Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2007
Publication Date: 4/1/2008
Citation: Jia, Y., Gealy, D.R., Lin, M., Wu, L., Black, H.L. 2008. Carolina foxtail (Alopecurus carolinianus): susceptibility and suitability as an alternative host to rice blast disease (Magnaporthe oryzae [formerly M. grisea]). Plant Disease. 92(4):504-507. doi:10.1094/PDIS-92-4-0504. Interpretive Summary: Rice blast disease is caused by Mangaporthe oryzae is an important threat to rice production around the world. Management of blast disease requires kenowledge of the pathogen and the host plants that it can proliferate on. A common winter annual grass, Carolina foxtail, has been found to be an alternative host for rice blast disease. A colleciton of Carolina foxtail samples was evaluated for susceptibility to US isolates of rice blast. Disease-like symptoms were observed. Conversely, the fungus isolated from the Carolina foxtail caused disease symptoms when rice was inoculated. These results indicate that Carolina foxtail can help blast disease to proliferate and persist in rice fields by sewing as an alternate host for the disease.
Technical Abstract: Rice blast disease caused by fungus Magnaporthe oryzae is known to be a continuous threat to rice production worldwide. Management of blast disese has been challenging due to under explored host range and potential overwintering hosts. Carolina foxtail (Alopecurus carolinianus) was found to be an alternative host for the rice blast fungus (Pyricularia oryzae) in the greenhouse. Carolina foxtail collected over four years in Arkansas was inoculated with a range of predominant races of rice blast fungus in the USA. Irregular, yellow and brown lesions without obvious gray centers were observed after each inoculation with M. oryzae isolates. Differences in these lesions were not observed among foxtail collections over the years. These disease-like lesions were consistently different from a typical blast lesion. Oyrzae races that differed in their pathogenicity toward rice cultivars also displayed differences in lesion development on Carolina foxtail. The most virulent isolate on rice cultivars also rapidly produced lesions on Carolina foxtail. These lesions developed sooner on Carolina foxtail than the most susceptible rice cultivars tested. Conversely, P. oryzae isolates cultured from these lesions in the infected Carolina foxtail also caused typical disease symptoms of blast indicating that they were also pathogenic toward rice cultivars. Susceptibility and suitability of Carolina foxtail as an alternate host to rice blast disease (P. oryzae) is discussed. We suggest that Carolina foxtail can be an overwinter host for the blast pathogen whch is important for managing blast disease worldwide.