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Professor ANAI Toyoaki and his research team have identified a gene conferring resistance to bacterial pustule in soybeans
For the first time globally, the resistance gene that has been utilized in the United States since the 1950s has been identified.
Abstract
Bacterial pustule is a soybean disease that occurs widely in warm regions. The National Agriculture and Food Research Organization (NARO) has identified the bacterial pustule resistance gene, rxp, which has been used in soybean breeding in the United States and other countries for over 70 years. Additionally, NARO has developed a DNA marker to efficiently select soybeans carrying this gene. Using this DNA marker, NARO is advancing the breeding of resistant soybean varieties.
Bacterial pustule*1 (hereafter referred to as "the disease") is a soybean disease caused by bacterial infection in warm and humid climates. It causes light yellow to light brown spots on the surface and underside of leaves. In severe cases, the entire leaf turns light yellow, leading to defoliation, plant death, reduced yield, and decreased quality due to smaller seed size. The National Agriculture and Food Research Organization (NARO) has identified the resistance gene, rxp (hereafter referred to as "the resistance gene"), and elucidated its DNA sequence. They have also developed a DNA marker*2 to introduce bacterial pustule resistance into Japanese soybean varieties.
In the United States, breeding materials with disease resistance that almost completely prevent bacterial pustule lesions have been used since the 1950s, resulting in nearly all soybean varieties being resistant to the disease. While resistance breakdown, a phenomenon where resistant varieties become susceptible due to rapid evolution of pathogens, is often observed, the bacterial pustule resistance used in North America has shown stable and strong resistance without breakdown for over 70 years. The newly developed DNA marker will facilitate the use of this gene in Japanese soybean breeding programs.
In our country, breeding focused on resistance to bacterial pustules has not been conducted until now, so many Japanese varieties do not possess genes for resistance to bacterial pustules. However, bacterial pustules frequently occur in warm and humid climates. With the recent trend of high temperatures during the growing season and the frequent and intensified storms, the area affected by bacterial pustules in Japan has been expanding, and the severity of outbreaks is also becoming a concern. Therefore, the National Agriculture and Food Research Organization (NARO) will expand the development of varieties with strong and stable resistance to bacterial pustules by utilizing the DNA markers developed in this study.
Glossary
*1 Bacterial Pustule in Soybean
In warm and humid climates, infection by a type of bacteria, Xanthomonas axonopodis pv. glycines (also known as Xanthomonas campestris pv. glycines), causes small light green spots to appear on the leaves. These spots gradually develop into lesions with brown centers and yellow halos. The bacteria spread through wind and rain, such as during typhoons. Severe infections can cause the entire leaf to turn pale yellow, leading to defoliation and even plant death.
*2 Selection Using DNA Markers
DNA markers are indicators used to detect differences in DNA sequences between varieties. When developing new varieties, determining the strength (resistance) of plants against diseases through actual cultivation is very labor-intensive. However, by using DNA markers to identify the presence of resistance genes, it is possible to select resistant soybean seeds before planting by extracting DNA from a part of the seed. These selected seeds can then be used for cultivation and breeding.
Paper Information
Taguchi-Shiobara F. et al. (2024) A single nucleotide insertion in Rxp confers durable resistance to bacterial pustule in soybean. Theor. Appl. Genet. 137：254
DOI: 10.1007/s00122-024-04743-5
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