Kikuyugrass is an invasive, warm-season turfgrass (C4) that was introduced into California in the 1920s. Although it is used in many sport, and residential turfgrass areas, very little focus has been on the improvement of the species. A comprehensive project was designed and implemented to address kikuyugrass management, improvement through anther culture, and genetic variation within California and other collections.
To study kikuyugrass management a field trial took place in 2012 and 2013 to identify cultural and chemical practices that are most important for producing quality turf and optimal playing conditions on golf course fairways. A 25 factorial design was used to evaluate mowing frequency, cultivation, trinexapac-ethyl, nitrogen, and fungicide treatments. Turf quality was assessed visually and by an instrument that measures “greenness” or Normalized Difference Vegetation Index (NDVI). Turf firmness and ball roll were measured with a Clegg Soil Impact Tester (2.5 kg hammer Gmax) and Pelz meter, respectively. Treatments of trinexapac-ethyl, heavy verticutting, and more frequent mowing practices produced the highest quality turfgrass by increasing firmness, improving turf quality and color, and reducing scalping. Androgenesis through anther culture was attempted on kikuyugrass in order to develop a less vigorous variety. Androgenesis has been successful on the closely related pearl millet but never attempted on kikuyugrass. Kikuyugrass and later pearl millet were tested with two types of media (C17 and Yu-Pei) combined with two different incubation regimes. No signs of mitosis were seen on any of the observed anthers and no embryos were formed in either species. The results were inconclusive and the possibility of successful androgenesis in kikuyugrass remains an open question.
To assess the presence of genetic variation as an indispensable condition for eventual breeding efforts, genotypes were sampled from collections in California (from around the state and at the University of California, Riverside), Hawaii, and Australia. A total of 20,000 single nucleotide polymorphism (SNP) makers were discovered using the Diversity Array Technology sequencing (DArTseq) platform. The hierarchical plot, gap statistics, and principle coordinate analysis all show that the 336 accessions in the study separated into three main clusters. The analysis shows that the amount of genetic variation is low, with 77% of the total genetic variation due to within population variation, while 23% is due to among population variation. The accessions from California show the least genetic variation with accessions from Australia and Hawaii showing a much broader degree of genetic diversity. Although California showed low genetic diversity, there may be enough variation between the accessions at the University of California, Riverside and those collected in the state to begin breeding a turf-type cultivar in California.