Australasian Plant Pathology最新文献

Fusarium species causes diseases of a diverse plant species. Though finger millets are resistance to a wide range of pathogens, sometimes, they are also attacked by various phytopathogens. During a survey in September, 2023, a serious leaf blight disease of finger millet (Eleusine coracana L.) was observed at agricultural fields of Morigaon district of Assam, India. The infected plant parts were collected from Morigaon district of Assam, during vegetative phase of the crop. The leaves displayed elliptical spots with grayish-white in centers and brown to reddish-brown margins. In severe cases, the affected leaves turned gray, the foliage withered, and the plants ultimately died. The pathogen was identified as Fusarium fujikuroi by morphological characteristics, pathogenicity test, molecular characteristics and phylogenetic analysis. This study reviles the first report of leaf blight in finger millet (Eleusine coracana L.).

Berkeleyomyces rouxiae is a highly destructive soil borne fungal pathogen causing a pandemic black root rot (BRR) disease of cotton seedlings in New South Wales, Australia. Accurate identification and differentiation of B. rouxiae from its morphological twin, B. basicola was solely based on DNA sequence analyses. In this study, we for the first time developed a duplex PCR assay for simultaneous detection and identification of B. rouxiae and B. basicola without the need for sequencing. Based on nucleotide variation in the MCM7 fragment, a new primer was designed to pair with the one developed by Nakane and Usami (2020) to specifically amplify a 159 bp amplicon of B. basicola. Subsequently, a duplex PCR assay was developed to simultaneously detect the two pathogens at a limit of an approximately 0.05 ng/µL. The duplex PCR was sensitive enough to detect B. rouxiae from crude extracts prepared from a 5-min-microwave-based DNA extraction protocol. Additionally, when used together with a nested PCR, the duplex PCR assay successfully detected the BRR pathogen in DNA extracts obtained directly from a small amount (15–30 mg) of diseased cotton tissue. This duplex PCR provides valuable diagnostic tool for detecting and monitoring the prevalence and distribution of BRR pathogens in cotton in Australia.

Gall rust disease caused by Uromycladium falcatarium is a major constraint to the productivity of Falcataria falcata, a fast-growing leguminous tree widely planted in tropical reforestation and agroforestry systems. Despite its ecological and economic importance, the landscape-level environmental and silvicultural drivers of gall rust incidence remain poorly understood. This study examined site-specific factors of disease incidence and severity in 125 plantations spanning five administrative regions and elevation ranges in Mindanao, Philippines. Results showed that both disease incidence and severity increased with elevation, particularly at elevations > 400 m above sea level (ASL), where infection levels frequently exceeded 75% of trees per plot. Stand density emerged as the most consistent structural predictor, with low-density stands (< 1000 trees/ha) having higher incidence and severity. Other contributing factors included insect species richness, high soil water holding capacity, and an interaction between elevation and slope aspect, wherein northeast-facing slopes had higher risk at low elevations. Disease severity was also associated by proximity to roads and an elevation-dependent effect of soil nitrogen. These findings suggest the multifactorial nature of gall rust outbreaks and the need for integrated, site-specific disease management strategies. Maintaining adequate stand density, improving drainage in waterlogged sites, and strategic site planning may reduce disease pressure. The study provides critical baseline information for sustainable F. falcata cultivation and forest health planning in tropical plantation landscapes.

Rice blast disease is present in most rice-growing regions of the world and parts of Australia, however it was not previously known to occur in New South Wales. In February 2024, leaf symptoms characteristic of rice blast were observed on rice in a commercial field near Lismore in northern NSW. The pathogen was isolated and identified based on morphological and molecular features. Isolates were used to inoculate seedlings, resulting in disease symptoms under controlled growth conditions, and the pathogen was re-isolated from leaf lesions. This is the first confirmed report of rice blast disease on cultivated rice in New South Wales.

During 2023 and 2024, surveys across plum orchards in Himachal Pradesh, India, revealed a high disease incidence of 80%, characterized by typical canker symptoms on branches and trunks frequently accompanied by gum exudation. Twenty-seven bacterial isolates were recovered from symptomatic tissues of the plum cultivar ‘Black Amber’, and four representative isolates (P5, P6, P7, and P8) were subjected to morphological, biochemical, and molecular characterization. The isolates were identified as Gram-positive, coccoid, catalase-positive, and urease-positive obligate aerobes. Pathogenicity was confirmed through both the detached twig method and in planta glasshouse inoculations. Of the tested isolates, only P5 consistently induced characteristic necrotic lesions, sunken cankers, and gum exudation 18 to 30 days post-inoculation, with symptoms eventually leading to shoot dieback. Koch’s postulates were satisfied through the successful re-isolation of isolate P5 from symptomatic tissues. Molecular characterization and phylogenetic analysis based on 16S rRNA, gyrB, and leuS gene sequencing (GenBank accessions PV162547.1, PV268675, and PV268676) confirmed the identity of the pathogen as Staphylococcus warneri. While this bacterium has been previously reported on Prunus species in Iran, this study represents the first report of S. warneri causing bacterial canker and gummosis of plum in India, identifying it as a significant emerging threat to the region's stone fruit production.

Gleditsia sinensis is an important economic tree species widely cultivated in China. In June 2019, stem canker symptoms were observed on G. sinensis trees in Zaozhuang City, Shandong Province. Combined with morphological characterization, phylogenetic analysis, and pathogenicity assays, the causal agent of the disease was identified as Aplosporella javeedii. This study represents the first report of A. javeedii infecting G. sinensis to induce stem canker.

Bhindi yellow vein mosaic virus (BYVMV) and okra enation leaf curl virus (OELCV) diseases cause substantial losses in okra production in the tropics. In developing a successful breeding strategy, okra geneticists must understand how BYVMV and OELCV disease resistance is inherited as well as recognise and utilize resistant genotypes. Six generations (P₁, P₂, F₁, F₂, BC₁, and BC₂) of two chosen crosses: Tolerant × Tolerant (T × T) and Tolerant × Susceptible (T × S) among two tolerant and a susceptible genotype for each disease were used to study the genetic control of host tolerance to BYVMV and OELCV diseases of okra. The inheritance study indicated that tolerance to BYVMV and OELCV disease was controlled by duplicate dominant genes in Tolerant × Tolerant (T × T) cross and duplicate recessive genes in Tolerant × Susceptible (T × S) cross. For both the disease reaction features, digenic epistasis was also found in the scaling and joint scaling tests. In addition, the study also indicated that Tolerant × Susceptible crosses for OELCV and BYVMV diseases produced offspring with tolerant genes for both the crosses. The results suggested selection in later generations (F₄ or F₅), or intermating among selected segregates, followed by one or two generations of selfing could break the undesirable linkage and allow accumulation of favourable alleles for improvement of these traits in okra.

Being the third-largest producer of the globe, Bangladesh's food and economic security is intrinsically linked to rice production. Diseases are a major threat to rice production worldwide, including Bangladesh. Rice blast and bacterial blight (BB) pose significant global threats to rice cultivation. We employed marker-assisted backcrossing to successfully introgress four resistance (R) genes, i.e., Pi9, Pb1, Xa4, and Xa21, into the genetic background of a susceptible rice cultivar BRRI dhan28 to increase its resistance. Pi9-US2 and Pb1-US2 were used as donors for Pi9 and Pb1 blast-resistant genes, respectively, while IRBB58 was the source for Xa4 and Xa21 BB-resistant genes. A rigorous breeding program involving successive backcrosses, self-pollination, and marker-assisted selection was implemented to generate F₁ to BC₃F₇ populations. Genotypic and phenotypic analyses of 400 BC₃F₂ populations demonstrated simple Mendelian inheritance patterns of blast and BB resistance. Among the 50 best selected fixed advanced BC₃F₇ lines, 37 exhibited resistances conferred by all four genes. The aAdvanced lines (ALs) exhibited a significantly low disease score (0–1) for rice blast and BB compared to the BRRI dhan28 (7–9). Marker-trait association analysis showed molecular markers negatively correlated with disease susceptibility. The multi-location trial demonstrated the broad-spectrum resistance of the selected ALs against blast and BB with improved yield and quality traits. Among the ALs, BR(Path)13784-BC3-63–6-4-HR6 or G35 gave the maximum average yield (6.74 t ha⁻¹) across the locations. The molecular markers used in this study can be a promising tool for candidate gene identification. Our advanced lines have the potential to be directly released as a commercial variety or used as a genetic stock in rice breeding programs to combine with other genes.