultivars which vary in susceptibility to preharvest sprouting. Preharvest sprouting tolerance was assessed on F2 plants using germination towels. Preharvest sprouting tolerance was inherited as a recessive trait which was controlled by one gene.

Triticum aestivum L. lines with added or substituted chromosomes of Lophopyrum elongatum were hybridized with rye to identify chromosomes in L. elongatum that influenced crossability of wheat with rye. The results indicated that chromosome 4Ee, in L. elongatum suppressed crossability of wheat with rye. It was suggested that homoeologous chromosome distribution of crossability genes in L. elongatum was different from that of wheat.

The Giemsa C-banding analysis of 11 accessions of T. tauschii from the middle reaches of the Yellow River and Xinjiang province in China and common wheat Chinese Spring was made. The clear C-band polymorphic variation among the T. tauschii accessions from the middle reaches of the Yellow River and the accessions from Xinjiang was observed, which is consistent with evidence of RFLPs and esterase analysis in Chinese T. tauschii. Modification in the C-banding pattern was noticed on some D-genome chromosomes of Chinese Spring compared with T. tauschii. The C-banding polymorphic variation of secondary constriction region in chromosome arm 5DS of T. tauschii was found.