فصلنامه بیماریهای گیاهی
سال پنجاه و ششم شماره 2 (تابستان 1399)

In order to identify, study phylogenetic relationships and evaluate the pathogenicity of graminicolous fungi on cereals in southern Iran during the spring and summer of 2017, some roots, stems and rhizosphere soil were collected from barley, maize, millet, rice, and wheat fields in Bushehr, Fars, Khuzestan and Kohgiluyeh and Boyer-Ahmad Provinces, Iran. Based on morphological and phylogenetic studies, 141 recovered isolates were identified as three species of Bipolaris (B. sorokiniana and two probable new taxa Bipolaris sp1 and Bipolaris sp.2), four species of Curvularia (C. australiensis, C. papendorfii, C. spicifera, C. verruculosa) and one species of Exserohilum (E. rostratum). pathogenicity test was conducted on leaves and roots of Eram cultivar of barley, 504 cultivar of maize, Parosou cultivar of millet, Lanjan cultivar of rice, and Azar cultivar of wheat. In both pathogenicity tests pathogenic and nonpathogenic isolates were observed. This is the first report of potential pathogenicity of C. papendorfii in all tested plants; C. verruculosa in barley, millet, rice and wheat; C. spicifera in barley, millet and maize; and C. australiensis in barley, maize and rice.

Plant-parasitic nematodes significantly reduce crop production. The stem and bulb nematode (Ditylenchus dipsaci) is one of the important pathogen of several ornamental and field crops including alfalfa. In this study, the reactions of seven alfalfa ecotypes to the nematode were investigated under greenhouse conditions. The experiment was conducted based on completely randomized design with three replicates. The results showed significant differences (p < 0.05) among inoculated ecotypes with the nematode in all morphological traits (except of root length) compared to the control. The nematode reproduced in all studied alfalfa ecotypes, but the rate of reproduction was different. The highest reproduction factor (RF) was observed on the ecotype Neishabouri (RF = 7.14) and the lowest on Feiz and Hamedani with reproduction factors of 1.24 and 1.85, respectively. The highest number of the nematode was observed in stems, rhizosphere and buds. The results showed that none of these ecotypes were resistant or tolerant to the stem and bulb nematode.

Biocontrol is one of the methods widely studied to reduce nematode damage. The biological control efficacy of two arbuscular mycorrhizal fungi, Glomus mosseae and G. intraradices and two antagonistic fungi, Pochonia chlamydosporia var. chlamydosporia and Purpureocillium lilacinum on disease indices and reproduction rate of root-knot nematode, Meloidogyne javanica were studied on three local cultivars of peach rootstocks namely Helendri, Shorabi3 and Gf677. The experiment was conducted as a factorial experiment in a completely randomized design with 30 treatments and five replications under greenhouse conditions. Evaluations were performed 90 days after nematode inoculation by measuring the plant growth parameters and growth and reproduction rate of M. javanica. Results of nematode reproduction indices showed more effect of P. chlamydosporia var. chlamydosporia on reduction of nematode biological activity than other biocontrol fungi. The number of galls, egg masses, second stage juveniles and reproduction factor in GF677 treated with this fungus decreased comparing to control, as 42.2, 41.8, 39 and 6.36 percent, respectively. Although the fungus was effective on all stages of nematode development, but the number of egg masses and number of eggs per egg mass were more affected.

Barley leaf stripe caused by the fungus Pyrenophora graminea, is one of the most important and devastating barley diseases in Iran. A total of 121 P. graminea isolates was recovered from cultivated barley in West Azerbaijan (Miyandoab region), East Azerbaijan (Miyaneh region), Ardebil (Ardebil region) and Zanjan (Khorramdareh region) provinces in 2016. After morphological and molecular identification, mating type primers were designed based on a conserved DNA binding (alpha domain) in MAT-1 and the high mobility group (HMG) domain in MAT-2. Frequency of mating type idiomorphs of P. graminea isolates were done by Multiplex PCR. Among 121 isolates, 56 isolates amplified by MAT-1 primer and 65 isolates by MAT-2 primer. Frequencies of two mating types in Khorramdareh (1) and Miyandoab populations had an excess of the MAT-1 and MAT-2 alleles, respectively. According to the results of the Chi-square test (X2), Miyaneh, Ardebil (1 and 2) and Khoramdareh (2) populations had not significant difference in compared with Khorramdareh (1) and Miyandoab populations. Therefore, these four populations have the highest potential for sexual reproduction than the two populations of Miyandoab and Khorramdareh (1). In addition, isolates from all of the populations were studied to evaluate the sexual fertility through directed crossing with opposite mating types. After six months, pseudothecia formed in media without mature asci and ascospores.

A tan colored, corky tissue was appeared on the skin of the fruit surface in the stem-end cavity, approximately 30 days after full blooming stage at the same time of rapid growth of epidermal cells in fruits and continued until the fruits fully grown. 30 samples with symptoms were brought to the laboratory during the growing season. For pathogenicity, conidial suspension was prepared in sterile distilled water with an approximate concentration of 1010 spores per ml of the single spores colonies and one ml of the above suspension was poured onto stem-end cavity of the scraped and non-scraped fruits, 4 fruits for each group. In the cavity of 4 fruits, distilled water without spores was poured, and in the cavity of 4 other fruits, no solution was poured. Fruits were kept in humid environment for 40 days. All fruits inoculated with spore suspension showed symptoms similar to orchard conditions whereas, in other fruits no symptoms were observed. The hyphae were transparent, with transverse walls and 2–10 μm thick. The single-celled conidia were transparent, smooth, and elliptical and varied in shape and size. Their size ranged 7.3 4 4.8 × 4.8–7 μm, similar to range reported by Zalar et al. (2008). The two-celled conidia were translucent to dark brown and their size ranged 15-24 × 6–10 μm. Comparing morphological characteristics of colonies, hyphae and conidia with literaturea yeast-like fungi, Aureobasidium pullulans, was detected as The causative agent of the stem-end russeting on golden delicious and red delicious fruits.

Chinese hibiscus, Hibiscus rosa-sinensis L., is a common ornamental shrub in warm and humid regions of Iran like Khuzestan province, southwestern Iran. During 2019, some Chinese hibiscus plants showing begomovirus like symptoms including vein enation and leaf cupping (Figure 1A) were observed in Ahvaz, Khuzestan province. New plants obtained from cuttings of symptomatic plants showed the same symptoms. Leaf samples were collected and the extracted total DNA was subjected to polymerase chain reaction (PCR). Degenerate primer pairs were used to detect DNA A and DNA B genomic fragments of begomoviruses and their associated betasatellites. PCR resulted to amplify ~500 bp fragment of DNA A (complete V2 and partial V1 ORFs) while DNA B as well as betasatellite were not detected. Amplified fragments were purified and sequenced in both virion and complementary sense. Analyses performed using the Blastx program indicated that the DNA sequences have 93 to 96% pairwise identity with isolates of Cotton leaf curl Multan virus. Phylogenetic analysis revealed host preference between different analyzed begomovirus isolates so that cotton leaf curl viruses originated from H. rosa-sinensis like Khuzestan isolate of CLCuMuV formed a separated cluster. To our knowledge, this is the first report of CLCuMuV incidence in Iran. Considering the widespread presence of the begomovirus whitefly vector in the country, this virus that can be a serious threat to other economically important crops in Iran.