Reaction of different vaccinium species to the blueberry leaf rust pathogen Thekopsora minima

Authors: Babiker, Ebrahiem; Stringer, Stephen; Smith, Barbara; Sakhanokho, Hamidou

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2018
Publication Date: 10/24/2018
Citation: Babiker, E.M., Stringer, S.J., Smith, B.J., Sakhanokho, H.F. 2018. Reaction of different vaccinium species to the blueberry leaf rust pathogen Thekopsora minima. HortScience. 53(10):1447-1452. https://doi.org/10.21273/HORTSCI13319-18.
DOI: https://doi.org/10.21273/HORTSCI13319-18

Interpretive Summary: Leaf rust is one of the most important disease of blueberry worldwide. To discover new sources of resistance to leaf rust pathogen, 15 southern highbush accessions, two interspecific hybrids, and accessions from five wild blueberry species were tested against an isolate of T. minima, the causal pathogen of blueberry leaf rust. Only two southern highbush accessions showed resistance to the pathogen whereas the tested accessions of the sparkleberry and Darrow's blueberry displayed immunity and resistance to the pathogen. Urediniospores of the fungus from overwintering leaves of Blue Ridge blueberry was found to be virulent on cultivated blueberries, suggesting that the fungus overwinter on leaves of Blue Ridge blueberry.

Technical Abstract: Blueberry leaf rust caused by Thekopsora minima, is a serious threat to blueberry production. To investigate the host range and characterize new sources of resistance, 15 southern highbush accessions, two interspecific hybrids (Vaccinium spp.), and accessions from five diploid Vaccinium species were tested against an isolate of T. minima. Only two southern highbush accessions displayed a moderate level of resistance whereas the two tested accessions of V. arboreum, displayed immunity against T. minima. The tested accessions of V. darrowii exhibited necrosis but with limited sporulation, indicating a high level of resistance. Sporulating lesions and brown spots were observed in tested accessions of V. elliottii and V. tenellum. Brown lesions, large pustules, and abundant sporulation were observed on V. pallidum accessions and their interspecific hybrids. As the lesions expand, defoliation was observed in V. pallidum accessions. When tested against rabbiteye and southern highbush blueberries, urediniospores of T. minima from overwintering leaves of V. pallidum was found to be virulent, suggesting that T. minima overwinter on leaves of V. pallidum. Based on the scanning electron microscopy and symptoms, we hypothesize that T. minima from V. elliottii, V. tenellum, V. pallidum, and V. corymbosum are not distinct and show no host specificity.