نشریه گیاه پزشکی کاربردی
سال چهارم شماره 3 (پیاپی 15، آذر 1394)

Potato leaf roll virus (PLRV), a species of Polerovirus gunes, causes one of the most important viral diseases in potato crop. Molecular characterizations of Iranian PLRV isolates have been studied using ORF0. Main potato cultivation areas in Azarbaijan, Ardabil, Isfahan, Khorasan, and Hamadan were visited and sampling conducted randomly and symptomatically. The samples were tested by DAS-ELISA method by using specific antibodies from Bioreba Co (Switzerland). ELISA results showed that on average, 9.6 % of the randomly collected samples were infected by PLRV, indicating wide distribution of PLRV in potato fields of Iran. Also, samples from Isfahan and Ardabil provinces showed highest and lowest infection with PLRV with 23.7% and 3.9%, respectively. Ten Iranian PLRV isolates have been selected and the ORF0 region of genome amplified by polymerase chain reaction using specific primers and sequenced. Comparing the nucleotide sequence alignment of 10 sequences obtained in this study with 23 other PLRV sequences showed 94.2 up to 100 % identity. Two Iranian isolates, Ar53 and Kh116 had the most identity with an isolate from Netherlands (Y07496). Phylogenetic analysis showed that PLRV isolates clustered in three groups which Iranian isolates fall in group with some European PLRV isolates.

Ascochyta blight caused by Ascochyta rabiei Pass. (Labr.)is one of the greatest disease in chickpeathat cause total yield loss if the environmental conditions are favorable. The use of resistant cultivars is the most effective management strategy for ascochyta blight in chickpea. In our study, 24 different isolates of A. rabiei from plants infected by this disease were obtained in provinces of Kermanshah and Ilam and then isolated and purified. For evaluation of the morphological characteristics, discs of colonies of fungal isolates were sown in PDA, CDA, CSA and WA media. For pathotypes identification, the isolates were sporulated on differential chickpea cultivars by concentrations with 106 spores per ml. 41 genotypes and chickpea cultivars inoculated by three A. rabiei pathotype like pathogenicity method in greenhouse. The severity of the disease index is noted from 1 to 9, according to the scale of Jan and Wiese and 12 days later when the intensity of symptoms reached to 90 percent on susceptible cultivar. The results of our study revealed morphological and genetic diversity of the fungus. In this survey, three pathotypes identified in different districts of Kermanshah and Ilam, respectively. Pathotypes 1 of 13 of total isolates was the most widely distributed then, pathotype II with 6 isolates and pathotype III with 5 isolates were the least ones. The response of 41 cultivars against three pathotype of A. rabiei, Adel, Azad cultivar that have just been released by the Agricultural Research Institute of Dryland over the past few years together with advanced line of Flip 03-109C against the pathotype III showed moderately resistant response while other lines and cultivars were susceptible or highly susceptible. In total, lines of Flip51-87C, Flip03-119C, Flip04-13C and Flip04-10C showed resistant or moderately resistant response for pathotypes.

Bacillus thuringiensis (Bt), belonged to Bacillaceae is one of the most important pathogenic bacteria and considered as an effective biological control agent in many pest management programs. This species can be an applied replacement for chemical pesticides. Diverse potentials of Bt on different pest species have emerged from not only its diverse serotypes, but also varied isolates. Helicopverpa armigera (Lepidoptera: Noctuidae) is a serious cotton pest with different plant host species. In this study, mortality rate of the pest larvae by two Iranian native isolates of Bt, from Yazd (YD5) and Boushehr (BR4) farmland was assessed. Then LC50 for each isolate on neonates obtained. Dipel was used as the control. Bioassay result showed that LC50 for Dipel, YD5 and BR4 were 68.2864 spore/ml, 48× 106 spore/ml and 77× 1012 spore/ml, respectively. YD5 showed partial higher performance in comparison to other native isolate.

Ascochyta blight caused by the fungus Ascochyta fabae Speg., is known as one of the most destructive diseases of faba bean worldwide. Yield losses due to attacks by this fungus can reach more than 90% when cultivars are sown under cool and wet conditions. Disease Control by using crop rotation, clean seed and chemical treatments cannot be fully effective. Therefore, using the resistant cultivars as a reduction factor of the disease severity and infection type is very important for disease control. At first, different fungal isolates were collected from northern areas of Iran, purification and pathogenicity was carried out on the susceptible cultivar of Barkat with spore suspension by concentrations of 106 spores per ml on leaves in the greenhouse condition. For identifying isolates virulence, the fungus inoculated was done on the susceptible cultivar of Barkat like pathogenicity test method. Disease severity index implemented when the symptoms appeared and was carried out 15 days after sporulating by Sillero and Rubiales method. The responses of 14 faba bean genotypes and cultivars were evaluated to disease in randomized complete block design in field conditions with three replications. Among total sampling of different regions, 10 pure isolates of A. fabae with high virulence totally obtained which indicated a high variability in Mazandaran and Golestan provinces. The results of resistance evaluation of faba bean genotypes and cultivars in field conditions revealed the resistance response of genotypes of G-faba-67, G-faba-95, G-faba-100, G-faba-133 and Zereshki cultivar along with disease severity index 25.66 to 40.33 percent and the other cultivars (6 genotypes and 3 cultivars) equal to 64% of all tested cultivars susceptible and genotypes showed a susceptible or highly susceptible response.

In the framework of study on the genus Septoria in Iran, several newly collected and herbarium specimens from Fungal Reference Collection of the Ministry of Agriculture-Jahad (IRAN) located at the Iranian Research Institute of Plant Protection, were studied. Among identified samples, five species viz. Septoria sambuci-ebuli sp. nov. on Sambucus ebulus L., Septoria fatehii sp. nov. on Alhagi sp., Septoriakhalkhalensis sp. nov. on Astragalus sp., Septoria javadii sp. nov. on Rubia sp. and Septoria osipyaniae sp. nov. on Populus sp. are newly described in this paper.

Allelochemicals are the main manager of interspecific relations which can convey different types of relations and behaviors of different organisms according to the chemical compound and its concentration, sender and receptor species. It is committed in plant world and plant apply infochemicals with different tasks to level up their fitness and employ natural enemies belong to Arthropoda for higher survivorship. In this paper, a review of previous researches on plant-natural enemies chemical ecology is presented.

Reduced cost of genome sequencing of organisms has led to increased number of sequenced genes. But the performance of these genes hasn’t been sequenced yet. However using comparative genetics and bioinformatics has been identified for investigation of sequenced genes function, the interpretation of these genes functions is a challenge. In this regard, sequencing of a large number of fungal plant pathogens and oomycete genomes has been completed. The next major challenge in modern fungal/oomycete biology is to translate the huge amount of genome sequence information into biological functions. Reverse genetics has emerged as a seminal tool for functional genomics investigations. Utilized techniques for reverse genetics like targeted gene disruption/replacement, gene silencing, insertional mutagenesis, and targeting induced local lesions in genomes, will contribute greatly to the understanding of gene function of fungal and oomycete pathogens. This study reviews the reverse genetics approaches which are used to study fungal genomes