Yellow mosaic disease (YMD), caused by begomoviruses and transmitted primarily by Bemisia tabaci, is a major constraint to mungbean production in South Asia. The present study investigated YMD epidemiology, whitefly population dynamics, resistance stability of advanced PRI mungbean lines, and the role of alternate hosts under natural field conditions during two consecutive growing seasons (2021-2022). In the susceptible cultivar Mung Kabuli, YMD incidence increased from 25.67% at flowering to 61.97% at maturity in 2021 and from 40.00% to 72.42% in 2022, coinciding with higher whitefly populations during the disease initiation phase. Advanced mungbean lines exhibited considerable variation in disease response; however, disease pressure increased substantially in 2022, resulting in a decline in resistance stability. Several genotypes previously categorized as resistant or moderately resistant showed increased susceptibility, with 21PRI4 shifting from moderately resistant to moderately susceptible and 21PRI3 from moderately susceptible to susceptible. Yellow mosaic symptoms were recorded on eight alternate plant hosts, among which urdbean, cowpea, pigeon pea, soybean, and jungle mat bean showed detectable begomovirus accumulation. Serological analysis revealed increased begomovirus particle concentration in Mung Kabuli and advanced lines during 2022 compared with 2021, indicating progressive virus accumulation under continuous infection pressure. The consistent presence of begomovirus in alternate hosts highlights their potential role as inoculum reservoirs. These findings demonstrate the dynamic nature of YMD epidemics and emphasize the need for durable resistance sources, molecular characterization of circulating begomoviruses, and integrated management strategies for sustainable mungbean production.
Climate change is increasingly influencing the distribution and outbreak dynamics of insect pests, particularly in tropical agro-ecosystems. This study modelled the current and future potential distribution of Oryctes rhinoceros in Malaysia using MaxEnt based on bioclimatic variables and climate change scenarios. A total of seven uncorrelated bioclimatic variables were analyzed. Precipitation of the driest quarter (Bio17), mean temperature of the wettest quarter (Bio8), and annual temperature range (Bio7) were identified as the most influential predictors. Model performance was robust, with an AUC of 0.818 and a TSS of 0.65, indicating good predictive accuracy and reliability. Results from response curves indicated O. rhinoceros favors moderate dry-season rainfall (100-500 mm), warm and humid conditions (27-28°C), and intermediate thermal seasonality (8-12°C annual temperature range). The Jackknife test further confirmed Bio17 as the dominant variable, followed by Bio8 and Bio7. Current distribution mapping showed variable infestation levels across Malaysia, with higher habitat suitability in states such as Kedah, Perak, Selangor, Terengganu, and Negeri Sembilan. Future projections revealed relatively stable distribution under SSP126 and SSP245 scenarios up to 2050; however, under the high-emission SSP585 scenario, a marked expansion of suitable habitats was observed. By 2070, all scenarios indicated increased habitat suitability, with SSP585 projecting widespread high to very high suitability across most Malaysian states, including Sabah, Sarawak, Selangor, and Peninsular regions. In conclusion, climate change is expected to significantly enhance the potential distribution and establishment risk of O. rhinoceros in Malaysia, particularly under high-emission pathways, emphasizing the need for proactive pest management and climate-adaptive control strategies.
Soybean (Glycine max L.) is an important legume crop valued for its high protein and oil content and its contribution to sustainable agriculture. In Uzbekistan, soybean cultivation has expanded in recent years, increasing the need for accurate identification of fungal pathogens affecting crop production. This study aimed to identify Alternaria species associated with soybean leaf spot using morphological characteristics and molecular analysis. Symptomatic soybean leaves were collected from fields in the Syrdarya region, and three fungal isolates were obtained. Colony morphology and microscopic examination revealed characteristics typical of Alternaria, including dark olivaceous colonies, septate conidiophores, and muriform conidia. A representative isolate (R-21) was subjected to ITS rDNA sequencing, and phylogenetic analysis confirmed its close relationship with reference isolates of Alternaria alstroemeriae available in GenBank. The combined morphological and molecular evidence identified the isolate as A. alstroemeriae associated with soybean leaf spot in Uzbekistan. Although pathogenicity tests and multilocus phylogenetic analyses were beyond the scope of the present study, these findings provide the first molecular evidence of the occurrence of A. alstroemeriae associated with soybean leaf spot in Uzbekistan. The results establish a baseline for future studies on pathogenicity, population diversity, epidemiology, and integrated disease management of this pathogen.
Citrus Greasy Leaf Spot (CGLS) is an emerging foliar disease that threatens citrus productivity in major growing regions of Pakistan. This study aimed to characterize the causal pathogen Zasmidium fructicola, assess its pathogenic variability, and evaluate host biochemical responses along with potential management strategies. Field surveys revealed that the highest disease severity index (41.13%) and disease incidence (56.01%) occurred in Sargodha, while the lowest values were recorded in Faisalabad. Grapefruit and mandarin were the most susceptible cultivars. Morphological characterization of fifteen fungal isolates confirmed their identity as Z. fructicola, exhibiting typical colony morphology and septate, pigmented conidia consistent with Mycosphaerellaceae. Molecular identification using ITS and TEF-1α gene regions showed 98-99% sequence similarity with reference strains, and phylogenetic analysis grouped all isolates into a well-supported clade, confirming species identity. Pathogenicity assays demonstrated significant variability among isolates, with SAK-1 and AKM-1 exhibiting the highest virulence on grapefruit, mandarin, and sweet orange. Biochemical analyses revealed that resistant cultivars showed higher activities of antioxidant enzymes (SOD, POD, CAT), phenolics, proteins, and soluble sugars, whereas susceptible cultivars exhibited reduced defense-related metabolites following infection. In vitro assays indicated that carbendazim and tebuconazole significantly inhibited mycelial growth, with up to 95.7% and 92.16% inhibition, respectively. Among botanical extracts, Syzygium aromaticum showed the highest antifungal activity, achieving up to 97% growth inhibition. In conclusion, Z. fructicola was confirmed as the causal agent of CGLS, exhibiting notable pathogenic variability and wide geographic distribution. Integrated management using resistant cultivars, fungicides, and botanical extracts offers an effective strategy for its sustainable control in citrus orchards.
Xanthomonas arboricola pv. juglandis causes bacterial blight of walnut, a highly destructive disease of walnut (Juglans regia) in the temperate climates of Pakistan. Although the geographical distribution and biochemical characterization of the pathogen in Azad Jammu and Kashmir (AJK) have been reported previously, its molecular characterization and pathogenicity on local cultivars remain largely unexplored. In the present study, we provided the first comprehensive molecular characterization and phylogenetic analysis of 20 X. arboricola pv. juglandis isolates recovered from infected walnut trees across multiple locations in AJK, along with one reference isolate from the University of Punjab, Lahore. The bacterial isolates were cultured, and genomic DNA was extracted. The 16S ribosomal RNA (rRNA) gene was amplified using universal bacterial primers, sequenced, and analyzed alongside reference sequences retrieved from GenBank. Phylogenetic analysis was performed using the maximum likelihood method with appropriate outgroup sequences. The 16S rRNA sequences exhibited high nucleotide identity (98.5-100%) with previously reported sequences of X. arboricola pv. juglandis, confirming the species and pathovar identity of the isolates. Phylogenetic analysis revealed two major genetically distinct clades among the studied isolates, indicating both evolutionary divergence and close relatedness to reference strains. Pathogenicity assays on walnut seedlings demonstrated that all isolates were virulent, producing disease severity scores ranging from 1.0 to 3.5, indicating moderate to high pathogenic potential. These molecular and pathogenicity findings enhance the understanding of the epidemiology of walnut bacterial blight in AJK and are expected to support the development of region-specific disease management strategies and breeding programs for sustainable walnut production.
