Australasian Plant Pathology最新文献

Ambrosia beetles have co-evolved symbiotic relationships with an array of fungal partners. Mutualistic fungal partners are often highly successful in vertical transmission between beetle generations. These persisting relationships can alter beetle behaviour, resulting in the opportunity to occupy new ecological niches and to spread geographically. In Australia, ambrosia beetles are not currently considered a significant pest in commercial Pinus plantations, where the bark beetle Ips grandicollis is known as the primary invader of stressed trees. However, in 2019, ambrosia beetles Xyleborus perforans and X. bispinatus, co-occurring with I. grandicollis, were found to have colonised a large proportion of drought-stressed trees in commercial Pinus plantations in north-east New South Wales. In this study, X. perforans (the most prevalent of two Xyleborus spp.) was collected from infested dead and dying trees in two NSW Pinus plantations. Fungal isolates of suspected Pinus pathogens were recovered from beetle mycangia and exoskeletons as well as ambrosia beetle galleries. Morphological examination and multilocus sequence analysis identified five fungi associated with X. perforans: Fusarium parceramosum, Fusarium aff. solani, Ophiostoma ips, Raffaelea deltoideospora and Sporothrix pseudoabietina. For Australia, this is the first report of F. parceramosum, as well as the first records of O. ips, R. deltoideospora and S. pseudoabietina being vectored by Xyleborus. Pathogenicity tests were performed on seedlings of three Pinus spp., with O. ips producing significantly longer lesions than the other fungi. This study demonstrates the potential for seemingly harmless ambrosia beetles to vector plant pathogens in Australian forests, providing a mode of disease transmission that should be considered in plantation management and forest biosecurity.

Xylella fastidiosa is an aggressive plant pathogenic bacterium of significant quarantine concern. Accurate and reliable detection tools are essential to minimise the risk of the pathogen’s spread and for outbreak control, as limited post-infection management strategies are possible. Here, we report the development of a specific and potentially field-deployable assay combining a pre-existing Loop-Mediated Isothermal Amplification (LAMP) assay and a Cas12a-based DNA Endonuclease-Targeted (DETECTR) Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) trans reporter for X. fastidiosa detection. The LAMP-CRISPR-Cas12a integrated assay detected the amplified target region of the X. fastidiosa specific rimM gene at the low femto-molar range within 10 min of initiation. The assay detected varied X. fastidiosa sub-species in a range of naturally infected and economically relevant host material, with no non-target amplification recorded. The results show integration of LAMP with CRISPR-based detection is a specific, sensitive and a potentially field-adaptable strategy for the detection of X. fastidiosa and has the potential for further operationally focused improvements.

Leaf rust (also called Brown rust) caused by Puccinia triticina Eriks severely reduces the grain yield of bread wheat and causes huge economic losses globally. Identification and development of wheat genotypes having resistance is only durable and ecofriendly solution to combat this devastating disease. Therefore, characterization of the 101 diverse panel of wheat genotypes was done to assess the resistance and diversity against leaf rust based on morphological parameters under natural field conditions. Field trials were conducted under Augmented Design during the two cropping seasons 2020-21 and 2021-22. Out of 101 genotypes, 09 genotypes (G10, G20, G28, G35, G55, G59, G69, G81 and G90) were found to be completely resistant, 63 genotypes were moderately resistant, 17 genotypes were moderately-susceptible to susceptible and 06 genotypes were susceptible to leaf rust. Ninety genotypes had Coefficient of Infection (CI) value between 0 and 20 exhibiting high resistance, 05 genotypes had CI value 21–40 and 06 genotypes had 41–100 CI value indicating moderate and low resistance respectively. Correlation analysis revealed that leaf rust significantly reduced the growth and yield of studied genotypes because the CI showed highly significant negative correlation with Spike Length (SL), Flag Leaf Area (FLA), Chlorophyll content index (CC), Spikelet per Spike (SS), Grain yield per Spike (GYS) and Thousand Grain Weight (TGW). The principal component analysis (PCA) showed that out of ten, three PCs had Eigenvalues greater than 01 which thus being significant contributed 53.84% of variations. Cluster analysis classified 101 genotypes into eight major clusters at Euclidean distance of 0.950.

Early recognition of symptoms of infection is essential to prevent diseases from spreading through nurseries and into planted systems. In plantations, symptoms of Ceratocystis manginecans infection are typically wilt and canker but symptoms may differ at the nursery stage and as yet have not been described for Eucalyptus pellita. In this study, disease symptoms were recorded over a three-month period in an E. pellita nursery and isolates trapped. Then, to clearly identify those relating to ceratocystis disease and any related mortality, two C. manginecans isolates were re-inoculated by either spraying or dipping of healthy plantlets raised by tissue culture and mini-cuttings. Many disease symptoms were observed in the nursery but only perithecia on the leaves and stems was a clear indication of the presence of a Ceratocystis pathogen. Nine pathogenic fungal species, including C. manginecans, were isolated and identified by DNA analysis. Koch’s postulates indicated that leaf blight associated with C. manginecans was black-brown in colour, irregular, with uneven edges and surrounded by a yellow margin or halo on the upper leaf surface. Mortality following inoculation of plantlets by spraying immediately after planting was > 70%; by contrast, mortality of mini-cuttings was < 50% if spraying was done just before transplanting but < 20% if done 7 or 14 days after transplanting. Isolate EP313C caused significantly greater mortality than isolate EP106C. The research showed that C. manginecans and other pathogens were present in the nursery environment and must be identified and managed as part of good nursery practice.

In this study, two efficient plant growth promoters coupled with potent antagonists viz. Pseudomonas monteilii strain-CRC1, Cedecea davisae strain-CRC2 and AM Fungi named Glomus intraradices (GI) were assessed individually and in combination for their potential to increase yield and essential oil yield as well as lessen the severity of the disease caused by Rhizoctonia solani in Pogostemon cablin (patchouli). In field trials, nine treatments were used: CRC1, CRC2, GI, CRC1 + CRC2, CRC1 + GI, CRC2 + GI, CRC1 + CRC2 + GI, un-inoculated vermicompost, and uninoculated soil as control, with five replications in randomised complete block design, where Rhizoctonia root-rot/wilt was a persistent problem. As compared to the control, the plants inoculated with CRC1 + CRC2 + GI performed best and significantly increased the plant height (87%), plant spread (50%), branch count (67%), herbs yield (67%), essential oil yield (69%) as well as reduced the percent disease index (68%) and percent wilt incidence (87.5%). Moreover, the Patchouli alcohol, a key component of its essential oil, was found to be markedly enhanced by 10% in CRC1 + CRC2 + GI inoculated plants. Furthermore, 43, 27 and 191% of higher uptake of NPK were observed in CRC1 + CRC2 + GI inoculated plants, respectively. After harvesting, a considerable abundance of CRC1, CRC2, and GI in the rhizosphere soil was observed. The results of this experiment indicate that higher herb yields and other observed plant attributes could be due to improved nutrient (NPK) uptake by the patchouli plants. The management of wilt disease and the production of high-quality essential oils in patchouli both can be accomplished with the help of the established consortium.

Cacao (Theobroma cacao) is a tropical plant that is grown throughout India. Cacao pods exhibiting chocolate brown patched symptoms were collected. The organism was isolated and cultured on V8 Agar from the diseased samples. The pathogenicity was proved on Cacao pods by inoculating mycelium of the organism and Koch’s postulates were proved by re-isolating the pathogen. The pathogen was identified as Phytophthora tropicalis based on cultural and morphological characters, followed by molecular investigations (ITS and COX1). This is the first report of Phytophthora tropicalis causing black pod of Cacao in India.

Badnaviruses infecting sugarcane, collectively called sugarcane bacilliform viruses (SCBVs), are reported worldwide and are responsible for causing leaf fleck disease in sugarcane. SCBVs are genetically heterogeneous members of the badnavirus species complex. The objective of this study was to evaluate the genetic diversity of sugarcane bacilliform viruses (SCBVs) in four distinct sugarcane growing sites in Ethiopia. Additionally, the study aimed to examine the transmission of SCBV through vectors. A total of 270 sugarcane leaf samples, including both virus-suspected (symptomatic) and asymptomatic leaves, were collected and tested using a PCR assay with SCBV-F and SCBV-R primer pairs. Out of these samples, 67 (24.8%) were found to be SCBV-positive. Phylogenetic analysis and pairwise sequence comparisons based on the partial RT-RNase H coding region showed that the SCBVs in Ethiopia are genetically diverse. The phylogenetic analysis revealed that isolates from the current study formed four clusters together with SCBV-G, L, Q and S isolates reported from different parts of the world. This suggests that the introduction of SCBV to Ethiopia may have occurred in multiple countries. The glasshouse experiments demonstrated the efficient transmission of SCBV from infected to healthy sugarcane plants by pink sugarcane mealybugs (Saccharicoccus sacchari), which are associated with the sugarcane crop in the field. These findings contribute to the current understanding of the genetic diversity of SCBVs in Ethiopia.

Wheat is among the top food crops and its production needs to be increased to tackle food security. In the developing world subsistence farmers are often unaware of resistant wheat varieties and cannot afford expensive fungicides. This study was designed to evaluate anti-fungal potential of biofabricated Zinc Oxide (ZnO) nanoparticles (NPs) to control leaf rust of wheat. Wheat variety Morocco was used because of its susceptibility to all known strains of Puccini triticina, the causal agent of wheat leaf rust. The green technology based ZnO NPs were prepared. Six treatments varying from 25 to 150 ppm of ZnO NPs concentrations were used. Treatments T4 to T7 provided a high level of protection against leaf rust. This technology will be useful for subsistence/organic farmers and will help them to avoid environmental pollution. The large-scale production of ZnO NPs is feasible and can lead to commercialization for broad-acre farmers.

Sorghum is the fifth most important cereal crop in the world. There is a high potential for sorghum production in Indonesia because of its drought tolerance and wide adaptability. Sorghum cultivation is constrained in Indonesia by pests and diseases. One such disease is tar-spot caused by the Phyllachora sp., an obligate fungal pathogen. Tar spot disease of sorghum has not been widely reported. This study reports the finding of Phyllachora species based on the morphology and molecular identification of tar spot on leaves of sorghum plants of Latu Monca and Latu Kaca local varieties.The pathogen was identified as Phyllachora species. This is the first report of tar spots of sorghum caused by Phyllachora in West Lombok Regency, West Nusa Tenggara Province, Indonesia.

Hormozgan province in the south of Iran is one of the main regions in producing tomatoes, eggplants, bell peppers, and other vegetables as well as sesame in the winter season. In a 2021–2022 survey for phytoplasmas in different areas of this province, phytoplasma–type symptoms were observed in tomato, bell pepper, eggplant and sesame crops and many weed plants including Chenopodium album, Taraxacum officinale, Erodium cicutarium, Physalis angulata, Convolvulus virgatus, Tephrosia apollinea, and Malva sylvestris. Nested PCR assays using primers P1/P7 followed by R16mF2/R16mR1 confirmed association of phytoplasma with all symptomatic plants. 16 S rRNA nucleotide sequencing followed by virtual RFLP analysis showed that all detected phytoplasma strains from different hosts and locations belonged to 16SrII-D subgroup, ‘Candidatus Phytoplasma australasia’. The latter seemed to be the dominant phytoplasma among herbaceous plants in the region. To our knowledge, this is the first world report of natural infection of T. officinale, E. cicutarium, P. angulata, C. virgatus, T. apollinea, and M. sylvestris by a 16SrII-D phytoplasma. These plants can act as alternative hosts for transmission of the phytoplasma strains to major agricultural plants including tomato, pepper, eggplant, sesame and probably other plants.