Phytoparasitica最新文献

A species of Heterodera has been known to parasitise cereals in Australia since the 1930s. It caused significant yield losses across Australia’s cereal growing regions until resistance breeding largely brought it under control, although it still occurs occasionally, especially in South and Western Australia. Australian cereal cyst nematode has long been considered to represent Heterodera avenae. However, in 2002 the name Heterodera australis was proposed for Australian cereal cyst nematode, as it could be distinguished from all non-Australian populations of H. avenae via biochemical and molecular methods. This new species proposal came with speculation that both H. avenae and H. australis might occur in Australia, and that H. australis might represent a native species. The name H. australis has generally not been accepted by Australian scientists, nor the notion that it is native. There remains some uncertainty as to the validity of H. australis and whether more than one species of cereal cyst nematode occur in Australia. Using a molecular barcoding approach (COI, 18S, ITS, 28S) we examined the species composition of cyst nematodes present in soil samples collected between 1989–2023 from Australian cereal growing regions. We find only one species of Heterodera parasitising cereals and, based on phylogenetic analyses, accept the validity of H. australis as the name best representative of this species. We also argue that, based on presently available evidence, H. australis is not native and was most likely introduced into Australia from Asia in the 1850s, rather than from Europe as has been generally assumed.

Foliar samples were collected from the tomato (Solanum lycopersicum) cultivar ‘IPA-6’ exhibiting begomovirus-like symptoms (apical leaf curling and chlorosis) in Iranduba (Brazilian Amazon). PCR tests with degenerate primers targeting DNA–A and DNA–B components of a sample designated as AM–035 were positive for both genomic regions. Full-length cognate DNA–A and DNA–B components of AM–035 were cloned and sequenced via Sanger dideoxy termination reaction. The complete sequence of the DNA–A component (MK878452) comprised 2,630 nucleotides (organized in five open reading frames – ORFs), and the DNA–B component (MK878451) displayed 2,593 nucleotides (two ORFs). The highest identities ranged from 90 to 92% with tomato chlorotic mottle Guyane virus (ToCMoGV) isolates from French Guiana, indicating a highly divergent Brazilian strain of this virus. The present work reinforces the scenario of the high diversity of tomato-infecting begomoviruses in Brazil. Further studies are needed to determine the distribution and prevalence of ToCMoGV across tomato-producing areas in the Brazilian Amazon River Basin.

Abstract

During the last 15 years in Serbia, there has been an invasion of H. annuus across the country. Plants were initially limited to non-cultivated areas near arable fields, while in recent years the species has started to occur and establish populations in crop fields, especially into wide-row crops. We tested eight herbicides in two greenhouse experiments: 1) a dose-response study; 2) an efficacy study with reduced herbicide rates adding an adjuvant. The tested herbicides showed satisfactory weed control, where all estimated effective doses 90 (ED₉₀) were lower than the recommended field rate for each herbicide, except for dicamba. The addition of non-ionic surfactants significantly increased the efficacy of glyphosate, mesotrione, rimsulfuron, and foramsulfuron. Whereas, there was no clear advantage to adding an adjuvant to bentazone and tembotrione, as the H. annuus population was already very sensitive (plants died in 1/8 of recommended rate in a dose-response study). All tested herbicides, except dicamba, can be used for satisfactory H. annuus control in maize, while glyphosate can be used for control of the species in non-agricultural lands.

Thrips have emerged as major sucking pests of American cotton Gossypium hirsutum L., limiting crop productivity through direct feeding and transmitting viral pathogens. Thrips have been long presumed to be a single species in cotton in northern India, with all the studies reporting it as onion thrips Thrips tabaci Lindeman (Thysanoptera: Thripidae). Even the majority of work from southern and central India reports it as the sole species in their studies conducted on pesticide efficacy, population dynamics, and host plant resistance etc. The present study entailed the sampling of cotton crop from 22 distinct locations representing the north-western, central, and southern zones of India using both morphological and molecular methods. The study reports the prevalence of a thrips species complex in cotton, which is dominated by melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), with the coexistence of other thrips species, viz., T. tabaci, Scirtothrips sp.,(Thysanoptera: Thripidae) and common blossom thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae). Our studies also throw light on the maiden reports of occurrence of orchid thrips, Chaetanaphothrips orchidii Moulton (Thysanoptera: Thripidae) and Asprothrips bimaculatus Michel & Ryckewaert (Thysanoptera: Dendrothripinae) thrips species in cotton from India. The genetic diversity analysis of T. palmi revealed the presence of cryptic species, and haplotyping showed the existence of 53 haplotypes globally, out of which two new haplotypes have been reported in the present study. The possible reasons for the change in cotton thrips composition from a single species to a complex over the years have also been analyzed using historical and conventional population dynamics data gathered over the past 15 years, which categorically indicated that the invasion of new species over the previous years might be responsible for the change in the population structure of thrips in cotton.

Graphical Abstract

Abstract

Soil degradation and climate change put stress on cultivated plants necessitating sustainable weed management practices that reduce herbicide usage and environmental pollution. Cover cropping has emerged as a viable alternative since it has many advantages over traditional herbicides in terms of cultivated plants, soil health, and weed suppression. This three-year study (2020–2023) aimed to examine the performance of cover crops (grass pea, berseem clover, common vetch + triticale, and phacelia) in a drip-irrigated vineyard with restricted water supply in southern Türkiye. The parameters monitored to evaluate the competition between cover crops and weeds were coverage, height, light intensity, shade capacity, dominance, density, and biomass. The common vetch + triticale mixture displaying the highest suppression rates followed by grass pea and phacelia. Cover crops’ height was inversely associated with weed biomass, which suggests that they have the potential to be effective weed management tools because it may provide substantial shading as well as competing performance. The findings of the study highlights the importance of environmentally friendly practices as cover cropping in reducing herbicide reliance and in promoting sustainable vineyard agriculture. Furthermore, the observations of cover crops align with the objectives of the Green Deal suggest a promising approach that enhances soil health be considered to conserve water and foster a more resilient agricultural ecosystem.

Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae) larvae inflict damage on host plants by consuming their leaves. Controlling them represents a key strategy for mitigating economic losses in Brazilian soybean cultivation. In this study, we elucidate the impact of dysbiosis, induced via exposure to the antibiotic tetracycline (TCN), on A. gemmatalis in the presence or absence of the protease inhibitors GORE1 and GORE2. These peptides, each comprising three amino acids (VAL-LEU-LYS and VAL-LEU-ARG, respectively), were investigated. In vitro analyses revealed that the affinity of trypsin-like enzymes for the substrate diminished in caterpillars with dysbiosis that were concurrently exposed to the peptides. Noteworthy differences emerged across treatments in survival analyses, nutritional parameters, and pupal weight. Among these, caterpillars exposed to the GORE2 peptide exhibited the highest mortality and lowest pupal weight. Histological alterations were observed in A. gemmatalis exposed to TCN and peptides. Digestive cells exhibited cytoplasmic vacuolation and heightened apocrine secretion within the intestinal lumen compared to the control group. The present study has successfully demonstrated notable shifts in protein degradation, particularly evident in the altered affinity of A. gemmatalis trypsin-like enzymes when subjected to TCN and the inhibitory effects of GORE1 and GORE2 peptides. Encouragingly, the antibiotic exposure exhibited no detrimental impacts on the survival, nutritional parameters, or overall fitness of A. gemmatalis. Moreover, our findings collectively underscore the potential efficacy of integrating GORE1 and GORE2 peptides for A. gemmatalis management. These peptides have demonstrated significant inhibitory capabilities, coupled with morphological alterations observed in midgut cells, possibly arising from the delayed expression of proteases. This morphological shift appears to impede the pest's nutrition and survival, positioning these tripeptides as a promising tool in addressing the challenges posed by this soybean pest.

Mango is affected by several fungal diseases, including dieback caused by species of the Botryosphaeriaceae family. Recently, mango dieback was reported from multiple locations in Israel. In this study, we isolated and characterized 11 representative fungal isolates belonging to Botryosphaeriaceae from symptomatic mango stems. Lasiodiplodia theobromae and Neoscytalidium dimidiatum are reported in this study as pathogens causing mango dieback in Israel, based on morphology, phylogenetic inference (using ITS and tef1-α regions) and pathogenicity assays. Representative isolates of L. theobromae and N. dimidiatum caused dieback symptoms on detached mango stems under controlled conditions and on mango trees outdoors, growing under natural conditions under shade nets. The pathogens were re-isolated from inoculated stems, fulfilling Koch’s postulates. Lasiodiplodia theobromae has not been previously reported in Israel, while N. dimidiatum has been recorded on pitahaya fruit causing internal black rot disease. In this study, we report in detail on mango dieback caused by L. theobromae and N. dimidiatum in Israel. Considering the economic impact of dieback disease on mango yield, further studies on epidemiology will assist in developing disease management strategies.

The native green apple aphid (Aphis pomi DeGeer) and the invasive green spirea aphid (Aphis spiraecola Patch) share apple as a common host plant during the summer months in Central Europe. Various studies suggest that, under certain conditions, the originally host-alternating A. spiraecola is able to overwinter on apple as a winter host, following a similar life history to A. pomi. In this study, we collected stem mothers (fundatrices) and aphids of the second generation (fundatrigeniae) from ten localities throughout Hungary for nine consecutive springs to assess whether A. spiraecola can overwinter on apple as a winter host. All the collected aphid individuals (1126 aphids from 114 stem colonies during the nine years of the study) belonged to A. pomi, indicating that A. spiraecola does not, or very rarely can, overwinter on apple under Central European conditions.

In the tea ecosystem, tea plants are exposed to attack by the smaller tea tortrix, Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae). Ascogaster reticulata Watanabe (Hymenoptera: Braconidae) is a solitary egg-larval parasitoid wasp that uses chemical cues from tea leaves to search for its host habitat. However, wasp responses to volatiles from egg-laden tea leaves, and plant signaling in response to oviposition by A. honmai, which also recruits parasitoids, are still unknown. Therefore, in this study, we examined wasp responses to volatiles from tea leaves treated with A. honmai egg or reproductive system (RS) homogenate. Although wasps did not show preference for volatiles of host egg-masses or RS homogenates themselves, they preferred egg-laden and RS-treated leaf volatiles to intact leaf volatiles. These results indicate that host plant responses involved in volatile emission attract wasps. Thus, we also investigated plant innate responses induced by A. honmai oviposition. Multiple defense related genes, including JA- and ET-signaling genes, were induced on RS-treated tea leaf. We also investigated gene expression profiles of the SA, JA and ET pathways in a nonhost plant, Arabidopsis thaliana. In A. thaliana, expression of SA and ET-signaling genes was induced by egg treatment, but that of JA-signaling genes was down-regulated. These results suggest that volatile compounds induced by JA pathway may attract A. reticulata to host plant tea leaves.

Mosaic disease spread by the whitefly, Bemisia tabaci, is the major threat to cassava cultivation. This study reveals the variations in cassava whitefly populations across 13 agro-ecological zones of Kerala State, India, and their virulence. Discriminant analysis of morphometric measurements of whitefly pupa from different agro-ecological zones showed more evident distinction compared to adult, and analysis of the whitefly genome using 10 selected ISSR primers has revealed two major clusters within the Sulthan Bathery population, as out group. Sequence analysis of the mitochondrial cytochrome oxidase1 gene showed the presence of two whitefly biotypes, Asia I and Asia II 5. This is the first report of whitefly biotype Asia I infesting cassava. The genetic variation could be the result of isolated speciation under highly diverse elevations and agro-ecological conditions. Cassava plants infested with the Asia I biotype had very low cassava mosaic disease severity compared to those infested with the Asia II 5 biotype. The present study, for the first time, provides molecular evidence of the possibility of more than one biotype of B. tabaci infesting cassava in India.