Evaluation of chickpea resistance against some isolates of Ascochyta rabiei, the causal agent of ascochyta blight.

Ascochyta blight, incited by Ascochyta rabiei (Pass.) Lab., is one of the most important fungal diseases that has been shown to cause significant yield losses on chickpeas in Kermanshah province, Iran. One of the most effective and reliable methods of controlling the disease has been the use of resistant cultivars worldwide. This requires the identification of the physiological races of the fungus in the region in advance. In this regard, pathogenicity of 30 isolates of A. rabiei was determined using 10 differential chickpea varieties (mean of 1-9 degree of disease in three replications) under greenhouse conditions. In this respect, isolates fell into four groups, whereas based on infection type three groups were identified using cluster analysis. Disease resistance of four chickpea cultivars, Hashem, Jam, ILC-482 and Bivanij, were evaluated against isolates from each of three groups separately and in combination in the greenhouse and field conditions (with 4 replications). The experiment was repeated twice with three replications in greenhouse. Chickpea cultivars were sprayed with fungal spore suspension (2x10(5) spores/ml). Results showed that Jam and Bivanij cultivars were susceptible under greenhouse as well as field conditions. Hashem was tolerant to group I and susceptible to groups II and III and in the field. ILC-482 was tolerant to groups II and I and susceptible to group III and the combination of groups under greenhouse condition.

Effect of synthetic combinations and tobacco root extract and the mixture of them on broomrape seed germination.

Various types of broomrape (Orobanche cermua), such as parasitic weeds, live on the roots of many important crops. Different methods may be advised to eradicate this parasite. But the seed size is so tiny with high stability in the soil and having strong connection with the host, it is very difficult to eradicate this parasite and there is no useful and economic method has not been suggested in this regard yet. The seeds of all types of broomrape germinate in the soil only when they are exposed to the secretions of the host's roots, therefore, providing special combinations that cause the parasite's seeds germinate in the absence of the host, can be an effective way in controlling this parasite. The effect of the tobacco root's extract and the synthetic combinations as well as their mixtures with different concentrations on the germination of the seeds of Orobanche cermua Loefi were tested to introduce an effective combination that can be used in controlling this parasite. This experiment includes 28 treatments in three replications. The tobacco root's extract was derived from the tobacco roots planted in pots containing Perlit in different stages and were prepared in different concentrations. Synthetic combinations (including combinations 1, 2 and 3) were also prepared with concentration of 1, 2 and 3 parts per million (ppm), then these combinations were tested as treatments on Broomrape's seeds. At the end of experiment, it was concluded that all the combinations used in different concentrations in this experiment significantly differ from the control treatment in their effects in causing the Broomrape's seeds germinate. Among all the combinations examined, the following were the most effective ones in the process of the germination of the Broomrape's seeds: 1. combination 2 with the concentration of one part per million, 2. combination 2 with the concentration of two parts per million, and 3 tobacco root's extract in the third stage.

Identification of physiological races of Blumeria graminis f. sp. tritici and evaluation of powdery mildew resistance in wheat cultivars in Sistan province, Iran.

Powdery mildew of wheat caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important fungal diseases in Iran. During the years 1998-2001, wheat fields in Sistan province were surveyed and powdery mildew infected samples were collected from various areas and transferred to the laboratory. In the greenhouse, fungal spores were purified and inoculated onto susceptible wheat cultivars using single pustule and single spore procedures. Selected pure isolates were inoculated onto the first leaves of eight differential wheat varieties for identifying physiological races. The results showed the existence of Bgt races 5, 11, 14, 19, 21, 24, 27, 28, 31, 32, 44, 50, 53, 58, 66, 73 and 84 in Sistan. These races were new to Sistan province and Iran as a whole. Among 17 races studied, races 11, 53 and 73 were important dominant races thus constituting 40% of total population. Race 53 constituted 16% of all isolates and was the dominant race in the area with 62.5% pathogenicity. Therefore, this race was introduced as the most virulent race during the period of this study. This study showed that Bgt isolates were compatible with host plant genes pm8, pm3 and pm3b but incompatible with gene pm4b. Powdery mildew resistance was evaluated using race 11 on 70 wheat cultivars during seedling stage as well as adult plant under both greenhouse and field conditions between 1999 and 2001. Among wheat lines tested for resistance against powdery mildew, cultivar Hirmand resembled the differential line Weihenst M1 in that both may possess gene pm4b and showed no symptoms under the greenhouse and field conditions. Cultivar Chamran was found to be highly resistant whereas Sorkhtokhm was susceptible. Other cutivars showed partial and gradual resistance against the powdery mildew disease.

Rice brown spot and susceptibility of some cultivars in north of Iran.

Rice brown spot is one of the important diseases in the world including Iran. 91 samples of the infected plants such as leaves and panicles were collected from different locations of Guilan province, North of Iran and the fungi isolated and studied for pathogenicity. Three species of Bipolaris (B. oryzae, Bipolaris sp. and B. cf. victoriae) were isolated more than other species with serious effects on the plants respectively. Reactions of 8 cultivars of rice, Neda, Nemat, Sepeed-rood, Bejar, Khazar, Domsephid, Hassan-saraee and Binam were studied in greenhouse to Bipolaris sp. and B. cf. victoriae in two stages of growth, on leaves and panicles, respectively. The results showed that in seedling stage on leaf there was no significant difference between these cultivars in case of infection rates. In heading stage, although there was no significant difference according to variance analysis, but according to Duncan test (5%) they could be divided into 3 groups. Neda, Sepeed-rood, Khazar and Binam, with the lowest infection rate, were in the first group Bejar, Domsephid and Hassan-saraee were classified into the second group and Nemat was in the third one. Curvularia sp., Nigrospora sp., Pyricularia grisea and Alternaria sp. were with minor prevalence in infection of the plants.

Damping-off in conifer seedling nurseries in Noshahr and Kelardasht.

To study the damping-off of conifer seedlings, we have collected samples from the roots of conifer seedlings (Pinus nigra, Picea excelsa, Abieces spp, Cupressus arizonica, Cupressus sempervirens) from nurseries in the south of Iran (Noshahr and Kelardasht). After disinfecting the samples, we have used standard media like PDA, MA and CLA. The following fungi were identified: Fusarium solani, Fusarium oxysporum, Fusarium sambucinum, Clamydosporium, Rhizoctonia solani, Cylindrocarpon spp., Alternaria spp, Macrophomina phaseoli. Amongst the above mentioned fungi, Fusarium spp. were the commonest ones. Pathogenecity tests of Fusarium spp. and Rhizoctonia solani on seedlings were done. Isolated fungal colonies were purified using single mycelium and single spore methods. Fungal isolates were identified after subculturing on PDA and CLA media by Nelson method. These isolates were Fusarium solani, F. oxysporium, F. sambucinum and F. clamydosporum. Other fungal isolates were Rhizoctonia spp. In order to determine the infectivity of Fusarium on their hosts, seeds of Pinus nigra, Cupressus arizonica and Cupressus sempervirens var. horizontalis were cultured in four repetitions each containing 2 seedlings. After a seasonal growth, seedlings were inoculated with a suspension of Fusarium spores (4.5 +/- 0.3 x 1016 spore/ml). Infection of P. nigra, Cupressus arizonica and Cupressus sempervirens var. horizontalis with F. solani and Pinus nigra and Cupressus semperivirens var. horizontalis with F. oxysporum was high whereas that of Cupressus arizonica with F. sambucinum, F. mondiforme and F. clamydosporum was moderate.