Cultural, Morphological Characterization and Aggressiveness of Alternaria alternata Causing Leaf Spot of Soybean

Background: Alternaria leaf spot caused by Alternaria alternata is one of the most important and destructive disease of soybean causing severe yield loss in all soybean growing areas of southern and eastern part of Rajasthan. Successful management of Alternaria leaf spot is mainly dependent on accurate and efficient detection of pathogen, amount of genetic and pathogenic variability present in pathogen population. The main reason for frequent “breakdown” of effective resistance is the variability that exists in the pathogen population, which necessitates a continual replacement of cultivars due to disease susceptibility. Methods: The twelve fungal isolates randomly were collected from six districts of major soybean growing part of Rajasthan i.e., Udaipur, Chittorgarh, Pratapgarh, Kota, Baran and Jhalawar. The culture was purified single spore techniques. These were then further compared among each other for any variations in cultural characters, colour of colonies, Growth rate, conidial morphology and pathogenic variability. Result: Twelve different isolates of A. alternata were obtained in pure culture and characterized for cultural, morphological variation and aggressiveness of this fungus varied in their cultural characters, colour of colonies, growth rate of isolates, conidial morphology and isolates also exhibited variations in incubation period, latent period, number and size of lesions were produced.

Outbreaks of crown rot in Fragaria x ananassa caused by Neopestalotiopsis mesopotamica in Ecuador

Strawberry crown rot is one of the most important diseases in Ecuador, with an incidence of up to 70% in the field. In the world, the strawberry crown rot is caused by different etiological agents, which makes efficient control of the disease difficult. In this study, 12 samples of strawberry plants were collected, at different stages of disease development, to determine the causative agent in Ecuador. The fungal isolates, consistent with the isolation, were identified and characterized using molecular and morphological approaches, and finally, Koch's postulate was carried out. Based on the form of growth, mycelial color, conidial morphology, and molecular characteristics (sequencing of the ITS and EF-1α region), the pathogen associated with the symptoms showed 99% similarity with the species Neopestalotiopsis mesopotamica. The result of Koch's postulates showed symptoms similar to those observed in field plants, in addition, the same inoculated isolate was recovered from artificially inoculated tissues. This is the first report of this fungus causing strawberry crown rot in Ecuador and in the world.

Figs S1-S4 & Table S1

Figure S1. Mean conidial dimensions (with error bars representing standard error) for all herbarium specimens and cultures examined, with the holotype of H. fragiforme represented by orange bars and the holotype of H. callorioides represented by green bars.Figure S2. Lectotype of H. fragiformis (A, C, E) and holotype of H. callorioides (B, D, F). A, B. Rehydrated sporodochia. C−F. Conidial chains. Scale bars: A, B = 500 μm. C−F = 10 μm.Figure S3. Conidia and conidial chains. A. Oosporidium sp. (DAOM 970823) identified using DNA sequencing. B. Holotype of Sphaerocolla aurantiaca (H). Both have similar conidial morphology and dimensions, suggesting that S. aurantiaca may be conspecific with Oosporidium margaritiferum. Scale bar = 10 μm. Figure S4. Nuclear staining of hyphae of DAOMC 251988, showing dikaryotic, binucleate hyphae, A, using near-UV light showing the stained nuclei and B with regular light. Scale bar = 20 μm. Table S1. Species, geographical location, host and herbaria for known type specimens of Hormomyces species.

Difference between isolates from brown eye spot and black spot lesions in coffee plants

The objective of this work was to evaluate the difference between the isolates from two cercospora leaf spot symptoms (brown eye spot and black spot) in relation to conidial morphology, mycelial growth, cercosporin production, and reproduction of symptoms in coffee leaves collected in three municipalities in the state of Minas Gerais, Brazil. There was a difference between the isolates for the studied variables, but without any relation to the type of symptom. The differences found were not associated with the origin of the isolates. The symptoms characterized as black spot were associated with different host conditions during the infection process.

Application of molecular methods for characterization of Botrytis fabae and Botrytis cinerea of faba bean

Application of the RAPD methods allowed to clearly characterization of isolates of Botrytis fabae and isolates of B. cinerea. Results from RAPD-PCR analysis indicate different groups. Clusters were related with groups based on conidial morphology, morphological characters of the isolates of Botrytis spp.

Studies on variability in Alternaria alternata (Kessler) causing leaf blight of Isabgol (Plantago ovata)

All the five isolates of Alternaria alternata isolated from different agro climate zone of Rajasthan were tested for their variability in terms of cultural, conidial, pathogenic characteristics and toxin production. All the five isolates differed in cultural characters i.e. dark black colored and very fast mycelial growth with smooth margins (90.00 mm), light black with white at centre and fast growing (80.00 mm), dark brown and medium mycelium growth with smooth margins (75.00 mm), black colored, medium flat mycelial growth with smooth margins (68.00 mm) and white with slightly black in colour with slow mycelial growth (65.00 mm) were observed in Aa-1, Aa-2, Aa-3, Aa-4 and Aa-5 respectively. The variability in conidial morphology of five different isolates was simple, septate, pale to dark brown in colour, often geniculate with one conidial scar. In respect of pathogenic variability, showed significant variations in terms of disease intensity and incubation periods. The isolates Aa-1 was highly pathogenic on Isabgol cv. RI-89 under artificial inoculation conditions showing 52.12% disease intensity followed by Aa- 3 ,Aa-2, Aa-4 and Aa-5 isolates. The variability in toxin production was reflected in terms of time taken in inducing wilting symptoms of Isabgol cuttings. Isolate Aa-1 was highly toxic followed by isolates Aa-2, Aa-3, Aa-4 and Aa-5. DOI: http://dx.doi.org/10.3329/sja.v12i2.21918 SAARC J. Agri., 12(2): 63-70 (2014)