New wheat-rye 5DS-4RS·4RL and 4RS-5DS·5DL translocation lines with powdery mildew resistance

Powdery mildew is one of the serious diseases of wheat (Triticum aestivum L., 2n = 6 × = 42, genomes AABBDD). Rye (Secale cereale L., 2n = 2 × = 14, genome RR) offers a rich reservoir of powdery mildew resistant genes for wheat breeding program. However, extensive use of these resistant genes may render them susceptible to new pathogen races because of co-evolution of host and pathogen. Therefore, the continuous exploration of new powdery mildew resistant genes is important to wheat breeding program. In the present study, we identified several wheat-rye addition lines from the progeny of T. aestivum L. Mianyang11 × S. cereale L. Kustro, i.e., monosomic addition lines of the rye chromosomes 4R and 6R; a disomic addition line of 6R; and monotelosomic or ditelosomic addition lines of the long arms of rye chromosomes 4R (4RL) and 6R (6RL). All these lines displayed immunity to powdery mildew. Thus, we concluded that both the 4RL and 6RL arms of Kustro contain powdery mildew resistant genes. It is the first time to discover that 4RL arm carries powdery mildew resistant gene. Additionally, wheat lines containing new wheat-rye translocation chromosomes were also obtained: these lines retained a short arm of wheat chromosome 5D (5DS) on which rye chromosome 4R was fused through the short arm 4RS (designated 5DS-4RS·4RL; 4RL stands for the long arm of rye chromosome 4R); or they had an extra short arm of rye chromosome 4R (4RS) that was attached to the short arm of wheat chromosome 5D (5DS) (designated 4RS-5DS·5DL; 5DL stands for the long arm of wheat chromosome 5D). These two translocation chromosomes could be transmitted to next generation stably, and the wheat lines containing 5DS-4RS·4RL chromosome also displayed immunity to powdery mildew. The materials obtained in this study can be used for wheat powdery mildew resistant breeding program.     

Evaluation of microcapsule trunk injections for the control of apple scab and powdery mildew

A 3‐year field trial was conducted using established apple cv. Crown Gold and English oak (Quercus robur L.) to assess the efficacy of eight fungicides applied via microcapsule trunk injection against the foliar pathogens apple scab (Venturia inaequalis) and powdery mildew (Phyllactinia sp). In both apple cv. Crown Gold and English oak, the fungicide myclobutanil was not taken up when microcapsules were inserted into the tree vascular system at the root flare. Disease severity in injected trees, excluding myclobutanil, was lower over the following two growing seasons compared to water‐injected controls indicating seven of the eight fungicides used in this study provided a significant degree of protection against scab and powdery mildew infection. A difference in the magnitude of pathogen control achieved was recorded between fungicides. Of the fungicides tested, penconazole, pyrifenox and carbendazim significantly reduced disease severity and significantly increased leaf chlorophyll (Fv/Fm) and SPAD values as a measure of tree vitality and chlorophyll content, respectively, in both apple cv. Crown Gold and English oak over two growing seasons after microcapsule injection. Based on the results of this investigation, it is suggested that these three fungicides be used in preference to thiabendazole, fosetyl‐aluminium, triadimefon and propiconazole for the control of apple scab and powdery mildew where outbreaks of these foliar pathogens are problematic.     

Leveillula buddlejae sp. nov., a new species with an asexual morph resembling phylogenetically basal Phyllactinia species

An asexual morph of a powdery mildew was found on Buddleja asiatica (Scrophulariaceae) in Nepal. The morphological traits of this powdery mildew strongly resemble those of Phyllactinia species (including Ovulariopsis) belonging to a phylogenetically basal group closely related to Leveillula species, but phylogenetic examinations and analyses clearly showed that this fungus pertains to Leveillula. Within the latter genus, it seems to be allied to L. duriaei, but clearly differs from this species in having conidiophores arising from superficial hyphae and narrower conidia with different length/width ratios. Therefore, the powdery mildew on B. asiatica is described as Leveillula buddlejae sp. nov.     

A novel strain of Pseudozyma aphidis from mulberry parasitises the conidia of mulberry powdery mildew fungus Phyllactinia sp. and its biocontrol effect in the fields

Plant surface is colonised with a vast community of non-pathogenic epiphytic microorganisms which play an important role in host defence. In the present study, we reported a fungus from mulberry leaf surface that showed an antagonistic effect against mulberry powdery mildew fungal pathogen Phyllactinia sp. This novel isolate is a yeast-like fungus that was identified as Pseudozyma aphidis CNm2012 based on morphologic and phylogenetic analysis. According to our research, P. aphidis CNm2012 directly acted on the powdery mildew conidia via parasitism which caused conidial atrophy, collapse and eventually, cleavage and death. During the parasitic process, we found the isolate could gather around the conidia of Phyllactinia sp. and form hyphae that grew on the conidial surface and utilise the conidia as a nutrient source. Field studies revealed that P. aphidis CNm2012 could suppress the disease incidence of mulberry powdery mildew caused by Phyllactinia sp., and reduce the disease severity. To our knowledge, it is the first report of P. aphidis directly against powdery mildew fungus Phyllactinia spp. by parasitism. Our results indicated that P. aphidis CNm2012 could be served as an environmentally friendly alternative of chemical pesticides to manage mulberry powdery mildew disease.     

Molecular mapping of a recessive powdery mildew resistance gene in spelt wheat cultivar Hubel

Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most important wheat diseases worldwide. The basis for wheat powdery mildew resistance breeding consists of screening diversified host genetic resources with a range of races of the powdery mildew pathogen. Spelt wheat (Triticum aestivum ssp. spelta 2n = 6x = 42, AABBDD) is a close relative of common wheat (T. aestivum ssp. aestivum) and contains several known disease resistance genes, including Pm1d, Yr5, and Lr65. Here, we report the identification and mapping of a powdery mildew resistance gene in spelt wheat cultivar Hubel, which was introduced to China from Europe and is resistant to Chinese Bgt isolate E09 at the seedling stage. Genetic analysis of a recombinant inbred line population derived from a cross of Hubel and a susceptible early maturing mutant line indicated that Hubel possessed a recessive powdery mildew resistance gene (temporarily designated MlHubel). Markers linked to MlHubel were identified using bulked segregant analysis, simple sequence repeat, and expressed sequence tag-derived sequence tagged site methods. The linked markers were physically located on wheat chromosome 2D. Comparative genomic analysis indicated that the genetic interval covering MlHubel in wheat is highly colinear with the corresponding regions on Brachypodium distachyon chromosome 5 and Oryza sativa chromosome 4. Accordingly, the genetic map of MlHubel was established in comparison with B. distachyon 5L and O. sativa 4L, with the closest marker Xgwm265 being 0.4 cM from MlHubel. The identification of the recessive powdery mildew gene in spelt wheat suggests the potential of this accession along with its closely linked markers in breeding for resistance to powdery mildew.     

First record of dill powdery mildew caused by Erysiphe heraclei DC in Egypt

In Egypt, powdery mildew was observed for the first time on dill plants, during annual disease surveys of March–May 2003 and 2005. Typical symptoms of powdery mildew of dill plant (Anethum graveolens L.) were observed in Gharbeia Governorate. Symptoms of powdery mildew became common on leaves, stems inflorescences and fruits as white irregular areas. These symptoms appeared at vegetative and early flowering stages then gradually increased through fruiting and pre-maturity stages. Samples of infected leaflets, stem, inflorescences and fruits were collected for examination by light and scanning electron microscope (SEM). Microscopic examination revealed that conidiophores were short, erect–69 × 6–10 μm in dimension, conidia were observed without conspicuous fibrosin bodies singly, elliposid to ovoid 25–33 × 10–16 μm in dimension, and the length to width ratio of conidia ranged from 1.7 to 2.0 and were produced singly. Cylindrical foot cells (22.0 × 8.0 μm) were followed by one or two shorter cells (12.5 × 7.5 μm). In spring, the sexual stage (cleistothecia) appeared on infected leaves and stems in spherical, gregarious measures 105–117 (111) × 100– 87.5 μm in diameter. Each cleistothecium contained (2–4) round to ovoid asci, 45–55 (50) × 45–25 (35) μm in dimension. The ascus contained (3–4) ellipsoid to ovoid ascospores, 20–17.5 × 15–10 (13.2) μm. Cleistothecia appendages are simple myceloid branched tips measuring 80–200 (140) μm in length and 3–5 (4) μm in diameter. Based on the observations of the morphology of its anamorph and teleomorph stages, the causal agent of dill powdery mildew was identified as Erysiphe heraclei which is reported for the first time in Egypt.     

Mango powdery mildew Oidium mangiferae an alternative food for the predatory mites Typhlodromus mangiferus and Typhlodromips swirskii (Phytoseiidae) in absence or presence increasing prey density of Oligonichus mangiferus (Tetranychidae) in Egypt

The predacious mites, Typhlodromus mangiferus Zaher and El-Borolossy and Typhlodromips swirskii (Athias-Henriot), reproduced successfully on mango powdery mildew Oidium mangiferae Berthet in absence or presence of spider mite prey Oligonichus mangiferus (Rahman and Sapra) under laboratory conditions of 25 ± 1°C and 60–65% R.H. Adult female of both predators consumed protonymphs of O. mangiferus at different experimental densities. The consumption rate increased with increasing prey densities up to 25 protonymphs/female/day and decreased significantly at 35 and 50 protonymphs/female/day for the two predatory mites. Addition of powdery mildew conidia to each prey density significantly reduced consumption of spider mites at 35 and 50 protonymphs/female/day. Mean eggs/female/day by T. swirskii and T. mangiferus was 0.30 and 0.72 when reared on powdery mildew conidia compared with 1.64 and 1.57 when fed on powdery mildew and tetranychid prey, respectively. This increase in reproduction would have compensated the reduction in protonymph prey consumption due to the presence of mildew conidia. Mite–mildew interactions are discussed.     

Antifungal activity of two alkaloids of Zephyranthes citrina and their field efficacy against powdery mildew (Erysiphe cichoracearum) of balsam

The anti-fungal activity of two alkaloids isolated from bulbs of Zephyranthes citrina was observed against 10 fungi, viz, Aternaria solani, A. triticina, Curvularia lunata, C. maculuns, Cercospora malvacearum, Erysiphe sp., Fusarium udum, Helminthosporium pisi, H. speciferum and Ustilago cynodontis. Different concentrations (200, 400, 600, 800, 1000 µg/ml of alkaloids (A and B) were used. Spore germination was inhibited at 600, 800, 1000 µg/ml. B alkaloid was used against Erysiphe cichoracearum causing powdery mildew in balsam (Impatiens balsamina) in the field as pre- and post-inoculation treatments at 1000, 1500, 2000 µg/ml doses. The extract was effective in both pre- and post-inoculation treatments. Foliar application of this alkaloid resulted in inducing synthesis of phenolic acid in the leaves of balsam. Maximum phenolics were detected in the leaves treated with 1500 µg/ml in both pre- and post-inoculation treatments. The increase in the production of phenolics in treated leaves of balsam can be correlated with the induction of resistance in treated plants against powdery mildew. The significant efficacy of the alkaloid under field conditions opens the possibility of its use by farmers for also controlling other diseases.     

Genetic analysis of a novel broad-spectrum powdery mildew resistance gene from the wheat-<Emphasis Type="Italic">Agropyron cristatum</Emphasis> introgression line Pubing 74

Main conclusion

A novel broad-spectrum powdery mildew resistance gene PmPB74 was identified in wheat- Agropyron cristatum introgression line Pubing 74. Development of wheat cultivars with broad-spectrum, durable resistance to powdery mildew has been restricted by lack of superior genetic resources. In this study, a wheat-A. cristatum introgression line Pubing 74, originally selected from a wide cross between the common wheat cultivar Fukuhokomugi (Fukuho) and Agropyron cristatum (L.) Gaertn (2n = 4x = 28; genome PPPP), displayed resistance to powdery mildew at both the seedling and adult stages. The putative alien chromosomal fragment in Pubing 74 was below the detection limit of genomic in situ hybridization (GISH), but evidence for other non-GISH-detectable introgressions was provided by the presence of three STS markers specific to A. cristatum. Genetic analysis indicated that Pubing 74 carried a single dominant gene for powdery mildew resistance, temporarily designated PmPB74. Molecular mapping showed that PmPB74 was located on wheat chromosome arm 5DS, and flanked by markers Xcfd81 and HRM02 at genetic distances of 2.5 and 1.7 cM, respectively. Compared with other lines with powdery mildew resistance gene(s) on wheat chromosome arm 5DS, Pubing 74 was resistant to all 28 Blumeria graminis f. sp tritici (Bgt) isolates from different wheat-producing regions of northern China. Allelism tests indicated that PmPB74 was not allelic to PmPB3558 or Pm2. Our work showed that PmPB74 is a novel gene with broad resistance to powdery mildew, and hence will be helpful in broadening the genetic basis of powdery mildew resistance in wheat.

     

Genetic dissection of powdery mildew resistance in interspecific half-sib grapevine families using SNP-based maps

Quantitative trait locus (QTL) identification in perennial fruit crops is impeded largely by their lengthy generation time, resulting in costly and labor-intensive maintenance of breeding programs. In a grapevine (genus Vitis) breeding program, although experimental families are typically unreplicated, the genetic backgrounds may contain similar progenitors previously selected due to their contribution of favorable alleles. In this study, we investigated the utility of joint QTL identification provided by analyzing half-sib families. The genetic control of powdery mildew was studied using two half-sib F₁ families, namely GE0711/1009 (MN1264 × MN1214; N = 147) and GE1025 (MN1264 × MN1246; N = 125) with multiple species in their ancestry. Maternal genetic maps consisting of 1077 and 1641 single nucleotide polymorphism (SNP) markers, respectively, were constructed using a pseudo-testcross strategy. Ratings of field resistance to powdery mildew were obtained based on whole-plant evaluation of disease severity. This 2-year analysis uncovered two QTLs that were validated on a consensus map in these half-sib families with improved precision relative to the parental maps. Examination of haplotype combinations based on the two QTL regions identified strong association of haplotypes inherited from ‘Seyval blanc’, through MN1264, with powdery mildew resistance. This investigation also encompassed the use of microsatellite markers to establish a correlation between 206-bp (UDV-015b) and 357-bp (VViv67) fragment sizes with resistance-carrying haplotypes. Our work is one of the first reports in grapevine demonstrating the use of SNP-based maps and haplotypes for QTL identification and tagging of powdery mildew resistance in half-sib families.     

Antifungal activities of Bacillus thuringiensis isolates on barley and cucumber powdery mildews

Fourteen Bacillus thuringiensis isolates having both insecticidal activity and in vitro antifungal activity were selected and tested for in vivo antifungal activity against tomato late blight, wheat leaf rust, tomato gray mold, and barley powdery mildew in growth chambers. All the isolates represented more than 70% disease control efficacy against at least one of four plant diseases. Specifically, 12 isolates exhibited strong control activity against barley powdery mildew. Under glasshouse conditions, four (50-02, 52-08, 52-16, and 52- 18) of the isolates also displayed potent control efficacy against cucumber powdery mildew. To our knowledge, this is the first report of B. thuringiensis isolates that have disease control efficacy against powdery mildew of barley and cucumber as well as insecticidal activity.     

Activity of triadimefon vapour against Erysiphe graminis f. sp. hordei

A series of experiments from 1978 to 1983 investigated the activity of triadimefon vapour against barley powdery mildew (Erysiphe graminis f. sp. hordei). In early experiments there was a pronounced protectant action when the dry product was used as the vapour source, and this protection persisted after test seedlings had been removed from the vicinity of the vapour source. In a glasshouse, sprayed seedlings remained sources of active vapour for at least 6 wk after spraying. In later experiments, effects of triadimefon vapour were much smaller, probably because the pathogen had become less sensitive to the fungicide. The dry product was no longer an effective vapour source but infection of test seedlings was still decreased if they were exposed to vapour emanating from impregnated absorbent paper or sprayed seedlings, presumably because the effective surface areas were much greater. Possible benefits and problems that arise from vapour action in glasshouse and field experiments are discussed.     

Effects of fungal infection and wounding on the expression of chitinases and β-1,3 glucanases in near-isogenic lines of barley

Chitinases (EC 3.2.1.14) and β -1.3 glucanases (EC 3.2.1.39) have been known to play a vital role in the defense of plants against fungal pathogens. The pattern of induction of these two enzymes subsequent to infection by powdery mildew was studied in 10 pairs of near-isogenic lines of barley ( Hordeum vulgare L.) which possess powdery mildew resistance genes. These isogenic lines have been grotiped according to their reaction to the fungus. The induction patterns varied between the resistant and the susceptible cultivars within each group and between different groups. More tsozymcs were induced in susceptible varieties of highly resistant groups and the overall levels and the number of isozymes of chitinases and β -1.3 glucanases were lower in groups with low resistance. The effect of powdery mildew infection and mechanical wounding on the cellular localization of chitinases and β -1.3 glucanases in barley leaves has also been studied. The 31 kDa leaf chitinase, L-CH2, and trace amounts of a 25 kDa chitinase. L-CH3. were present in healthy leaves. Wounding increased the levels of L-CH3 within I ft h. Powdery mildew infection increased the levels of L-CH3 both in intercellular fluid and in intracellular extract of leaves. A /3-I.3 glucanase. GH, also increased after infection and wounding. In infected barley leaves, GL-1 was present both in intercellular space and intracellular extract. It is concluded that powdery mildew resistance genes exhibit qualitative and quantitative differences in the expression of chitinases and β -1.3 glucanases. Further, chitinases and β -1.3 glucanases appear to be a response to active infection rather than the factors responsible for disease resistance.     

Localisation of genes for resistance against Blumeria graminis f.sp. hordei and Puccinia graminis in a cross between a barley cultivar and a wild barley (Hordeum vulgare ssp. spontaneum) line

The aims of this investigation have been to map new (quantitative) resistance genes against powdery mildew, caused by Blumeria graminis f.sp. hordei L., and leaf rust, caused by Puccinia hordei L., in a cross between the barley ( Hordeum vulgare ssp. vulgare) cultivar "Vada" and the wild barley ( Hordeum vulgare ssp. spontaneum) line "1B-87" originating from Israel. The population consisted of 121 recombinant inbred lines. Resistance against leaf rust and powdery mildew was tested on detached leaves. The leaf rust isolate "I-80" and the powdery mildew isolate "Va-4", respectively, were used for the infection in this experiment. Moreover, powdery mildew disease severity was observed in the field at two different epidemic stages. In addition to other DNA markers, the map included 13 RGA (resistance gene analog) loci. The structure of the data demanded a non-parametric QTL-analysis. For each of the four observations, two QTLs with very high significance were localised. QTLs for resistance against powdery mildew were detected on chromosome 1H, 2H, 3H, 4H and 7H. QTLs for resistance against leaf rust were localised on 2H and 6H. Only one QTL was common for two of the powdery mildew related traits. Three of the seven QTLs were localised at the positions of the RGA-loci. Three of the five powdery mildew related QTLs are sharing their chromosomal position with known qualitative resistance genes. All detected QTLs behaved additively. Possible sources of the distorted segregation observed, the differences between the results for the different powdery mildew related traits and the relation between qualitative and quantitative resistance are discussed.     

Antifungal activity of ethanolic extract of Archu (Rheum emodi) on powdery mildew (Erysiphe cichoracearum) and its role in the induction of resistance in balsam (Impatiens balsamania)

Rheum emodi, vernacularly known as Archu, is one of the important high altitude medicinal plants widely distributed in Himalayan regions. Though widely used in Ayurveda for curing various human diseases, its use in plant diseases is limited. Ethanolic extract of Rheum rhizome was assayed against spore germination of Alternaria solani, Heliminthosporium penniseti and Curvularia palliscens. The inhibition of spore germination was concentration dependent. Maximum inhibition was obtained at 4000 and 5000 ppm followed by 3000, 2000 and 1000 ppm. However, the extract was highly effective in the pre-inoculation treatment against powdery mildew (Erysiphe cichoracearum) of balsam (Impatiens balsamania) under field conditions. High performance liquid chromatographic (HPLC) analysis of balsam leaves showed increased synthesis of phenolic acids, which has been correlated with induced resistance in inhibiting the disease intensity of balsam powdery mildew.     

Lr67/Yr46 confers adult plant resistance to stem rust and powdery mildew in wheat

Key message

We demonstrate that Lr67/Yr46 has pleiotropic effect on stem rust and powdery mildew resistance and is associated with leaf tip necrosis. Genes are designated as Sr55, Pm46 and Ltn3 , respectively.

Abstract

Wheat (Triticum aestivum) accession RL6077, known to carry the pleiotropic slow rusting leaf and yellow rust resistance genes Lr67/Yr46 in Thatcher background, displayed significantly lower stem rust (P. graminis tritici; Pgt) and powdery mildew (Blumeria graminis tritici; Bgt) severities in Kenya and in Norway, respectively, compared to its recurrent parent Thatcher. We investigated the resistance of RL6077 to stem rust and powdery mildew using Avocet × RL6077 F₆ recombinant inbred lines (RILs) derived from two photoperiod-insensitive F₃ families segregating for Lr67/Yr46. Greenhouse seedling tests were conducted with Mexican Pgt race RTR. Field evaluations were conducted under artificially initiated stem rust epidemics with Pgt races RTR and TTKST (Ug99 + Sr24) at Ciudad Obregon (Mexico) and Njoro (Kenya) during 2010–2011; and under natural powdery mildew epiphytotic in Norway at Ås and Hamar during 2011 and 2012. In Mexico, a mean reduction of 41 % on stem rust severity was obtained for RILs carrying Lr67/Yr46, compared to RILs that lacked the gene, whereas in Kenya the difference was smaller (16 %) but significant. In Norway, leaf tip necrosis was associated with Lr67/Yr46 and RILs carrying Lr67/Yr46 showed a 20 % reduction in mean powdery mildew severity at both sites across the 2 years of evaluation. Our study demonstrates that Lr67/Yr46 confers partial resistance to stem rust and powdery mildew and is associated with leaf tip necrosis. The corresponding pleiotropic, or tightly linked, genes, designated as Sr55, Pm46, and Ltn3, can be utilized to provide broad-spectrum durable disease resistance in wheat.     

Mapping resistance to powdery mildew in barley reveals a large-effect nonhost resistance QTL

Key message

Resistance factors against non-adapted powdery mildews were mapped in barley. Some QTLs seem effective only to non-adapted mildews, while others also play a role in defense against the adapted form.The durability and effectiveness of nonhost resistance suggests promising practical applications for crop breeding, relying upon elucidation of key aspects of this type of resistance. We investigated which genetic factors determine the nonhost status of barley (Hordeum vulgare L.) to powdery mildews (Blumeria graminis). We set out to verify whether genes involved in nonhost resistance have a wide effectiveness spectrum, and whether nonhost resistance genes confer resistance to the barley adapted powdery mildew. Two barley lines, SusBgt_SC and SusBgt_DC, with some susceptibility to the wheat powdery mildew B. graminis f.sp. tritici (Bgt) were crossed with cv Vada to generate two mapping populations. Each population was assessed for level of infection against four B. graminis ff.spp, and QTL mapping analyses were performed. Our results demonstrate polygenic inheritance for nonhost resistance, with some QTLs effective only to non-adapted mildews, while others play a role against adapted and non-adapted forms. Histology analyses of nonhost interaction show that most penetration attempts are stopped in association with papillae, and also suggest independent layers of defence at haustorium establishment and conidiophore formation. Nonhost resistance of barley to powdery mildew relies mostly on non-hypersensitive mechanisms. A large-effect nonhost resistance QTL mapped to a 1.4 cM interval is suitable for map-based cloning.

     

The phytopathogen powdery mildew affects food-searching behavior and survival of <Emphasis Type="Italic">Coccinella septempunctata</Emphasis>

The diet of entomophagous coccinellids is mainly based on aphids and other food sources such as pollen, nectar, or fungal spores. Knowledge of their foraging behavior on plants infected by powdery mildew and their survival on fungal spores is currently limited. In this study, we investigated the olfactory response of Coccinella septempunctata to odor emission of barley plants infected by powdery mildew and their survival on fungal spores in the presence or absence of aphids. Odors released by powdery-mildew infected plants were more attractive for ladybirds compared to those of uninfected controls. After 3 days, the survival rate of ladybirds feeding only on powdery-mildew spores was less than 50%, while for ladybirds feeding exclusively on Rhopalosiphum padi aphids, the survival rate was close to 90%. After 15 days, the highest survival rate (almost 80%) was observed for ladybirds feeding on plants with both aphids and powdery mildew. Molecular analyses confirmed the presence of fungal spores in ladybird guts when feeding either on powdery mildew or on a mixed diet. Our results provide new insights into foraging behavior of entomophagous coccinellids revealing the potential of powdery mildew to be utilized as important non-essential food in a mixed diet, but also its lethal effect if consumed alone.     

Effects of elevated atmospheric CO2 and temperature on the management of powdery mildew of zucchini

The impact of combined environmental factors, such as temperature and CO₂, on the control of the powdery mildew of zucchini, caused by Podosphaera xanthii, and of different control measures has been studied on plants grown in phytotrons. Five experimental trials were conducted, and the powdery mildew severity of both treated and untreated zucchini plants was found to be significantly affected by the interaction between temperature (three different regimes: 16–18; 18–22; 22–26°C), CO₂ (two concentrations: 400–450 and 800–850 ppm) and the treatments. However, at the end of the trials, the efficacy of all the products was not affected by the different, tested environmental conditions. Sulphur consistently provided the highest disease control (75%–85% efficacy). Among the resistant inducers that were tested, calcium oxide was the most effective, in terms of powdery mildew control under all the conditions tested in phytotrons, reducing disease severity from 46% to 61%. Foliar applications of phosphite (14%–28% efficacy), Ampelomyces quisqualis (12%–23% efficacy) and potassium silicate (13%–24% efficacy) only slightly reduced the disease severity for all the tested temperature regimes and CO₂ concentrations, compared to the untreated control. The results obtained under our experimental conditions show that a possible increase in CO₂ concentration and temperature, which is expected for the next few years, should not influence the efficacy of the tested resistance inducers or of sulphur against powdery mildew on zucchini. Moreover, the suppressive effect of calcium oxide is in light of its possible use in greenhouses for zucchini powdery mildew control under 400–450 ppm of CO₂ and under enriched condition of 800–850 ppm of CO₂.     

喷施硅对蒙古黄芪抗氧化酶活性以及产量和品质的影响北大核心CSCD

以蒙古黄芪为试验材料,设置大田随机区组试验,研究苗期、开花期和根茎伸长期叶面喷施不同浓度硅(500、1000、2000和4000 mg/L)对蒙古黄芪生长发育、抗氧化酶活性、药材产量和品质的影响,并检测施硅对黄芪白粉病、根腐病的防治效果,以揭示硅对增强黄芪抗病性、提升品质和产量的影响机理,为生产中蒙古黄芪的高效栽培提供理论依据。结果表明:(1)在不同生育时期,喷施不同浓度硅能增加蒙古黄芪株高、茎粗、株幅和叶绿素含量,促进蒙古黄芪生长,并以2000 mg/L硅处理效果较佳。(2)不同生育时期喷施硅能提高蒙古黄芪叶片SOD、CAT、POD和APX等抗氧化酶活性,降低MDA含量,以开花期、根茎伸长期2000 mg/L硅处理较佳。(3)施硅能有效降低蒙古黄芪白粉病、根腐病的病情指数,当施硅浓度为2000 mg/L时防效均达到最高,并分别达到47.05%和39.08%。(4)施硅处理能有效提高蒙古黄芪单株干、鲜生物量、产量以及可溶性浸出物和黄芪甲苷含量等品质指标,并在2000 mg/L硅浓度处理下均达到最佳水平,此时可溶性浸出物和黄芪甲苷含量分别比对照显著提高了16.48%和31.96%。研究发现,叶面喷施适宜浓度硅可显著增强蒙古黄芪对白粉病、根腐病的抗性,促进植株生长,进而显著提高药材产量,改善药材品质,并以硅浓度为2000 mg/L时效果最佳。