Development of Simple Sequence Repeat Markers, Fertility Study and Seed Yield Heritability Estimates in Bermudagrass

Abstract

The objectives of this study were to: develop and characterize genomic simple sequence repeat (SSR) markers in C. transvaalensis from its four SSR libraries enriched with [CA]n, [GA]n, [AAG]n, and [AAT]n; study selfing and outcrossing fertility in C. dactylon var. dactylon under open-pollinating conditions using SSR markers; and estimate heritability for seed yield and its two components, inflorescence prolificacy and seed set percentage in C. dactylon var. dactylon. There were 981 unique SSR markers developed and effective with reliable amplifications of targeted bands in C. transvaalensis donor DNA. Up to 93% of the 981 markers were polymorphic in eight C. transvaalensis plants and 544 markers were effective in all genotypes. A set of 917 markers amplified heritable alleles examined with six F1 progeny of African bermudagrass parents `T577' x `Uganda'. In the fertility study, 25 clonal common bermudagrass plants were planted in a randomized complete block design with 3 replications at Perkins and Stillwater, OK. DNA samples were isolated from 1439 progeny germinated from open-pollinated seed of 25 seed parents. After comparing the progeny alleles to those of their respective maternal parents using 11 selected SSR markers, only two progeny were identified to be selfed, indicating an extremely high outcrossing rate of 99.86% in common bermudagrass under open-pollinating field conditions. The field trials were also used to collect data of seed yield, inflorescence prolificacy and seed set percentage in both 2012 and 2013. Half-sib families differed for all three traits, indicating the presence of additive gene action. Family � location effects were observed for seed set and seed yield. All three traits showed family � year interaction effects, while a significant family � location � year interaction existed in the two components. Narrow-sense heritability estimates (0.18 and 0.26-0.68) for seed yield, respectively based on variance component analysis and parent-offspring regressions, indicated a complex genetics of seed yield. Heritability estimates were moderate to relatively high for inflorescence prolificacy (0.30-0.55) and seed set (0.41-0.78). The results indicated that genetic improvement could be achieved if phenotypic selection is applied for seed yield components and conventional genotypic evaluation is needed for seed yield increase.