| The exploitation,innovation and utilization of new genetic resources are the major tasks of the studies on rice germplasm resources.In this study,a total of 118 rice genotypes of six different types of gemplasms including indica rice,japonica rice,weedy rice,NERICA rice,African rice(O.glaberrima)and introgression lines collected from or developed in different countries or regions were used as the experimental materials.The agronomic traits,drought resistance at seedling stage and cold tolerance at germination stage of the tested materials were evaluated respectively to screen and identify the elite germplasms which have favorable performance in integrated agronomic traits,drought and cold resistance for rice breeding work.The main results are as follows:1.Because the highly photoperiod sensitive African rice can not heading in Wuhan,field experiment were conducted on the remaining five types of rice germplasms containing 97 rice genotypes to evaluate the agronomic traits.Significant differences were observed in most of the agronomic traits among these materials indicating a rich genetic diversity.The weedy rice has highest biomass,and its plant height,dry weight per panicle and grain weight per panicle were also relatively higher.And the grain yield per panicle(grain weight per panicle)of introgression lines ranged 2.37-6.81 g,higher than other types of materials,and it also has higher therotical yield.2.The materials were divided into four groups by cluster analysis: Group 1 contains japonica genotypes and a few indica genotypes;Group 2 contains NERICA genotypes;Group 3 contains introgression lines carrying African rice genes and most indica genotypes;and Group 4 consists of weedy rice strains.The genetic distance between Group 1 and Group 2 is relatively closer due to their similar genetic origin.Both the introgression lines and NERICA rice were derived from the interspecific crosses between African rice and Asian rice.3.Sixty six large-panicle genotypes were identified through the evluation of agronomic traits,including 13 NERICA,30 introgression lines,15 indica genotypes),and 8 weedy rice,respectively.There are 2 multiple-spike genotypes and 1 large-grain genotypes,both japonica genotypes.One genotypes with was japonica genotypes.An introgression line recorded the highest seed setting rate.Twenty four genotypes with high yield per plant were identified including 9 introgression lines,9 indica genotypes and 4 weedy rice accessions.4.Based on the integrative analysis of 21 morphological indexes of drought resistance at seedling stage,4 genotypes performing strong drought resistence were screened out by using the average subordinate degree of drought resistance,including 1 japonica varieties,2 indica varieties and 1 Africa rice accessions;forty seven genotypes were identified as medium drought resistence materials,including 15 NERICA varieties,2 japonica varieties,14 introgression lines,11 indica varieties,1 weedy rice accessions and 4 Africa rice accessions,respectively.5.The results of seedling drought resistance test showed that the survival rate performed significant positive correlationship with leaf relative water content,the width of second upper leaf under the central leaf,the width of first leaf under the central leaf,the caducity resistance degree of leaf,the stem and leaf fresh weight,and leaf fresh weight.The correlation analysis was conducted between average membership degree of drought resistance(D value)and the seedling traits.The results showed that the average membership degree of drought resistance performed significant positive correlationship with 19 indexes except the length of first and third leaf under the central leaf.Among them,the correlation coefficients between average membership degree of drought resistance and survival rate,leaf caducity resistance degree,root fresh weight,stem and leaf fresh weight,leaf fresh weight were greater than 0.7.The results indicated that the average membership degree of drought resistance is suitable for the evaluation of drought resistance in seedlings stage.6.The cold tolerance of 118 rice varieties in germination stage were directly evaluated by germination rate,and 33 genotypes were identified as strong cold tolerant with germination rate over 80%,and 38 genotypes were identified as midium cold tolerant materials.However,a significant positive correlation between germination rate and germination coefficient,relative germination rate,relative germination coefficient were observed,the correlation coefficient between germination rate and germination coefficient was the largest(R=0.957).Therefore,the membership function method was used to evaluate the cold tolerance at germination stage,the strong cold resistance group containing 15 genotypes,including 1 japonica genotypes,5 introgression lines,3 indica varieties and 6 weedy rice accessions,respectively.7.The correlation between the average membership degree of cold tolerance D value and other traits was assessed.It was found that the D value of the average membership degree performed significant positive correlation with the germination rate(correlation coefficient R=0.965),germination coefficient(R=0.971),germination rate(R=0.960),relative germination coefficient(R= 0.917),and negative correlation with the average germination days(R=-0.545).It indicated that the average membership degree of cold tolerance D value can be applied to the evaluation of cold tolerance at Germination Stage.8.Combining the test results of drought resistance at seeding stage,cold tolerance at germination stage and yield per plant,the 97 rice materials were comprehensively evaluated.Five genotypes yielded more than 40 g grain weight per plant,performed more than 0.7 of the average membership degree of drought resistance D value,and more than 70% of the germination rate under cold treatment,including 3 indica genotypes,1 japonica genotype and 1 introgression line. |
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