Second, Japanese scholar (1982) first proposed that the common wild rice had been differentiated between indica and japonica before it was domesticated into cultivated rice, and according to the isozyme analysis, it was considered that the common wild rice in China was japonica, while the common wild rice in South Asia was indica. Sano et al. (1989) also think that Dongxiang common wild rice in China is japonica rice through the study of rDNA. In order to further study whether there is indica-japonica differentiation in China, Wang Xiangkun et al. (1994) selected 57 1 portion of common wild rice from seven provinces in China, and made cluster analysis according to the morphological characteristics of 10, so as to distinguish wild rice from japonica rice and distinguish four isoenzymes of esterase (Est) and acid phosphatase. Firstly, the tested wild rice materials were identified as heterozygous, cultivated and homozygous by Est-x isozyme analysis, and then four isozyme gene loci of 92 homozygous common wild rice were analyzed. The results showed that 92 homozygous common wild rice varieties formed 17 type at 4 isozyme loci (Table 2-24).

Table 2-24 Types of combinations of 92 homozygous common wild rice in China according to 4 isozyme loci

Table 2-24 Types of combinations of 92 homozygous common wild rice in China according to 4 isozyme loci (continued)-1

As can be seen from Table 2-24, the isozymes of common wild rice in China have indica-japonica differentiation, and the japonica type is dominant, and mainly concentrated in the 14 type, which is specifically manifested as Cat- 1, Amp-2, Est-20 and Acp-20, that is, except Amp-2, the other three loci are indica. Random Amplified Polymorphic DNA(RAPD) analysis of 27 common wild rice genomes in China also showed that japonica rice was the main type of common wild rice in China, but both isozyme analysis and RAPD analysis showed that indica rice types also existed in common wild rice in China.

Wang Xiangkun et al. have made a great deal of research on isoenzymes and DNA, and found that most common wild rice have indica-japonica differentiation except a few primitive common wild rice. The indica-japonica differentiation in nuclear DNA, mitochondrial DNA, chloroplast DNA and DNA repeats is consistent, but most of them are inconsistent. The nuclear DNA of common wild rice in China is mostly japonica, and some are indica. The mtDNA of common wild rice is mostly indica rice and a few japonica rice; The ratio of indica to japonica cpDNA of common wild rice is roughly 1∶ 1 (Wang Xiangkun, 1996).

Cai Hongwei et al. (1993) selected 132 common wild rice materials from 7 provinces (regions) in China and 159 common wild rice materials from 27 foreign countries, and studied indica-japonica differentiation of common wild rice through four isozyme loci of Est, Acp, Cat and AMP in seedling leaves. The results showed that there was indica-japonica differentiation in common wild rice in China. 92 homozygous materials of common wild rice in China distributed continuously from indica type to japonica type, accounting for 47.82%, 14. 13% and 25.00% of the total, respectively. Three types account for 86.95%. 9.78% and 3.26% obviously differentiated into japonica type and indica type. Judging from the regional distribution of indica-japonica differentiation of common wild rice, the common wild rice in Dongxiang, Jiangyong and Chaling, Hunan with higher latitudes is mainly japonica, while the common wild rice in Guangxi has obvious indica-japonica differentiation. Compared with foreign countries, most of the common wild rice in foreign countries are indica rice and indica rice, while the common wild rice in China is japonica rice, but some of them are indica rice.

The common wild rice in Yuanjiang, Yunnan Province belongs to a relatively homozygous and primitive perennial wild rice. Its habitat is located on the hillside at an altitude of 780m, far from cultivated rice, and its bagged self-bred offspring are not separated. Yuan Pingrong et al. (1995) analyzed and determined esterase and catalase isoenzymes of 45 materials. Esterase showed that the leaves of Pu-ye in Yuanjiang were indica, but there was no characteristic band of japonica, and catalase showed japonica. This inconsistency indicates that there is also the possibility of indica-japonica differentiation in Puye, Yuanjiang. Studying its internal differentiation is of great significance to trace the origin and evolution of cultivated rice in China.