IRANIAN JOURNAL OF PLANT PATHOLOGY
Year:2003 | Volume:39 | Issue:1-2|Papers Count:15

Thirteen sugar beet cultivars exhibiting increasing levels of resistance to Cercospora leaf spot were used in order to study the following resistance components to the disease w1der controlled conditions in greenhouse: incubation period, percent of infected leaves, the number of necrotic spots per cm2, lesion diameter and number of conidia produced on necrotic spots. Incubation length was determined by two different methods. In both of them degree – days was used instead of time to record the incubation period. In the first method degree-days cumulation during the time between inoculation and appearance of spots in fifty percent of plants, was considered as incubation time and in another method the appearance of fifty percent of spots was used to determine the incubation time. All the resistance components were involved in host resistm1cesignificantly. With few exceptions, by increasing in level of resistance, the number of spots per cm2, lesion diameter, percent of infected leaves and spore yield were decreased and incubation length was increased.    

In order to identify the Aphelenchoides species of cereals (wheat, barley, com and rice), 120 soil and root samples were collected from different fic1ds in Isfahan province. The nematodes were extracted from samples by centrifugal floatation technique. The extracted nematodes were transferred to glycerine. Then permanent slide were mounted. The nematodes were identified by morphological and morphometrical characters. In this study seven species of the genus Aphelenchoides were identified as following: I-Aphelenchoides asterocaudatus 2-Aphelenchoides centralis 3-Aphelenchoides composticola 4-Aphelenchoides lanceolatus 5-Aphelenchoides limberi 6-Aphelenchoides sacchari 7-Aphelenchoides spicomucronatus Among these species A. asterocaudatus, A. composticola and A. spicomucronatus are reported from Iran for the first time      

In order to investigate the competitive effects of different densities of wild mustard and winter wheat, one experiment was conducted in the greenhouse of the college of agriculture-Shiraz University at Badjgah (1999-2000). The experiment was randomized complete block design with 4 replications using substitutive method. The design consisted of 5 treatments of different ratios of wheat to wild mustard (4:0, 3:1, 2:2, 1:3, 0:4). Results indicated that increasing wild mustard ratio in each plot didn't have significant effect on height, number of tiller and flag leaf area of wheat and didn't show distinctive trend. Competition indices also showed that wheat and wild mustard had identical competitive ability.    

The effectiveness and durability of four systemic fungicides, benomyl (BEN), fthalide (FTH), pyroquilon (PYR) and tricyclazole (TRIC) for control of rice blast disease was investigated by in vivo and in planta tests. Fungicides used once for rice root treatment as suspension in irrigation water. In greenhouse, treated rice plants were exposed to disease infection, in blast nursery, at different times and disease incidence was evaluated one week later. In field experiments, treated rice plots were compared for leaf blast. panicle blast, and yield with control (untreated) plots. The results indicated that HEN, PYR and TRIC could be taken up and systemically translocated in rice plants and be effective to control blast disease of foliage. In greenhouse, HEN could control disease up to 50% at I day after treatment (DAT) and to 100% at 2 DAT but in spite of rapid uptake and efficacy, had shorter lasting efficacy so that controlled disease up to 14 DAT and then reduced its efficacy. PYR and TRIC could control disease at 4 DAT but had long lasting efficacy and controlled disease up to 28 DAT. In comparison, only partial disease control could be obtained by FTH during 4-21 DAT. In the field, PYR and TRIC significantly controlled leaf blast but in the cases of panicle blast and yield were not significantly different with control. Once application of BEN could not provide considerable control of disease, probably because of its shorter lasting efficacy, and was not significantly differel1twith FTH and control.      

During 1994-1997 a devastating and widespread dieback and decline on stone fruit trees especially on apricot, cherry and almond was observed in various regions of Semnan, Kerman and West Azarbaidjan provinces. Orchards in various parts of the provinces were surveyed and samples of affected roots, crowns, twigs and blossoms were collected and brought to the laboratory. Samples were taken weekly and surface sterilized and cultured on PDA, MA media and on PARPH without disinfection. On the basis of morphological and limited physiological characteristics, eight fungal species, namely Monilinia laxa,Verticillium dahliae, Phytophthora cactorum, Armillaria sp. Cytospora leucostoma, Cytospora sp. Pleospora sp., and Scytalidium dimidatum were identified. Pathogenicity tests of the all isolates were studied using two methods. For detached branches of apricot (cv Gaisi) and cherry (cv Black Mashad) and also inoculation 2-3 year- old seedlings were used in the greenhouse. Selected isolates of M.laxa were sparyed on 3-4 year old apricot seedlings with suspension of 5000 spores per mililiter in stage of early blossom and greenhouse condition. The result showed that only V. dahliae, P. cactorum and m. laxa were pathogenic on apricot and cherry.      

The genus Fusarium has a cosmopolitan distribution with representatives occurring in most parts of the world. Individual species may have more restricted distribution, often being confind to particular climate. This survey was undertaken in five areas with a range of climates in south eastern. New South Wales, Australia. Soil samples and plant debris were collected from 4 to 8 sites of each area. Fusarium species were isolated from all soil samples and plant debris using the dilution plant technique and debris plating technique respectively. Selective media (Pepton PCNB Agar=PPA) and Carnation Leaf Agar (CLA) were used for growth of the cultures. Plates were incubated in controlled conditions with alternating temperature regime 25ºC day and 20ºC night with a 12hr photoperiod. Twenty one species of Fusarium were isolated from soil and plant debris. The cosmopolitan species F. solani, F. oxysporum and F. equiseti were recovered from all areas, F. compactum and F. nygamai from the warmest area (Lake Cargellingo), while F. crookwellense. F. culmorum. F. tricinctum and F. sporotrichioides recovered only from the coolest area (Batlow). F. sambucinum was recovered most frequently from cool areas. F. proliferatum. F. chlamydosporum, F. graminearum and F. scirpi were isolated from moderate to warm areas, whereas F. anthophilum. F. lateritium. F. merismoides and F. babinda tended to occur in wet temperate areas near the coast. Species such as F. acuminatum F. aveanceum and F. semitectum did not show distinctive patterns in their distribution within the region surveyed. This survey has Fusarium species continued an empirical association between climate and distribution of Fusarium species.        

A total of 80 Streptomyces strains were isolated from major potato growing areas of Iran including, Hamedan, Esfahan, Khorasan and Chahar Mahal-e Bakhtiary provinces during 2000. Forty six representative Streptomyces strains were selected and their morphological and physiological features determined. The strains were grouped by numerical analysis of their phenotipic features. Five phena were differentiated. The first phenon was identified as S. scabies. The second cluster of the strains was similar to S. turgidiscabies and also to a lesser extent to the causal agent of russet scab. Some characteristics of the third and fourth clusters of the strains including spiral spore chain, gray mass spore color on YMEA and melanin production from tyrosine were similar to S. scabies but others were similar to S. europeaiscabies and S. stelliscabies and in the last one being similar to S. acidiscabies. This is the first report for S. scabies from Iran. In host range studies the representative strains were pathogenic on potato (Solanum tuberosum), radish (Raphanus sativus), bean (Phaseolus vulgaris) and beet (Beta vulgaris). Tested strains were reisolated from artificially infected but symptomless corn (Zea maus), tomato (Lycopercicum esculentum), carrot (Daucus carota), Ientis (Lense sp.), eggplant (Solanum melongena) and Amaranthus sp. Plants but not from the inoculated wheat (Triticum aestivum), barley (Hordeum vulgaris), rape seed (Brassica napus) or alfalfa (Medicago sativa) plants under greenhouse conditions.