Utilization of Aromatic Rice in Improving Grain Quality of Hybrid Rice

To improve grain quality of the high-yielding hybrid rice in China, we introduced the aromatic rice MR365. an improve Indian cultivar with aroma and other desirable grain quality characters such as long grain and low chalkiness, from IRRI in 1984 and began to transfer its aroma and good quality characters into the existing maintainer lines with good combining ability but poor grain quality.In the meantime,we also conducted the research on the inheritance of aroma for incerasing the breeding efficiency. Through years of research and breeding practices, two cytoplasmic male sterile(CMS)lines Xiangxiang2 A and Xingxiang A and a series of quasi-aromatic hybrids mated from these aromatic CMS lines have been developed and released for commercial production in China. It was found that the inheritance of aroma in MR365 and its dervatives including Xiangxiang2 A,XinxiangA and Xiang2B S was controlled by one pair of recessive major genes based on the identification of aroma by the KOH-soaking method. We also found that there existed disparity in aroma degree among different grains of F2 generation,and different aromatic CMS lines derived from the same aromatic donor such as Xiangxing2 A and Xinxiang A had also a little difference in the degree of aroma,which implies that,besides the major genes,aroma may also be affected by the genetic backgrounds or minor genes.Xiangxiang 2 A,developed from the cross of V20A//V20B/MR365,is the first aromatic CMS line bred in China. It is not only aromatic but has good grain quality and combining ability. Using it as female parent,Xiangyou 63(Xiangxiang 2A/Minghui 63),the first quasi-aromatic hybrid rice combination in China,was developed and approved to release to farmers in 1995.Xiangyou63 is characteristic of quasi-aromatic or partially aromatic(because only a portion of or NOT ALL grains are aromatic),good grain quality,high-yielding ability, good blast resistance and wide adaptability.However,Xiangiang2 A has an evident drawback,i.e.,instability in male sterility under higher temperat