Studies On The Stress Tolerance In Hainan Wild Rice (Oryza Rufipogon Griff.)

In order to explore the tolerance of�Hainan'common wild rice(CWR,Oryza rufipogon Griff.),and to provide theoretical support for its application,the morphological and physiological indicators of stresstolerance between�Hainan'CWR and other control materials,i.e.,CWRaccessions from different regions and typical cultivated rice phenotypes,were compared subjected to cold,drought,and high salinity at their vegetative growth stage.The following results were obtained:1)After 5 days of cold stress(average daily mean temperature was8.12?,average daily minimum temperature was 3.6?,and average daily maximum temperature was 12.6?),�Hainan'CWR did't curl,while the control materials(�Dongxiang'CWR,�Chaling'CWR,indicacultivar 93-11,and japonica cultivar Nipponbare)showed different degrees of curling or even withering.After above cold stress,the net photosynthetic rate,stomatal conductance,apparent quantum efficiency,carboxylation efficiency,chlorophyll content,and maximal photon quantum efficiency of photosystem?(F_v/F_m)of all the test materialsdecreased,but the declined rate of�Hainan'CWR was significantlysmaller than those of cultivated rice controls(Nipponbare and 93-11)while not significantly different from the other CWR accessions.After the cold stress,the relative conductivity and free proline content of all materials increased,but the increased percentage of the relativeconductivity of�Hainan'CWR was significantly less than those of 93-11and�Chaling'CWR,while the increased percentage of of free prolinecontent was significantly higher than that of 93-11.2)After 7 days of drought(soil moisture content was 16%-20%,and average daily mean temperature was 22.7?),the root-to-shoot ratio of�Hainan'CWR increased by 38.87%,lower than the increased rate of�Dongxiang'CWR by 47.36%,but higher than those(6.29%-26.53%)of four control materials as Brazilian upland rice,�Guilin'CWR,93-11,and Nipponbare.After the drought,the free proline content of�Hainan'CWRincreased by 62.71%,which was not significantly different from that of Dongxiang wild rice(63.63%),but significantly higher than those(7.87%-46.89%)of the other four control materials.After above drought,the net photosynthetic rate,stomatal conductance,and chlorophyllcontent of all materials decreased,of which�Hainan'CWR and�Dongxiang'CWR decreased almost the same,however,it decreasedsignificantly smaller than the other four control materials.3)After treating�Hainan'CWR,�Dongxiang'CWR wild rice,�Chaling'CWR,Haidao 86,Nipponbare,and 93-11 seedlings with150mM NaCl for 5 days,the leaves of all materials showed curling and yellowing,but the degree was different.After this salt stress,thechlorophyll content of all materials decreased,but the decline of�Hainan'CWR was significantly smaller than that of 93-11 while the difference with other materials was not significant.After the salt stress,the free proline content of all materials increased,but the increased rate of�Hainan'CWR is significantly greater than that of 93-11,while thedifference with other materials is not significant.After the salt stress,the relative conductivity and malondialdehyde content of all materialsincreased,but the two indicators of�Hainan'CWR increased significantly lower than those of 93-11 or 93-11 and�Chaling'CWR,while thedifference with other materials is not significant.The above results indicate that:(1)The cold tolerance of�Hainan'CWR is stronger than that of cultivars Nipponbare and 9311,and it is notweaker than that of�Dongxiang'CWR and�Chaling'CWR under thecold stress temperature and development stage in this study;(2)Thetolerance of�Hainan'CWR is similar to�Dongxiang'CWR,but stronger than that of�Guilin'CWR,Brazil upland rice,Nipponbare,and 93-11;(3)�Hainan'CWR is less salt-tolerant than Haidao 86,but stronger than�Dongxiang'CWR,�Chaling'CWR,Nipponbare,and 93-11.