Genetic Analysis of a Yellow Mutant pylm in Pak-choi
ZHANG Kun;LIU Zhi-yong;SHAN Xiao-fei;LIU Wen-jie;MEI Fa-bo;QU Gao-yang;FAN Wei-qiang;FENG Hui;College of Horticulture, Shenyang Agricultural University;
A stably inherited yellow mutant, designated as pylm, was derived from pak-choi variety Huaguan introduced from Japan Musashino Seed Company by isolated microspore culture. Compared with the normal pak-choi, the mutant exhibited a slender phenotype with yellowed leaves and obviously elongated hypocotyls. The determination of photosynthetic pigment content showed that pylm leaves exhibited a 62%, 75%, 58% and 66% reduction in Chl a, Chl b, carotenoid and total chlorophyll,respectively, compared to the control line in seven-week-old plants. The measurement of photosynthetic parameters showed that the mutant was lower in the net photosynthetic rate, stomatal conductance and transpiration rate than those of the control line.Ultrastructure analysis revealed that there were irregularly shaped chloroplasts with an incomplete structure in pylm. Genetic analysis revealed that the mutant trait was interactively controlled by two loci of recessive genes(py1 and py2). Genetic model for the pylm mutant was proposed according to the genetic analysis of the mutant trait. With using the genetic model and principles of genetics, the genetic analysis of the mutant trait was further validated by F_3 and F_4families constructed by the pylm mutant and the Chinese cabbage DH line FT. Two pairs of the mutant genes(py1 and py2) could be studied separately by using the F_4 families obtained from this research. Only a difference in single locus of F_4 families created the possibility for isolating and mapping of two pairs of the mutant genes from each other. These results laid a foundation for mapping and cloning of mutant genes and verified the molecular mechanism of gene interactions.