Identification and Genetic Mapping of a Lesion Mimic Mutant in Rice

A lesion mimic stripe mutant, designated as Ims1 （lesion mimic stripe 1）, was obtained from the M2 progeny of a ^60Co y-radiation treated japonica rice variety Jiahua 1. The Ims1 mutant displayed propagation type lesions across the whole growth and developmental stages. Physiology and histochemistry analysis showed that the mutant exhibited a phenotype of white stripe when grown under high temperature （30 ℃）, and the lesion mimic caused by programmed cell death under low temperature （20 ℃）. The genetic analysis indicated that this lesion-mimic phenotype is controlled by a single locus recessive nuclear gene. Furthermore, by using simple sequence repeat markers and an F2 segregating population derived from two crosses of Ims1 ×93-11 and Ims1 ×Pei＇ai 64S, the Imsl gene was mapped between markers Indel1 and MM0112-4 with a physical distance of 400 kb on chromosome 6 in rice.

Genetic Analysis and Molecular Mapping of Light-Sensitive Red-Root Mutant in Rice

The light-sensitive red-root mutant, designated as HG1, was newly observed from an indica rice variety, Nankinkodo, when seedlings were grown with roots exposed to natural light. The root color of the mutant began to turn slight-red when the roots were exposed to the light at the intensity of 29 ）Jmol/（m^2·s）, then turned dark-red at the light intensity of 180 pmol/（m^2·s）, suggesting that the root color of the mutant was evidently sensitive to light. Furthermore, genetic analysis showed that the character of light-sensitive red-root of the HG1 mutant was controlled by a single dominant gene, tentatively designated as Lsr. With simple sequence repeat markers, Lsrgene was located between the markers RM252 and RM303 on chromosome 4 with the genetic distances of 9.8 cM and 6.4 cM, respectively. These results could be useful for fine mapping and cloning of Lsrgene in rice.

Genetic Analysis and Mapping of a Thermo-sensitive White Stripe-Leaf Mutant at Seedling Stage in Rice(Oryza sativa)

A thermo-sensitive white stripe-leaf mutant （tws） was selected from the M2 progeny of a japonica variety, Jiahua 1, treated by ^60 Co γ-radiation. In comparison with the wild type parent, the mutant displayed a phenotype of white stripe on the 3rd and 4th leaves, but began to turn normal green on the 5th leaf when grown at low temperatures （20℃ and 24℃）. Furthermore, the content of total chlorophyll showed an obvious decrease in the leaves with white stripe. These results suggest that the expression of the mutant trait was thermo-sensitive and correlated with the leaf age of seedlings. The genetic analysis indicated that the mutant trait was controlled by a single recessive nuclear gene, designated as tws. In addition, by using SSR markers and an F2 segregating population derived from the cross between the tws mutant and 9311, tws was mapped between the markers MM3907 and MM3928 with a physical distance of 86 kb on dce chromosome 4.