Abstract: 【Objective】Leaf blade is the main location of photosynthesis in high plants. A moderate narrowing could enhance crop quality and yield by fascinating the utilization of solar energy and has been paid wide attentions in crop breeding. A novel dominant narrower leaf mutant has been identified and the results provided a foundation in the research of leaf morphological formation and plant type breeding in Oryza sativa.【Method】A narrow leaf mutant (Dnal1) was discovered from the progeny of indica restorer line Jinhui10 with seeds treated by ethyl methanesulfonate and the trait of narrow leaf has inherited steadily after seven generations’ self-fertility. The flag, second and third leaf blades were utilized for detecting leaf widths and rolled indexes at the blooming stage, meanwhile, the middle position of flag leaf was used for paraffin section. At the filling stage, the characteristics of chloroplast pigment, photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) were measured. The Dnal1 was crossed with indica line Xinong1A and japonica line Zhonghua11, respectively, and the F1 and F2 generations were used for genetic analysis. Additionally, gene mapping was performed based on the F2 recessive individuals of Dnal1/Zhonghua11. The Dnal1 and the wild type were cultivated in paddy field with the spacing in the rows and between the rows 13.36 cm×20.04 cm and 16.7 cm×26.72 cm, respectively. At the maturity stage, agronomic traits were analyzed and they were plant height, efficient panicle per plant, filled grain number per panicle, seed setting ratio, 1000-seed weight, seed length and seed width. At last, theory yield per 667m2 was estimated.【Result】The Dnal1 displayed narrower leaf blades in the life and the width of flag leaf, second leaf and third leaf were 0.96, 0.89 and 0.88 cm, respectively; correspondingly, those of the wild type were 19.6, 19.41 and 18.42 cm, respectively. The number of large vascular bundles in the mutant had no significant difference with those of the wild type and the number of small vascular bundles decreased by 44.13%, leading to the significant difference. In detail, the number of small vascular bundles between the large vascular bundles was six in the wild type, and three in the Dnal1. The leaf blades of Dnal1 displayed slightly curling and the rolled indexes of flag, second and third leaf blades were 11.2, 12.1 and 11.8, respectively, while those of the wild type were zero. In addition, the colour of leaf blades of Dnal1 was darker than those of wild type with a slight higher content of chloroplast a. The increases were detected for the values of the water use efficiency and the decrease was identified for the parameters of the photosynthetic rate, transpiration rate and stomata conductance in the Dnal1, while only the alteration of stomata conductance led to the level of significant difference between the Dnal1 and the wild type. The culm and seed of Dnal1 were narrower than those of the wild type, while no changing in plant height and seed length was detected. The seed width of Dnal1 was 2.33 mm, which was significantly lower than those of the wild type (2.78 mm), therefore, the 1000-seed weight decreased significantly in the Dnal1. The yield of per unit area in the Dnal1 reduced under the lower plant density while increased under the higher plant density than those of the wild type, which was caused by higher efficient panicle per plant and seed setting ratio. For the combinations of Xinong1A/ Dnal1 and Dnal1/Zhonghua11, the widths of F1 flag leaves were 0.99 cm and 0.94 cm, respectively, both have no significant differences with the wild type’s 0.96 cm; in the F2 generations, the plants could be classified as two groups according to the leaf width, the narrow-leaf individuals to those with broad leaves has no significant difference with the ratio of 3:1, suggesting that the narrow leaf trait of Dnal1 was controlled by a dominant nuclear gene. Finally, the DNAL1 was mapped on chromosome 2 between SSR marker RM13646 and RM1307 with the physical distance 391 kb in this paper. 【Conclusion】 Dnal1 was a dominant narrow leaf mutant coming from EMS-inducement and showed higher yield potential when cultivated under the higher planting density. The DNAL1 was mapped on chromosome 2 with 391 kb physical distance.

Key words: rice (Oryza sativa) , dominant narrow leaf , gene mapping , photosystems , plant type breeding