淹水和干旱条件下水稻根系形成的QTLs及候选基因分析_英文_

遗 传 学 报 Acta Genetica Sinica, February 2006, 33 (2)：141–151 ISSN 0379-4172

QTLs and Candidate Genes for Rice Root Growth Under Flooding and Upland Conditions

ZHENG Bing-Song1,2, YANG Ling1, MAO Chuan-Zao1, ZHANG Wei-Ping1, WU Ping1,①

1. The State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310029, China

2. School of Forestry & Biotechnology, Zhejiang Forestry University, Lin’an 311300, China

Abstract: To investigate the genetic factors underlying constitutive and adaptive root growth under different water-supply condi-tions, a double haploid (DH) population, derived from a cross between lowland rice variety IR64 and upland rice variety Azucena, with 284 molecular markers was used in cylindrical pot experiments. Several QTLs for seminal root length (SRL), adventitious root number (ARN) and total root dry weight (RW) respectively, under both flooding and upland conditions were detected. Two identi-cal QTLs for SRL and RW were found under flooding and upland conditions. The relative parameters defined as the ratio of pa-rameters under the two water-supply conditions were also used for QTL analysis. A comparative analysis among different genetic populations was performed for the QTLs for root traits and several consistent QTLs for root traits across genetic backgrounds were detected. Candidate genes for cell expansion and elongation were used for comparative mapping with the detected QTLs. Four cell wall-related expressed sequence tags (ESTs) for OsEXP2, OsEXP4, EXT and Xet were mapped on the intervals carrying the QTLs for root traits.

Key words: Oryza sativa L.; flooding and upland; QTLs; root trait; candidate genes

In the upland areas where rice is grown under rainfed system, drought is one of the main environ-mental factors that cause a substantial reduction in yield. To reduce the loss of rice yield in rainfed low-land areas, new rice varieties with good adaptation to drought are required. To develop drought-tolerant varieties with a higher potential yield is one of the major objectives of rice breeding programs for rain-fed lowland ecosystems.

Plant roots play an important role in water and nutrient acquisition. Both constitutive and adaptive root growth are implicated in the improved performance of rice under fluctuating water con-ditions[1,2]. Champoux et al. [3] found significant in-teraction between rooting depth and water regime. Lowland rice develops its root system under flooding condition, which results in a different root morphol-ogy from that under upland condition. A deep and Received: 2005-04-26; Accepted: 2005-07-22

thick root system with a greater ability to penetrate compacted soils is associated with drought resis-tance[4]. Greater root elongation results in improved water extraction from deeper layers, which helps plants to avoid drought. Upland rice usually has a deep root system, which allows the crop to satisfy its water requirements in aerobic soil conditions[5].

Modification of rice root system by conventional breeding is difficult because evaluating root traits under field conditions is laborious and tedious. DNA marker-assisted selection technology could be used as an alternative strategy to develop a “drought-tolerant root system”-oriented breeding program. Many quan-titative trait loci (QTLs) associated with adaptive root characteristics under upland conditions have been reported based on different genetic populations[3, 6-16]. Mapping candidate genes has been successfully used to understand allelic information at QTLs[17, 18]. Rice

This work was supported by the Key Basic Research Special Foundation of China (No. G1999011700). ① Corresponding author. E-mail: docpwu@http://doc.guandang.net; Tel: +86-571-8697 1130；Fax: +86-571-8697 1323

142 遗传学报 Acta Genetica Sinica Vol.33 No.2 2006

high-density linkage maps and the positions of many

genes or expressed sequence tags (ESTs) in the rice genome can be used in the candidate gene approach to clone QTLs.

In this report, we investigate the QTLs for root growth under both flooding and upland conditions using a double haploid (DH) population derived from a cross between lowland indica variety IR64 and up-land japonica variety Azucena at the early seedling stage. The results were compared with those of pre-viously reported QTLs for root traits from different mapping populations under flooding and/or upland conditions. ESTs for cell expansion and elongation were used for a candidate gene analysis.

1 Materials and Methods

1. 1 Plant material and pot experiments

A double haploid (DH) population consisting of 96 lines from a cross between IR64, a lowland indica variety, and Azucena, an upland tropical japonica vari-ety, was used for sandy soil culture experiments using cylindrical pots under different water-supply condi-tions in a plant growth room at Zhejiang University, China. Seeds of each DH line and the parents were germinated at 37℃ for 2 d before planted in cylindrical polyvinyl chloride (PVC) pot (15.5 cm inner diameter and 55 cm height) filled with sandy soil (3.5% clay, 2.5% silt, 93.5% sand; pHwater 1:1(v/v) 6.0) up to 5.0 cm from the top of the cylindrical pots. The cylindrical pots were arranged with a randomized complete block design with 3 replications and nine plants each pot from each line. Under upland condition, the cylindrical pots were sealed at the bottom with a stainless steel screen and put in a plastic tray and the water content of the pots from 0-15 cm, 15-30 cm and 30-45 cm below the sandy soil surface was determined at 0 d, 1 d, 5 d, 10 d and 14 d after drainage treatment with the time domain reflectometry method (TDR) (Moisture pointTM MP-917, Environmental Sensors Inc. Canada) using a volumetric analysis. For flooding culture, the half-strength Yoshida’s nutrient so …… 此处隐藏：29542字，全部文档内容请下载后查看。喜欢就下载吧 ……