ABSTRACT The soilborne plant‐pathogenic fungus Verticillium nonalfalfae causes Verticillium wilt in hop. Infections caused by its highly virulent (lethal) pathotype can lead to the development of a severe level of disease that poses a major threat to hop production. In this study, we investigated the occurrence of mycoviruses in V. nonalfalfae isolates representing different geographical regions and virulence groups using double‐stranded RNA isolation and high‐throughput sequencing. Notably, Verticillium albo‐atrum partitivirus 1 (VaaPV1) was detected in 46 of 90 isolates (51.1%), including both lethal and mild pathotypes. Thirty isolates were sequenced, revealing low genetic divergence, with nucleotide identities of 93.9%–100% for RdRp and 94.5%–100% for CP. The low dN/dS ratio of the RdRp gene (0.119) further indicated strong purifying selection. VaaPV1 was efficiently maintained during fungal growth: hyphal tipping failed to eliminate the virus from any of 70 regenerated cultures, while only 13 of 73 cultures regenerated from protoplasts were virus‐free. Furthermore, VaaPV1 was transmitted horizontally through hyphal anastomosis from all tested donor isolates. Comparisons between infected and isogenic virus‐free isolates revealed no significant differences in fungal growth or virulence on hop, indicating that VaaPV1 establishes a cryptic infection without detectable phenotypic effects under the conditions tested. Overall, our findings demonstrate that VaaPV1 is highly prevalent, genetically conserved and stably maintained in hop‐associated V. nonalfalfae , providing a baseline for future studies of the ecological and biological significance of mycovirus infections in this vascular wilt pathogen.
ABSTRACT Alfalfa Verticillium wilt is a soil‐borne disease that severely limits alfalfa yield and quality, yet effective control measures remain scarce. In this study, four Bacillus strains (i.e., Bacillus amyloliquefaciens LYZ1125, B. velezensis LYZ1126, B. atrophaeus LYZ1127 and B. subtilis LYZ1128) were used singly or in combination to evaluate their biocontrol efficacy. In greenhouse, the strains reduced disease incidence by approximately 60%, decreased the disease index by about 80%, and achieved 80% control efficacy, significantly outperforming the chemical fungicides 0.0052 mg L −1 trifloxystrobin‐tebuconazole (60%) and 0.0446 mg L −1 azoxystrobin (30%). The biocontrol treatments promoted alfalfa growth, increasing plant height, stem diameter, root length, and dry weight per plant by 25%–37%, 20%–27%, 17%–48% and 39%–88%, respectively. Used singly or in combination, they also induced systemic resistance, with salicylic acid and jasmonic acid increasing by 15%–86% and over 33%, respectively. Net photosynthetic rate and chlorophyll content increased by approximately twofold and 4%–83%, respectively, along with enhanced peroxidase activity, while hydrogen peroxide and malondialdehyde accumulation decreased compared with the control. Alfalfa quality improved, with crude protein, soluble sugar, magnesium, and potassium increasing by 8%–30%, 3%–16%, 9%–22%, and 3%–14%, respectively, and reductions in acid and neutral detergent fibre. In the field, alfalfa Verticillium wilt occurred only in the control and thiram‐treated plots, with an incidence rate of approximately 1%. Bacillus mixture (1:1:1:1) outperformed single strains and controls, effectively managing wilt and promoting alfalfa growth via resistance and photosynthesis.
ABSTRACT Spot blotch caused by Bipolaris sorokiniana (teleomorph Cochliobolus sativus ) has become an increasingly important disease of wheat, particularly in regions characterized by warm, humid conditions and late‐sown crop environments. The disease is widely prevalent in the warm and humid wheat‐growing regions of South Asia, particularly across the Indo‐Gangetic Plains. Under favourable conditions, the disease may cause yield losses of about 50%, with an average loss of 15%–20%. With the continuously increasing global population, maintaining stable wheat production requires effective management of spot blotch, which has emerged as a major threat in several wheat‐growing regions. In this context, the present review summarizes key aspects of B. sorokiniana biology and provides an overview of its distribution, disease development, and associated impacts on wheat cultivation. This review also discusses epidemiological factors and challenges in disease prediction due to its complex symptoms. In addition, it provides insights into the wheat– B. sorokiniana pathosystem at the histological and molecular levels to better understand trophism. A range of strategies has been explored for managing spot blotch in wheat. These include the identification of quantitative trait loci (QTLs) associated with resistance, followed by their use in breeding programmes through marker‐assisted selection. Recent advances in genomics‐based tools and their potential to support more effective disease management in the future are discussed.
ABSTRACT Apple production faces significant economic losses due to powdery mildew caused by Podosphaera leucotricha . Rapid and accurate detection is essential for disease control. Here, we describe a loop‐mediated isothermal amplification (LAMP) assay for the specific identification of P. leucotricha . Primers were designed based on the internal transcribed spacer (ITS) region of ribosomal DNA. The reaction temperature and time were optimised based on the earliest threshold time (Tt) and highest endpoint fluorescence intensity. The optimal conditions were determined as 64°C for 20 min. The LAMP assay proved highly specific, showing no cross‐reactivity with any of the non‐target fungal species tested. Detection sensitivity reached as low as 10 −2 fg μL −1 of target DNA. When tested on naturally infected apple leaves from the field, the LAMP assay successfully detected P. leucotricha , with results consistent with conventional PCR analysis. The LAMP assay presented here offers a rapid, reliable and practical solution for on‐site diagnosis of apple powdery mildew.
ABSTRACT The genetic basis of adult plant resistance (APR) in oat to Puccinia coronata f. sp. avenae (Pca), causal agent of oat crown rust (OCR), was investigated through comprehensive analysis of a nested association mapping (NAM) population. Four NAM subpopulations were generated by crossing four donor oat genotypes carrying APR to crown rust with a crown rust‐susceptible founder genotype. Parent‐specific alleles and the genetic variation associated with OCR resistance were explored across nine field environments at three Australian sites in New South Wales and Queensland over 7 years with differing environmental conditions and pathogen pressure. We identified 11 genomic regions associated with adult‐stage crown rust resistance across seven of the 21 oat chromosomes. Two regions on chromosomes 3D (~60 Mb) and 5D (~385 Mb) were detected in more than one environment, including the most virulent pathotype mixture at PBIC, while three closely spaced QTLs detected under the same conditions were observed on chromosome 6A. The donors were confirmed to carry multiple minor resistance loci with cumulative effects, highlighting their value as sources of APR for broad‐spectrum and potentially durable resistance to OCR. Among the loci identified, the regions on 3D and 5D appear to be of greatest value for breeding because they conferred resistance under high pathogen pressure across multiple environments.
