Physiological characters and gene mapping of a dwarf and wide-leaf mutant <italic>osdwl1</italic> in rice (Oryza sativa L.)

Abstract

<p indent=0mm>Plant height is one of the important factors affecting rice lodging. The semi-dwarf rice varieties possess high level of lodging resistance, and could reduce yield loss and improve grain quality. Thus, it is very important to study the molecular and physiological mechanism of dwarf formation in rice. In this study, a stable hereditary dwarf and wider-leaf mutant <italic>osdwl1</italic> was obtained from ⁶⁰Co γ-radiated <italic>indica</italic> restore line Zixuan 1, and its morphological and physiological characteristics, cytological observation, genetic analysis and gene mapping were investigated. Under field condition, the mutant <italic>osdwl1</italic> exhibited dwarf and wider-leaf after the tillering stage due to shorter length of the parenchyma cells, and its panicle length and all internodes length were significantly shorter compared with wild type plants at mature stage. Paraffin sections and scanning electronic microscopy (SEM) observation revealed that the number of small vascular (SV) bundles and the distance between SVs increased significantly, resulting in wider-leaf blade in <italic>osdwl1</italic>. Moreover, the number of microhairs on the abaxial and adaxial epidermis were also increased significantly in <italic>osdwl1</italic>. In addition, starting at the 3–4 leaf seedling stage, yellowing was visible at the upper middle parts of old leaves in <italic>osdwl1</italic>. Physiological analysis and transmission electron microscopy (TEM) observation indicated that the lamellar structure of chloroplast was distorted and began to collapse in some mesophyll cells, which led to the reduction of total chlorophyll contents, net photosynthetic rate and <italic>F</italic>_v/<italic>F</italic>_m ratio of the second and third leaves from top in <italic>osdwl1</italic> at the heading stage. Relative to the wild type plants, the soluble protein content, catalase (CAT) and superoxide dismutase (SOD) activities were significantly decreased, which in turn resulting in the accumulation of H₂O₂ and O₂^܋, and a steady increase of malondialdehyde (MDA) contents in the mutant leaves. Genetic analysis and gene mapping showed that <italic>osdwl1</italic> was controlled by a single recessive nuclear gene, located in a region of 333 kb between SSR marker RM19297 and the InDel marker ID269-2 on the short arm of chromosome 6. The results would further facilitate the cloning and functional analysis of <italic>OsDWL1</italic> gene.