Evaluation of Resistance of US Rice Breeding Lines to the Rice Blast Pathogen

Abstract

Rice blast, caused by the fungus Magnaporthe oryzae (anamorph: Pyricularia oryzae), is a ubiquitous disease that threatens rice production in the USA and worldwide. Growing resistant cultivars is the most economical and effective way to manage this disease. Multiple races exist in the M. oryzae population in the USA. It is necessary to know the resistance spectrum of rice cultivars to the prevalent rice blast races in the areas where they are grown. Twelve isolates of M. oryzae collected from the southern US rice-growing region were used in this study. The genetic diversity of these isolates was evaluated with genetic and molecular methods, and the pathogenicity to different rice blast resistance genes was determined by the disease reaction of two sets of near-isogenic lines containing one blast R gene per line. From 2005 to 2016, about 200 Uniform Regional Rice Nursery (URRN) breeding lines have been tested with 9-12 reference isolates annually, and a total of 2377 breeding lines have been tested. The varieties with good resistance to rice blast disease have been identified. The results could be useful for the management of rice blast disease in the southern US rice production area.

Dynamics of spatial and temporal population structure of Pyricularia oryzae in Taiwan

“…2). Mounting evidence has shown that Pi9(t) and Pita-2 are highly resistant to all rice blast isolates, 3,[27][28][29][30][31][32][33][34][36][37][38] indicating that Pi9(t) and Pita-2 are broadly resistant to P. oryzae. However, Pia, Pii, Pik-s, Piz-t, Pit, Pi3, and Pi5(t) are not resistant to the test isolates, which may be attributed to high genetic similarities of the ten rice cultivars (Fig.…”

“…26 Many studies have found that Pi9(t) and Pita-2 exhibit a broad spectrum resistance to P. oryzae using MLs DVs. 3,[27][28][29][30][31][32][33][34][35][36][37][38] The population of the rice blast fungus in the fields was intensively investigated during 1960-1990 in Taiwan. Chien classified 1871 isolates of Taiwan rice blast fungus collected between 1960 and 1987 into 78 physiological races and seven groups using Taiwan DVs.…”

“…So far, more than 30 countries use the LTH MLs to identify the physiological races of rice blast fungus and as the genes source for resistance breeding 26 . Many studies have found that Pi9(t) and Pita‐2 exhibit a broad spectrum resistance to P. oryzae using MLs DVs 3,27–38 …”