Fungicide Resistance Phenotypes of Botrytis cinerea Isolates from Commercial Vineyards in South West Germany

Fungicide resistance frequencies of Botrytis cinerea populations in the German Wine Road region were determined for 4 years. Strains showing specific resistance against carbendazim, iprodione or fenhexamid were found to occur wide‐spread, but at low frequencies. In contrast, cyprodinil resistance increased from 5.4% in 2006 to 21.9% in 2008 and 16% in 2009, and strains resistant to boscalid increased from 2% in 2006 to 26.7% in 2009. Strains with multidrug resistance (MDR) phenotypes were found at high frequencies. One of the three MDR phenotypes, MDR1, with reduced sensitivity to cyprodinil and fludioxonil, was dominating, representing 19% to 35% of the total population. Strains with a combination of cyprodinil resistance and MDR1 were found to be strongly increasing in 2008 and 2009.     

云南番茄致病疫霉的交配型、甲霜灵敏感性及毒力类型

对2003~2004年云南省番茄致病疫霉的交配型、甲霜灵敏感型、毒性因子及毒力类型进行了系统的测定和分析。结果表明:云南番茄致病疫霉只存在A1交配型,未发现A2交配型或自育型。甲霜灵抗性和中抗菌株是主要菌系,抗性、中抗、敏感菌株分别占测定菌株的51.2%、31.7%、17.1%。云南番茄致病疫霉居群对已知的抗性基因R1、R2、R3、R4、R6、R7、R8、R9、R10、R11有毒性,其毒性频率在9.8%~95.1%之间。测定的61个菌株中检测到26种不同的毒力类型,每种类型平均含有5.2个毒性因子,其中毒力类型1.3.4.7.9出现频率最高,为优势的毒力类型,出现频率为44.3%,其次为1.3.4.6.7.9、1.3.7.9,出现频率均为4.9%,其它23种毒力类型出现频率仅在1.6%~3.3%之间。云南番茄致病疫霉居群显示了复杂的表型特征。     

Management of the late blight (Phytophthora infestans) disease of potato in the southern hills of India

Late blight of potato is considered to be the most devastating problem causing severe yield losses in potato worldwide. Among the different management strategies, the use of resistant cultivars is the most viable option, but the non‐availability of enough quantity of quality seed materials of resistant cultivars forces the farmers to grow susceptible cultivars with proper fungicide scheduling. Therefore, in the present study, chemical control using fungicide has been attempted with newer molecules in the susceptible cultivar along with a resistant cultivar as a positive control. All the tested fungicides were found safe, and no phytotoxicity was observed with any chemical at the applied rate. In resistant cultivar, no late blight was appeared in both the years, whereas maximum AUDPC was observed in the untreated control (276.3) and minimum (41.7) in mancozeb‐cymoxanil + mancozeb based scheduling which was found on par with chlorothalonil‐famoxadone + cymoxanil (51.3) and chlorothalonil‐ametoctradin + dimethomorph (53.5) based scheduling. Among the treatments, resistant cultivar, Kufri Girdhari followed by chlorothalonil‐ametoctradin + dimethomorph and mancozeb‐cymoxanil + mancozeb based fungicidal scheduling were proven as the best treatments for both the crop seasons resulting in the highest yield parameters. The disease severity showed a strong negative correlation with the tuber yield of potatoes in both the years. Based on overall observations including BC ratio, it can be concluded that, wherever seed material of resistant cultivar is available farmers should grow the same or else with susceptible cultivars the fungicidal scheduling based on mancozeb‐cymoxanil + mancozeb or chlorothalonil‐ametoctradin + dimethomorph can be followed to obtain the maximum returns with effective management of late blight at the southern hills of India.     

The effect of eight fungicides on germination of Conidiobolus obscurus resting spores

Conidiobolus obscurus resting spore germination was greater than 60% after 21 days incubation in 700 ppm concentrations of Rhodiasoufre, Pelt 44, Dithane M-45, Plantvax, and Saprol. No germ tubes were produced under the same treatment with Bavistine, Quin 20, or Benlate at the same dosage. Germination in distilled water was 85%. After only 24 hr contact with Quin 20 (700 ppm) followed by a distilled water wash, germination was not reduced. A higher ability to penetrate the spore wall may account for greater fungicide activity. Resting spores were found to be more resistant to certain fungicides than conidia; however, no general rule could be applied.     

Role of Nematodes and Soil-borne Fungi in Cotton Stunt

The nematodes, Pratylenchus brachyurus, Trichodorus christiei, and T. porosus and the soil-borne fungi, Rhizoctonia solani, Pythium debaryanum, P. irregulare, P. ultimum, and Fusarium spp. were the pathogens most frequently found in the roots and rhizosphere of field-grown cotton (Gossypium hirsutum) showing "stunt" symptoms. Field-plot application of the nematicide D-D (l,2-dichloropropane, 1,3-dichloropropene) at 373.4 liter/ha (40 gal/A) significantly increased plant growth and yield. A fungicidal mixture of Dexon (p-dimethylaminobenzenediazo sodium sulfonate at 23.5 kg/ha (2l lb/A) and Terraclor (pentachloronitrobenzene at 25.2 kg/ha (22.5 lb/A) was phytotoxic, but combined nematicide/fungicide treatments were not. Greenhouse temperature-tank experiments in soils from two locations showed significantly improved root and shoot growth following methyl bromide fumigation at both 25 C and 18 C and more severe "stunt" at the lower temperature.     

Characterization of adaptability components of Brazilian isolates of Macrophomina pseudophaseolina

Macrophomina pseudophaseolina is a new Macrophomina species reported on different crop and weed species in Brazil, India and Senegal, but to date there are no studies about its adaptability components. In this work, a collection of 62 M. pseudophaseolina isolates obtained from roots of the weed species Trianthema portulacastrum and Boerhavia diffusa collected in Northeastern Brazil, was used to: (a) study the effect of temperature and salinity on mycelial growth, (b) to determine their sensitivity to the fungicide carbendazim and (c) to assess their aggressiveness on melon and watermelon seedlings. Results showed variability among M. pseudophaseolina isolates. The optimum temperature for mycelial growth ranged between 26.4 and 38.1ºC. NaCl reduced the in vitro growth of all isolates, which were also highly sensitive to the fungicide carbendazim, exhibiting EC₅₀ values ranging from 0.013 to 0.089 mg/L a.i. Disease severity values on melon and watermelon seedlings showed that M. pseudophaseolina isolates were more aggressive in melon than in watermelon. Information about adaptability components of M. pseudophaseolina obtained in this study could be incorporated on breeding programs for melon and watermelon crops.     

A new point mutation in the iron–sulfur subunit of succinate dehydrogenase confers resistance to boscalid in Sclerotinia sclerotiorum

Research has established that mutations in highly conserved amino acids of the succinate dehydrogenase (SDH) complex in various fungi confer SDH inhibitor (SDHI) resistance. For Sclerotinia sclerotiorum (Lib.) de Bary, a necrotrophic fungus with a broad host range and a worldwide distribution, boscalid resistance has been attributed to the mutation H132R in the highly conserved SdhD subunit protein of the SDH complex. In our previous study, however, only one point mutation, A11V in SdhB (GCA to GTA change in SdhB), was detected in S. sclerotiorum boscalid‐resistant (BR) mutants. In the current study, replacement of the SdhB gene in a boscalid‐sensitive (BS) S. sclerotiorum strain with the mutant SdhB gene conferred resistance. Compared with wild‐type strains, BR and GSM (SdhB gene in the wild‐type strain replaced by the mutant SdhB gene) mutants were more sensitive to osmotic stress, lacked the ability to produce sclerotia and exhibited lower expression of the pac1 gene. Importantly, the point mutation was not located in the highly conserved sequence of the iron–sulfur subunit of SDH. These results suggest that resistance based on non‐conserved vs. conserved protein domains differs in mechanism. In addition to increasing our understanding of boscalid resistance in S. sclerotiorum, the new information will be useful for the development of alternative antifungal drugs.     

Environmental fate of the triazole fungicide propiconazole in a rice-paddy-soil lysimeter

Environmental fate of the triazole fungicide propiconazole, 1-[[2(2,4-dichlorophenyl)-4-propyl-1,3-diox olane-2-yl]methyl]1H-1,2,4-triazole, in soil was investigated using lysimeters simulating a rice-paddy-soil conditions. Two lysimeters composed of different soil types, a sandy loam (lysimeter A) and silty clay (lysimeter B), were used. Propiconazole (Tilt 250^R EC) plus [U-¹⁴C]-propiconazole was applied over a two-year period to the soil surface of the lysimeters. Propiconazole fate in the lysimeters was assessed by measuring total radioactivity in the leachate, evolved ¹⁴CO₂, and ¹⁴C-residues in the soil and rice plants. The amounts of applied ¹⁴C in the leachate from lysimeter A were 4.4 and 5.2% in the first and second year, respectively. A background level of (0.00005% of applied) ¹⁴C in the leachate from lysimeter B was detected, suggesting negligible movement of the fungicide to groundwater in the silty clay soil. The amount of ¹⁴CO₂ evolved from lysimeter A accounted for 7.8 and 12.2% of applied ¹⁴C in the first and second year, respectively, whereas those from lysimeter B were 5.7 and 7.1%. Total ¹⁴C detected in the rice plants grown in lysimeter A were 7.3 and 9.8% of applied ¹⁴C in the first and second year, respectively, which compared to 3.0 and 7.6% in lysimeter B. Most of the applied ¹⁴C was detected in the top 10 cm soil layer, suggesting that propiconazole remains close to the soil surface after application in soil. Degradation products of propiconazole identified in the lysimeter soils were 1-[[2(2,4-dichlorophenyl)-2-(1,2,4-triazole -1-yl) ketone (DP-1), 1-(2,4-dichlorophenyl)-2-(1,2,4-triazole-1- yl) ethanol (DP-2) and 1-[[2(2,4-dichlorophenyl)-4-hydroxypropyl-1,3-dioxolane-2-yl]methyl]1H-1,2,4-triazole (DP-3 and DP-4).     

新型微生物杀真菌剂诺沃霉素稳定性研究

诺沃霉素是一种新型微生物杀真菌剂,具有广谱抗真菌活性。该产物目前用于农作物杀菌剂的开发。为评价该化合物的开发前景,进行了诺沃霉素在加热、光照、室温贮存等条件下的稳定性测试。结果表明,诺沃霉素在环境pH 5.0~6.0时较为稳定,对紫外线及阳光有较好的稳定性。诺沃霉素水乳剂稳定性较差,但制成可湿性粉剂后,基本满足农药稳定性要求。     

Bio‐preparation of (R)‐DMPM using whole cells of Pseudochrobactrum asaccharolyticum WZZ003 and its application on kilogram‐scale synthesis of fungicide (R)‐metalaxyl

Methyl (R)‐N‐(2,6‐dimethylphenyl)alaninate ((R)‐DMPM) is a key chiral intermediate for the production of (R)‐metalaxyl, which is one of the best‐selling fungicides. A new strain, Pseudochrobactrum asaccharolyticum WZZ003, was identified as a biocatalyst for the enantioselective hydrolysis of (R,S)‐DMPM. The key parameters including pH, temperature, rotation speed and substrate concentrations were optimized in the enantioselective hydrolysis of (R,S)‐DMPM. After the 48 h hydrolysis of 256 mM (R,S)‐DMPM under the optimized reaction conditions, the enantiomeric excess of product (e.e._p) was up to 99% and the conversion was nearly 50%. Subsequently, the unhydrolyzed (S)‐DMPM was converted to (R,S)‐DMPM through the n‐butanal‐catalyzed racemization. Furthermore, stereoselective hydrolysis of (R,S)‐DMPM catalyzed by whole cells of P. asaccharolyticum WZZ003 was scaled up to kilogram‐scale, offering (R)‐MAP‐acid with 98.6% e.e._p and 48.0% yield. Moreover, (R)‐metalaxyl was prepared at kilogram scale after subsequent esterification and coupling reactions. Therefore, a practical production process of (R)‐DMPM and (R)‐metalaxyl with the prospect of industrialization was developed in this study. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:921–928, 2018