草坪草币斑病菌对甲基硫菌灵、异菌脲和丙环唑的敏感性

依据鉴别浓度检测了中国不同地理来源的114株草坪草币斑病菌对甲基硫菌灵的敏感性,并采用菌丝生长速率法测定了供试菌株对异菌脲和丙环唑的敏感性。结果显示:对甲基硫菌灵敏感的菌株共98株,占总数的85.96%,抗性菌株16株,占总数的14.04%;在8个有甲基硫菌灵施药历史的采样点中,5个点检测到了抗性菌株。异菌脲和丙环唑对草坪草币斑病菌的EC50值分别在0.012 1~1.264 4和0.000 4~0.100 4 μg/mL之间,平均EC50值分别为（0.525 6 ± 0.207 7）和（0.015 2 ± 0.020 1）μg/mL,最大EC50值和最小EC50值分别相差104.7和251.0倍。敏感性频率分布结果显示,币斑病菌对异菌脲和丙环唑已出现敏感性下降的亚群体。与从未施过相关药剂地区的币斑病菌群体相比,分离自8个有施药历史地块的菌株群体对异菌脲的敏感性均显著降低,4个有施药历史地块的群体对丙环唑的敏感性显著降低。相关性分析显示,对丙环唑最不敏感的10株币斑病菌对异菌脲的敏感性均呈现下降趋势,且两者间存在一定的正相关关系（ρ = 0.755 4,P < 0.000 1）,推测这部分菌株可能存在多药抗药性。本研究结果可为杀菌剂的合理使用及币斑病的有效防治提供理论支持。     

Characterization of genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in field isolates of Penicillium digitatum

Genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in isolates of Penicillium digitatum were evaluated and compared to those characterized in other fungi. Resistant isolates were naturally occurring in packinghouses and were not associated with crop losses. For the phenylpyrrole fludioxonil, EC50 values were 0.02 to 0.04 microg/ml for sensitive, 0.08 to 0.65 microg/ml for moderately resistant (MR), and > 40 microg/ml for highly resistant (HR) isolates. Two fludioxonil-sensitive isolates evaluated were also significantly more sensitive to the unrelated dicarboximide fungicide iprodione, that also disrupts osmotic regulation, than the MR and HR isolates. There was no consistent relationship, however, between the HR and MR isolates and their sensitivity to iprodione or osmotic stress. Although, two nucleotide substitutions were found in a sequence analysis of the N-terminal amino acid repeat region of the os-1-related histidine kinase gene among isolates of P. digitatum, these were not correlated with fludioxonil resistance. In mycelia not exposed to fludioxonil, the amount of phosphorylated OS-2-related protein (PdOS-2) was higher in fludioxonil-sensitive isolates and lowest in the HR isolate. An increase in PdOS-2 was observed for sensitive and resistant isolates after exposure to fludioxonil. In addition, glycerol content in untreated mycelia of the fludioxonil-sensitive isolate was significantly higher than in resistant isolates. After exposure to fludioxonil, glycerol concentrations significantly increased in the sensitive and MR isolates, but not in the HR isolate. Thus, our studies indicate that the mode of action of fludioxonil in P. digitatum is probably the mitogen-activated protein kinase pathway that stimulates glycerol synthesis in sensitive and MR isolates. The general suppression of this pathway in resistant isolates was supported by the fact that growth and sporulation of MR and HR isolates were significantly reduced from that of sensitive isolates. In studies on the mode of action of anilinopyrimidines (AP), EC50 values for mycelial growth of P. digitatum and the previously characterized Botrytis cinerea were determined for cyprodinil and pyrimethanil using a defined culture medium without and with the addition of selected amino acids and homocysteine. The addition of amino acids resulted in a reduced toxicity of the two AP fungicides in both fungi, but the effect of each additive was significantly lower for P. digitatum than for B. cinerea. This suggests that methionine biosynthesis is not the primary target site of APs in P. digitatum.     

Activity of carbendazim,dimethachlon, iprodione,procymidone and boscalid against Sclerotinia stem rot in Jiangsu Province of China

Carbendazim (MBC) was widely used to control Sclerotinia stem rot routinely during the 1980s in China, but development of MBC resistance in the causal agent Sclerotinia sclerotiorum led to control failures of this disease. In this study it was found that the MBC resistance in S. sclerotiorum populations was widespread throughout Jiangsu Province with a resistance frequency of 29.54% in the 1786 collected isolates during the growing seasons of 2006 to 2008. The resistance frequencies differed among sampled cities, ranging from 3.1% to 54.9%. The field MBC-resistant isolates showed comparable mycelial growth, sclerotia production and pathogenicity to the wild-type sensitive isolates, which suggested that the field MBC-resistant isolates might have sufficient parasitic fitness to compete with the field MBC-sensitive isolates in the field. In the in vitro sensitivity test, boscalid showed greater activity against S. sclerotiorum than dicarboximide fungicides (dimethachlon, iprodione and procymidone). The treatment 50% boscalid (WG) 125 g a.i. ha⁻¹ was comparable in efficacy to the treatment 50% iprodione (WP) 600 g a.i. ha⁻¹, and better than other treatments of 6% dimethachlon (WP) 690 g a.i. ha⁻¹ and 50% procymidone (WP) 337.5 g a.i. ha⁻¹, whereas MBC failed to control Sclerotinia stem rot (control efficacy only 16.0%). The most active agent for controlling Sclerotinia stem rot was boscalid in our study.     

In vitro Variability of a number of characteristics ofSclerotinia sclerotiorum

Studies were made of the variability ofSclerotinia sclerotiorum (Lib.) de Bary: (i) growth rate when cultivated on potato-dextrose agar (PDA); (ii) thein vitro resistance of this organism to the fungicides benomyl, vinclozolin and procymidone; and (iii) the size and number of sclerotia formed on PDA. The isolates used were collected from eggplants, French beans and tomatoes cultivated in the same locality, but although marked differences were observed among them, especially in growth rate and formation of sclerotia, it was not possible to establish groups or categories among the isolates studied, or to relate the observed variability to their origins. Temperature was a decisive factor for formation of sclerotia on PDA. No correlation was found between size and number of sclerotia, and growth rate. The ED₅₀ level for both vinclozolin and procymidonein vitro was 2 mg l⁻¹, whereas that for benomyl was below the minimum level used, and therefore could not be established.     

Production and viability of sclerotia from fungicide-resistant and fungicide-sensitive isolates of Botrytis cinerea, B. elliptica and B, tulipae

Production of sclerotia by isolates of three Botrytis spp. differing in resistance to benzimidazole and dicarboximide fungicides was compared in vitro. Sensitive isolates of B. cinerea and B. tulipae produced fewer sclerotia than benzimidazole-resistant isolates, but there were no differences in the size of sclerotia within each species. For B. elliptica, sclerotia of dicarboximide-resistant isolates were larger and less numerous than those of sensitive isolates. Sclerotia from fungicide-resistant and -sensitive isolates of B. elliptica. B. tulipae and B. cinerea were produced in vitro, placed in nylon bags, set in loam soil at soil depths of 0, 10 and 20 cm, and recovered periodically after 1-18 months. Sclerotial viability declined during the 18 months, and was lowest at the soil surface for sclerotia of B. cinerea and B. tulipae. For B. elliptica, sclerotial viability of fungicide-sensitive isolates was reduced to 50% after 18 months, compared to 21 % for dicarboximide-resistant isolates, when averaged over all depths. Sensitive isolates of B. tulipae maintained a trend of higher viability than benzimidazole-resistant ones, and fungicide-sensitive isolates showed greater viability at 18 months (49%) than did benzimidazole-resistant ones (27%). No differences in sclerotial viability were apparent between the fungicide-resistant and -sensitive isolates of B. cinerea, with an average viability of 77% after 18 months. After 18 months of field exposure, all isolates retained their original fungicide-resistance groupings, indicating the persistence of fungicide resistance in sclerotia.     

Sensitivity to iprodione and boscalid of Sclerotinia sclerotiorum isolates collected from rapeseed in China

Baseline sensitivity of Sclerotinia sclerotiorum, causal agent of stem rot of rapeseed, to a dicarboximide fungicide iprodione was determined using 50 isolates (historic population) collected in 2001 from the rapeseed fields without a previous history of dicarboximide usage. The 50% effective concentration (EC₅₀) values to iprodione of these wild-type isolates ranged from 0.163 to 0.734 μg/ml with a mean of 0.428 μg/ml. In 2007 and 2008, 111 isolates (current population) were collected from rapeseed fields with 4–5 years of iprodione application. The EC₅₀ values of these 111 isolates ranged from 0.117 to 0.634 μg/ml. The historic and current populations were not significantly (P > 0.05) different in sensitivity to iprodione. The EC₅₀ values of these 161 isolates to a carboxamide fungicide boscalid ranged from 0.002 to 0.391 μg/ml with a mean of 0.042 μg/ml. In the laboratory, three iprodione-resistant (IR) isolates HA17-IR, SZ31-IR, and SZ45-IR were induced from wild-type isolates HA17, SZ31, and SZ45, respectively. The EC₅₀ values of the IR isolates were 200-fold higher than those of the original wild-type parents. The IR isolates showed an increase in osmotic sensitivity. The IR isolate HA17-IR lost its ability to produce sclerotia, and showed a significantly lower virulence on rapeseed leaves than its parent isolate HA17. In contrast, the IR isolate SZ31-IR had a significantly higher virulence than its wild-type parent SZ31. PCR assays showed that the partial two-component histidine kinase (os-1) gene, which is the putative target gene of iprodione, was deleted in the low virulent IR isolate HA17-IR. DNA sequence analysis showed that each of the other two IR isolates SZ31-IR and SZ45-IR had two point mutations in their partial os-1 genes. These results indicate that the mutations in os-1 gene may be associated with dicarboximide sensitivity, sclerotial development, and virulence in S. sclerotiorum.     

山东省不同地区蔬菜菌核病菌对四霉素的敏感性

采用菌丝生长速率法测定了四霉素对采自山东省不同地区不同蔬菜作物的151株菌核病菌的毒力作用,同时比较了其对蔬菜菌核病菌不同生育阶段的抑制活性,并通过离体叶片法评价了四霉素对蔬菜菌核病的防治效果。结果表明:菌核病菌对四霉素比较敏感,敏感性频率呈单峰正态分布,151株病菌菌丝生长的平均EC₅₀值为 (0.29 ± 0.01) μg/mL,该值可作为蔬菜菌核病菌对四霉素的敏感基线。此外,经四霉素处理后,该病菌的菌核数量以及干重明显降低,菌核明显变小;2 μg/mL的处理对菌核萌发的抑制率达到100.00%。 离体黄瓜叶片接种试验表明,四霉素对菌核病具有较好的保护和治疗效果,且保护作用较为显著。在质量浓度为20 μg/mL时,四霉素对该病的防效显著高于对照药剂多菌灵和异菌脲。因此,四霉素具有防治蔬菜菌核病的潜在价值,可进一步通过田间试验验证其应用效果。     

Molecular diversity of binucleate <Emphasis Type="Italic">Rhizoctonia</Emphasis> AG-A in China

AG-A belongs to the binucleate Rhizoctonia (BNR) anastomosis group (AG) of the Ceratobasidium teleomorph, which parasitizes the roots of many plant species. Ninety nine isolate species of AG-A were obtained from Tibet, Sichuan, and Yunnan Province in China. All isolates were divided into three types based on their cultural characteristics. Type I: abundant aerial mycelia, dense hyphae, loose sclerotia; Type II: abundant aerial mycelia, no sclerotia. Type III: sparse aerial mycelium and no sclerotia. All of the isolates infected the seedlings of Chinese mustard and Chinese cabbage, causing the formation of lesions on the stem and a brown discoloration of the roots. Sequence analysis of the 5.8S rDNA-ITS showed a similarity of 98–100% among the isolates. Inter Simple Sequence Repeat (ISSR) was used to detect genetic variation in binucleate Rhizoctonia spp. Forty two AG-A isolates were amplified using 15 random primers. From a total of 164 bands, 144 bands (87.8%) were polymorphic in the 42 tested isolates. A dendrogram showing genetic relationships between the isolates was constructed using unweighted pair-group averages based on genetic distances. According to the dendrogram, the 42 tested isolates could be aligned into three clusters with a genetic similarity coefficient of 0.29, the first clusters including 27 isolates with III of culture characteristics on PDA; the second clusters included eight isolates with I of cultural characteristics on PDA; the third cluster included seven isolates with II of cultural characteristics on PDA. The results of ISSR analysis showed an association between the hosts of these isolates. Our results showed that ISSR analysis can reveal more molecular variation among isolates of AG-A than sequence analysis using the 5.8S rDNA-ITS.     

水稻纹枯病菌菌核上的真菌和细菌种类及其对水稻纹枯病菌生长的影响

 A total of 136 fungal and 86 bacterial isolates were isolated from the sclerotia of Rhizoctonia solani,collected from three different sources.These fungal isolates were identified as the following 12 genera:Alternaria,Aspergillus,Cladosporium,Coniothyrium,Curvularia,Gliocladium,Fusarium,Metarhizium,Peni-cillium,Phoma,Phytophthora and Trichoderma.Some isolates of Trichoderma and Gliocladium were found to inhibit the growth of R.solani strongly in vitro.Among the 86 bacterial isolates,20 of them could inhibit the growth of R.solani,whereas 5 isolates were found to promote the growth of mycelia and the formation of sclerotia of R.solani.These bacterial isolates with antagonistic actives to R.solani were identified as Bacillus and Pseudomonas.     

Potential for Integrated Control of Sclerotinia sclerotiorum in Glasshouse Lettuce Using Coniothyrium minitans and Reduced Fungicide Application

ABSTRACT All pesticides used in United Kingdom glasshouse lettuce production (six fungicides, four insecticides, and one herbicide) were evaluated for their effects on Coniothyrium minitans mycelial growth and spore germination in vitro agar plate tests. Only the fungicides had a significant effect with all three strains of C. minitans tested, being highly sensitive to iprodione (50% effective concentration [EC(50)] 7 to 18 mug a.i. ml(-1)), moderately sensitive to thiram (EC(50) 52 to 106 mug a.i. ml(-1)), but less sensitive to the remaining fungicides (EC(50) over 200 mug a.i. ml(-1)). Subsequently, all pesticides were assessed for their effect on the ability of C. minitans applied as a solid substrate inoculum to infect sclerotia of Sclerotinia sclerotiorum in soil tray tests. Despite weekly applications of pesticides at twice their recommended concentrations, C. minitans survived in the soil and infected sclerotia equally in all pesticide-treated and untreated control soil trays. This demonstrated the importance of assessing pesticide compatibility in environmentally relevant tests. Based on these results, solid substrate inoculum of a standard and an iprodione-tolerant strain of C. minitans were applied individually to S. sclerotiorum-infested soil in a glasshouse before planting lettuce crops. The effect of a single spray application of iprodione on disease control in the C. minitans treatments was assessed. Disease caused by S. sclerotiorum was significantly reduced by C. minitans and was enhanced by a single application of iprodione, regardless of whether the biocontrol agent was iprodione-tolerant. In a second experiment, disease control achieved by a combination of C. minitans and a single application of iprodione was shown to be equivalent to that of prophylactic sprays with iprodione every 2 weeks. The fungicide did not affect the ability of C. minitans to spread into plots where only the fungicide was applied and to infect sclerotia. These results indicate that integrated control of S. sclerotiorum with soil applications of C. minitans and reduced foliar iprodione applications was feasible, did not require a fungicide tolerant isolate, and that suppression of Sclerotinia disease by C. minitans under existing chemical control regimes has credence.     

Incidence of benomyl and iprodione resistance in isolates of Botrytis cinerea in tomato crops in England and Wales in 1986

In 1986, mass-mycelial isolates of Botrytis cinerea from 67 tomato crops in England and Wales were examined for benomyl and iprodione resistance. Of the 706 isolates obtained, 62.7% were resistant to benomyl at 2μg/ml and 43.2% were resistant to iprodione at 2 μg/ml. Iprodione resistance persisted in the absence of a dicarboximide spray programme. The incidence of benomyl resistance has not decreased since the last survey in 1984 in spite of a considerable reduction in the use of benzimidazole fungicides. There were no clear indications that the use of dichlofluanid influenced the incidence of benomyl or iprodione resistance. Disease control was poorer in crops with a higher incidence of iprodione resistance.     

核盘菌侵染循环类型的研究

 对核盘菌科7个种21个代表菌株的研究结果表明,核盘菌分4种侵染循环类型:1.土传病害类型:包括人参菌核病、细辛菌核病和向日葵小菌核病菌,其特点是子囊孢子在侵染循环中不起作用,以菌丝体为初侵染源,病健株接触构成再侵染。2.子囊孢子气传病害类型:包括油菜、黄瓜、大豆、莴苣、萝卜、红花和紫云英菌核病,其特点是气传的子囊孢子致病力强,从寄主的花、衰老叶或伤口侵入,以病健组织接触构成再侵染。3.分生孢子气传病害类型:包括黄瓜、油菜、葡萄和大葱灰霉病,其特点是在自然条件下未见有性世代,以气传的分生孢子从寄生的花和衰老叶侵染,以分生孢子和健病株接触构成再侵染。4气传、种传、土传病害兼有型:包括向日葵菌核病,其特点是子囊孢子从花或茎侵染造成盘腐和茎腐,菌核、带菌种子萌生菌丝体侵染造成苗腐和立枯。病健组织接触构成再侵染。     

Evaluation of chemical fungicides for control of onion white rot

Nine chemicals in 1976 and six in 1977 were evaluated in a five × five simple lattice design for control of Sclerotium cepivorum Berk., the causal agent of white rot of onions. The trial was conducted on organic muck soil in Burnaby, British Columbia, with uniform high levels of added (1976) or natural (1977) inoculum. The percentage of white rot infection, weight of healthy bulbs harvested and percentage of emergence were measured. There were significant differences, according to treatment, in the percentage of white rot infection of onion at harvest. Two chemicals, vinclozolin and iprodione, provided promising results as broadcast treatments on organic muck soils. A comparison of the results, in relation to differences in the distribution of inoculuin between the 1976 and 1977 trials, suggested that the major point of control may have been against mycelial growth through soil from sclerotia, remote to onion seedlings and/or from infected plants to healthy plants.     

Distribution and fitness of isolates of Botrytis cinerea with multiple fungicide resistance in Spanish greenhouses

Forty-nine greenhouses of vegetable crops were surveyed in southeast Spain at the beginning of the disease season in December 1992 to estimate frequencies of resistance to benzimidazoles, dicarboximides and N -phenylcarbamates (NPC) in B. cinerea . Out of 261 isolates collected, 28% were sensitive to both benzimidazoles and dicarboximides, 15% were benzimidazole-resistant and dicarboximide-sensitive, 8% were benzimidazole-sensitive and dicarboximide-resistant and 46% were benzimidazole- and dicarboximide-resistant. Resistance to benzimidazole, dicarboximide and N -phenylcarbamate was determined by measuring the ability of each isolate to grow in the presence of carbendazim, procymidone and diethofencarb fungicides respectively. Carbendazim- or procymidone- resistant isolates were found in all surveyed greenhouses. Three isolates were found with resistance to carbendazim, procymidone and diethofencarb collected in two adjacent greenhouses that were sprayed with the carbendazim and diethofencarb mixture. All other isolates were sensitive to the mixture because they were either sensitive to carbendazim and resistant to diethofencarb or vice versa. Fitness of 31 isolates of B. cinerea was determined in vivo by measuring their sporulation and lesion growth rate on leaf disks. No fitness costs were associated with resistance to iprodione (dicarboximide) and benomyl (benzimidazole). Isolates with EC₅₀ values higher than 101 mg/L for benomyl and 1.6 mg/L for iprodione were considered to be field resistant (they caused visible lesions on cucumber leaf disks treated with each fungicide).     

桃褐腐病菌(Monilinia fructicola)对3种杀菌剂的敏感性

采用生长速率法测定了采自北京平谷区3个桃园的125株桃褐腐病菌对甲基硫菌灵、戊唑醇和异菌脲3种杀菌剂的敏感性,发现甲基硫菌灵对桃褐腐病菌的EC50主要分布在1.0×10^-5～0.2μg/mL,戊唑醇对桃褐腐病菌的EC₅₀主要分布在0.006～0.022μg/mL之间。异菌脲对桃褐腐病菌的EC₅₀主要分布在0.15～0.55μg/mL之间。研究结果表明,北京地区的桃褐腐病菌对这3种杀菌剂都比较敏感,未产生明显的抗药群体。建立了褐腐病菌对异菌脲抗药性的敏感基线。而且,数据分析表明:甲基硫菌灵、戊唑醇和异菌脲之间均不存在交互抗性。     

Relationships between aflatoxin production and sclerotia formation among isolates of <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Flavi</Emphasis> from the Mississippi Delta

Aspergillus section Flavi isolates, predominately A. flavus, from different crops and soils differed significantly in production of aflatoxin and sclerotia. About 50% of the isolates from corn, soil and peanut produced large sclerotia, while only 20% of the rice isolates produced large sclerotia. There was a higher frequency of small sclerotia-producing isolates from rice compared to the other sources and isolates that did not produce sclerotia were significantly less likely to be toxigenic than strains that produced large sclerotia.     

Studies on the Inherent Resistance Risk to Fenhexamid in Botrytis cinerea

After chemical mutagenesis with N-methyl-N-nitrosoguanidine (MNNG) two phenotypes that were highly or moderately resistant to fenhexamid, were isolated from a wild-type strain of Botrytis cinerea, at a mutation frequency of 0.9 × 10^–5. Resistance factors, based on EC⁵⁰ values, were 460–570 and 10–15, respectively. The mutation(s) for resistance to fenhexamid did not affect the sensitivity of mutant strains to the benzimidazole benomyl, the phenylpyridinamine fluazinam, the anilinopyrimidine cyprodinil, the guanidine iminoctadine or to the sterol-biosynthesis-inhibiting fungicides fenarimol, fenpropimorph and tridemorph. On the contrary, an increased sensitivity (EC⁵⁰ ratios of 0.2–0.6) of fenhexamid-resistant strains to the phenylpyrrole fludioxonil and the dicarboximide iprodione was observed. Study of fitness parameters of fenhexamid-resistant isolates of both phenotypic classes showed that these mutation(s) had no effect on mycelial growth and sensitivity to high osmolarity, but they did affect one or more of some other characteristics, such as sporulation, conidial germination and sclerotia production. In tests on cucumber seedlings under greenhouse conditions, all highly fenhexamid-resistant isolates tested presented decreased infection ability compared with the wild-type. Preventive applications of a commercial formulation of fenhexamid, Teldor 50 WP, were effective against lesion development on cotyledons by the wild-type, but ineffective, even in high concentrations, against disease caused by the fenhexamid-resistant isolates. The risk of resistance problems arising during commercial use of fenhexamid is discussed.     

番茄早疫病菌对异菌脲的敏感基线及其抗性突变体的生物学特性

采用菌落直径法测定了山西省五寨县42株番茄早疫病菌Alternaria solani菌株对异菌脲的敏感性。结果表明,异菌脲对各菌株的EC50值在1.225~2.674 μ g/mL之间,平均为2.556 μ g/mL, 由于所有菌株均采自未使用过异菌脲的地区,该平均值可作为番茄早疫病菌对异菌脲的相对敏感基线。为了评价番茄早疫病菌对异菌脲的抗性风险,以敏感菌株为试材,通过紫外诱导和药剂驯化(10代)的方法获得了21株抗性突变体,比较了敏感菌株和突变体的生物学特性。结果表明:异菌脲对突变体的EC50值均大于100 μ g/mL,达到高抗性水平;突变体的抗药性稳定,在无药PDA平板上继代培养10次后抗性不丧失;突变体在生长速率及致病力方面较敏感菌株有所下降,产孢量及分生孢子萌发率与敏感菌株相比无显著差异,孢子的竞争能力明显弱于敏感菌株。     

Resistance of Cercospora beticola Sacc isolates to thiophanate methyl (benzimidazole), demethylation inhibitors and quinone outside inhibitors in Morocco

Sugar beet is a major crop in Morocco and Cercospora leaf spot is one of its most important fungal diseases. In Morocco, thiophanate methyl (benzimidazole) and difenoconazole (demethylation inhibitor, DMI) have been used extensively in the management of Cercospora leaf spot. In this study, samples of Cercospora beticola Sacc were collected from four major production areas. The identification of all isolates was confirmed using a PCR test with specific primers. Radial mycelia growth of each isolate in unmodified potato dextrose agar medium was compared to mycelia growth in the same medium modified with thiophanate methyl (1, 5, 10 and 50 ppm) or the DMIs difenoconazole, epoxiconazole and tetraconazole (0.1, 0.5, 1, 5, 10 and 50 ppm) or the quinone outside inhibitors (QOIs) azoxystrobin and trifloxystrobin (1, 5, 10 and 50 ppm). The percentage of inhibition obtained was used for the half maximal effective concentration (EC₅₀) calculation. All the isolates showed resistance to the thiophanate methyl molecule to different degrees. Three groups were identified: low resistance with EC₅₀ less than 100 ppm, moderate resistance with EC₅₀ between 100 and 1000 ppm, and very resistant with EC₅₀ more than 1000 ppm. For difenoconazole, 41% of isolates were sensitive (EC₅₀ < 0.05 ppm) and 59% were resistant, while for tetraconazole and epoxiconazole 6% were sensitive (EC₅₀ < 0.01 ppm), 66.7 % had medium resistance (0.01 < EC₅₀ < 1 ppm) and 27.3% were resistant (EC₅₀ > 1 ppm). For QOIs, azoxystrobin was less effective for mycelial inhibition than trifloxystrobin, with 54.5% of isolates with resistance to azoxystrobin (EC₅₀ > 100 ppm).     

Multiple resistance of Botrytis cinerea from kiwifruit to SDHIs,QoIs and fungicides of other chemical groups

BACKGROUND: Botrytis cinerea Pers.: Fr. is a high‐risk pathogen for fungicide resistance development that has caused resistance problems on many crops throughout the world. This study investigated the fungicide sensitivity profile of isolates from kiwifruits originating from three Greek locations with different fungicide use histories. Sensitivity was measured by in vitro fungitoxicity tests on artificial nutrient media. RESULTS: Seventy‐six single‐spore isolates were tested for sensitivity to the SDHI fungicide boscalid, the QoI pyraclostrobin, the anilinopyrimidine cyprodinil, the hydroxyanilide fenhexamid, the phenylpyrrole fludioxonil, the dicarboxamide iprodione and the benzimidazole carbendazim. All isolates from Thessaloniki showed resistance to both boscalid and pyraclostrobin, while in the other two locations the fungal population was sensitive to these two fungicides. Sensitive isolates showed EC₅₀ values to boscalid and pyraclostrobin ranging from 0.9 to 5.2 and from 0.04 to 0.14 mg L^?1 respectively, while the resistant isolates showed EC₅₀ values higher than 50 mg L^?1 for boscalid and from 16 to > 50 mg L^?1 for pyraclostrobin. All QoI‐resistant isolates carried the G143A mutation in cytb. Sensitivity determinations to the remaining fungicides revealed in total eight resistance phenotypes. No isolates were resistant to the fungicides fenhexamid and fludioxonil. CONCLUSION: This is the first report of B. cinerea field isolates with resistance to both boscalid and pyraclostrobin, and it strongly suggests that there may be a major problem in controlling this important pathogen on kiwifruit. Copyright © 2010 Society of Chemical Industry