Analysis of quantitative trait loci affecting chlorophyll content of rice leaves in a double haploid population and two backcross populations |
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Authors: | Gonghao Jiang Jing Zeng Yuqing He |
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Affiliation: | 1. National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research and National Center of Crop Molecular Breeding, Huazhong Agricultural University, Wuhan 430070, PR China;2. College of Life Science, Heilongjiang University, Haerbin 150080, China |
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Abstract: | Chlorophyll content, one of the most important physiological parameters related to plant photosynthesis, is usually used to predict yield potential. To map the quantitative trait loci (QTLs) underlying the chlorophyll content of rice leaves, a double haploid (DH) population was developed from an indica/japonica (Zhenshan 97/Wuyujing 2) crossing and two backcross populations were established subsequently by backcrossing DH lines with each of their parents. The contents of chlorophyll a and chlorophyll b were determined by using a spectrophotometer to directly measure the leaf chlorophyll extracts. To determine the leaf chlorophyll retention along with maturation, all measurements were performed on the day of heading and were repeated 30 days later. A total of 60 QTLs were resolved for all the traits using these three populations. These QTLs were distributed on 10 rice chromosomes, except chromosomes 5 and 10; the closer the traits, the more clustering of the QTLs residing on common rice chromosomal regions. In general, the majority of QTLs that specify chlorophyll a content also play a role in determining chlorophyll b content. Strangely, chlorophyll content in this study was found mostly to be lacking or to have a negative correlation with yield. In both backcross F1 populations, overdominant (or underdominant) loci were more important than complete or partially dominant loci for main-effect QTLs and epistatic QTLs, thereby supporting previous findings that overdominant effects are the primary genetic basis for depression in inbreeding and heterosis in rice. |
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Keywords: | a, additive effect BC, backcross BCF1, backcross F1 d, dominance DH, double haploid E-QTLs, epistatic quantitative trait loci GF, grain-filling degree HMP, mid-parental heterosis ICa, leaf chlorophyll a content at developmental stage I ICb, leaf chlorophyll b content at developmental stage I IICa, leaf chlorophyll a content at developmental stage II IICb, leaf chlorophyll b content at developmental stage II II/ICa, ratio of IICa to ICa II/ICb, ratio of IICb to ICb IISF, SPAD values of the flag leaves measured at 30 days after heading IISS, SPAD values of the second leaves measured at 30 days after heading II/ISF, the ratio of IISF to ISF II/ISS, the ratio of IISS to ISS ISF, SPAD readings of the flag leaves measured on the day of heading ISS, SPAD readings of the second leaves measured on the day of heading KGW, grain weight per 1000 grains LR, likelihood ratio LOD, log likelihood value M-QTLs, main-effect quantitative trait loci PL, panicle length QTLs, quantitative trait loci R2, relative contribution of a genetic component RIL, recombinant inbred line SDEN, setting grain density per panicle SP, spikelet per panicle SS, seed-setting rate SSR, simple sequence repeat TC, testcross TP, number of tillers per plant WY, Wuyujing WYF1, DH × WY WYHMP, mid-parental heterosis in WYF1 YD, grain yield per plant ZS, Zhenshan ZSF1, DH × ZS ZSHMP, mid-parental heterosis in ZSF1 population |
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