Molecular Dissection of Quantitative Variation in Bermudagrass Hybrids (Cynodon dactylon x transvaalensis): Morphological Traits

Bermudagrass (Cynodon spp. L.) is the most important warm-season genera grown for forage or turf purposes. It shows extensive variation in morphological characteristics and growth attributes, but the genetic basis of this variation is little understood. Detection and tagging of quantitative trait loci (QTL) affecting above-ground morphology with diagnostic DNA markers would provide a foundation for genetic and molecular breeding applications in bermudagrass. Here, we report early findings regarding genetic architecture of one foliage (canopy height, HT), two stolon (stolon internode length, ILEN and length of the longest stolon LLS), and two leaf traits (leaf length, LLEN and leaf width, LW) in an interspecific population (110 F₁ individuals) derived from a cross between Cynodon dactylon (T89) and C. transvaalensis (T574). For each trait, separate and joint environment analyses were performed on phenotypic data collected across 2 to 5 environments (locations, and/or years or time). Analysis of variance showed significant differences (P < 0.001) among the hybrids for all response traits. Exploratory analysis of marker-trait associations detected 74 QTL and 135 epistatic interactions. Composite interval mapping (CIM) and mixed-model CIM (MCIM) identified 32 main effect QTL (M-QTL) and 13 epistatic QTL (E-QTL). Colocalization of QTL for plant morphology partially explained significant correlations among traits. M-QTL qILEN-3-2 (for ILEN), qLLS-7-1 (for LLS), qLEN-1-1 (for LLEN), and qLW-3-2 (for LW) were ‘stable’ across multiple environments, representing candidates for fine mapping and applied breeding applications. QTL correspondence between bermudagrass and divergent grass lineages promise accelerated progress in predictive breeding of bermudagrass.