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Leaf fall disease is a significant factor contributing to the decline in rubber plant production. Global climate change has altered temperature, humidity, and rainfall, impacting the dynamics of this disease by often increasing its severity and broadening its geographical distribution. This disease, affecting rubber plants, is primarily caused by various fungal pathogens, including Colletotrichum spp., Pestalotiopsis spp., and Phytophthora spp. The emergence and spread of these pathogens are closely associated with environmental conditions. This study investigates how climatic variables influence the development and distribution of leaf fall disease, with the goal of informing the development of effective management strategies. The research focuses on rubber plantations in Southeast Asia, specifically in Indonesia, Malaysia, and Thailand. This study synthesizes scientific literature that examines the correlation between climate change and diseases affecting rubber plants, as well as the evolutionary dynamics of the associated fungal pathogens. The literature review underscores that climate change plays a crucial role in affecting rubber plant productivity in relation to pathogen dynamics and overall plant health. Moreover, the rise in environmental temperatures linked to climate change encourages the growth and development of leaf fall disease pathogens in rubber plants. In addition, without proper mitigation efforts, the continued progression of climate change may lead to more frequent and severe outbreaks, further jeopardizing rubber production and farmer livelihoods.

Rubber tree Corynespora leaf fall (CLF) disease, caused by the fungus Corynespora cassiicola, is one of the most damaging diseases in rubber tree plantations in Asia and Africa, and this disease also threatens rubber nurseries and young rubber plantations in China. C. cassiicola isolates display high genetic diversity, and virulence profiles vary significantly depending on cultivar. Although one phytotoxin (cassicolin) has been identified, it cannot fully explain the diversity in pathogenicity between C. cassiicola species, and some virulent C. cassiicola strains do not contain the cassiicolin gene. In the present study, we report high-quality gapless genome sequences, obtained using short-read sequencing and single-molecule long-read sequencing, of two Chinese C. cassiicola virulent strains. Comparative genomics of gene families in these two stains and a virulent CPP strain from the Philippines showed that all three strains experienced different selective pressures, and metabolism-related gene families vary between the strains. Secreted protein analysis indicated that the quantities of secreted cell wall-degrading enzymes were correlated with pathogenesis, and the most aggressive CCP strain (cassiicolin toxin type 1) encoded 27.34% and 39.74% more secreted carbohydrate-active enzymes (CAZymes) than Chinese strains YN49 and CC01, respectively, both of which can only infect rubber tree saplings. The results of antiSMASH analysis showed that all three strains encode ~60 secondary metabolite biosynthesis gene clusters (SM BGCs). Phylogenomic and domain structure analyses of core synthesis genes, together with synteny analysis of polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) gene clusters, revealed diversity in the distribution of SM BGCs between strains, as well as SM polymorphisms, which may play an important role in pathogenic progress. The results expand our understanding of the C. cassiicola genome. Further comparative genomic analysis indicates that secreted CAZymes and SMs may influence pathogenicity in rubber tree plantations. The findings facilitate future exploration of the molecular pathogenic mechanism of C. cassiicola.

Pestalotiopsis leaf fall disease (PLFD) has been on the increase in recent years, resulting in diminished latex yield in many rubber producing countries. Thus far, some reports have pointed to the presence of fungal pathogen(s) other than Pestalotiopsis sp. in the diseased leaves. To decipher the diversity of fungal pathogens, a total of 110 early-stage and another 110 late-stage symptomatic leaves were sampled from 12 Hevea clones in seven different areas in Malaysia during wintering and wet seasons at different times of the year. A total of 487 fungal isolates were obtained; 241 were from the early-stage and 246 from the late-stage symptomatic leaves. These isolates were clustered into 11 morphotypes based on colony appearance and microscopic observation of the spore. The diversity analysis revealed significant differences in morphotype richness and evenness when comparing different rubber clones, seasonal effects, and locations by which the fungal isolates were sampled. Five isolates representative of the five predominant morphotypes associated with PLFD were analysed using the Internal Transcribed Spacer (ITS) markers and BLAST analysis. Their closest relative species were identified as Colletotrichum conoides , Neopestalotiopsis surinamensis , Lasiodiplodia theobromae , Phyllosticta fallopiae and Letendraea cordylinicola. This study enhanced our understanding of PLFD, particularly the diversity and distribution of fungal communities associated with the disease across different rubber clones, seasons, and locations in Malaysia. The identification of these fungal isolates associated with PLFD symptoms paves the way for further research into their pathogenicity and the development of targeted management strategies to mitigate the disease.

Pestalotiopsis leaf fall disease (PLFD) has emerged as a significant and detrimental foliar disease affecting Hevea brasiliensis in Malaysia since 2017. The disease poses a severe threat to rubber plantations, leading to economic losses and impacting the country’s rubber industry. Understanding the factors contributing to lesion incidence and the potential presence of a fungal complex is crucial for effective disease management. This study aimed to address key objectives, including the identification of primary fungal pathogens responsible for lesion development and examination of the role of co-infections in lesion incidence. To achieve these objectives, five fungal isolates ( Neopestalotiopsis surinamensis , Colletotrichum conoides , Lasiodiplodia theobromae , Phyllosticta fallopiae and Letendraea cordylinicola ) previously identified through the Internal Transcribe Spacer (ITS) regions were subjected to in vitro artificial inoculation experiments on detached rubber leaves. Various combinations of these fungal isolates were tested to evaluate their interactions as possible causal pathogens of PLFD. Three variables were assessed, viz. type of water source (sterile distilled water and rainwater), presence of leaf wounds, and inoculation techniques (conidial suspensions and mycelial agar plugs). Lesion incidence was evaluated based on sporulating occurrences on the detached leaves, recorded seven days after inoculation. Statistical analysis, including non-parametric Pearson’s chi-square tests revealed that the fungal isolates Lasiodiplodia theobromae , Colletotrichum conoides and Neopestalotiopsis surinamensis were the primary contributors to lesion incidence, accounting for 83%, 69%, and 57% of cases, respectively. The study also revealed that lesion incidence was not significantly influenced by inoculation techniques or type of water source but was greater in wounded leaves compared to unwounded leaves. Co-inoculation experiments demonstrated increased lesion incidence, highlighting the role of co-infections in disease severity. Importantly, this study elucidated a potential fungal complex associated with PLFD and provided insights into its epidemiology. The findings contribute to deeper understanding of the disease, offering valuable guidance for effective disease management strategies in H. brasiliensis cultivation in Malaysia.

Thailand, the leading producer of rubber, is currently grappling with Corynespora leaf fall disease, a condition caused by Corynespora cassiicola (Berk. & Curt.) Wei., leading to defoliation and significant yield losses. In this context, 74 endophytic Trichoderma strains isolated from the foliage of healthy rubber trees were assessed for their antagonistic capabilities against C. cassiicola under controlled laboratory conditions. Specifically, isolates of T. atroviride (1 strain), T. asperellum (4 strains), T. hamatum (4 strains), T. harzianum (4 strains), and T. viride (2 strains) were identified based on their pronounced antagonistic potential, as determined through detached leaf and dual culture assays. These isolates were further evaluated for their disease control efficacy under greenhouse conditions. Among the evaluated Trichoderma strains, T. harzianum KUFA 0760 was observed to exhibit significant antagonistic effects in mitigating Corynespora leaf fall disease, achieving a 49.27% reduction in disease incidence tested by the detached leaf method. This was closely followed by T. asperellum KUFA 0754 and T. harzianum KUFA 0762, which suppressed disease severity by 44% and 45%, respectively. These findings warranted the selection of these strains for subsequent determination of their biocontrol efficacy against the disease under field conditions. In these trials, T. harzianum KUFA 0762 emerged as the most effective, leading to a 36–40% reduction in disease prevalence, while T. harzianum KUFA 0760 achieved a 27% reduction in disease severity. Contrastingly, the application of carbendazim was found to have the highest efficacy, resulting in a 57–59% decrease in disease incidence. Additionally, all tested Trichoderma strains demonstrated compatibility with the recommended fungicide for this disease, mancozeb, at a concentration of 3000 ppm. The outcomes of this investigation underscore the significant biocontrol potential of endophytic Trichoderma spp. against rubber tree diseases. The results advocate for the utilization of such biocontrol agents as either standalone alternatives to chemical fungicides or as part of an integrated pest management strategy, in combination with fungicidal treatments, for the effective control of Corynespora leaf fall disease.

Main conclusionIAA cooperates with JA to inhibit SA and negatively regulates rose black spot disease resistance.Black spot disease caused by the fungus Marssonina rosae is the most prevalent and severe ailment in rose cultivation, leading to the appearance of black spots on leaves and eventual leaf fall, significantly impacting the utilization of roses in gardens. Salicylic acid (SA) and jasmonic acid (JA) are pivotal hormones that collaborate with indole-3 acetic acid (IAA) in regulating plant defense responses; however, the detailed mechanisms underlying the induction of black spot disease resistance by IAA, JA, and SA remain unclear. In this study, transcript analysis was conducted on resistant (R13–54) and susceptible (R12–26) lines following M. rosae infection. In addition, the impact of exogenous interference with IAA on SA- and JA-mediated disease resistance was examined. The continuous accumulation of JA, in synergy with IAA, inhibited activation of the SA signaling pathway in the early infection stage, thereby negatively regulating the induction of effective resistance to black spot disease. IAA administration alleviated the inhibition of SA on JA to negatively regulate the resistance of susceptible strains by further enhancing the synthesis and accumulation of JA. However, IAA did not contribute to the negative regulation of black spot resistance when high levels of JA were inhibited. Virus-induced gene silencing of RcTIFY10A, an inhibitor of the JA signaling pathway, further suggested that IAA upregulation led to a decrease in disease resistance, a phenomenon not observed when the JA signal was inhibited. Collectively, these findings indicate that the IAA-mediated negative regulation of black spot disease resistance relies on activation of the JA signaling pathway.

The rubber tree is an important economic tree in Thailand. Recently, the cultivation of rubber trees in Thailand has suffered from a novel leaf fall disease with diverse symptoms, including leaf spot and leaf blight, resulting in severe leaf defoliation. Fungi from the Lasiodiplodia genus, which causes leaf disease in rubber trees, have not been reported in Thailand. Our research aimed to identify Lasiodiplodia associated with leaf blight disease in Thailand by examining morphological characteristics and completing a multi-gene sequence analysis and pathogenicity test to fulfill Koch’s postulates. The internal transcribed spacer regions, translation elongation factor 1-α, and β tubulin 2 were sequenced for the multi-gene sequence analysis. In total, we recovered 14 isolates with 6 of those isolates. Of the six pathogenetic isolates, LST001, LST002, LYT003, LSrt001, and LSrt002 were determined to be Lasiodiplodia chonburiensis, and isolate LYL005 was determined to be L. theobromae. To the best of our knowledge, this is the first report of L. chonburiensis and L. theobromae being associated with leaf blight disease in rubber trees in Thailand or elsewhere.

Background Alternaria blotch disease in Himachal Pradesh, India, caused by Alternaria spp., adversely affects apple cultivars, resulting in reduced fruit size and quality accompanied by premature leaf fall. Methods and results Sixteen Alternaria isolates from apple growing regions underwent comprehensive analysis including morphology, pathogenicity, and molecular characterization. Variations in conidiophore and conidia dimensions, shapes, and divisions were observed among isolates. Pathogenicity assays revealed differences in incubation periods, latent phases, and disease responses. Molecular characterization via nuclear ITS rDNA and RAPD analysis indicated 99–100% homology with Alternaria alternata , Alternaria mali , and other Alternaria spp., with a close phylogenetic relationship to Chinese isolates. Differentiation of isolates based on origin, cultural characteristics, and morphology was achieved using RAPD markers. Conclusions The study identifies diverse genotypes and morphotypes of Alternaria contributing to apple blotch disease in Himachal Pradesh. These findings highlight the complexity of the pathogenic environment and hold significant implications for disease management in apple orchards.

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones.

Apple blotch, caused by Marssonina coronaria, is a serious and widely distributed fungal disease that causes huge losses to apple production especially in South and East Asia. The pathogen causes black spots on apple fruits, leaves and premature defoliation, resulting in weakened physiological balance of the host, reduced tree vigor and decreased yield. It is not clear when the pathogen first occurred in Europe but the disease has become increasingly important in Europe due to its unexpected occurrences in European organic orchards in the last decade. Hence, information on the pathogen host range and geographical distribution, symptoms, biology and disease cycle, as well as epidemiology is vital in developing control strategies. Only the asexual stage of the pathogen has been observed in Europe to date. Therefore, mating and sexual recombination mechanism of the pathogen as well as its overall evolutionary potential is unknown. Altogether, population genetics, importance of primary inoculum, overwintering and the time point of disease outbreak are less researched issues of this pathogen. Host resistance is thought to be the most reliable means to prevent the further spread of this pathogen in organic orchards. However, knowledge about the disease and its interaction with the host is a prerequisite for breeding durable resistant apple cultivars. This review highlights the information available from previous research on M. coronaria and its occurrence on apple.