Bacillus amyloliquefaciens YN201732 Produces Lipopeptides With Promising Biocontrol Activity Against Fungal Pathogen Erysiphe cichoracearum

Bacillus amyloliquefaciens YN201732 is an endophytic bacteria with high biocontrol efficiency and broad-spectrum antimicrobial activities. In order to clarify the main active ingredients and their antifungal mechanisms against powdery mildew of tobacco, this study is focused on lipopeptide obtained through acid precipitation and organic solvent extraction. HPLC and LCMS-IT-TOF were used to separate and identify antimicrobial lipopeptides. Findings revealed that bacillomycin D plays an important role against surrogate fungal pathogen Fusarium solani. Synthetic pathways of sfp, bacillomycin D, and fengycin were separately disrupted. The sfp gene knockout mutant B. amyloliquefaciens YN201732M1 only showed minor antagonistic activity against F. solani. While Erysiphe cichoracearum spore germination was inhibited and pot experiments displayed a significant decrease in tobacco powdery mildew. The spore inhibition rate of YN201732M1 was only 30.29%, and the pot experiment control effect was less than 37.39%, which was significantly lower than that of the wild type. The inhibitory effect of mutant YN201732M2 (deficient in the production of bacillomycin D) and mutant YN201732M3 (deficient in the production of fengycin) on the spore germination of E. cichoracearum were 50.22% and 53.06%, respectively, suggesting that both fengycin and bacillomycin D had potential effects on spore germination of powdery mildew. Interestingly, in a greenhouse assay, both B. amyloliquefaciens YN201732M2 and YN201732M3 mutants displayed less of a control effect on tobacco powdery mildew than wild type. The results from in vitro, spore germination, and greenhouse-pot studies demonstrated that antimicrobial lipopeptides especially bacillomycin D and fengycin may contribute to the prevention and control of tobacco powdery mildew. In addition, gene mutation related to lipopeptide synthesis can also affect the biofilm formation of strains.

Mycoses as causes of biotic stress in sunflower production

Osjetljivost suncokreta na biotski stres uvelike određuje vrijednosti agronomskih svojstava. Uzročnici biotskog stresa mogu biti različiti, a u svijetu pa tako i u Hrvatskoj se po svome utjecaju izdvajaju bolesti. Uslijed pojave različitih biljnih bolesti, u pojedinim godinama prinosi zrna i ulja suncokreta mogu biti reducirani i preko 50%. Najčešći uzročnici bolesti suncokreta su gljive, a prema stupnju štete koje prave ističu se Sclerotinia sclerotiorum, Diaporthe/Phomopsis helianthi i Plasmopara halstedii te u nešto manjoj mjeri Alternaria helianthi, Phoma macdonaldii, Puccinia helianthi, Verticillium spp., Botrytis cinerea, Macrophomina phaseolina i Erysiphe cichoracearum. Kreiranje otpornih/tolerantnih linija iz divljih formi suncokreta, a zatim transfer poželjnih gena u komercijalne linije i hibride je najčešći oblik povećanja otpornosti/tolerantnosti linija i hibrida suncokreta na biotski stres. U ovom postupku značajnu ulogu ima primjena molekularnih markera. Pored toga važan je stalni monitoring, ali i pravovremena primjena agrotehničkih, kemijskih i bioloških mjera.

Вміст біохімічних речовин у рослин Phlox paniculata L. в умовах Лісостепу України

Досліджено питання стійкості декоративних рослин Phlox paniculata L. до біотичного стресу. За результатами дослідження листків рослин 11 сортів Phlox paniculata з різним ступенем ураження збудником борошнистої роси (Erysiphe cichoracearum DC. f. phlogis Jacz.) визначено кількісний вміст біохімічних речовин (проліну, катехінів, флавонолів та антоціанів) в умовах Лісостепу України. Виявлено, що рослини, уражені збудником борошнистої роси, характеризувалися нижчим рівнем флавонолів (сорти 'Poliarnyi' – 0,268 мг/г, 'Mohuchii' – 0,354 мг/г), неуражені – вищим вмістом (сорти 'Mohuchii' – 0,729 мг/г та 'Fiosin' – 0,719 мг/г). Окрім цього, встановлено тенденцію до істотного збільшення вмісту катехінів у цілому на 8˗21 % в уражених борошнистою росою рослин, порівняно із неураженими. Відзначено певну закономірність щодо вмісту антоціанів: в уражених рослин він був на 18˗48 % вищим, ніж у неуражених. Зроблено висновок, що вторинні метаболіти є маркерами відповідної реакції та стійкості рослинного організму до стресу різного походження, оскільки під дією стресу, спричиненого збудником борошнистої роси, збільшується вміст флавонолів, катехінів та антоціанів. На відміну від інших показників, рівень проліну істотно не залежить від ступеня ураженості рослин Phlox paniculata збудником борошнистої роси, оскільки в цьому механізмі захисту рослин від стресу, спричиненого збудником борошнистої роси, діє інший механізм із залученням вторинних метаболітів.

The dynamics of powdery mildew development on pumpkins

Goal. To determine the spread and development of powdery mildew on pumpkins in the Forest-Steppe of Ukraine. Methods of investigation. The experiments were carried out in 2016—2018 biennium in the Right-Bank Forest Steppe of Ukraine (Khmelnytsky region) on the following varieties: common pumpkins — Ukrainskyi bahatoplidnyi, hull-less — Shtyriiskyi. Assessment of severity and spread of powdery mildew was carried out by conventional methods. The records were taken by visual method at 51, 73 and 89 stages (BBCH scale). Ten plants per plot were selected and spread and severity of the disease in percentage were determined. Results of investigation. During the period of investigation, powdery mildew was observed on the pumpkins of both varieties annually. Its first sympthoms were noted at the 15—17 stage. According to the morphological and biometric features, the pathogen identified as Erysiphe cichoracearum (DC.) V.P. Heluta. In the varieties studied, powdery mildew was found with a non-significant difference in severity and spread. In 2016, the severity of powdery mildew on pumpkins of variety Ukrainskyi bahatoplidnyi varied in the range of 15.4—19.5%, disease spread — 45.1—49.6%, on variety Shtyriiskyi development was 13.3—17.5%, distribution — 46.2—48.1%. In 2017, we obtained the following results: the disease severity for common pumpkins was in the range 13.2—17.4%, disease spread — 42.8—46.7%, for hull-less pumpkins disease severity was 12.2—16.8%, disease spread — 41.7—45.3%. In 2018, severity of powdery mildew was higher than in previous years, accounting for 21.2—26.7% with spread 50.4—55.2% on common pumpkins, and 19.4—25.3% with spread 48.8—54.2% on hull-less pumpkins. The correlation analysis of the data showed that the closest correlation between the spread and the development of the disease was observed with the precipitation and GTC in June. Conclusions. Dynamics of severity of powdery mildew during 2016—2018 years on common and hull-less pumpkins were studied. At stage of full ripening, the maximum rates of spread and severity of the disease were noted, which averaged 49.2—50.5% and 19.9—21.2% over the three years, respectively. No significant difference in the powdery mildew infection between common pumpkins (variety Ukrainskyi bahatoplidnyi) and hull-less pumpkins (variety Shtyriiskyi) was found. The defining conditions for the development of powdery mildew on pumpkins are the weather conditions in June, most notably the presence of increased moisture during this period.

Applying Wollastonite to Soil to Adjust pH and Suppress Powdery Mildew on Pumpkin

Although not considered an essential nutrient, silicon (Si) can be beneficial to plants. Si accumulator species such as pumpkin (Cucurbita pepo var. pepo) can absorb Si from soil. Si uptake may reduce plant susceptibility to fungal diseases such as cucurbit powdery mildew (Podosphaera xanthii and Erysiphe cichoracearum). We previously reported that wollastonite, an Organic Materials Reviews Institute–approved natural mineral, can increase soil Si level, increase soil pH, provide pumpkin plants with Si, and increase their resistance to powdery mildew. In this study, we examined the optimum application rate of wollastonite for pumpkins grown in pots and exposed to cucurbit powdery mildew. We confirmed that wollastonite has liming capabilities similar to regular limestone. Regardless of the application rates, wollastonite and limestone showed similar effects on soil chemistry and plant mineral composition. Pumpkin plants grown with the lower doses of wollastonite amendments (3.13 and 6.25 tons/acre) had the greatest tissue Si concentrations and demonstrated the greatest disease resistance. We conclude that wollastonite is a useful material for organic cucurbit (Cucurbitaceae) growers who want to increase soil pH and improve plant resistance to powdery mildew at the same time. Applying wollastonite at rates beyond the amount required to achieve a desirable soil pH for pumpkin production did not further increase Si uptake, nor did it further suppress powdery mildew development.

Checklist of ascomycetous microfungi of the Nuratau Nature Reserve (Uzbekistan)

A checklist of ascomycetous microfungi of the Nuratau Nature Reserve (Nuratau Mountains, Uzbekistan) was compiled for the first time as a result of field research conducted in 2009–2017. In total, 197 species, 3 varieties and 51 forms of micromycetes belonging to 66 genera and 30 families have been identified. Among them 19 species (Asteromella tanaceti, Camarosporium achilleae, Diplocarpon alpestre, Diplodia celtidis, Hendersonia ephedrae, Mycosphaerella artemisiae, Neopseudocercosporella capsellae, Phoma hedysari, P. mororum, Phyllosticta prostrata, P. silenes, P. trifolii, Ramularia trifolii, Rhabdospora eremuri, Selenophoma nebulosa, Septoria cyperi, S. dauci, S. ranunculacearum, S. trifolii) and one form (Erysiphe cichoracearum f. tanaceti) were found for the first time for the mycobiota of Uzbekistan. 30 species of microfungi were recorded on 31 new host plants. The most abundant species are representatives of the cosmopolitan genera Ramularia, Septoria, Erysiphe, Leveillula, Mycosphaerella, Phoma, Cytospora, Sphaerotheca, Phyllosticta and Marssonina. The annotated checklist includes data on host plant, location, date and collection number of every species.

Occurrence of powdery mildew disease of Gerbera in Kerala

A purposive sampling survey on the hilly tracts of Wayanad, Kerala revealed the existence ofpowdery mildew disease in gerbera crops, grown under both protected and open field condition.Among the other fungal diseases of gerbera, powdery mildew disease causes decisive damageto the ornamental cut flower crop, thereby decline in the industrial value of the crop. Symptomof the disease include as white powdery mat on the upper surface of leaf lamina that graduallyturned pale yellow to brown. Powdery mildew existed in two locations of Wayanad viz.,Ambalavayal and Chulliyode where highest per cent disease severity (PDS) of 50.72 wasobserved at Chulliyode and 47.2 per cent was observed at Ambalavayal during November-December. In Ambalavayal, the disease was non-significant and no correlation existed betweenweather parameters and disease progress. But, in Chulliyode, correlation studies revealed thatit was significant with positive correlation to relative humidity and a reverse relation existedwith temperature and rainfall. The weather data clearly depicts that at a low rainfall of 96 mmand above average relative humidity of 80.27 per cent during November-December was thecongenial factor influencing the disease development. But during summer, decline in relativehumidity (78.37%) and rainfall (63.13 mm) caused a slight reduction in mean per cent diseaseseverity of 49.12 per cent and 33.6 per cent at Chulliyode and Ambalavayal respectively.Morohological and cultural characters of the pathogen depicts presence of two distinct organismviz., Golovinomyces cichoracearum (Erysiphe cichoracearum) and Podosphaera sp. as thecausative organism of the disease. Golovinomyces cichoracearumproduced hyaline, septatemycelia with globose conidia with irregular peripheral end formed in a chain and Podosphaerasp. produced superficial, hyaline, coenocytic mycelium with oval or ellipsoidal, catenate conidiawith dimension ranging from 22.1-30.18 x 13.36-18.08ìm formed in unbranched erectconidiophores.