Disomic Inheritance and Segregation Distortion of SSR Markers in Two Populations of Cynodon dactylon (L.) Pers. var. dactylon

RESEARCH ARTICLE Disomic Inheritance and Segregation Distortion of SSR Markers in Two Populations of Cynodon dactylon (L.) Pers. var. dactylon Yuanwen Guo1, Yanqi Wu1*, Jeff A. Anderson2, Justin Q. Moss2, Lan Zhu3 1 Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, Oklahoma, United States of America, 2 Department of Horticulture and Landscape Architecture, Oklahoma State University, Stillwater, Oklahoma, United States of America, 3 Department of Statistics, Oklahoma State University, Stillwater, Oklahoma, United States of America * a11111 OPEN ACCESS Citation: Guo Y, Wu Y, Anderson JA, Moss JQ, Zhu L (2015) Disomic Inheritance and Segregation Distortion of SSR Markers in Two Populations of Cynodon dactylon (L.) Pers. var. dactylon. PLoS ONE 10(8): e0136332. doi:10.1371/journal.pone.0136332 Editor: Guihua Bai, USDA, UNITED STATES Received: March 16, 2015 Accepted: August 1, 2015 Published: August 21, 2015 Copyright: © 2015 Guo 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. Funding: This research was sponsored by the United States Golf Association, United States Department of Agriculture Specialty Crops Research Initiative (SCRI) award 2010-51181-21064, and China Scholarship Council. Competing Interests: The authors have declared that no competing interests exist. Abstract Common bermudagrass [C. dactylon (L.) Pers. var. dactylon] is economically and environmentally the most important member among Cynodon species because of its extensive use for turf, forage and soil erosion control in the world. However, information regarding the inheritance within the taxon is limited. Accordingly, the objective of this study was to determine qualitative inheritance mode in common bermudagrass. Two tetraploid (2n = 4x = 36), first-generation selfed (S1) populations, 228 progenies of ‘Zebra’ and 273 from A12359, were analyzed for segregation with 21 and 12 simple sequence repeat (SSR) markers, respectively. It is concluded that the inheritance mode of tetraploid bermudagrass was complete or near complete disomic. It is evident that the two bermudagrass parents had an allotetraploid genome with two distinct subgenomes since 33 SSR primer pairs amplified 34 loci, each having two alleles. Severe transmission ratio distortions occurred in the Zebra population while less so in the A12359 population. The findings of disomic inheritance and segregation ratio distortion in common bermudagrass is significant in subsequent linkage map construction, quantitative trait locus mapping and marker-assisted selection in the species. Introduction Common bermudagrass [C. dactylon (L.) Pers. var. dactylon] is the best known and economically most important species in the genus Cynodon L. C. Rich. because of its widespread geographic distribution, important economic uses and enormous genetic variability [1,2]. The warm-season, sod-forming and perennial grass has been widely used for turf installation, forage production, soil stabilization and remediation in tropical and warmer temperate regions around the world [3]. In the United States, turf bermudagrass, including common bermudagrass and interspecific hybrids between common bermudagrass and African bermudagrass (C. transvaalensis Burtt-Davy), is a major warm-season turfgrass; whereas forage bermudagrass, PLOS ONE | DOI:10.1371/journal.pone.0136332 August 21, 2015 1 / 10 Disomic Inheritance and Segregation Distortion of Bermudagrass encompassing common bermudagrass and interspecific hybrids between common bermudagrass and C. nlemfuensis Vanderyst, has been planted on approximately 12 million hectares as livestock herbage [4]. The knowledge of ploidy level and meiotic chromosome behavior is important for genetic research and breeding new cultivars [5]. Although the basic chromosome number of Cynodon species initially was mistakenly reported to be x = 10 [6] the confirmed basic chromosome number of Cynodon is x = 9 [7,8]. Among a series of ploidy levels (2n = 2x = 18, 3x = 27, 4x = 36, 5x = 45, and 6x = 54), tetraploid common bermudagrass is the most popular and prevalent form in nature [8–13]. During the meiosis of tetraploid common bermudagrass, chromosomes usually form 18 bivalents, but irregular pairing forms have been observed, including two or more univalents, or one or two quadrivalents [8, 14, 15]. Observing meioses of hybrids of 50 crosses within and between C. dactylon var. dactylon geographic races (tropical, temperate, and seleucidus), Harlan and de Wet indicated that most crosses that displayed bivalent pairing were found in hybrids between parents of similar geographic origins with exceptions [14]. The qualitative inheritance mode is essential information in a species not only because it illuminates homologous chromosome pairing behavior and transmission of alleles from parents to progenies, but also provides basic knowledge for linkage map construction, and marker-trait association like quantitative trait locus (QTL) mapping. The mode of allelic inheritance can also influence breeding procedures that are used for cultivar development. Bethel et al. reported that the tetraploid bermudagrass parent, T89, exhibited polysomic inheritance (with an autotetraploid genome) based on the ratio of 22 repulsion versus 102 coupling linkages revealed with single dose restriction fragment markers [16]. However, with the same mapping population, Harris-Shultz et al. indicated that T89 had two alleles segregating at each locus for 15 simple sequence repeat (SSR) loci except one progeny suggesting the parent displayed disomic inheritance and may be a segmental allotetraploid or allopolyploid rather than an autotetraploid [17]. Since tetraploid common bermudagrass is extremely diverse and widely distributed around the world [2,10], more work is needed to examine inheritance, segregation and genomic structure of the taxon. Therefore, our hypotheses were that the qualitative inheritance of tetraploid common bermudagrass was tetrasomic and that the species had an autopolyploid genome (i.e., two subgenomes were from the same diploid species). Accordingly, the specific objective of this study was to investigate the inheritance mode and segregation regularity in two common bermudagrass populations. Materials and Methods Plant materials To facilitate codominant marker segregation analysis, two populations of first-generation selfed (S1) progenies were created and used to investigate the inheritance of common bermudagrass. The parent for one population was ‘Zebra’ (2n = 4x = 36) that was a variegated plant found in an F1 bermudagrass population growing on the Oklahoma State University Agronomy Research Farm at Stillwater, Oklahoma in 1971, and it was so named because its (...truncated)