Establishment Of A Method For Analysis Of Root Hair Length And Diversity In Rice

Rice is not only an important food crop, but also a model monocot species. Root hairs are important organs of plants, known to not only absorb water and nutrients from the rhizosphere, but also act as the site of interaction between plants and soil microorganisms. While in dicot model Arabidopsis mechanisms controlling root hair development have been extensively studied, in rice how root hairs develop and exert their functions remains largely unknown. Compared to Arabidopsis, rice has more root hairs with higher density, and thus difficult to quantify.In this study, using ZH5and ZS97as research materials and Image J as the imaging analysis software, we established a rapid and precise method for the quantitative analysis of rice root hair length. Using this method we carried out an analysis on the root hair length of rice cultivars in a rice mini core collection, and identified cultivars with extreme long or short root hair length. We further dissect the role of auxins in the control of root hair elongation. In addition, we performed an analysis with a ZH5/ZS97RIL population and conducted preliminary QTL mapping for genetic factors controlling root hair length.At present the main results obtained are as follows:1. A novel method for measuring the root hair length in rice was established. By using different culture time and culture conditions, and comparing root hair length quantification data obtained from different parts of rice roots, an optimal experimental condition for the measurement of rice root hair length was established. That is to use3-d-old rice seedlings cultured at28℃and under a16/8h light/dark cycle, and use the root tip region for the quantitative analysis of the overall root hair length in the rice primary root.2. An investigation on the diversity of root hair length among different rice cultivars was performed using a rice mini core collection. Six cultivars with extremely short root hair length and eight with extremely long root hair length were identified. 3. Using rice cultivars with extreme root hair length phenotypes, the effects of sucrose and various auxin (2,4-D, NAA, IAA) on root hair elongation were investigated, in order to identify factors that determine root hair length in rice.4. Preliminary QTL mapping of loci that control root hair length in rice was performed using ZH5/ZS97RIL population and newly established root hair length measurement method. The results of measurement were analyzed with MapMaker and winCart2.0and the initial positioning of QTL was determined by composite interval mapping.5. Using ZH5, ZH11and ZS97as research materials, the effects of environmental stresses, such as drought stress (PEQ mannitol) and low temperature stress (4℃treatment), on root elongation zone size, root hair initiation site and root growth rate were quantitatively analyzed.