Combining Ability of Different Agronomic Traits and Yield Components in Hybrid Barley

RESEARCH ARTICLE Combining Ability of Different Agronomic Traits and Yield Components in Hybrid Barley Xinzhong Zhang1,2,3,4☯, Liangjie Lv1,2,3,4☯, Chao Lv1,2,3,4, Baojian Guo1,2,3,4, Rugen Xu1,2,3,4* 1 Jiangsu Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, China, 2 Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou, China, 3 Key Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, China, 4 Institute of Barley Research, Yangzhou University, Yangzhou, China ☯ These authors contributed equally to this work. * Abstract OPEN ACCESS Citation: Zhang X, Lv L, Lv C, Guo B, Xu R (2015) Combining Ability of Different Agronomic Traits and Yield Components in Hybrid Barley. PLoS ONE 10(6): e0126828. doi:10.1371/journal.pone.0126828 Academic Editor: Meixue Zhou, University of Tasmania, AUSTRALIA Received: January 14, 2015 Accepted: April 8, 2015 Published: June 10, 2015 Copyright: © 2015 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was funded by the National Natural Science Foundation of China (30971779, 31071407, 31128014), the National Barley and Highland Barley Industrial Technology Specially Constructive Foundation of China (CARS-05), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and the Scientific Research Initial Fund for New Researchers in Yangzhou University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Selection of parents based on their combining ability is an effective approach in hybrid breeding. In this study, eight maintainer lines and nine restorer lines were used to obtain 72 crosses for analyzing the general combining ability (GCA) and special combining ability (SCA) for seven agronomic and yield characters including plant height (PH), spike length excluding awns (SL), inter-node length (IL), spikes per plant (SP), thousand kernel weight (TKW), kernel weight per plant (KWP) and dry matter weight per plant (DWP). The results showed that GCA was significantly different among parents and SCA was also significantly different among crosses. The performance of hybrid was significantly correlated with the sum of female and male GCA (TGCA), SCA and heterosis. Hu1154 A, Mian684 A, 86F098 A, 8036 R and 8041 R were excellent parents with greater general combining ability. Five crosses, Hu1154 A×8032 R, Humai10 A×8040 R, Mian684 A×8037 R, Mian684 A×8041 R and 86F098 A×8037 R, showed superior heterosis for most characters. Introduction Barley (Hordeum vulgare L.) ranks the fourth in terms of planting area and total production among all cereal crops in the world [1]. It has been widely used as a health food, animal feed and fermentable material for the beer industry. Great progress has been made on barley heterosis studies [2] with the development of barley three-line breeding system based on cytoplasmic male sterility (CMS), maintainer and restorer lines [3]. The first commercial hybrid variety ‘Colossus’ was released in the UK in 2002 [4]. Since then, Syngenta Ltd released more than ten six-row winter hybrid barley varieties based on the CMS system. Over 200,000 ha of hybrid barley varieties were sown in Europe [4]. Heterosis exists widely in barley hybrids but varies greatly among crosses [2]. The mid-parent heterosis of barley grain yield ranged from 0.7 to 19.9% among different hybrids with an average value of 11.3%, while better-parent heterosis ranged from -1.7 to 18.3% with a slightly lower value of 9.2% [5]. Hence, selection of hybrids with superior heterosis from a large PLOS ONE | DOI:10.1371/journal.pone.0126828 June 10, 2015 1/9 Combining Ability of Agronomic and Yield Traits in Hybrid Barley Competing Interests: The authors have declared that no competing interests exist. number of crosses is cost-effective in breeding programs. One of the key issues for the successful use of hybrid barley is to identify parents that have a high combining ability for producing hybrids with greater heterosis. Evaluation of all possible crosses are time-consuming and laboursome in breeding programs. Certain lines have the ability to combine well with other lines, suggesting that these lines have good GCA. When an inbred combines well only in certain crosses, that means that it has good SCA [6]. Combining ability is effective for the selection of excellent parents in early generations [7]. GCA provides a simple approach to predict additive effects contributing to heterosis [8] and SCA also plays an important role on heterosis [9]. Combining ability has been successfully used to identify superior combinations in rice [10,11], maize [12,13,14] and wheat [15,16]. In barley, combining ability has been reported for various traits, including spike traits [17], flour pasting properties [18], salinity tolerance [19], and waterlogging tolerance [20]. Parents having high GCA values could be used to produce improved lines in hybridization programs and better hybrids can be produced in combination with high SCA values [17]. A moderate and significant correlation between mid-parent and hybrid performance and slightly lower correlation between the sum of GCA effects and performance of the hybrid itself were found when using 124 sixrowed winter barley hybrids based on CMS × restorer to examine the potential in predicting the hybrid performance of grain yield based on mid-parent values or GCA effects [5]. The objectives of this study were to: 1) study combining ability of different agronomic traits and yield components; and 2) study the relationships between heterosis and combining ability thus to provide a theoretical basis for parent selection in the use of hybrid varieties. Materials and Methods Materials and field experiment Eight CMS lines (A) and nine restorer lines (R) (Table 1) were used to make 72 hybrids. All the lines were sourced from the Barley Research Institution of Yangzhou University. The experiment was performed at the Experimental Farm of Yangzhou University (119.4°E, 332.3°N) in the 2011 growing season. All 72 possible hybrids were produced by manual pollination. Forty seeds of each parent and hybrid were sown in a 5-row plot with a 1.2 m rowlength and 20 cm between rows. The experiment was arranged in three replicates. For all trials, the fertilizer used included: 150 kg/ha before sown, 75 kg/ha at seedling stage and 75 kg/ha used at elongation stage. Aphids were sprayed at both seedling and flowering stages. Pinoxaden was applied to control weeds before winter. At maturity, eight plants were r (...truncated)