Genetic Analysis And Gene Mapping On A Rice Albino Mutant XGS

In plant chloroplasts, chlorophyll is an important pigment in photosynthesis. Its significant change always results in the difference of leaf color, so chlorophyll deficient mutation is also called leaf color mutation. In rice, many chlorophyll deficient mutants exhibiting albino, chlorina, stripe, virescent, yellow-green and zebra leaves have been recorded. These mutants have been used primarily for basic studies such as exploitation of the mechanism of photosynthesis, investigation of chlorophyll biosynthesis, and identification of the function of the mutated genes. It's also plays an important role in hybrid rice production as a screening marker.In this paper, a rice green-revertible albino mutant XGS has been investigated in the pheanotype, the relationship with temperature, the ultramicro-structure of chloroplast, and genetic traits. Furthermore, the mutant gene was mapped preliminarily with micro-satellite marker.1. Different from other albino mutants, the leaf color change of XGS is insensitive with temperature alter. The leaves of the mutant XGS were white before the 3-leaf-stage and the first leaf and second leaf then gradually turned green when the third leaf extended. All the third leaf and the following leaves appeared normal green. In the 4-leaf-stage, the seedling of the mutant had become green compared to normal plant except the first two leaves exhibited pale green.2. The content of chlorophyll a, chlorophyll b and caroteniod was investigated and compared between the albino mutant and the normal material 02428 at two growth stages. The results showed that the contents of chlorophyll a, chlorophyll b and carotenoid in the 2-leaf-stage of XGS were 14.5%, 19.1% and 14.0% compared with those in 02428. However, the difference of pigment content declined obviously in the 4-leaf-stage, and the percentage of the three pigments in reverted-green mutant to 02428 increased to 76.8%, 56.65%, and 93.25%.3. Chloroplast structure was observed by transmission electron. As a result, the chloroplast of albino mutant developed abnormally. It kept the extrinsic morphous but granal stacks in the mutant appeared less dense and lacked granal membranes inside. Compared to the normal material 02428, granal development in albino mutant was slower and the granal membranes in the XGS mutant increased when the leaf returned to green.4. The albino mutant XGS has been crossed with normal plant 02428, 9311, shuhui527 and japonica. Seedling of F₁ behaved green, seedling of F₂ appeared separation of leaf color (albino and green). Separation ratio fitted for 3:1 (green seedling/albino seedling) by x² -test, in accordance with single gene inheritance. At the same time, the segregation of the fertility of XGS fitted the 3:1 Mendelian ratio too, and the fertile plant was dominant versus sterile one was recessive. Therefore, the albino mutated gene was a recessive gene and un-linkage with the other gene that controlled thermo-photoperiod-sensitive mal-sterility. In addition, the allelism test was used to detect whether the green-revertible albino trait was controlled by a same gene in the two different cultivars, XGS and al12. The F₁ crossed by XGS and al12 appeared normal green. It is showed the two mutated gene were located in unequal sites.5. The F₂ population of XGS and 02428 was used for the map population. Utilized the SSR markers well-distributed on 12 pairs of rice chromosomes, the mutated gene was located between RM287 and RM209 on rice chromosome 9, and the genetic distances were 0.7cM and 7.2cM. The gene was considered to be a new green-revertible albino mutant gene in rice, and temporarily designated as al13.