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1.
ABSTRACT A spatially explicit model describing saprophytic colonization of dead cyclamen leaf tissue by the plant-pathogenic fungus Botrytis cinerea and the saprophytic fungal antagonist Ulocladium atrum was constructed. Both fungi explore the leaf and utilize the resources it provides. Leaf tissue is represented by a two-dimensional grid of square grid cells. Fungal competition within grid cells is modeled using Lotka-Volterra equations. Spatial expansion into neighboring grid cells is assumed proportional to the mycelial density gradient between donor and receptor cell. Established fungal biomass is immobile. Radial growth rates of B. cinerea and U. atrum in dead cyclamen leaf tissue were measured to determine parameters describing the spatial dynamics of the fungi. At temperatures from 5 to 25 degrees C, B. cinerea colonies expanded twice as rapidly as U. atrum colonies. In practical biological control, the slower colonization of space by U. atrum thus needs to be compensated by a sufficiently dense and even distribution of conidia on the leaf. Simulation results confirm the importance of spatial expansion to the outcome of the competitive interaction between B. cinerea and U. atrum at leaf scale. A sensitivity analysis further emphasized the importance of a uniform high density cover of vital U. atrum conidia on target leaves. 相似文献
2.
ABSTRACT The colonization of dead onion leaves by Botrytis aclada and the fungal antagonists Aureobasidium pullulans, Chaetomium globosum, Glio-cladium catenulatum, and Ulocladium atrum and the interactions between B. aclada and each of the four antagonists were studied at the microscopic and ultrastructural level. This approach was used in an attempt to understand the colonization pattern of these fungi and the nature of the biocontrol activity of the antagonists that have shown a potential to suppress spore production of Botrytis spp. on necrotic plant tissues. When applied alone, B. aclada and U. atrum were found throughout the leaf tissues in high densities after an incubation period of 6 days at 18 degrees C in a moist chamber. C. globosum and G. catenulatum colonized only the outer portions of the leaf, whereas A. pullulans appeared to be concentrated in the leaf stomata. When pathogen and antagonists were applied together, ultrastructural observations revealed that cells of B. aclada were plasmolyzed in the presence of G. catenulatum, suggesting a reaction to antifungal molecules. Antibiosis also seemed to be involved, albeit to a lesser extent, in the antagonistic interactions between B. aclada and A. pullulans or C. globosum. No evidence of direct parasitism was recorded. On the other hand, U. atrum appeared to completely exclude B. aclada from dead onion tissues when both fungi competed for the substrate. Ultrastructural observations of the in vitro interaction between the two fungi did not reveal parasitism or antibiosis by either fungus. Based on previous records of its biocontrol potential and observations of its colonizing properties, it appears that U. atrum can compete for and utilize necrotic tissues rapidly and extensively, thus, excluding competitors without any other antagonistic action. 相似文献
3.
ABSTRACT Ulocladium atrum (strain 385) consistently reduced Botrytis cinerea sporulation on necrotic fragments of strawberry leaves. On these tissues, two strains of U. atrum (isolates 18558 and 18559) showed lower antagonistic activities than the reference strain 385. Colonization of strawberry leaflets by the three U. atrum strains appeared similar in the absence of B. cinerea, whether quantified by chitin or immunological assays. The second method (based on anti-U. atrum antibodies) revealed that strawberry leaflet colonization by U. atrum 385 was better than by the other U. atrum strains in the presence of B. cinerea. An immunoassay using anti-B. cinerea antibodies revealed that the colonization of B. cinerea in tissues was lower in the presence of U. atrum 385 than with the two other U. atrum strains. The enzymatic activities produced by U. atrum 385 during the colonization phases of necrotic tissues were compared to B. cinerea and U. atrum strains 18558 and 18559. U. atrum 385 had the highest lipase, pectate lyase, and cellobiase activities while B. cinerea had the highest endo-beta-1,4-glucanase activity. The study of lytic activities hydrolyzing the fungal cell wall revealed higher beta-1,3-glucanase activity with U. atrum 385, which was stimulated by B. cinerea on necrotic strawberry leaflets. These results suggest that plant and fungal cell wall-degrading enzymes produced by U. atrum 385 may play a complementary role in the competitive colonization of dead strawberry leaves against B. cinerea. 相似文献
4.
ABSTRACT The saprophytic fungus Ulocladium atrum was selected for its ability to competitively exclude Botrytis spp. from aboveground necrotic plant tissues which can play a crucial role in the epidemiology of diseases caused by necrotrophic Botrytis spp. Fungal growth in necrotic aboveground tissues can be hampered by fluctuating water availability. Adaptation to these adverse conditions is a key factor for the successful establishment of an antagonist population in this niche. Conidia of U. atrum germinated at water potentials between -1 and -7 MPa on water agar. Germinated conidia survived one to three interruptions of moist incubation by periods at -10 or -42 MPa. The speed of germination was significantly slower with interruption of the moist period as compared with the control, which had continuously moist incubation. However, the maximum germination percentage was the same for conidia incubated with or without interruption of the moist incubation. In bioassays with necrotic cyclamen leaves at -1, -3, and -7 MPa, U. atrum significantly reduced the sporulation of B. cinerea by more than 80%. The results demonstrate that U. atrum tolerates water stress during competitive substrate colonization with B. cinerea. The antagonist is, therefore, an attractive candidate for field applications on aboveground tissues. 相似文献
5.
The survival and saprophytic competitive ability of the Botrytis spp. antagonist Ulocladium atrum in lily canopies 总被引：1，自引：0，他引：1
Philip A.G. Elmer Jürgen Köhl 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(5):435-447
In 1995, conidia of Ulocladium atrum were applied to a canopy of green lily (Lillium spp.) leaves in order to investigate its survival, colonisation of artificially induced necrotic leaf tissues and competitive ability against Botrytis spp. and naturally occurring saprophytes. U. atrum conidia density cm-2 at the top and middle canopy levels was not significantly different following application of the antagonist with a propane powered backpack sprayer. In repeat experiments, conidia density on leaves at the lower canopy level was 18% to 20% of that deposited onto leaves at the top of the lily canopy. There was a significant (P < 0.001) linear decline of U. atrum conidia over time and after 21 days conidia density had declined by up to 73%. Germination of U. atrum on green leaves in the field reached a maximum of 81%, seven days after antagonist application. Conidial viability, measured as germination potential, declined slightly (100% to 88%) after seven days exposure to field conditions but there were no further changes in the germination potential even after 21 days of field exposure. The germination potential was not affected by canopy level. The ability of surviving U. atrum conidia to colonise necrotic tissues, artificially induced with paraquat, was measured. U. atrum colonisation was consistently highest on necrotic leaves at the top level of the canopy and consistently lower on leaves from the bottom canopy level. Necrotic leaf colonisation by U. atrum decreased over time from 51% (necrosis induced immediately after antagonist application) to 21% when necrosis was induced 21 days after antagonist application. A significant (P < 0.001) linear relationship (R2 = 0.713) between colonisation of necrotic tissues and conidia density prior to induction of necrosis was detected. When necrosis was induced immediately after antagonist application, U. atrum outcompeted commonly occurring saprophytic Alternaria spp. and Cladosporium spp. The ability of U. atrum to significantly reduce colonisation by Alternaria spp. was maintained for up to 21 days. Botrytis spp. did not occur in these field experiments. It was concluded that U. atrum had the ability to survive and persist in the phyllosphere for up to 21 days in the field and provided further evidence that U. atrum has the necessary survival characteristics to be a successful biological control agent of Botrytis spp. 相似文献
6.
ABSTRACT The early infection and colonization processes of Colletotrichum acutatum on leaves and petals of two almond cultivars with different susceptibility to anthracnose (i.e., cvs. Carmel and Nonpareil) were examined using digital image analysis of light micrographs and histological techniques. Inoculated tissue surfaces were evaluated at selected times after inoculation and incubation at 20 degrees C. Depth maps and line profiles of the digital image analysis allowed rapid depth quantification of fungal colonization in numerous tissue samples. The results showed that the early development of C. acutatum on petals was different from that on leaf tissue. On petals, conidia germinated more rapidly, germ tubes were longer, and fewer appressoria developed than on leaves. On both tissues, penetration by the pathogen occurred from appressoria and host colonization was first subcuticular and then intracellular. On petals, colonizing hyphae were first observed 24 h after inoculation and incubation at 20 degrees C, whereas on leaves they were seen 48 to 72 h after inoculation. Intercellular hyphae were formed before host cells became necrotic and macroscopic lesions developed on petals >/=48 h and on leaves >/=96 h after inoculation. Histological studies complemented data obtained by digital image analysis and showed that the fungus produced infection vesicles and broad hyphae below the cuticle and in epidermal cells. In both tissues, during the first 24 to 48 h after penetration fungal colonization was biotrophic based on the presence of healthy host cells adjacent to fungal hyphae. Later, during intercellular growth, the host-pathogen interaction became necrotrophic with collapsed host cells. Quantitative differences in appressorium formation and host colonization were found between the two almond cultivars studied. Thus, on the less susceptible cv. Nonpareil fewer appressoria developed and host colonization was reduced compared with that on cv. Carmel. 相似文献
7.
ABSTRACT The effect of treatments with conidial suspensions of Ulocladium atrum and Gliocladium roseum on leaf rot of cyclamen caused by Botrytis cinerea was investigated under commercial greenhouse conditions. Spraying U. atrum (1 x 10(6) conidia per ml) or G. roseum (2 x 10(6) conidia per ml and 1 x 10(7) conidia per ml) at intervals of 2 to 3 weeks during the production period and spraying U. atrum (1 x 10(6) conidia per ml) at intervals of 4 to 6 weeks resulted in a significant reduction of natural infections of petioles by B. cinerea. U. atrum or G. roseum (1 x 10(7)conidia per ml) was as effective as the standard fungicide program. B. cinerea colonized senesced leaves within the plant canopy and infected adjacent petioles and leaves later. The antagonists colonized senesced leaves and reduced B. cinerea development on these leaves. Thus, the inoculum potential on petioles adjacent to necrotic leaf tissues was reduced. The fate of U. atrum conidia on surfaces of green cyclamen leaves during a 70-day period after application was studied. The number of conidia per square centimeter of leaf surface remained relatively constant during the entire experiment. Sixty percent of the conidia sampled during the experiments retained the ability to germinate. When green leaves were removed from the plants to induce senescence and subsequently were incubated in a moist chamber, U. atrum colonized the dead leaves. Senesced leaves also were colonized by other naturally occurring fungi including B. cinerea. On leaves treated with U. atrum from all sampling dates, sporulation of B. cinerea was significantly less as compared with the untreated control. Our results indicate that early applications of U. atrum before canopy closure may be sufficient to achieve commercially satisfactory control of Botrytis leaf rot in cyclamen. 相似文献
8.
ABSTRACT Biocontrol activity of Candida saitoana and its interaction with Botrytis cinerea in apple wounds were investigated. When cultured together, yeast attached to Botrytis sp. hyphal walls. In wounded apple tissue, C. saitoana restricted the proliferation of B. cinerea, multiplied, and suppressed disease caused by either B. cinerea or Penicillium expansum. In inoculated apple tissue without the yeast, fungal colonization caused an extensive degradation of host walls and altered cellulose labeling patterns. Hyphae in close proximity to the antagonistic yeast exhibited severe cytological injury, such as cell wall swelling and protoplasm degeneration. Colonization of the wound site by C. saitoana did not cause degradation of host cell walls. Host cell walls in close contact with C. saitoana cells and B. cinerea hyphae were well preserved and displayed an intense and regular cellulose labeling pattern. In addition to restricting fungal colonization, C. saitoana induced the formation of structural defense responses in apple tissue. The ability of C. saitoana to prevent the necrotrophic growth of the pathogen and stimulate structural defense responses may be the basis of its biocontrol activity. 相似文献
9.
A radioimmunosorbent assay was developed for Botrytis cinerea which can be used to detect as little as 100 ng of Botrytis mycelium (dry weight). Of 22 fungi tested in the assay, all significant reaction was restricted to members of the Sclerotiniaceae. No reaction was obtained with representative isolates of Aspergillus, Alternaria or Peiticillium. Other Botrytis species gave the most reaction relative to B. cinerea. and related genera such as Monilinia and Sclerotinia yielded small reactions. The assay can be used to detect fi. cinerea infection of grape berries when as little as 0.1 % of homogenate from infected fruit is mixed with homogenate from sound fruit to simulate a minor infection. The assay of free run juice from various lots of grapes was highly correlated with visual assessments of infection in the field. Pursuant to various theories concerning bloom time infection, the assay was used to analyse the B. cinerea content of immature berry tips and floral debris; however, no evidence of such colonization was obtained. 相似文献
10.
野生药用植物内生真菌的分离及拮抗菌株筛选 总被引：1，自引：0，他引：1
为挖掘生防新资源,采用组织分离法从21种野生药用植物不同组织部位分离纯化内生真菌,以6种植物病原菌为靶标菌筛选拮抗菌株,并根据形态学及分子生物学对菌株进行鉴定,在此基础上研究了高效拮抗菌株对靶标菌菌丝生长及孢子萌发的影响。结果表明:从分离纯化的478株内生真菌中筛选出11株高活性拮抗菌株,分属于青霉属Penicillium、平脐蠕孢属Bipolaris、棘壳孢属Pyrenochaeta、镰孢属Fusarium、粒毛盘菌属Lachnum、垫壳孢属Coniella和Neonectria 7个属,其中青霉属占比最高,达36.36%。平皿对峙试验表明, 棘壳孢菌12-R-5对灰葡萄孢表现出高效性和专一性,其对菌丝抑制率达66.67%。含药平皿试验表明,菌株12-R-5发酵滤液10倍稀释液对灰葡萄孢菌丝生长抑制率达100%,与其他处理差异显著。菌株12-R-5 10倍发酵滤液处理灰葡萄孢10 h,孢子不萌发;100倍稀释液处理对孢子萌发抑制率为91.01%。显微镜观察发现,棘壳孢菌使灰葡萄孢菌丝扭曲变形,膨大肿胀及断裂,部分菌丝发生抑缩、消融现象。说明棘壳孢菌12-R-5菌株具有很好的生防潜力及应用前景。 相似文献
11.
枯草芽孢杆菌G3菌株的抗菌物质及其特性 总被引：29，自引：3，他引：29
产几丁质酶枯草芽孢杆菌G3菌株的固体培养物在黄瓜灰霉病菌和番茄叶霉病菌抑菌试验中证实,抑菌活性物质存在于过滤上清液中,它们是从酸沉淀物中提取出的伊枯草菌素、生物表面活性素和存在于盐析粗蛋白中的几丁质酶。在叶霉孢子萌发试验中,伊枯草菌素微弱地抑制孢子萌发但强烈破坏芽管和新生菌丝;生物表面活性素和几丁质酶则强烈抑制孢子萌发并长久性地抑制芽管伸长。在PDA平板上的灰霉菌丝抑菌试验中,伊枯草菌素抑制菌丝生长,引发菌丝顶端膨大,形成泡囊,泡囊破裂后原生质外泄;几丁质酶抑制菌丝生长,引发产生不规则的菌丝团;生物表面活性素在平皿上对菌丝则不显示出抑菌活性。 相似文献
12.
Population dynamics of epiphytic mycoflora and occurrence of bunch rots of wine grapes as influenced by leaf removal 总被引：1，自引：0，他引：1
Population dynamics of epiphytic fungi associated with the summer bunch rot complex of five wine grape ( Vitis vinifera ) varieties in commercial vineyards in the San Joaquin Valley of California were monitored every two weeks by berry washings during 1989-1992. Vines in the five replicated experiments were subjected to basal leaf removal or left unaltered. Although numerous genera of fungi were isolated, species of Cladosporium, Aspergillus, Penicillium and Alternaria predominated. Population densities of most fungal taxa increased at or after véraison. Leaf removal in the fruiting zones of bilateral cordon-trained vines generally reduced ( P >0·05) mid to late season numbers of epiphytic mycoflora: species of Penicillium, Botrytis and Aspergillus were most commonly reduced. Populations of Alternaria spp. and yeasts were not consistently affected by leaf removal. Numbers of fungi were no lower on berries when leaves were removed from both sides of vines than when leaves were removed only from the shaded side. Incidence and severity of bunch rots (sour rot, rots caused by Botrytis cinerea, Aspergillus niger , and total rot) at harvest were consistently reduced where leaves had been removed in comparison to vines where no leaves were removed. In one experiment, berries from vines sprayed with the grower's choice of pesticides at 50% or 100% of label rates had similar numbers of epiphytic mycoflora in both cases frequently lower than those from unsprayed controls. There was a significant interaction between chemical rate and leaf removal on the incidence of sour rot at harvest. Timing and extent of leaf removal did not affect population dynamics of epiphytic fungi, or incidence or severity of bunch rots ( P ≤0·05) at harvest in other trials. 相似文献
13.
ABSTRACT The course of colonization of leaf mesophyll by the causal agent of grapevine downy mildew, Plasmopara viticola, in a susceptible and a resistant grapevine genotype was examined in order to characterize the development of the pathogen in compatible and incompatible host-pathogen interactions. Within a few hours after inoculation, the pathogen was established in the susceptible Vitis vinifera cv. Müller-Thurgau and formed primary hyphae with a first haustorium. No further development occurred in the following 10 to 18 h. The next step, in which the hyphae grew and branched to colonize the intercellular space of the host tissue, was observed 1.5 days after inoculation. After 3 days, the intercostal fields were entirely filled with mycelium and sporulation was abundant under favorable environmental conditions. The first infection steps were essentially the same in the resistant V. rupestris. However, the invasive growth of P. viticola was delayed, and further development ceased before the intercostal fields were filled with mycelium. 相似文献
14.
Tomato cultivar Moneymaker was independently inoculated with Alternaria alternata, Cunninghamella elegans, Fusarium culmorum, F. oxysporum f.sp. lycopersici, F. oxysporum f.sp. pisi and Stromatinia gladioli and analysed ultrastructurally. The extent and amount of superficial fungal growth on tomato roots was similar but C. elegans , a saprophyte, was exceptional in that hyphae were not closely appressed to plant surfaces and did not adhere to plant cell walls.
In general, the type of plant responses to fungal colonization and infection were similar in all of the interactions studied, with the exception of C. elegans which did not infect tomato root tissue. The failure to penetrate tomato roots by C. elegans may have been associated with the lack of hyphal adhesion to plant cell walls. Migration of cytoplasm and wall apposition/penetration papilla formation were regularly observed in tomato root tissue beneath appressed hyphae and at sites of fungal infection. Specific cellular reactions in the exodermis, namely the formation of wall 'inclusions' and appearance of 'sensitive' cells, indicated that exodermal cells were particularly responsive to fungal challenge.
Fusarium oxysporum f.sp. lycopersici , a pathogen of tomato, invaded tomato root tissue more extensively than the other fungi inoculated onto tomato roots. Infection of tomato by the other fungi studied was variable, and the extent and success of fungal invasion was tentatively associated with their necrotrophic capability and typical host range. 相似文献
In general, the type of plant responses to fungal colonization and infection were similar in all of the interactions studied, with the exception of C. elegans which did not infect tomato root tissue. The failure to penetrate tomato roots by C. elegans may have been associated with the lack of hyphal adhesion to plant cell walls. Migration of cytoplasm and wall apposition/penetration papilla formation were regularly observed in tomato root tissue beneath appressed hyphae and at sites of fungal infection. Specific cellular reactions in the exodermis, namely the formation of wall 'inclusions' and appearance of 'sensitive' cells, indicated that exodermal cells were particularly responsive to fungal challenge.
Fusarium oxysporum f.sp. lycopersici , a pathogen of tomato, invaded tomato root tissue more extensively than the other fungi inoculated onto tomato roots. Infection of tomato by the other fungi studied was variable, and the extent and success of fungal invasion was tentatively associated with their necrotrophic capability and typical host range. 相似文献
15.
Stilbene glucoside levels and the resistance of Sitka spruce (Picea sitchensis) tissues to colonization by root- and butt-rotting fungi 总被引：1，自引：0，他引：1
The relationship between constitutive stilbene glucoside (astringin and isorhapontin) levels in Sitka spruce (Picea sitchensis) bark and resistance of these tissues to colonization by the root- and butt-rot fungi Heterobasidion annosum and Phaeolus schweinitzii was determined in vitro in excised bark tissues. Two experimental systems were developed. In one, 15-mm-diameter bark discs taken from mature forest trees were challenged with mycelial cultures of the fungi; in the other, 70- or 100-mm lengths of stem, up to c. 30 mm diameter, were similarly challenged at the lower cut end. The extent of fungal colonization or necrosis in the challenged tissues was determined. The results indicated that both systems were capable of detecting differences in bark susceptibility to colonization between individual trees. No consistent correlation between stilbene levels and resistance to colonization by either fungus was found. 相似文献
16.
Jürgen Köhl Wilma M. L. Molhoek Carin H. van der Plas Nyckle J. Fokkema 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(3):251-259
In this study, the hypothesis was tested that removal of substrate for sporulation ofBotrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop. Suppression of sporulation ofBotrytis spp. could be an attractive option for biological control ofBotrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on whichBotrytis spp. sporulates was reduced. In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm–2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists. 相似文献
17.
本研究从黑龙江省土壤中分离获得一株木霉, 运用生物学特征和ITS序列分析相结合的方法将其鉴定为拟康宁木霉Trichoderma koningiopsis?薯块活体抑菌测定表明, 该木霉对接骨木镰孢Fusarium sambucinum?马铃薯早疫病菌Alternaria solani?立枯丝核菌Rhizoctonia solani (AG3和AG5)等病原真菌引起的马铃薯病害具有抑制作用?对峙培养试验结果显示, 该木霉对上述病原菌的生长具有拮抗作用, 平均抑制率均超过50%, 且该木霉生长速度快于上述病原真菌, 以竞争生长方式抑制病原菌菌丝生长和菌核形成?采用扫描电子显微镜观察发现, 该木霉可通过缠绕或并行生长等方式寄生在上述病原真菌菌丝上?以上结果表明, 从土壤中分离获得的拟康宁木霉具备良好的生防潜力, 可为马铃薯种植中多种真菌病害的统防统治提供良好的生防菌株? 相似文献
18.
2004年7~12月在关中盆地西部,每月分别从0~10、10~20、20~30和30~40 cm 4个土层采集树莓根际土样,系统研究树莓根际AM真菌时空分布和土壤因子之间的相关性。结果表明,树莓能与AM真菌形成良好的共生关系。AM真菌的最高定殖率并不伴随有最大孢子密度,最高定殖率发生在9月,达86%,而最大孢子密度出现在11月,平均密度为14个/g土。土壤碱解氮与孢子密度呈极显著负相关,土壤有机质与孢子密度呈显著负相关,土壤pH与菌丝定殖率呈显著负相关,与泡囊定殖率呈极显著负相关。在检测和评估土壤生态状况和植物形成菌根的能力等方面,宿主植物根际AM真菌的孢子密度和AM真菌不同结构的定殖程度是十分有用的指标。 相似文献
19.
Estimation of amounts of Phytophthora infestans mycelium in leaf tissue by enzyme-linked immunosorbent assay 总被引：2，自引：2，他引：0
A polyclonal antiserum, prepared in a rabbit immunized with a mycelium extract of Phytophthora infestans , reacted in an enzyme-linked immunosorbent assay (ELISA) with mycelial extracts of two Phytophthora species but not with those of 10 other micro-organisms found on potato. P. infestans mycelium in leaf tissue was readily detected by ELISA using either the plate-trapped antigen or F(ab')2 antibody-fragment techniques. The amount of mycelium in leaf extracts was estimated by comparing the values obtained in ELISA with those for known concentrations of P. infestans mycelium. 相似文献
20.
ABSTRACT We describe a method to evaluate the virulence of Mycosphaerella fijiensis, the causal agent of black leaf streak disease (BLSD) of banana and plantain. The method is based on the delivery of weighed slurries of fragmented mycelia by camel's hair brush to 5-by-5-cm areas on the abaxial surface of banana leaf blades. Reliable BLSD development was attained in an environmental growth chamber with stringent lighting and humidity controls. By localizing inoculum onto small areas of large leaves, we achieved a dramatic increase in the number of strains that can be tested on each leaf and plant, which is critical for comparing the virulence of numerous strains concurrently. Image analysis software was used to measure the percentage of each inoculated leaf section showing BLSD symptoms over time. We demonstrated that the level of disease of four isolates was correlated with the weight of the mycelium applied and relatively insensitive to the degree of fragmentation of hyphae. This is the first report demonstrating that weighed mycelial inoculum, combined with image analysis software to measure disease severity, can be used to quantitatively assess the virulence of M. fijiensis under rigorously controlled environmental conditions. 相似文献