不同锰浓度环境下OsNRAMP5突变对水稻耐热性和主要经济性状的影响

OsNRAMP5是水稻吸收镉、锰的主效转运蛋白。OsNRAMP5突变造成水稻镉含量大幅度降低,使其成为镉低积累水稻分子育种中最重要的靶标基因,而其突变造成的锰含量大幅度降低是否会影响水稻农艺性状和环境适应性一直备受关注且存在争议。以籼稻华占、粳稻中花11这2种不同遗传背景下同一突变位点的osnramp5突变株系为材料,采用不同锰浓度水培和大田试验比较分析了它们的耐热性和主要经济性状。结果表明,苗期在正常浓度锰供应条件下,2种遗传背景的osnramp5突变株系耐热性并未明显下降,但在环境锰不足的条件下,2种遗传背景osnramp5突变株系的耐热性均大幅度下降。在土壤锰含量为312 mg/kg的正常锰浓度大田条件下,籼稻华占的osnramp5突变株系产量和稻米品质较野生型均无显著差异,但粳稻中花11的osnramp5突变株系的千粒重和胶稠度降低;开花期高温使2种遗传背景的osnramp5突变株系的每穗总粒数、结实率和千粒重均显著下降,且造成粳稻中花11的osnramp5突变株系的垩白粒率和垩白度上升。在土壤锰含量为102mg/kg的低锰浓度大田条件下,2种遗传背景的osnramp5突变株系的有效穗、每穗总粒数、结实率和千粒重均显著下降,垩白粒率和垩白度上升。说明籼稻的osnramp5突变株系在富含锰的镉污染地区有很大的应用潜力,但在种植时应避开抽穗期高温和低锰田块,而粳稻的osnramp5突变株系在南方稻区的环境适应性较差。

Effects of OsNRAMP5 Mutation on Heat Tolerance and Main Economic Traits of Rice under the Conditions of Different Manganese Concentration

OsNRAMP5 is the main transporter responsible for the uptake of cadmium(Cd) and manganese(Mn) in rice. The OsNRAMP5 mutation causes a drastic decrease in the Cd content in rice, making it the most important target gene in molecular breeding of rice with low Cd accumulation. Whether the significant reduction of the Mn content caused by the OsNRAMP5 mutation will affect the agronomic traits and environmental adaptability of the osnramp5 mutants has been concerned and controversial. The osnramp5 mutants with the same mutation locus from two different genetic backgrounds of indica rice Huazhan and japonica rice Zhonghua 11 were compared in heat tolerance and main economic traits by the hydroponic culture and field experiments with different external Mn concentration. The results showed that the heat tolerance at seedling stage of the osnramp5 mutants with these two genetic backgrounds was similar to that of their wild types at the normal Mn supply, but decreased significantly at the insufficient Mn supply. Under the field conditions with the normal soil Mn content at 312 mg/kg, the yield and grain quality were not significantly different between indica rice Huazhan and its osnramp5 mutants, but the 1 000-grain weight and gel consistency in the osnramp5 mutants of japonica rice Zhonghua 11 were significantly lower than those in their wild type. High temperature at flowering stage significantly decreased the number of spikelets per panicle, seed setting rate and 1 000-grain weight of the osnramp5 mutants with both genetic backgrounds, and increased the chalky grain rate and chalkiness degree of the osnramp5 mutants of japonica rice Zhonghua 11. Under the field conditions with low soil Mn content at 102 mg/kg, compared with their wild types, the number of effective panicles, the number of spikelets per panicle, seed setting rate and 1 000-grain weight of the osnramp5 mutants with both genetic backgrounds were all significantly reduced, whereas the chalky grain rate and chalkiness degree of those osnramp5 mutants were greatly increased. It is indicated that the osnramp5 mutants of indica rice has a great potential for application in the fields contaminated by Cd and rich in Mn, but the high temperature at heading stage and low Mn fields should be avoided when planting. However, the japonica rice osnramp5 mutants have poor environmental adaptability in the southern rice growing area.