Project description:The Mango Sudden Decline (MSD), also referred to as Mango Wilt, is an important disease of mango in Brazil, Oman and Pakistan. This fungus is mainly disseminated by the mango bark beetle, Hypocryphalus mangiferae (Stebbing), by infected plant material, and the infested soils where it is able to survive for long periods. The best way to avoid losses due to MSD is to prevent its establishment in mango production areas. Our objectives in this study were to: (1) predict the global potential distribution of MSD, (2) identify the mango growing areas that are under potential risk of MSD establishment, and (3) identify climatic factors associated with MSD distribution. Occurrence records were collected from Brazil, Oman and Pakistan where the disease is currently known to occur in mango. We used the correlative maximum entropy based model (MaxEnt) algorithm to assess the global potential distribution of MSD. The MaxEnt model predicted suitable areas in countries where the disease does not already occur in mango, but where mango is grown. Among these areas are the largest mango producers in the world including India, China, Thailand, Indonesia, and Mexico. The mean annual temperature, precipitation of coldest quarter, precipitation seasonality, and precipitation of driest month variables contributed most to the potential distribution of MSD disease. The mango bark beetle vector is known to occur beyond the locations where MSD currently exists and where the model predicted suitable areas, thus showing a high likelihood for disease establishment in areas predicted by our model. Our study is the first to map the potential risk of MSD establishment on a global scale. This information can be used in designing strategies to prevent introduction and establishment of MSD disease, and in preparation of efficient pest risk assessments and monitoring programs.
Project description:Ceratocystis accommodates many important pathogens of agricultural crops and woody plants. Ceratocystis fimbriata, the type species of the genus is based on a type that is unsuitable for a precise application and interpretation of the species. This is because no culture or DNA data exist for the type specimen. The aim of this study was to select a reference specimen that can serve to stabilize the name of this important fungus. We selected a strain, CBS 114723, isolated from sweet potato in North Carolina, USA, in 1998 for this purpose. The strain was selected based on the availability of a living culture in a public depository. A draft genome sequence is also available for this strain. Its morphological characteristics were studied and compared with the existing and unsuitable type specimen as well as with the original descriptions of C. fimbriata. The selected strain fits the existing concept of the species fully and we have consequently designated it as an epitype to serve as a reference specimen for C. fimbriata.
Project description:Carotenoid is a tetraterpene pigment beneficial for human health. Although the carotenoid biosynthesis pathway has been extensively studied in plants, relatively little is known about their regulation in sweet potato. Previously, we conducted the transcriptome database of differentially expressed genes between the sweet potato (Ipomoea batatas) cultivar 'Weiduoli' and its high-carotenoid mutant 'HVB-3'. In this study, we selected one of these candidate genes, IbNAC29, for subsequent analyses. IbNAC29 belongs to the plant-specific NAC (NAM, ATAF1/2, and CUC2) transcription factor family. Relative IbNAC29 mRNA level in the HVB-3 storage roots was ~1.71-fold higher than Weiduoli. Additional experiments showed that the contents of α-carotene, lutein, β-carotene, zeaxanthin, and capsanthin are obviously increased in the storage roots of transgenic sweet potato plants overexpressing IbNAC29. Moreover, the levels of carotenoid biosynthesis genes in transgenic plants were also up-regulated. Nevertheless, yeast one-hybrid assays indicated that IbNAC29 could not directly bind to the promoters of these carotenoid biosynthesis genes. Furthermore, the level of IbSGR1 was down-regulated, whose homologous genes in tomato can negatively regulate carotene accumulation. Yeast three-hybrid analysis revealed that the IbNAC29-IbMYB1R1-IbAITR5 could form a regulatory module. Yeast one-hybrid, electrophoretic mobility shift assay, quantitative PCR analysis of chromatin immunoprecipitation and dual-luciferase reporter assay showed that IbAITR5 directly binds to and inhibits the promoter activity of IbSGR1, up-regulating carotenoid biosynthesis gene IbPSY. Taken together, IbNAC29 is a potential candidate gene for the genetic improvement of nutritive value in sweet potato.
Project description:Biocontrol offers a promising alternative to synthetic fungicides for the control of a variety of pre- and post-harvest diseases of crops. Black rot, which is caused by the pathogenic fungus Ceratocytis fimbriata, is the most destructive post-harvest disease of sweet potato, but little is currently known about potential biocontrol agents for this fungus. Here, we isolated several microorganisms from the tuberous roots and shoots of field-grown sweet potato plants, and analyzed their ribosomal RNA gene sequences. The microorganisms belonging to the genus Pantoea made up a major portion of the microbes residing within the sweet potato plants, and fluorescence microscopy showed these microbes colonized the intercellular spaces of the vascular tissue in the sweet potato stems. Four P. dispersa strains strongly inhibited C. fimbriata mycelium growth and spore germination, and altered the morphology of the fungal hyphae. The detection of dead C. fimbriata cells using Evans blue staining suggested that these P. dispersa strains have fungicidal rather than fungistatic activity. Furthermore, P. dispersa strains significantly inhibited C. fimbriata growth on the leaves and tuberous roots of a susceptible sweet potato cultivar ("Yulmi"). These findings suggest that P. dispersa strains could inhibit black rot in sweet potato plants, highlighting their potential as biocontrol agents.
Project description:Black spot disease, which is caused by the pathogenic fungal Ceratocystis fimbriata, seriously affects the production of sweet potato and its quality during postharvest storage. In this study, the preliminary identification of the rhizosphere actinomycete strain SPS-33, and its antifungal activity of volatiles in vitro and invivo was investigated. Based on morphological identification and phylogenetic analysis of the 16S rRNA gene sequence, strain SPS-33 was identified as Streptomyces lavendulae. Volatile organic compounds (VOCs) emitted by SPS-33 inhibited mycelial growth and sporulation of C. fimbriatain vitro and also induced a series of observable hyphae morphological changes. In an in vivo pathogenicity assay, exposure to SPS-33 significantly decreased the lesion diameter and water loss rate in sweet potato tuberous roots (TRs) inoculated with C. fimbriata. It increased the antioxidant enzymes' activities of peroxidase, catalase, and superoxide dismutase as well as decreased malondialdehyde and increased total soluble sugar. In the VOC profile of SPS-33 detected by a headspace solid-phase micro extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), heptadecane, tetradecane, and 3-methyl-1-butanol were the most abundant compounds. 2-Methyl-1-butanol, 3-methyl-1-butanol, pyridine, and phenylethyl alcohol showed strong antifungal effects against C. fimbriata. These findings suggest that VOCs from S. lavendulae SPS-33 have the potential for pathogen C. fimbriata control in sweet potato postharvest storage by fumigant action.
Project description:Heat treatment is a widely applied technique in the preservation of fruits and vegetables, effectively addressing issues such as disease management, rot prevention, and browning. In this study, we investigated the impact of heat treatment at 35 °C for 24 h on the quality characteristics and disease resistance of two sweet potato varieties, P32/P (Ipomoea batatas (L.) Lam. cv 'Pushu13') and Xinxiang (Ipomoea batatas (L.) Lam. cv 'Xinxiang'). The growth in vitro and reproduction of Rhizopus stolonifer were significantly inhibited at 35 °C. However, it resumed when returned to suitable growth conditions. The heat treatment (at 35 °C for 24 h) was found to mitigate nutrient loss during storage while enhancing the structural characteristics and free radical scavenging capacity of sweet potato. Additionally, it led to increased enzyme activities for APX, PPO, and POD, alongside decreased activities for Cx and PG, thereby enhancing the disease resistance of sweet potato against soft rot. As a result, the heat treatment provided a theoretical basis for the prevention of sweet potato soft rot and had guiding significance for improving the resistance against sweet potato soft rot.
Project description:Rabproteins are the largest members of the small G protein family and are widely distributed in eukaryotes. It comprises eight subfamilies and is responsible for regulating vesicle transport, plant growth and development, and biotic and abiotic stress responses. In this study, the small G protein gene StRab5b was cloned from potato, and its biological information, expression profile and induced expression level, overexpression and gene silencing were examined on regulating potato resistance to Phytophthora infestans using PCR, qPCR and Virus-induced gene silencing (VIGS). Our results indicate that the amino acid of StRab5b shows the highest and lowest homology with NbRab5b in N. benthamiana and StRab in potato respectively. StRab5b expression varied among different potato tissues and varieties, and was induced by P. infestans infection. Transiently ectopic expression of StRab5b in N. benthamiana enhanced its resistance to P. infestans, whereas, silencing of StRab5b and its homologous gene facilitated pathogen infection in potato and N. benthamiana respectively. Furthermore, stable expression of the StRab5b gene in potatoes enhanced its redox-stress response capacity, as manifested by the accumulation of H2O2 in infected leaves and subsequent increase in the activity and expression of ROS scavenging enzymes, thereby attenuating the development of P. infestans and ultimately reducing the lesions on infected potato leaves. In addition, the LOX gene transcripts and JA level were upregulated rapidly after inoculation with P. infestans. Collectively, our results suggest that StRab5b positively regulates the resistance against potato late blight (PLB) via JA-mediated defense signaling pathway.
Project description:Theobroma cacao is one of the main crops of economic importance in the world as the source of raw material for producing chocolate and derivatives. The crop is the main source of income for thousands of small farmers, who produce more than 80% of the world's cocoa supply. However, the emergence, re-emergence and proliferation of pathogens, such as Ceratocystis spp., the causative agent of Ceratocystis wilt disease and canker disease, have been affecting the sustainability of many crops. Fungal control is laborious, often depending on fungicides that are expensive and/or toxic to humans, prompting researchers to look for new solutions to counteract the proliferation of these pathogens, including the use of biological agents such as mycoviruses. In this study, we investigated the diversity of microorganisms associated with the T. cacao pathogens Ceratocystis cacaofunesta and Ceratocystis fimbriata with a focus on the virome using RNA sequencing data available in public databases. We used a comprehensive bioinformatics pipeline containing several steps for viral sequence enrichment and took advantage of an integrated assembly step composed of different assemblers followed by sequence similarity searches using NCBI nonredundant databases. Our strategy was able to identify four putative C. cacaofunesta viruses (hypovirus, sclerotimonavirus, alphapartitivirus and narnavirus) and six C. fimbriata viruses (three alphaendornaviruses, one victorivirus and two mitoviruses). All the viral sequences identified showed similarity to viral genomes in public databases only at the amino acid level, likely representing new viral species. Of note, we present the first report of viruses associated with the cacao pathogens C. cacaofunesta and C. fimbriata and the second report of viral species infecting members of the Ceratocystidaceae family. Our findings highlight the need for further prospective studies to uncover the real diversity of fungus-infecting viruses that can contribute to the development of new management strategies.