Mining Applicable Elite Alleles of Growth Duration, Plant Height and Panicle Number per Plant by Conditional QTL Mapping in Japonica Rice
Rice Science, 2011, 18(3): 196 203
Copyright © 2011, China National Rice Research Institute Published by Elsevier BV. All rights reserved
Mining Applicable Elite Alleles of Growth Duration, Plant Height and
Panicle Number per Plant by Conditional QTL Mapping in Japonica Rice
JIANG Jian-hua1, ZHAO Qi-bing2, LIU Qiang-ming1, CHEN Lan1, CHEN Fu-long2, QIAO Bao-jian2, HONG De-lin1
(1State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China; 2
Fengshou Seed Corporation Limited, Plantation of Sihong County of Jiangsu Province, Sihong 223905, China)
Abstract: Unconditional and conditional QTL mapping were conducted for growth duration (GD), plant height (PH) and effective panicle number per plant (PN) using a recombinant inbred line (RIL) population derived from a cross between two japonica rice varieties Xiushui 79 and C Bao. The RIL population consisted of 254 lines was planted in two environments, Nanjing and Sihong, Jiangsu Province, China. Results showed that additive effects were major in all of QTLs for GD, PH and PN detected by the two methods, and the epistatic effects explained a small proportion of phenotypic variation. No interactions were detected between additive QTL and environment, and between epistatic QTL pairs and environment. After growth duration was adjusted to an identical level, RM80-160bp was detected as an applicable elite allele for PN, with an additive effect of 0.71. When effective panicle number per plant was adjusted to an identical level, RM448-240bp was detected as an applicable elite allele for GD, with an additive effect of 4.64. After plant height was adjusted to an identical level, RM80-160bp was detected as an applicable elite allele for PN, with an additive effect of 0.62, and RM448-240bp was detected as an applicable elite allele for GD, with an additive effect of 3.89. These applicable elite alleles could be used to improve target traits without influencing the other two traits.
Key words: japonica rice; growth duration; plant height; effective panicle number per plant; unconditional QTL mapping; conditional QTL mapping; recombinant inbred line
After more than 40 years studies on japonica hybrid rice in China, the area of japonica hybrids planted annually is 8 280 000 hm2, less than 6% of the total area of japonica rice (Deng et al, 2006; Tang et al, 2008). There are two critical reasons for the slow development of japonica hybrid rice. One is the narrow adaptive ability of a single hybrid (Tang et al, 2008), and the other is the indistinctive competition heterosis of hybrids compared with standard pure line cultivars, due to less effective panicle number per plant (Li and Hong, 2004 and 2005; Jin et al, 2005), despite of larger panicle and more number of spikelets per panicle (Hua et al, 2007) in hybrids. In general, more spikelet number per panicle was negatively correlated with effective panicle number per plant (Xu et al, 2005), and grain yield per unit area was positively correlated with growth duration (Su et al, 2003). DNA molecular basis of the complicated relationship has been analyzed by large number of QTL mapping research (Li et al, 1995 and 2000; Lin et al, 1998; Maheswaran et al, 2000; Cao et al, 2001;
Received: 30 November 2010; Accepted: 26 February 2011 Corresponding author: HONG De-lin (delinhong@http://doc.xuehai.net)
Xing et al, 2001; Kennard et al, 2002; Yuan et al, 2003). However, most of these studies did not consider the influence of other traits on the QTL for the target trait. Therefore, the elite alleles identified by above studies may not be applicable to genetic improvement, especially elite alleles of target trait detected in genetic segregating populations derived from indica-japonica crosses. It is difficult to get expected results when elite alleles were introduced into the materials to be improved, due to the influence of the loci for plant height and growth duration, etc. To mine applicable elite alleles for adaptive ability and the related trait of effective panicle number per plant, unconditional QTL mapping and conditional QTL mapping for the traits of growth duration, plant height and effective panicle number per plant were conducted in two growth environments by using a recombinant inbred line (RIL) population.
MATERIALS AND METHODS
Rice materials
The population in this study consisted of 254 RILs
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