Report Of Wilt Research Articles

First Report of Wilt Caused by Fusarium nanum (FIESC 25) on Mungbean (Vigna radiata) in Pakistan.

Mungbean, Vigna radia (L.) R. Wilczek, is ranked 2nd next to chickpea (Cicer arietinum) in total cultivation and production in Pakistan. In August of 2022 and 2023, mungbean plants (cv. PRI Mung-2018) were found wilting in a field at the Ayub Agricultural Research Institute, Faisalabad, Pakistan. Wilted leaves turned yellow, died, but remained attached to the stem. Vascular tissue at the base of the stem showed light to dark brown discoloration. Roots were stunted with purplish brown to black discoloration. Symptomatic mungbean plants were collected from fields at five different locations (20 samples/location). Disease incidence was similar among the five fields, ranging from 5 to 10% at each location depending upon type of germplasm and date of sowing. For fungal isolation and morphological identification, symptomatic stem and root tissues were cut into ~5 mm2 pieces with a sterilized blade. Tissues were surface-sterilized for one min in a 0.5% sodium hypochlorite solution, rinsed twice in sterilized water, air dried on sterilized filter paper, and aseptically placed on potato dextrose agar (PDA) containing 0.5 g/L-1 streptomycin sulphate. Plates were incubated for 3-4 days at 25 ± 2°C with a 12-h photoperiod. Single-spore cultures were used for morphological and molecular analyses. Isolates on PDA grew rapidly and produced abundant white aerial mycelium that turned off-white to beige with age. Macroconidia were hyaline, falcate, typically 3-to-6 septate with a pointed apical cell and a foot-shaped basal cell, measuring 24.5-49.5 x 2.7-4.7 μm (n = 40). Globose to obovate chlamydospores measuring 5.8 ± 0.5 μm (n = 40) were produced singly or in chains and were intercalary or terminal and possessed roughened walls. The morphological data indicated the isolates were members of the genus Fusarium (Leslie and Summerell 2006). To obtain a species-level identification, a portion of translation elongation factor 1-α (TEF1), the largest subunit of RNA polymerase (RPB1), and the second largest subunit of RNA polymerase (RPB2) region were PCR amplified and sequenced using EF1/EF2 (O'Donnell et al. 1998), Fa/G2R (Hofstetter et al. 2007), and 5f2/7cr (Liu et al. 1999) primers, respectively. DNA sequences of these genes were deposited in GenBank under accession numbers MW059021, MW059017 and MW059019, respectively. The partial TEF1, RPB1 and RPB2 sequences were queried against the Fusarium MLST database (https://fusarium.mycobank.org/page/Fusarium_identification), using the polyphasic identification tool. The BLASTn search revealed 99.9% identity of the isolate to F. nanum (Xia et al. 2019), formerly FIESC 25 of the F. incarnatum-equiseti species complex (MRC 2610, NRRL 54143; O'Donnell et al. 2018). To confirm pathogenicity, roots of 3-5 leaf stage mungbean seedlings were soaked in a 106 spores ml-1 conidial suspension of the fungus for 15 min and then planted in 10 cm pots containing sterilized soil. Mock-inoculated plants with sterile water served as a negative control. Twenty pots that were used for each inoculated and control treatment were maintained at 25 ± 2°C, 14:8 h photoperiod, and 80% relative humidity in a growth chamber. After 15 days, leaf yellowing, internal browning from the base of stems and root discoloration was observed in all the inoculated plants. The uninoculated negative control plants remained asymptomatic. Fusarium nanum was re-isolated from artificially inoculated plants and identified by colony growth, conidial characteristics on PDA and molecular analyses (TEF1). To our knowledge, this is the first report of wilt caused by F.nanum on mungbean in Pakistan. In Pakistan, mungbean cultivation in irrigated areas has increased in recent years. It has been introduced frequently in citrus orchards, crop rotation of maize and sesame, intercropping with sugarcane and as green manure. However, citrus, maize, sesame and sugarcane are also hosts of Fusarium spp. Therefore, this information warrants sustainable crop protection and may have an impact on further interaction of F. nanum with other wilt pathogens.

First Report of Wilt of Syzygium malaccensis Caused by a Member of the Fusarium oxysporum Species Complex in Brazil

First Report of Wilt of <i>Syzygium malaccensis</i> Caused by a Member of the <i>Fusarium oxysporum</i> Species Complex in Brazil

First report of wilt and necrosis caused by Diplodia seriata on cowpea in Tennessee, USA

Cowpea (Vigna unguiculata) is a productive vegetable, grain, forage or cover crop legume that is particularly adapted to subtropical and tropical climates where stresses such as drought, high temperature and marginal soil conditions are …

First Report of Fusarium Wilt of Chicory (Cichorium intybus) Caused by Fusarium oxysporum in Italy.

In the summer of 2009, a wilt of chicory was observed on 25 to 30% of 30-day-old Cichorium intybus L. cv. Clio plants grown outdoors on a commercial farm in Piedmont (northern Italy). Affected plants were chlorotic and stunted with poorly developed root systems compared with healthy plants. Black streaks were observed in the stem and proximal part of the leaf vascular system in wilted plants. Fusarium oxysporum Schltdl. was isolated from symptomatic vascular tissue on a Fusarium-selective medium (1) from 80% of samples. Grown on potato dextrose agar (PDA) for 4 days at 23°C, the colonies, initially white and later pale pink, produced hyaline microconidia that were oval-elliptical and cylindrical in shape measuring 5.6 to 14.9 (average 10.2) × 2.1 to 4.5 (3.0) μm, borne on short monophialides measuring 8.2 to 16.1 (average 13.2) × 2.1 to 4.2 (3.3) μm. Macroconidia were slightly curved, three-septate, with a slightly hooked apical cell and a foot-shaped basal cell measuring 24.9 to 41.6 (average 32.2) × 3.2 to 5.2 (4.3) μm. Chlamydospores were both terminally and intercalary, solitary but also in short chains (2 to 4 elements) measuring 21.1 to 41.0 (average 27.2) μm (2). The internal transcribed spacer (ITS) rDNA region was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis of the 527-bp amplicon (GenBank Accession No. HQ644423) obtained had 98% sequence identity with F. oxysporum (GenBank Accession No. FJ605247). The translation elongation factor-1α (EF-1α) gene was amplified using primers EF-1/EF-2 and sequenced (GenBank Accession No. GU564259). The 663-bp fragment had 99% sequence identity with F. oxysporum (GenBank Accession Nos. EU313540, EU313539, and DQ837696). Pathogenicity tests were conducted on 15-day-old chicory plants from two cultivars (Clio and Katia). Thirty-five plants per cultivar were inoculated by dipping their roots in a 1 × 106 CFU/ml suspension of isolate FusCic45B recovered from wilted chicory. Inoculated and noninoculated plants were transplanted into five pots filled with 10 liters of steamed mix (peat/perlite/sand, 60:20:20 vol/vol) and were maintained in a glasshouse at 25 to 27°C. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 15 days after inoculation on all inoculated plants. Plants of cv. Clio were more susceptible. F. oxysporum was always reisolated from infected plants using the Fusarium-selective medium. All noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of wilt caused by F. oxysporum on chicory, C. intybus, in Italy as well as worldwide.

First Report of Fusarium Wilt of Endive (Cichorium endivia) Caused by Fusarium oxysporum in Italy.

In the summer of 2007, a wilt of endive (Cichorium endivia) cv. Myrna plants was observed on several commercial farms near Alessandria in northern Italy. Approximately 40% of the plants on each farm were symptomatic. Affected plants were stunted and yellow and their root systems were poorly developed. Basal leaves eventually wilted. Black streaks were observed in the proximal part of the leaf vascular system. Fusarium oxysporum was consistently isolated from symptomatic vascular tissue on a Fusarium-selective medium (1). To confirm identification of the pathogen, the translation elongation factor 1α and the ribosomal DNA intergenic spacer (IGS) region were partially sequenced (2). Genomic DNA was extracted from mycelia growing on potato dextrose agar. Amplification of the EF-1α region generated a sequence of 648 bp; the IGS amplicon was 2,500 bp. The EF-1α sequence (GenBank Accession No GQ398152) was 99% similar to the sequence of a F. oxysporum strain isolated from soil and a strain pathogenic on cotton plants (GenBank Accession No. EU246574). The IGS sequence (GenBank Accession No GQ398153) was 97% similar to the sequence of a F. oxysporum strain (GenBank Accession No. EF661647). Pathogenicity tests were conducted on 15-day-old endive plants (cv. Myrna). Ten plants were inoculated by dipping their roots in a 1 × 106 CFU/ml suspension of one of the isolates recovered from a wilted endive plant. Inoculated and noninoculated plants were transplanted into pots filled with steamed soil and maintained in a glasshouse at 23 to 28°C. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 60 days after inoculation. F. oxysporum was consistently reisolated from infected plants. Noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of wilt caused by F. oxysporum on endive in Italy.

First Report of Wilt Caused by Verticillium dahliae on Cosmos (Cosmos bipinnatus) in Italy.

Cosmos (Cosmos bipinnatus Cav., Asteraceae) is an herbaceous plant that is grown for landscape use. During August and September of 2008 in five public and three private gardens located in Monopoli (Apulia, southern Italy), 3 to 8% of the plants showed severe symptoms of vine decline, stunting, gradual yellowing and wilting of the leaves, and final collapse of the whole plant. External symptoms were associated with brown or black streaking of the vascular tissue of roots, collar, and stem. Dead plants had numerous microsclerotia embedded in the xylem of plant tissues. Stem, collar, and root sections (0.5 cm long) from symptomatic plants collected in five gardens were surface disinfested in 5% NaOCl for 1 min and transferred to petri dishes containing potato dextrose agar (PDA) amended with 100 μg ml-1 of streptomycin sulfate and 10 μg ml-1 of neomycin. After 10 days of incubation, at 25°C in the dark, hyaline hyphae with dark microsclerotia (37 to 112 μm) and verticillate conidiophores were produced. Conidia were single celled and hyaline with dimensions of 3.3 to 7.8 × 1.8 to 3.3 μm (mean dimensions 4.2 × 2.5 μm). According to morphological characteristics, the fungus was identified as Verticillium dahliae Kleb. (1) (isolates no. Vd1818, Vd1819, and Vd1820 stored in a collection at the Department DiSACD, University of Foggia). Molecular analyses were performed on the basis of nucleotide sequences of the internal transcribed spacer region (ITS1-5.8S-ITS2) of ribosomal DNA. ITS sequences of this fungus, compared with sequences found in GenBank and attributed to V. dahliae (no. GQ130129, GQ130130, GQ130131), showed 98 to 99% sequence similarity. Healthy 40-day-old plants of C. bipinnatus (garden cosmos) cv. Sonata Pink Blusk and C. sulphurous (yellow cosmos) cv. Bilbo, obtained from seeds previously disinfested for 1 min in 3% NaOCl and ascertained to be healthy by isolation on PDA medium, were used for pathogenicity tests. Plants were grown in 3-liter pots in a steam-disinfested peat, sand, and soil mixture (2:1:1) in the greenhouse at 23 to 26°C. Ten plants of each cultivar were inoculated by root dipping into a conidial suspension of each fungal isolate (1.5 × 106 CFU ml-1). Six noninoculated cosmos plants of each cultivar served as controls. The experiment was repeated three times. First symptoms of wilting were observed on all inoculated plants of each cultivar 20 days after the inoculation; at 40 days, symptom severity ratings on plants were taken, in which 1 = asymptomatic, 2 = stunted, 3 = wilting, and 4 = dead. All three isolates caused vascular discoloration, stunting, wilting, and plant death. The mean disease rating was 3.2 and did not differ significantly among isolates. The pathogen was consistently reisolated from infected plants, fulfilling Koch's postulates. Noninoculated plants remained healthy. To our knowledge, this is the first report of Verticillium wilt on cosmos in Italy. The finding is important since other ornamental plants that are susceptible to Verticillium wilt are also grown in landscapes in the region. The disease was previously reported in Turkey (2).

First Report of Wilt and Dieback on Pokeweed (Phytolacca decandra) Caused by Phytophthora nicotianae.

Pokeweed (Phytolacca decandra, synonym Phytolacca americana) is a root perennial plant that produces a succulent annual stem. In late June 2001, a severe dieback occurred on a group of pokeweed plants being grown as ornamentals in a garden in Rome. Disease symptoms consisted of leaf wilting followed by collapse of the plant. Stem collars and roots had dark brown-to-black water-soaked lesions. A wet rot was observed on plants with advanced disease symptoms. Isolations, from sections of roots and stems previously washed in running tap water, were made on PARBhy selective medium (10 mg of pimaricin, 250 mg of ampicillin [sodium salt], 10 mg of rifampicin, 50 mg of hymexazol, 15 mg of benomyl, 15 g of malt extract, and 20 g of agar in 1,000 ml of H2O) (2), followed by incubation at 20°C. A species of Phytophthora identified based on morphological and cultural characteristics (1) was isolated consistently from rotted roots and collars of diseased plants. All isolates produced papillate, spherical, ovoid to obturbinate, noncaducous sporangia and terminal and intercalary chlamydospores. Hyphal swellings with hyphal outgrowths were present. Observed characteristics were similar to those described for P. nicotianae. Isolates were mating type A2 with amphigynous antheridia in paired cultures with the A1 tester isolate of P. nicotianae. Identification was confirmed by comparing restriction fragment length polymorphism patterns of the internal transcribed spacer region of ribosomal DNA with those obtained from previously identified Phytophthora species. Pathogenicity tests were conducted on 10 2-month-old potted pokeweed plants. Inoculum was prepared by inoculating sterilized millet seeds moistened with V8 broth with plugs of mycelium and growing for 4 weeks. The inoculum was added to potting soil at 3% (wt/vol), and sporulation was induced by flooding the soil for 48 h. Five uninoculated plants were used as controls. Plants were maintained outdoors and assessed for symptoms within 2 months after inoculation. Wilting, root rot, and dark brown lesions on the collar developed on inoculated plants. The pathogen was reisolated from the inoculated plants and morphologically identical to the original isolates, which confirmed P. nicotianae as the causal agent of the disease. Few diseases have been reported on Phytolacca decandra. This species is not only an invasive weed, but is also cultivated as an ornamental and medicinal plant. In addition, antiviral (PAP) and antifungal (Pa-AFP) proteins that are used as a remedy for several human and plant infections have been extracted from the plant. To our knowledge, this is the first report of P. nicotianae on pokeweed.