1
|
Lipps SM, Castell-Miller C, Morris CE, Ishii S, Samac DA. Diversity of Strains in the Pseudomonas syringae Complex Causing Bacterial Stem Blight of Alfalfa ( Medicago sativa) in the United States. Phytopathology 2024:PHYTO02230059R. [PMID: 37913751 DOI: 10.1094/phyto-02-23-0059-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Alfalfa growers in the Intermountain West of the United States have recently seen an increased incidence in bacterial stem blight (BSB), which can result in significant herbage yield losses from the first harvest. BSB has been attributed to Pseudomonas syringae pv. syringae and P. viridiflava; however, little is known about the genetic diversity and pathogenicity of these bacteria or their interaction with alfalfa plants. Here, we present a comprehensive phylogenetic and phenotypic analysis of P. syringae and P. viridiflava strains causing BSB on alfalfa. A multilocus sequence analysis found that they grouped exclusively with P. syringae PG2b and P. viridiflava PG7a. Alfalfa symptoms caused by both bacterial groups were indistinguishable, although there was a large range in mean disease scores for individual strains. Overall, PG2b strains incited significantly greater disease scores than those caused by PG7a strains. Inoculated plants showed browning in the xylem and collapse of epidermal and pith parenchyma cells. Inoculation with a mixture of PG2b and PG7a strains did not result in synergistic activity. The populations of PG2b and PG7a strains were genetically diverse within their clades and did not group by location or haplotype. The PG2b strains had genes for production of the phytotoxin coronatine, which is unusual in PG2b strains. The results indicate that both pathogens are well established on alfalfa across a wide geographic range and that a recent introduction or evolution of more aggressive strains as the basis for emergence of the disease is unlikely.
Collapse
Affiliation(s)
- Savana M Lipps
- Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, U.S.A
| | | | | | - Satoshi Ishii
- Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN 55108, U.S.A
- BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, U.S.A
| | - Deborah A Samac
- Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, U.S.A
- U.S. Department of Agriculture-Agricultural Research Service-Plant Science Research Unit, St. Paul, MN 55108, U.S.A
| |
Collapse
|
2
|
Manan F, Shi G, Gong H, Hou H, Khan H, Leng Y, Castell-Miller C, Ali S, Faris JD, Zhong S, Steffenson BJ, Liu Z. Prevalence and Importance of the Necrotrophic Effector Gene ToxA in Bipolaris sorokiniana Populations Collected from Spring Wheat and Barley. Plant Dis 2023; 107:2424-2430. [PMID: 36724100 DOI: 10.1094/pdis-08-22-2011-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Bipolaris sorokiniana is a necrotrophic fungal pathogen that causes foliar and root diseases on wheat and barley. These diseases are common in all wheat- and barley-growing regions, with more severe outbreaks occurring under warm and humid conditions. B. sorokiniana can also infect a wide range of grass species in the family Poaceae and secrete ToxA, an important necrotrophic effector also identified other wheat leaf spotting pathogens. In this study, the prevalence and virulence role of ToxA were investigated in a collection of 278 B. sorokiniana isolates collected from spring wheat and barley in the Upper Midwest of the United States or other places, including 169 from wheat leaves, 75 from wheat roots, 30 from barley leaves, and 4 from wild quack grass leaves. ToxA was present in the isolates from wheat leaves, wheat roots, and wild grass leaves but was absent from isolates collected from barley leaves. Prevalence of ToxA in wheat leaf isolates (34.3%) was much higher than that in wheat root isolates (16%). Sequencing analysis revealed the presence of two haplotypes, with the majority being BsH2. All ToxA+ isolates produced the functional effector in liquid cultures. Pathogenicity assays revealed that ToxA+ isolates caused significantly more disease on spring wheat lines harboring Tsn1 than their tsn1 mutants, suggesting that the ToxA-Tsn1 interaction plays an important role in spot blotch development. This work confirms the importance of ToxA in B. sorokiniana populations infecting wheat and, thus, the need to eliminate Tsn1 from spring wheat cultivars to reduce susceptibility to spot blotch.
Collapse
Affiliation(s)
- Fazal Manan
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | - Gongjun Shi
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | - Hongmei Gong
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | - Hongyan Hou
- Mathematics Department, Minnesota State University-Moorhead, Moorhead, MN 56560
| | - Hannah Khan
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | - Yueqiang Leng
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | | | - Shaukat Ali
- Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57006
| | - Justin D Faris
- United States Department of Agriculture-Agricultural Research Service Cereal Crops Research Unit, Edward T. Schafer Agricultural Research Center, Fargo, ND 58102
| | - Shaobin Zhong
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| | | | - Zhaohui Liu
- Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
| |
Collapse
|