Category Archives: Journal of Phytopathology

New Melastomataceae hosts of Chrysoporthe species in Brazil

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Abstract

The angiosperm Melastomataceae family is one of the most abundant plant families worldwide and in the Brazilian cerrado, with significant environmental importance in regenerating degraded areas, especially those previously occupied by pastures. Recently, Chrysoporthe Gryzenhout & M. J. Wingf. species were reported in Brazil, causing canker, branch dieback, and mortality in native Melastomataceae. This leads to the demand for further investigation and understanding of these pathosystems. During field surveys, typical signs and symptoms associated with Chrysoporthe infection were found in Rhynchanthera grandiflora (Aubl.) D C. and Miconia theaezans (Bonpl.) Cogn. in southern Minas Gerais. Through phylogenetic analysis of the BT1 and BT2 fragments of the β-tubulin gene and morphological characterization of the isolates obtained, it was possible to identify C. doradensis Gryzenh. & M. J. Wingf. occurring in R. grandiflora and C. puriensis M. E. S. Oliv., T. P. F. Soar. & M. A. Ferr. occurring in R. grandiflora and M. theaezans. Furthermore, pathogenicity assays confirmed the pathogenicity of both species to their hosts.

Characterization of Alternaria alternata isolates from different citrus species grown in Tunisian Cap Bon peninsula

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Abstract

The prospection of citrus trees affected by Alternaria alternata in Tunisian Cap Bon peninsula for 2 years, 2018 and 2019, showed a variation in the percentage of isolation frequency depending on the region, age of citrus trees and citrus species and varieties. Thirty isolates of A. alternata from citrus species were characterized and studied for their variability. The isolates were subjected to morphological identification using macroscopic and microscopic features and molecular characterization through PCR amplification of their internal transcribed spacer regions. A high morphological and molecular diversity within A. alternata isolates was detected. The molecular sequencing results precisely confirmed that these fungal isolates belong to A. alternata strains. Pathogenicity test showed that A. alternata T1 and T9 isolates were capable of causing disease symptoms only on young leaves of clementine plant (MA3 variety). These findings are useful in the development of sustainable strategies to manage Alternaria in citrus-growing areas in Tunisia.

Coat protein genealogy and complete genome characterization of field isolates of rice yellow mottle virus from Zambia

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Abstract

Rice yellow mottle virus (RYMV) is widespread in mainland Africa and adjoining islands but to date its occurrence in Zambia is unknown. In March 2022, field surveys were conducted in Luapula, Northern, Western and Eastern provinces of Zambia to determine the occurrence of RYMV and its genetic relationship with global isolates of the virus. Thirty-three paddy rice fields were visited and 108 leaf tissue samples were collected for analysis. The incidence of yellow mottle symptoms ranged from 25% to 43% in 10 (30.3%) of 33 fields and RYMV was detected in 35 (32.4%) of 108 samples by RT-PCR with virus-specific primers. A subset of 27 RYMV-positive samples was constituted from which full-length (720 bp) coat protein (CP) regions were amplified followed by bidirectional Sanger sequencing. Phylogenetic analysis of the CP cistron revealed distinct clustering of the isolates from Zambia in a monophyletic clade as subtype of the RYMV strain S4. Three isolates were randomly selected and used to obtain complete RYMV genomes of 4448–4449 nucleotides (nt). Comparative analysis of both the CP and the complete RYMV genomes from Zambia with their corresponding sequences in GenBank revealed that they shared 92%–93.2% nt identities with strain S4 isolates. These results confirm for the first time occurrence of RYMV strain S4 in Zambia and further reinforce the need for phytosanitary vigilance to safeguard rice production in Zambia.

Rapid and visual detection of grapevine fleck virus using recombinase polymerase amplification combined with lateral flow strips

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Abstract

Grapevine flack virus (GFkV) causes fleck disease and leads to severe symptoms when the infection occurs with multiple viruses. Restricting the propagation of GFkV-infected grapevines is the ideal management strategy to control the spread of this virus. Therefore, the development of rapid detection methods for GFkV is urgently required. In the present study, we developed a rapid and reliable assay based on the reverse transcription-recombinase polymerase amplification (RT-RPA) combined with lateral flow strips (LFS) using sequence-specific primers and a probe-based coat protein sequences for the GFkV detection in grapevines. The GFkV RT-RPA-LFS assay was optimized at 38°C for 10 min and an extra 5 min LFS incubation time. The optimized RT-RPA-LFS assay had similar sensitivity to RT-PCR and showed no cross-reaction with major viruses infecting grapevines in Korea. The assay was successfully validated for GFkV detection in grapevine field samples. This study provides a reliable technique for rapidly detecting GFkV as an alternative diagnostic approach for producing virus-free grapevine nurseries.

Morphological and molecular characterization of Fusarium incarnatum as a causal disease agent of pepper (Capsicum annuum) fruit rot

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Abstract

Chilli pepper (Capsicum annuum L.) is one of the most important commercially cultivated and consumed vegetables in Turkey. During a disease survey, typical symptoms of fruit rot were observed on mature chilli pepper fruits in several surveyed fields and on dried pepper fruits obtained from local retailers/bazaars in Hatay Province, Turkey. Disease incidence varied from 15 to 45% of the plants in the inspected fields. Following standard isolation procedures, 40 fungal isolates were isolated, purified and single-spore cultures were obtained from surface-disinfected, rotted dried pepper tissue. Of these isolates, six fungal isolates with dense, cottony white aerial mycelia that became beige with age, were isolated on a potato sucrose agar. All isolates were found to be pathogenic on artificially inoculated chilli pepper fruit. Based on morphological characteristics, the isolates were initially identified as Fusarium incarnatum (Desm.) Sacc. 1886. Morphological identification of F. incarnatum isolates was further confirmed by MALDI-TOF and molecular analyses using the sequences of the i nternal t ranscribed s pacer (ITS), partial t ranslation e longation f actor-1α (TEF-1α) and second largest subunit of RNA polymerase II (RPB2) loci. Phylogenetic analysis based on ITS, TEF-1α, RPB2 and concatenation of TEF-1α, RPB2 loci sequences performed with several isolates of Fusarium spp. confirmed that representative fungal isolates (MKUZF1 and MKUZF4) belong to F. incarnatum. To our knowledge, this is the first report of F. incarnatum causing fruit rot in chilli peppers grown in Turkey.

Genetic diversity and resistance assessment among maize genotypes against banded leaf and sheath blight (caused by Rhizoctonia solani f. sp. sasakii) utilizing SSR markers

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A field investigation was carried out during the consecutive kharif seasons of 2021 and 2022 to assess the resistance response of 38 maize genotypes against banded leaf and sheath bight (BLSB). The trials were conducted at CCS Haryana Agricultural University, Regional Research Station, Karnal (India) under artificial epiphytotic conditions. Throughout both seasons, six genotypes (HKI 163, HKI 193-2, HKI 488, IQPMH-18-2, HKI 194-7 and HKI 1128) exhibited resistant reactions, one genotype (HM 8) showed susceptible reaction, whereas 19 genotypes showed moderately resistant response to BLSB. To analyse molecular aspects of BLSB resistance, genomic DNA was extracted and PCR amplification was performed using 22 SSR markers. Ten SSR markers (bnlg238, bnlg161, bnlg127, bnlg339, bnlg615, bnlg1272, phi077, phi080, phi035 and umc1275) revealed distinct banding patterns in resistant and susceptible genotypes. Among these, marker bnlg339 exhibited a band size of 120 bp across 14 genotypes, with six (HKI 163, HKI 193-2, HQPM 5, IQPMH-18-2, HKI 194-7 and HKI 1128) classified as resistant and eight (HKI 193-1, HKI 1657, HKI 1378, HPQM 1, HKI 1659, HPQM 2, T Bio 259 ER and HKI 191-2-5) as moderately resistant, resembling the amplified profile of the resistant check genotype (HKI 163). Similarly, the markers phi080 and bnlg1272 exhibited differential amplified profile of approximately 150 bp and 240 bp, respectively, in 10 (five resistant and five moderately resistant) and 12 (four resistant and eight moderately resistant) maize genotypes throughout the study. The percentage of polymorphism for the SSR markers varied from 0 to 100%, with an average value of 95.45% per primer among all genotypes. The identification of resistant and moderately resistant genotypes and characterization of specific SSR markers associated with resistance offer practical tools for breeders to develop BLSB-resistant maize varieties, ultimately enhancing crop resilience and food security.

Cucumber mosaic virus subgroup IA isolates infect four varieties of Nandina domestica in China

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Abstract

Cucumber mosaic virus (CMV) subgroup IA isolates were first identified from Nandina domestica plants in Zhejiang province of China by small RNA deep sequencing followed by bioinformatics analysis and was confirmed by RT-PCR amplification, 5′ and 3′ RACE and DNA sequencing. The complete nucleotide sequences of this virus shared the highest sequence similarities (97–98%) with CMV subgroup IA isolate CTL RNA1 and RNA3 (GenBank accession no: EF213023, EF213025) and RP48 RNA2 (KC527727), respectively; and converged with CMV subgroup IA isolates into a branch in phylogenetic tree using full length nucleotide sequences. Pathogenicity test confirmed that this virus can be mechanically transmitted to N. domestica, Nicotiana tabacum and N. benthamiana. All thirty randomly collected samples of four major N. domestica varieties (N. domestica cv. Hong Baoshi, Nana, Fire Power and Xiu Dada) in Lin'an Zhejiang province were positive for CMV subgroup IA. This is the first report of CMV subgroup IA isolate on varieties of N. domestica in China.

Detection of a PCR‐based mating type for native intraspecific Beauveria bassiana isolates

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This study developed a PCR-based mating-type analysis of 30 intraspecific Beauveria bassiana isolates after ITS phylogenetic analysis. Out of 30 isolates, only 11 B. bassiana isolates, viz., Bb4, Bb5, Bb11, Bb18, Bb19, Bb20, Bb23, Bb25, Bb27, Bb28, and Bb29, exhibited amplification of the mating-type loci and were thought to be heterothallic. All of these isolates, with the exception of Bb20, had MAT1 mating-type amplification. All these 11 isolates were clustered together with the MAT1- and MAT2-specific reference strains of B. bassiana in the maximum likelihood phylogenetic analysis of mating-type genes (IFO 31953 and IFO 31676, respectively). Although the PCR products obtained by the mating-type assay were short, the phylogenetic trees of the mating-type genes gave better resolution than that of the ITS region. Understanding the mating type of fungi can clarify the biological species concept and the identification of sex-related genes in fungi without the presence of teleomorphs. So, combining phylogenetic, developmental, and mating research on each teleomorph specimen has the potential to clarify the systematics of Beauveria species.

Morphological and pathological characterization of Colletotrichum species causing anthracnose of litchi leaves in Guangxi, China

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Litchi (Litchi chinensis Sonn.) is an evergreen subtropical fruit tree native to southern China. Litchi is vulnerable to a wide range of diseases affecting yield and fruit quality. Anthracnose is one of the main diseases during the period of growth and storage, which has a serious impact on the quality and production of litchi. In December 2020 to May 2021, typical anthracnose symptoms were observed on litchi leaves in different orchards in Qinzhou City, Guangxi Province, Southern China. According to colony features, conidial and appressorial morphology, and sequence analysis of several genomic regions (internal transcribed spacer (ITS) region, chitin synthase (chs-1), actin (act), calmodulin (cal), glyceraldehyde-3-phosphate dehydrogenase (gapdh), β-tubulin (tub2) and the intergenic region of apn2 and MAT1-2-1 (ApMat)), 44 isolates were obtained, and 26 were identified as three Colletotrichum species: C. fructicola (50%), C. siamense (42.31%), C. gigasporum (7.69%). The pathogenicity tests were performed with conidial suspension and mycelia plugs to inoculate wounded litchi seedlings. The results of pathogenicity tests showed that the virulence of C. gigasporum was the weakest, and the virulence of C. fructicola was the strongest. This is the first report of C. gigasporum causing anthracnose of litchi worldwide.

Aflatoxin levels and Aspergillus species in maize in the Province of Isabela, Philippines

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The province of Isabela is the top maize producer in the Philippines. The intensive cultivation and the tropical climate in the region may favour fungal growth and aflatoxin contamination in maize grains. Thus, the study aimed to determine the occurrence of aflatoxin and mycotoxigenic Aspergillus species in maize varieties in this region. Samples were obtained in six municipalities from hybrid (Bt) maize (n = 101) and open-pollinated varieties (n = 6) during the dry season (March and April) of 2019. Aflatoxin levels were quantified through enzyme-linked immunosorbent assay, and Aspergillus species were identified through cultural and molecular methods. Aflatoxin was detected in 50.5% of maize samples; 49.5% of samples were less than the limit of detection (3 μg/kg), 16.8% with 3–20 μg/kg, 10.9% with 21–50 μg/kg and 22.8% above 50 μg/kg. Samples within the acceptable level were 66.3% for food (<20 μg/kg) and 77.2% for animal feed (<50 μg/kg), while 22.8% of samples were above the acceptable level of the Philippine National Standard for raw maize grains. More than 90% of Aspergillus species detected were A. flavus. Other species identified were A. tamarii and A. terreus. Despite the dry production season in the province with low relative humidity during harvesting, inadequate post-harvest practices and the presence of A. flavus elevated the level of aflatoxin in sample grains. Additional work involving multi-year surveys is needed to confirm the results and conclusions of this study.