ISSR Analysis on Genetic Diversity of the 34 Populations of Oryza meyeriana Distributing in Yunnan Province,China

The genetic diversity of the 34 populations of wild rice Oryza meyeriana Baill. distributed in Yunnan Province, China was analyzed using 13 inter-simple sequence repeat （ISSR） markers. A total of 168 bands were amplified, of which 135 polymorphic bands were discovered and the percentage of polymorphic bands （PPB） was 80.36%. A genetic diversity was revealed as Nei＇s gene diversity （H） = 0.2666 and Shannon information index （I） = 0.4028 at population level. The 34 populations were divided into different groups based on administrative regions, latitude and longitudes, river areas, altitudes of their origins, and their indexes such as Na （number of alleles）, Ne （effective number of alleles）, H, I and PPB were calculated. Richer genetic diversity was found in the wild rice populations distributed in Simao Prefecture than that in Lingcang Prefecture or Xishuangbanna Prefecture whereas the least genetic diversity was in Baoshan Prefecture or Dehong Prefecture. Rich genetic diversity was also discovered in the wild rice populations originated from higher than 710 m altitude around the middle and lower reaches of the Lancang River belonging to the Pacific Ocean drainage system. The 34 populations could be classified into two groups, one group covered the wild rice distributing in Simao Prefecture only while the other group covered ones in Lingcang, Xishuangbanna and Dehong Prefectures. The issue on how to effectively conserve the wild rice germplasm was discussed.

Effect of Cold-Water Irrigation on Grain Quality Traits in japonica Rice Varieties from Yunnan Province,China

The response of grain quality traits to cold-water irrigation and its correlation with cold tolerance were studied in 11 japonica rice varieties from Yunnan Province, China. The results indicated that the response of grain quality traits to the cold-water stress varied with rice varieties and grain quality traits. Under the cold-water stress, grain width, chalky rice rate, whiteness, 1000-grain weight, brown rice rate, taste meter value, peak viscosity, trough viscosity, breakdown viscosity and final viscosity significantly decreased, whereas grain length-width ratio, head rice rate, alkali digestion value, protein content and setback viscosity markedly increased. However, the other traits such as grain length, amylose content, milled rice rate, peak viscosity time and pasting temperature were not significantly affected by the cold-water stress. Significant correlations were discovered between phenotypic acceptability and cold response indices of taste meter value, protein content, peak viscosity and breakdown viscosity. Therefore, it would be very important to improve the cold tolerance of Yunnan rice varieties in order to stabilize and improve their eating quality.

Evaluation of the Pathotypes of Xanthomonas oryzae pv. oryzae and Preliminary Analysis of the Resistant Reactions of Main Japonica Rice in the Yunnan Plateau, China

The pathogenicity of 36 isolates of Xanthomonas oryzae pv. oryzae （Xoo）, which were collected from japonica rice varieties in the Yunnan Plateau, China, was evaluated. It was evaluated on 29 rice varieties including a set of seven varieties to identify pathogenicity, i.e., Haonuoyang, TN1, Kogyoku, Zhenzhu＇ai, IR26, Nanjing 33, and Kinmaze, which may be considered as a set of differential varieties for Xoo races from Yunnan japonica rice. The efficiency of the seven varieties was further confirmed. The results showed reversible and specific interactions between isolates and varieties. The isolates were classified into nine pathotypes from pathotyp Ⅰ to Ⅸ according to their pathogenic reactions on the seven rice varieties. The pathotype V was the epidemic, whereas pathogen Ⅶ was the most pathogenic. Most japonica varieties grown in the Yunnan Plateau were susceptible to Xoo. The rice lines IRBB21 （Xa-21）, Zhachanglong （Xa-22,, Xa- 24,）, and IR1545-339 （xa-5）, which were resistant to all the isolates tested, can be used as donors of resistant genes for bacterial blight in japonica rice breeding in the Yunnan Plateau.

QTL Analysis of Some Agronomic Traits in Rice Under Different Growing Environments

The culm length, panicle length, spikelets per panicle and panicle exsertion were evaluated by using F2：3 population including 200 lines derived from the cross of indica and japonica Milyang 23/Jileng 1 under five different environments of Beijing （natural normal growing environment）, Kunming （natural cold environment）, Gongzhuling of China （cold water irrigation） and Chuncheon of Korea （natural normal growing environment and cold water irrigation）, and QTLs of these traits were analyzed by using SSR markers. The results showed that 44 QTLs related to these agronomic traits were detected under five different growing environments, and these QTLs have been located on 11 chromosomes except chromosome 9. The QTLs for qCLla, qCL1b, qCL5a, qCL6b, qPLla, qPL3a, qPL6b, qPL6c, qPL7b, qSP8b, qSPlc, qSP11a, qSP12, and qPE1 have been detected under more than two growing environments, and those that were little affected by environments, were stable QTLs. Among them, qCLla, qCLlb, qPLla, qSPlc, and qPE1 explained 24.2-55.2%, 22.7-39.9%, 12.5-27.7%, 14.4-33.5%, and 26.6-28.7% of observed phynotypic variation, respectively, which were major genes mainly appearing as overdominance. These QTLs cause the increase in action to culm length, panicle length, spikelets per panicle, and panicle exsertion under cold environment, showing that these QTLs were correlated with cold tolerance.

Specific Spikelet Fertility as an Indicator of Cold Tolerance Identification at Booting Stage in Rice

By using the parents, Kunmingxiaobaigu, a landrace variety with cold tolerance from Yunnan, China, and Towada, a cold-sensitive variety bred in Japan, as well as their F8 and F9 RIL progenies as test materials, cold tolerance of rice at the booting stage in 2002 and 2003 under four different altitudes （environments）, and the correlationship between spikelet fertility and specific spikelet fertility （spikelet fertility of nine spikelets from the 3rd to the 5th spikelets of three primary branches at the top of each panicle） of single plant were analyzed, The data revealed a significant correlationship between spikelet fertility and specific spikelet fertility with the range from 0.7364 to 0.9011. However, under the cold stress environments, the correlation coefficients were higher than those without cold stress. On the other hand, the panicle exsertion was correlated to both spikelet fertility and specific spikelet fertility. Moreover, the heredity analysis suggested that specific spikelet fertility could replace spikelet fertility as an identification indicator, while panicle exsertion could be used as a partial indicator of cold tolerance identification at the booting stage in rice.