Evaluating alfalfa mosaic virus symptoms, susceptibility, and seed transmission along with the population structure across global kura clover (Trifolium ambiguum M. Bieb) germplasm

Abstract

Perennial groundcover (PGC) research is an expanding field of study focused on utilizing the soil-protecting characteristics of perennial plants as permanent intercrops in row-crop agriculture systems. However, there are some risks that PGC could serve as a “green bridge” between cash crops. Alfalfa mosaic virus (AMV) is one such disease that could infect legume PGCs, like kura clover (Trifolium ambiguum M. Bieb), and potentially be transmitted to cash-crop companions (e.g., soybean). The objectives of the current study were to (i) evaluate AMV symptoms and susceptibility in kura clover and (ii) explore population structure and genetic diversity patterns utilizing simple sequence repeat markers across the United States Department of Agriculture National Germplasm Plant Service kura clover collection and various breeding populations from the University of Minnesota. Results showed that 96% tested kura clover field plants had AMV infection and the rate of seed transmission from parent to offspring was 0.4%. Genetic structure among kura clover germplasms generally revealed a ploidy-based separation where diploid and hexaploid cytotypes from distinct genetic clusters and tetraploid germplasm manifest an intermediate pattern. The results indicated substantial AMV sensitivity among broadly based kura clover germplasm, and the risks of both yield losses and “green bridge” due to AMV infection in kura clover should be considered.