Genetic Analysis Of A Broad-spectrum Blast Resistance Gene D12 And Its Employment In Marker-assisted Selection

Rice is one of the most important crops in the world,which is also a staple food for the people in our country.Rice blast,caused by Magnaportheg risea,is one of the most devastating diseases in rice.One of the economic and useful methods to control this disease is to improve the resistance of rice to rice blast by employing resistance genes.One objective of this work was to study the genetic basis of rice blast resistance gene d12 by using a near isogenic line thoughout the whole stage of rice development by nature infection.The use of a BC₂F₂ near isogenic line in the Zhenshan97 background allowed us to analyze dl2 on chromosome 12.At two different time points of tillering stage,dl2 contributed differently to the total variation of leaf blast resistance in this BC₂F₂ population,47.1%for TL58(leaf blast resistance 58 days after germination at tillering stage,TL58) with LOD=31.7 and 37.9%for TL75(leaf blast resistance 75 days after germination at tillering stage,TL75) with LOD=24.1,respectively.The additive effect and dominance effect of dl2 are 1.2608 and -1.0475 for TL58 and 0.7326 and -0.7689 for TL75,respectively.No effect of dl2 was detected on leaf blast resistance at heading stage for HL98(leaf blast resistance 98 days after germination at heading stage,HL98).The decreasing effects of dl2 on rice blast throughout the life cycle of rice suggested that dl2 was a development-related resistance gene.Another objective of this work was to improve the resistance of four rice cultivars,'Zhenshan 97B','Zhong 9B','Jing 23B' and 'Chunxiang 29B',by introgressing of dl2 into these cultivars though molecular marker-assisted selection(MAS).It is worthy to note that the blast resistance of two cultivars,'Zhenshan 97B' and 'Zhong 9B',were improved while other traits,like plant high and heading date,were not changed.Our results might have important implications for durable resistance breeding and improve our understanding in development-related disease resistance genes in plants.