Genetic Analysis Of Esp1 Mutant And Mapping Of ESP1 (t) Gene In Rice

It will play an increasingly important role to select rice mutants and clone the mutant genes in rice breeding, especially in rice molecular breeding. A rice mutant with enclosed sheathed panicle 1(esp1) was gotten from a rice restorer line ZaoR974 by using 60Coγ-ray irradiation in our laboratory in 2007. In this paper, we focused on the studies of the observeation of the morphological traits, test of gibberellin sensitivity, genetic analisis of esp1 mutant, and mapping of the corresponding gene of esp1 mutant. The main results are as follows.1. Morphological traits of the esp1 mutantObservations showed that the esp1 mutant and the ZaoR974 are similar in growth duration and leaves of main stem and almost similar in their phenotypes at the vegetative growth stage. But they are different in the length of uppermost internode and the length of panicle. Comparion with the ZaoR974, the spikelet of the esp1 mutant developed slowly at the beginning of differentiation, which leds to sharply shorten the panicle length and reduces the grain numbers. And the esp1 was sinificantly shorter in the uppermost internode than the ZaoR974, so that its panicle is covered by flag leaf sheath.2. The effects of gibberellic acid on the esp1 mutantIn order to study the effects of exogenous gibberellic acid (GA3) on both of the lengths of uppermost internode and panicle, the esp1 mutant was treated by different concentrations of GA3 at the end ofⅧstage of the spike development. Results showed that exogenous GA3 obviously elongated the upper-second and third internodes, but no obvious change was obversed in the uppermost internode, indicating it is gibberellin-insensitive, and exogenous GA3 was not able to release the sheathed panicle in practice.3. Genetic analysis of esp1 mutantIn the total 3212 plants of F2 population of esp1 crossing with Nipponbare, there were 2387 normal plants and 825 mutant plants respectively, which was good fit to 3:1 ratio. In the total 1056 plants of BCF1(esp1/Nipponbare//esp1) population, there were 542 normal plants and 514 mutant plants respectively, that was good fit to 1:1 ratio. The results suggested that the esp1 mutant trait is controlled by a single recessive gene. The gene was named ESP1(t) tentatively.4. The relationship between ESP1(t) and euiIn the two F2 populations of esp1 mutant crossing with Xe1B(carrying eui1)and Xe2B(carrying eui2)respectively, the normal plants, the esp1 mutants and the eui mutants were good fit to 9:3:4 ratio, indicating that both the eui1 and eui2 were recessive epistasis over ESP1(t).5. Mapping of ESP1(t)Based on the previous study, 88 SSR markers were choosed from the rice12 chromosomes to analyze their polymorphism between the esp1, ZaoR974 and the 825 mutants derived from the population of esp1 crossing with ZaoR974. It was found that SSR markers RM332,RM167 and RM202 on chromosome 11 were linked to ESP1(t). By using Mapmaker/Exp 3.0 program, the ESP1(t) was located at between RM167 and RM202, 9.65 cM away from RM167 and 4.75 cM away from RM202, respectively.Based on above result, 19 new markers were designed according to the rice genome sequence to further analyze their polymorphism between the esp1 and ZaoR974. 6 markers RM3137, RM26281, GRM40, GRM38, GRM43b (InDel marker) and GRM17 were polymorphic. By the use of Mapmaker/Exp 3.0 program, a molecular map was constructed. From the map, the arrangement between the ESP1(t) and the markers was RM3137-RM26281- ESP1(t)-GRM38-GRM43b-GRM17。their genetic distances were 1.62 cM to RM3137, 0.28 cM to RM26281, 0.08 cM to GRM38, 0.53cM to GRM43b and 1.39 cM to GRM17, respectively , and ESP1(t)was co-segregation with GRM40 marker.