Emerging fungal pathogen of an invasive grass: Implications for competition with native plant species.

Infectious diseases and invasive species can be strong drivers of biological systems that may interact to shift plant community composition. For example, disease can modify resource competition between invasive and native species. Invasive species tend to interact with a diversity of native species, and it is unclear how native species differ in response to disease-mediated competition with invasive species. Here, we quantified the biomass responses of three native North American grass species (Dichanthelium clandestinum, Elymus virginicus, and Eragrostis spectabilis) to disease-mediated competition with the non-native invasive grass Microstegium vimineum. The foliar fungal pathogen Bipolaris gigantea has recently emerged in Microstegium populations, causing a leaf spot disease that reduces Microstegium biomass and seed production. In a greenhouse experiment, we examined the effects of B. gigantea inoculation on two components of competitive ability for each native species: growth in the absence of competition and biomass responses to increasing densities of Microstegium. Bipolaris gigantea inoculation affected each of the three native species in unique ways, by increasing (Dichanthelium), decreasing (Elymus), or not changing (Eragrostis) their growth in the absence of competition relative to mock inoculation. Bipolaris gigantea inoculation did not, however, affect Microstegium biomass or mediate the effect of Microstegium density on native plant biomass. Thus, B. gigantea had species-specific effects on native plant competition with Microstegium through species-specific biomass responses to B. gigantea inoculation, but not through modified responses to Microstegium density. Our results suggest that disease may uniquely modify competitive interactions between invasive and native plants for different native plant species.

Identification and fine mapping of spot blotch (Bipolaris sorokiniana) resistance gene Sb4 in wheat.

KEY MESSAGE: A new spot blotch (Bipolaris sorokiniana) resistance gene Sb4 was mapped in a genomic interval of 1.34 Mb on wheat chromosome 4BL. Spot blotch, caused by Bipolaris sorokiniana, has emerged as a serious concern for cultivation of wheat in warmer and humid regions of the world, which results in substantial yield losses and descends with quality. In this study, we identified and mapped a spot blotch resistance gene, designated as Sb4, against B. sorokiniana in wheat. Bulked segregant RNA-Seq (BSR-Seq) analysis and single-nucleotide polymorphism mapping showed that Sb4 is located on the long arm of chromosome 4B. A genetic linkage map of Sb4 was constructed using an F4 mapping population developed from the cross between 'GY17' and 'Zhongyu1211,' and Sb4 was delimited in a 7.14-cM genetic region on 4BL between markers B6811 and B6901. Using the Chinese Spring reference sequences of chromosome arm 4BL, 13 new polymorphic markers were developed. Finally, Sb4 was mapped in a 1.19-cM genetic interval corresponding to a 1.34-Mb physical genomic region of Chinese Spring chromosome 4BL containing 21 predicted genes. This study provides a foundational step for further cloning of Sb4 using a map-based approach.

Gonorrhea-positive sinus cultures in a 15-year-old with allergic fungal sinusitis.

This article describes a patient with gonorrhea in sinus cultures and allergic fungal sinusitis. A multidisciplinary team was assembled to deliver the results to the minor patient and her family and provide support and resources for long-term care.