جستجوی مقالات مرتبط با کلیدواژه « leptosphaeria maculans » در نشریات گروه « گیاهپزشکی »

This study has carried out for distinguishing of Leptosphaeria maculans and L. biglobosa (aggressive and ‎non-aggressive groups respectively) using colony growth, ability for pycnidium and pigment production in four ‎mediums and temperatures of Forty nine isolates (Zaman Mirabadi et al., 2010) (totally 784 treatments) in three ‎replication and three times. The result of analysis variation has shown that significant difference between isolates ‎considering colony growth in the different mediums and temperature treatments. The maximum and the minimum ‎colony growth was observed in 30⁰c –v8 juice Agar (48.05 mm) medium and 15⁰c-Czapek Dox Agar (17.01 mm) ‎respectively after 12 days. The greatest and lowest pigment production in the different temperature was observed in ‎PDA and MEA (except in 30⁰c). The minimum and maximum pigment production was observed in 15⁰c and 30⁰c ‎respectively. The percentage of presence yellow-orange and brown pigment was‏ ‏variable in the different treatments. ‎Brown pigment in V8 and CDA was dominated while yellow- orange was seen in PDA and MEA. 93.78 % isolates ‎produced pigment in Czapek Dox Broth. The maximum pycnidium production was observed in V8 and 20⁰c. ‎According to the obtained results, Dasht-Naz, Eslamabad, Fazelabad, Kohi khail and bykar ayesh were belonged to ‎aggressive species (L.maculans) and Talokola, Lala, Khalkhail and mustard isolate too were located as L.biglobosa.

The rapeseed (Brassica napus) is an important oilseed crop throughout the world for oil production. Blackleg disease which caused by Leptosphaeriamaculans is one of the most important disease of rapeseed in Iran. Among pathogenicity groups PG-1 (Leptosphaeria biglobosa) and PG-2, PGT (L. maculans) has been reported on rapeseed from Mazandaran and Golestan provinces of northern Iran (Fernando et al. 2007, Mirabadi et al. 2010). The samples (leaves, stem, flowers and seed) with symptoms of diseases such as discoloration, deformation, wrinkled and presence of pycnidia were collected during 2013-2016 from canola crops in North Iran. In addition, some of the stem debris with stem canker symptoms was examined for the presence and absence of pathogen sexual (perfect) state. Diseased tissues (leaves, stems, flowers and seed) were surface sterilized to obtain pathogen isolates following the procedure described by West et al. (2002) and Chen et al. (2010). Single ascosporic cultures of the fungus were isolated from psedothecia using the method developed by Li et al. (2004). In all 102 isolates when the causal pathogen was isolated from infected tissues, it was identified as L. maculans, by colony morphology/ pigment production on potato dextrose agar (PDA) and potato dextrose broth (PDB) respectively (Boerema et al. 2004), and species specific polymerase chain reaction (PCR) (Liu et al. 2006). The pycnidia of the fungus were black, globose to subglobose in shape, parts of pycnidia have pale pink droplet overflowed from the ostiole and Asci are clavate to cylindrical, bitunicate and 8 spores. Moreover, all isolates were classified as highly virulent using PCR with virulence type specific primers (Kuusk et al. 2002). Thirty-two isolates of L. maculans were used for determining the pathogenicity test using a cotyledon inoculation method. Pathogenicity of the isolates was confirmed by spraying a conidial suspension of the fungus (2×107 conidia mL-1) on cotyledons of Westar, Quinta and Glacier cultivars. All plants were maintained in a growth chamber at 22°C with 16 h light period and relative humidity of 80%. The first review of the plants was performed after 5 days and changes during experimenting plants have been observed after 12 days using the scale of 0–9 developed by Chen & Fernando (2006) which 0 to 3 reaction was considered as resistant (R), 4 to 6 as intermediate (I) and 7 to 9 as susceptible (S) (Fig. 1). Sixteen of isolates were classified as belonging to pathogenicity group PG-4. They were characterized by their ability to sporulate on the three differential hosts (S=7-9). Three isolates were PG-3, they sporulated on Westar and Glacier, and caused brown, non sporulating lesion on Quinta (I=4-6). The remaining isolates belonged to PG-2 and PGT. Moreover, our findings provided evidence that L. maculans (PG-4) is present on oilseed rape seeds in the North Iran. Our results showed that an understanding of possible shift in fungus populations will be of value in developing strategies for successful management of blackleg disease such as longer rotation between canola crops, new resistant cultivars against all PG isolates and strict regulations concerning crop seed trade. In addition, the current study is the first report on the identification of L. maculans (PG-3, PG-4) from oilseed in Northern Iran.

Ascospore dimensions of eight populations of Leptosphaeria maculans and L. biglobosa, causal agents of rapeseed blackleg disease, isolated from debris of rapeseed (Brassica napus) and wild mustard (Sinapis arvensis) were evaluated in Mazandaran and Golestan provinces. Results of ANOVA indicated significant differences in the dimensions of ascospores of the different populations. The greatest length and width of sexual spores were 87.5 and 12.5 micrometer, respectively. Variations in the range of Length and width of ascospores in the studied populations was measured, 46.25 and 7.5 micrometer, respectively also these variations were 6.25 and 2.5 micrometers greater than the dimensions of ascospores reported by other studies in the world. The length of sexual spores isolated from stem debris of mustard was much bigger than those of canola. Germination percentage of most studied populations was more than reported in other studies, so likely the most of studied populations of different regions belong to non aggressive group. Sexual spores of aggressive types have greater number of germ tubes, shorter in length, twisted and originate from the middle cells. While in the nonaggressive type the germ tubes grow out of end cells and are not twisted. With regard to morphological characteristics of sexual spore germ tube and also cotyledon test characteristics, field symptoms, pigment production and colony growth rate it was determined that ascospores of the studied populations from Dasht-e-Naz of Sari, Kohikheil and Fazel Abad were of the aggressive type (L. maculans) and most of population in Lala, Mazarustaq and Talookola areas belonged to nonaggressive type (L. biglobosa). There was no correlation between germ tube characteristics of fungus populations on mustard and their pathogenicity.

Ascospore dimensions of eight populations of Leptosphaeria maculans and L. biglobosa, causal agents of rapeseed blackleg disease, isolated from debris of rapeseed (Brassica napus) and wild mustard (Sinapis arvensis) were evaluated in Mazandaran and Golestan provinces. Results of ANOVA indicated significant differences in the dimensions of ascospores of the different populations. The greatest length and width of sexual spores were 87.5 and 12.5 micrometer, respectively. Variations in the range of Length and width of ascospores in the studied populations was measured, 46.25 and 7.5 micrometer, respectively also these variations were 6.25 and 2.5 micrometers greater than the dimensions of ascospores reported by other studies in the world. The length of sexual spores isolated from stem debris of mustard was much bigger than those of canola. Germination percentage of most studied populations was more than reported in other studies, so likely the most of studied populations of different regions belong to non aggressive group. Sexual spores of aggressive types have greater number of germ tubes, shorter in length, twisted and originate from the middle cells. While in the nonaggressive type the germ tubes grow out of end cells and are not twisted. With regard to morphological characteristics of sexual spore germ tube and also cotyledon test characteristics, field symptoms, pigment production and colony growth rate it was determined that ascospores of the studied populations from Dasht-e-Naz of Sari, Kohikheil and Fazel Abad were of the aggressive type (L. maculans) and most of population in Lala, Mazarustaq and Talookola areas belonged to nonaggressive type (L. biglobosa). There was no correlation between germ tube characteristics of fungus populations on mustard and their pathogenicity.