Category Archives: Journal of Phytopathology

Evaluation of Ascochyta resistance in chickpea genotypes with quantitative polymerase chain reaction assay

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Abstract

Ascochyta blight caused by Ascochyta rabiei is a globally important chickpea disease. Host resistance to Ascochyta blight is considered the most practical and effective means of control, but breeding has been hindered by a lack of effective resistance sources, and time-consuming, labour-intensive traditional methods to screen the resistance level of chickpea genotypes. This paper evaluated the progression of pathogen infection and the disease reaction of chickpea genotypes to Ascochyta blight by traditional and molecular methods. The resistance level of 84 chickpea genotypes was assessed by a quantitative polymerase chain reaction assay (qPCR) using a standard curve produced by various known amounts of pathogen DNA and compared with disease scores based on visual assessments 8 days after inoculation. Disease assessments revealed statistically significant differences between the resistance levels of chickpea genotypes, while the quantity of target DNA in the samples inoculated with the pathogen ranged from 0.004 to 83.37 ng. Our results showed a close relationship between the visual assessment of disease severity and the quantification of the target DNA in chickpea genotypes. The genotypes Tüb-35, Tüb-47, Tüb-26, Tüb-82, Tüb-65 and Tüb-69 were classified as highly resistant to Ascochyta blight based on the results of both assays used for screening chickpea genotypes. This qPCR analysis could be used to quantify disease progression in plant tissues and screen chickpea genotypes as a potential alternative to visual assessment of resistance levels in breeding programmes.

High‐throughput sequencing of maize dwarf mosaic virus from common reed in a wetland

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Abstract

Common reed is a widespread aquatic grass in wetland areas of Turkey. In reed samples, RNAs with the sequence of the Maize dwarf mosaic virus (MDMV) were found using high-throughput sequencing. The nearly complete genome sequence comprised 9514 nucleotides. It contains a 5′ UTR of at least 145 nucleotides, a 3′ UTR of at least 237 nucleotides, and an ORF encoding a single polyprotein of 3041 amino acid residues. Two partial sequences were 7709 nt and 7858 nt long, respectively. Three reed sequences contained 22 nt, 25 nt, and 80 nt insertions in the 5′UTR, respectively. The coding region of MDMV TR-34 (49%) was more conserved than UTRs (34.3%) compared to Johnsongrass mosaic virus (JGMV), Sugarcane mosaic virus (SCMV), and Sorghum mosaic virus (SrMV). MDMV-TR34 reed isolate shares 91%–53.1% nucleotide identity and 98.2%–49% amino acid sequence similarity with other MDMV and three potyvirus sequences, respectively. Recombination analysis indicated six putative recombination events. In 2020–2022, the survey studies showed that 25 of 260 reed samples were infected with MDMV at the infection rate of 9.6% in Tekirdag province. This result is the first report of the complete nucleotidesequence of MDMV in the common reed, a reservoir host for cereals growing areas in Turkey.

Characterization of sugarcane mosaic virus from Cymbopogon spp. plants in Brazil

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Abstract

In April 2022, virus-like symptoms were observed in a Cymbopogon spp. plant grown in the backyard of a house and in Java citronella (C. winterianus) plants in a flower shop in Piracicaba, São Paulo State, Brazil. In April 2023, ca. 700,000 Ceylon citronella (C. nardus) plants showing symptoms of mosaic were observed in a field crop in Dois Corrégos (SP). Evidence for a possible potyvirus infection was revealed by electron microscopy and confirmed by molecular assays. Nucleotide sequencing of amplicons from RT-PCR identified the potyvirus infecting a Cymbopogon spp. plant, Java and Ceylon citronella as sugarcane mosaic virus (SCMV, genus Potyvirus). Phylogenetic analysis of the coat protein gene indicated that the SCMV isolates from Cymbopogon (C1), Java (JC1), and Ceylon citronella (CC) belong to the clade of SCMV from sugarcane. The C1 isolate, and an isolate from sugarcane (SCMV-SU) (control) were mechanically transmitted to Java citronella, sorghum, sugarcane and maize plants. Aphis gossypii transmitted the C1 and SU isolates to Java citronella plants, while Melanaphis sacchari transmitted only the SU isolate to Java citronella plants. This is the first molecular characterization of SCMV from Cymbopogon spp. plants.

Meloidogyne arenaria infecting Matricaria chamomilla in Brazil

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Abstract

Plants of Matricaria chamomilla L. (Asteraceae), well-known medicinal species, showing root galls, were collected in Pelotas, state of Rio Grande do Sul (Brazil). Based on morphological (perineal patterns and males), morphometric (males) and esterase phenotypes (Est A2), we identified the infecting nematode as the root-knot nematode M. arenaria. Under greenhouse conditions, four M. chamomilla plants were inoculated with about 1000 specimens obtained from the isolate. We observed about 207 ± 72 nematodes g−1 of roots, confirming its pathogenicity. To the best of our knowledge, this is the first record of M. arenaria parasitizing M. chamomilla in Brazil and elsewhere.

Evaluation of native isolates of Trichoderma spp. for controlling potato late blight caused by Phytophthora infestans in Nepal

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Abstract

Late blight, caused by Phytophthora infestans, is the most devastating disease of potato worldwide that can cause up to 100% crop loss under disease conducive conditions. The present study was carried out to evaluate and identify effective Trichoderma isolates against the disease. Thirty-nine isolates of Trichoderma spp. isolated at Nepal Plant Disease and Agro Associates (NPDA), Kathmandu from Likhu areas of Nuwakot, Nepal were screened against P. infestans in detached leaf assay for their efficacy in reducing the lesion size of late blight. Fifteen isolates significantly reduced lesion size by 19%–46% compared with the control (water spray). Of them, top 10 isolates along with Sanjeevni (T. viride), a commercial product were tested in field experiments under natural epiphytotic conditions at Thansing and Dhikure of Likhu Rural Municipality in 2020–2021 and 2022–2023 crop years, respectively. The Trichoderma isolates significantly (p < .001) increased plant growth, tuber yield and reduced disease severity in both years. In 2020–2021, isolates, TL1-2A, TL4-81A and TL5-21A reduced disease severity by 37.3%, 37.2% and 30.4%, respectively. The isolate TL1-2A also significantly increased plant height, ground coverage and tuber yield by 41.2%, 30.3% and 72.3%, respectively compared with the control (water spray). In 2022–2023, TL1-2A reduced disease severity by 40.2% and increased tuber yield by 46.4%. Other isolates, though significantly different from control, did not have satisfactory effect on disease control and tuber yield. In both years, the isolate TL1-2A significantly reduced the disease, and increased plant growth and tuber yield. Thus, TL1-2A isolate can be a potential candidate as a biocontrol agent for the integrated management of potato late blight in Nepal.

Pythium and related species on blueberry plants in South Africa

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Abstract

The blueberry industry is one of the successful and expanding agricultural cropping systems in South Africa. As a result of this growth, research into identifying plant disease agents has become increasingly important, yet there are relatively few scientific reports published on the subject in the country. The aim of this study was to identify the causal agents of stunting and leaf scorch on blueberry plants and evaluate their pathogenicity. Root samples were collected from a commercial southern highbush blueberry planting in North West, South Africa. The resulting isolates were identified based on sequence data from the rDNA-ITS. Three Pythiaceae were identified including Globisporangium ultimum var. sporangiiferum, Globisporangium splendens and Pythium aphanidermatum. Results of pathogenicity trials showed that the isolated species were able to cause disease on 40% of the plants. This is the first official report for G. ultimum var. sporangiiferum in South Africa and the first report of G. ultimum var. sporangiiferum and P. aphanidermatum from blueberry plants.