Occurrence of Root Rot caused by Fusarium fujikuroi on Adzuki Bean in Korea

^1,2 Hyunjoo Ryu¹ Sung Kee Hong¹ Ho Jong Ju^2,3 Hyo-Won Choi^1,*

¹Crop Protection Division, National Institute of Agricultural Sciences, Wanju 55365, Korea
²Department of Agricultural Biology, Jeonbuk National University, Jeonju 54896, Korea
³Institute of Agricultural Science and Technology, Jeonbuk National University, Jeonju 54896, Korea

Abstract

In July 2020, wilting symptoms were observed among adzuki bean plants (Vigna angularis var. angularis L.) in the fields in Yeosu, Korea. Infected plants showed yellowing of leaves, browning inside the stems, splitting of stem bark, and wilting. When these plants were uprooted, their roots were found to be brown. The fungal pathogens NC20-737, NC20-738, and NC20-739 were isolated from symptomatic stem and root tissues. These pathogens were identified as a Fusarium fujikuroi species complex based on their morphological characteristics. Molecular identification was performed using the DNA sequence of translation elongation factor 1 alpha and the RNA polymerase Ⅱ second largest subunit regions. The nucleotide sequences of all three isolates were similar to the F. fujikuroi reference isolates NRRL 13566 and NRRL 5538 of the National Centre for Biotechnology Information GenBank. A pathogenicity test was conducted by the soil inoculation method with cornmeal sand inoculum. Approximately 3 weeks after inoculation, symptoms were observed only in the inoculated adzuki bean seedlings. To the best of our knowledge, this is the first report of Fusarium root rot caused by F. fujikuroi in adzuki beans, both in Korea and worldwide.

Figures & Tables

Fig. 1. Disease index of Fusarium root rot in adzuki bean plants. 0=no symptoms; 1=necrosis of root tissue and less than 30% of average root volume; 2=necrosis of root tissue and less than 31-60% of average root volume; 3=root tissue necrosis, lack of root volume more than 61% and poor growth; 4=complete necrosis of root tissue and no roots or plants death.