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Conidial Suspension (conidial + suspension)
Selected AbstractsEffect of hot-water treatments in vitro on conidial germination and mycelial growth of grapevine trunk pathogensANNALS OF APPLIED BIOLOGY, Issue 2 2010D. Gramaje In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, Cn. macrodidymum and eight species of the genus Phaeoacremonium to hot-water treatments (HWTs) in vitro was evaluated. Conidial suspensions and plugs of agar with mycelia were placed in Eppendorf vials and incubated for 30, 45 or 60 min in a hot-water bath at 41, 42, 43, 44, 45, 46, 47, 48 or 49°C for Cylindrocarpon spp. and at 49, 50, 51, 52, 53, 54 or 55°C for Ca. luteo-olivacea and Phaeoacremonium spp. In general, conidial germination and the colony growth rate of all pathogens decreased with increased temperature and time combinations. Cylindrocarpon spp. were more sensitive than Ca. luteo-olivacea and Phaeoacremonium spp. to HWT temperatures. Conidial germination of Ca. luteo-olivacea was inhibited by treatments above 51°C,30 min, while treatments up to 54°C,60 min were necessary to inhibit the mycelial growth. For Cylindrocarpon spp., conidial germination was inhibited by treatments above 45°C,45 min, while treatments above 48°C,45 min were necessary to inhibit the mycelial growth. Regarding Phaeoacremonium spp., treatments up to 54°C,60 min were necessary to completely inhibit both conidial germination and mycelial growth. These results suggest that current HWT protocols at 50°C for 30 min may be sufficient to control Cylindrocarpon spp. However, it would be necessary to develop HWT using higher temperatures to reduce the incidence of Ca. luteo-olivacea and Phaeoacremonium spp. infections. [source] Isolation of entomopathogenic fungi from the soil and their pathogenicity to two fruit fly species (Diptera: Tephritidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2008P. Sookar Abstract The occurrence of deuteromycetous entomopathogenic fungi was determined by examining 224 soil samples from 19 locations in three climatic zones of Mauritius. Three sites were sampled per location: one site under vegetables cultivation, one site under sugar cane plantation and one natural site each within 1 km of each other. Soil samples were baited with the waxmoth larvae Galleria mellonella L. and incubated in the dark at 15, 20, 25 or 30°C for 7, 14 and 21 days. Entomopathogenic fungi were isolated from 77 out of 224 (38.6%) soil samples. Metarhizium anisopliae was isolated from 42 (18.8%) samples, Beauveria bassiana from 24 (10.7%), Metarhizium spp. and Paecilomyces fumosoroseus from 5 (2.2%) each and Beauveria spp. from 1 (0.4%). It was observed that M. anisopliae was isolated more frequently from soils under vegetables as compared to soils under sugarcane or habitat with natural vegetation. Beauveria bassiana was isolated more frequently at the lowest incubation temperature (15°C) while M. anisopliae isolates were recovered more frequently at higher temperatures (25 and 30°C). The pathogenicity of seven isolates of M. anisopliae, five isolates of B. bassiana and two isolates of P. fumosoroseus towards the adults of Bactrocera zonata and Bactrocera cucurbitae was tested by topical application of conidial suspension of 1 × 106 conidia/ml. All the isolates tested were pathogenic to the two fruit fly species. Mortality of B. zonata varied between 12.0 and 98.0% and between 2.0 and 94.0% in B. cucurbitae at 5 days post-treatment. Our results suggest that entomopathogenic fungi present locally, could be integrated for the control of B. zonata and B. cucurbitae. [source] In vitro Selection for Fusarium Wilt Resistance in GladiolusJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2008Idrees Ahmad Nasir Abstract Cormels pieces of four Fusarium susceptible Gladiolus cultivars (Friendship, Peter Pears, Victor Borge and Novalux) formed friable calli when cultured in vitro on Murashige and Skoog basal medium containing various concentrations of auxin and cytokinin. The friable calli established cell suspensions. Plantlet regeneration was obtained from the control callus, control cell suspension derived callus and in vitro selected Fusarium oxysporum Schlecht. resistant cell-lines of Friendship. The in vitro cormlets showed 85,95% germination after breaking dormancy of 8 weeks at 4 °C. Cell suspensions of all four Gladiolus cultivars were found to be highly sensitive to fusaric acid. Gradual increase in fusaric acid concentrations to the cell-suspension cultures decreased cell growth considerably. One albino plant was found from the second generation of the in vitro selected cell line of Friendship. The albino plant was found to be highly susceptible to F. oxysporum. The cormlets of all in vitro selected cell lines of Friendship were inoculated with a conidial suspension of the F. oxysporum before planting and were also sprayed with the same spore suspension for further characterization when the height of plants was about 6 cm. The four selected cell lines showed the same response whether or not they were inoculated with conidia of the F. oxysporum. Plantlets of all of the selected cell lines exhibited significant growth as compared with the control after application of conidia of the F. oxysporum. [source] Development of Greenhouse Inoculation Procedures for Evaluation of Partial Resistance to Cercospora zeae-maydis in Maize InbredsJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2005G. Asea Abstract Greenhouse experiments were conducted to determine the effects of inoculation methods on incubation period, lesion length, percentage leaf area affected and sporulation of Cercospora zeae-maydis on young maize (Zea mays L.) plants inoculated at V3 growth stage. Seedling plants were inoculated by four methods: (i) application of conidial suspension while puncturing the leaves within the whorl several times, (ii) spraying conidial suspension on leaves, (iii) placing colonized agar into lateral slits in leaves and (iv) placing colonized agar into whorls. Analysis of variance revealed a significant effect of genotype and inoculation method on several components of resistance and overall disease severity. Application of conidial suspension while puncturing the whorl was found to be the least laborious method, and it produced characteristic symptoms of gray leaf spot. Consistent trends were observed in classification of inbreds to resistant, susceptible and intermediate classes. Increasing the duration of exposure to high humidity by placing plastic bags over plants for 5 days significantly increased disease severity (P , 0.001). Cercospora zeae-maydis produced conidia in all the lesions examined. Spore production was generally most abundant in lesions on susceptible inbreds that displayed necrotic lesion types (LT) and least abundant in lesions on resistant inbreds that were characterized by chlorotic and fleck LTs. The results demonstrated that inoculations in the greenhouse can provide an indication of inbred responses to C. zeae-maydis and may be useful in evaluating resistance and in studies of host,pathogen interactions. [source] Increased effectiveness of the Trichoderma harzianum isolate T-78 against Fusarium wilt on melon plants under nursery conditionsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2009Agustina Bernal-Vicente Abstract BACKGROUND: The use of isolates of the genus Trichoderma to control Fusarium wilt in melon plants is one of the most recent and effective alternatives to chemical treatments. In this work we have studied the immobilization of the isolate Trichoderma harzianum T-78 on different carriers as an efficient method to control vascular Fusarium wilt of melon in nurseries. Different formulations were developed: liquids (spore suspension, guar gum and carboxymethylcellulose) and solids (bentonite, vermiculite and wheat bran). RESULTS: The introduction of F. oxysporum resulted in a significant decrease in seedling fresh weight. The treatments which gave a lesser reduction in weight and showing a greater biocontrol effect were the liquid conidial suspension and the solid treatments with bentonite and superficial vermiculite. Microbiological analyses revealed that the conidial suspension and all the solid treatments, except wheat bran, significantly decreased F. oxysporum populations. Of all the treatments assayed, bentonite produced the greatest decline in the F. oxysporum population. CONCLUSIONS: The most effective treatments against Fusarium wilt on melon plants were the solid treatments bentonite and superficial vermiculite. These two treatments gave the greatest plant weight, the lowest percentage of infected plants and the greatest T. harzianum population throughout the assay. Copyright © 2009 Society of Chemical Industry [source] Chromosomal location of Fusarium head blight resistance genes and analysis of the relationship between resistance to head blight and brown foot rotPLANT BREEDING, Issue 1 2000A. Mentewab Abstract In order to identify chromosomes involved in resistance to Fusarium head blight, a set of 21 substitution lines of Triticum macha (resistant) chromosomes into ,Hobbit''sib'(susceptible) were evaluated in trials over 2 years. For the first year's trial, all plants were inoculated on the same day with a conidial suspension of F. culmorum. For the second trial, individual plants were inoculated precisely at mid anthesis of each plant over a period of 2 weeks. The disease level was assessed by visual scoring, relative ear weight and F. culmorumn -specfic quantitative polymerase chain reaction. The results showed that T. macha chromosomes 1B, 4A and 7A conferred good overall resistance, suggesting that they carry important genes for resistance. In two additional trials, T. macha and ,Hobbit''sib' were evaluated for resistance to brown foot rot. The results showed that T. macha was more susceptible than ,Hobbit',sib', indicating that stem base disease response is not correlated with head blight resistance in these cultivars. [source] Novel infection strategies of Colletotrichum acutatum on ripe blueberry fruitPLANT PATHOLOGY, Issue 1 2008P. S. Wharton The infection and colonization process of Colletotrichum acutatum on ripe blueberry fruit from two cultivars with different susceptibility to anthracnose were examined using light and confocal laser scanning microscopy. Ripe fruit from susceptible cv. Jersey and resistant cv. Elliott were drop-inoculated with a conidial suspension of C. acutatum, and epidermal peels were evaluated at selected times after inoculation and incubation. Results from pre-penetration studies demonstrated that there were significant differences in the rate of formation of melanized appressoria between the two cultivars, with the rate of formation being faster in the susceptible one. In both cultivars, penetration by the pathogen occurred via appressoria 48 h post-inoculation (hpi). However, in the susceptible cv. Jersey, C. acutatum then adopted an intracellular hemibiotrophic-like infection strategy, whereas in the resistant cv. Elliott subcuticular intramural-like infection occurred. In cv. Jersey by 108 hpi, intracellular growth of the pathogen led to the formation of numerous acervuli, with orange conidial masses. By 120 hpi, the conidial masses had coalesced covering the entire inoculated area. In cv. Elliott, acervuli were not seen until 144 hpi and contained few conidia. These results demonstrate for the first time the ability of C. acutatum to adopt a different infection and colonization strategy depending on the susceptibility of the host tissue being colonized. [source] Plant defence reactions against fusarium wilt in chickpea induced by incompatible race 0 of Fusarium oxysporum f.sp. ciceris and nonhost isolates of F. oxysporumPLANT PATHOLOGY, Issue 6 2002J. M. Cachinero Germinated seeds of ,kabuli' chickpea cv. ICCV 4 were inoculated with a conidial suspension of the incompatible race 0 of Fusarium oxysporum f.sp. ciceris (Foc) or of nonhost F. oxysporum resistance ,inducers', and 3 days later were challenged by root dip with a conidial suspension of highly virulent Foc race 5. Prior inoculation with inducers delayed the onset of symptoms and/or significantly reduced the final amount of fusarium wilt caused by race 5. However, the extent of disease suppression varied with the nature of the inducing agent; the nonhost isolates of F. oxysporum were more effective at disease suppression than the incompatible Foc race 0. Inoculation with the inducers gave rise to synthesis of maackiain and medicarpin phytoalexins in inoculated seedlings; these did not accumulate in plant tissues but were released into the inoculum suspension. Inoculation with inducers also resulted in accumulation of chitinase, ,-1,3-glucanase and peroxidase activities in plant roots. These defence-related responses were induced more consistently and intensely by nonhost isolates of F. oxysporum than by incompatible Foc race 0. The phytoalexins and, to a lesser extent, the antifungal hydrolases, were also induced after challenge inoculation with Foc race 5. However, in this case the defence responses were induced in both preinduced and noninduced plants infected by the pathogen. It is concluded that the suppression of fusarium wilt in this study possibly involved an inhibitory effect on the pathogen of preinduced plant defences, rather than an increase in the expression of defence mechanisms of preinduced plants following a subsequent challenge inoculation. [source] Components of Partial Disease Resistance in Wheat Detected in a Detached Leaf Assay Inoculated with Microdochium majus using First, Second and Third Expanding Seedling LeavesJOURNAL OF PHYTOPATHOLOGY, Issue 4 2006R. A. Browne Abstract The use of first, second and third expanding seedling leaves of wheat (L1, L2 and L3 respectively), inoculated with conidial suspensions of Microdochium majus (syn. Microdochium nivale var. majus) in a detached leaf assay, for detecting components of partial disease resistance (PDR) was investigated across a range of wheat cultivars. Incubation periods (period from inoculation to first appearance of symptoms; a dull grey,green water-soaked lesion) and latent periods (period from inoculation to the first appearance of sporodochia) were longest and lesions smallest on L3. The expression of PDR components on L2 was intermediate to those on L1 and L3. The longer latent periods on L3 typically occurred after leaf senescence contrasting with latent periods on L1 and L2 where sporulation most frequently occurred on relatively green leaf tissue. Cultivar differences in the first appearance of symptoms, incubation period, which occurred before any leaf senescence was observed, correlated significantly across all leaf positions. Similarly cultivar differences in latent period were correlated for L1 and L2. However, latent periods on L3, which were the least consistent between cultivars across experiments, were not correlated with those of L1 or L2 in any experiment. The results indicate that due to the delay in sporulation until after leaf senescence, observations on latent period in L3 are less representative of what occurs in the whole plant where infection of living tissue is of greatest interest. This work indicates that the selection of the first or second expanding leaf of wheat is optimal for the use in the detached leaf assay using M. majus for studying components of PDR. [source] Genotypic difference for the susceptibility of Japanese, Chinese and European pears to Venturia nashicola, the cause of scab on Asian pearsPLANT BREEDING, Issue 4 2008K. Abe Abstract Venturia nashicola, the cause of scab on Asian pears, is distinct from Venturia pirina, a causal fungus of European pear scab. Although scab caused by V. nashicola is one of the most serious diseases in the Japanese pear (Pyrus pyrifolia Nakai var. culta Nakai), information available regarding resistant breeding against V. nashicola is limited. In this study, 12 genotypes of Japanese pear, seven genotypes of Chinese pear (Pyrus ussuriensis Maxim.) and four genotypes of European pear (Pyrus communis L. var. sativa DC.) and/or their offspring were evaluated for susceptibility to V. nashicola with leaf and fruit inoculation tests. At 30,40 days after full bloom in their developmental stage, unfolded young leaves and fruit were inoculated with conidial suspensions of V. nashicola for each genotype, and the responses were rated at 30 days postinoculation for the inoculated leaves and at 42 days postinoculation for the inoculated fruits. No visible symptoms were found in European pear ,Bartlett' and ,La France' and their respective offspring ,290-36' and ,282-12', in the Japanese pear ,Kinchaku' and in the Chinese pears ,Cangxili' and ,Hongli'; these genotypes were evaluated as highly resistant to V. nashicola. Necrotic lesions without sporulation were observed in the Chinese pears ,Qiubaili', ,Manyuanxiang', ,Yuanbali' and ,Xiangyali', which were regarded as resistant. Sporulating lesions were formed on the other genotypes, such as the major Japanese pear cultivars ,Kosui' and ,Nijisseiki', which were regarded as susceptible. The response of inoculated leaves coincided well with that of inoculated fruit for each genotype. When the severity of scab symptoms on scab-susceptible genotypes was further rated with disease severity (DS) values, a genotypic difference was observed for overall DS values in a successive 2-year measurement among the susceptible genotypes. Based on the DS values of leaf and fruit scabs, the Japanese pears ,Niitaka', ,Shinko', ,Nijisseiki', ,Gold Nijisseiki', ,Osa Nijisseiki' and ,Shinsui' were considered to be less susceptible to V. nashicola than the typical susceptible cultivar ,Kosui'. [source] Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhousePLANT BREEDING, Issue 5 2001Q. Chen Abstract Fusarium head blight (FHB, scab), caused by Fusarium graminearum Schwabe, is a serious and damaging disease of wheat. Although some hexaploid wheat lines express a good level of resistance to FHB, the resistance available in hexaploid wheat has not yet been transferred to durum wheat. A germplasm collection of Triticum durum× alien hybrid lines was tested as a potential source of resistance to FHB under controlled conditions. Their FHB reaction was evaluated in three tests against conidial suspensions of three strains of F. graminearum at the flowering stage. Two T. durum×Thinopyrum distichum hybrid lines, ,AFR4' and ,AFR5,, expressed a significantly higher level of resistance to the spread of FHB than other durum-alien hybrid lines and a resistant common wheat line ,Nyu-Bay'. Genomic in situ hybridization using total genomic DNA from alien grass species demonstrated that ,AFR5' had 13 or 14 alien genome chromosomes plus 27 or 28 wheat chromosomes, while ,AFR4' had 22 alien genome and 28 wheat chromosomes. All of the alien chromosomes present in these two lines belonged to the J genome. ,AFR5' is likely to be more useful as a source of FHB resistance than ,AFR4' because of its relatively normal meiotic behaviour, high fertility and fewer number of alien chromosomes. ,AFR5' shows good potential as a source for transferring FHB resistance gene into wheat. The development of T. durum addition lines carrying resistance genes from ,AFR5' is underway. [source] Modelling the effect of cuticular crack surface area and inoculum density on the probability of nectarine fruit infection by Monilinia laxaPLANT PATHOLOGY, Issue 6 2009C. Gibert The effects of cuticular crack surface area and inoculum density on the infection of nectarine fruits by conidia of Monilinia laxa were studied using artificial inoculations with conidial suspensions and dry airborne conidia during the 2004 and 2005 seasons, respectively. Additionally, the effect of ambient humidity on fruit infection was evaluated in the 2005 experiment. An exploratory analysis indicated that (i) ambient humidity did not significantly explain the observed variability of data, but that (ii) the incidence of fruit infection increased both with increasing inoculum density and increasing surface area of cuticular cracks. The product of these two variables represented the inoculum dose in the cracks, and was used as a predictor of fruit infection in the model. Natural infection in the orchard was observed to increase throughout the season in both 2004 and 2005. The relationship between the probability of fruit infection by M. laxa and the artificially inoculated dose in the cuticular cracks was well described by a logistic regression model once natural inoculum density was taken into account (pseudo R2 = 65%). This function could be helpful for estimating the risk of fruit infection at harvest based on fruit size and natural inoculum density. [source] | ||||||||||