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Black spot disease (PBS) caused by Alternaria alternata is an economic disease of pear (Pyrus pyrifolia Nakai). Developing cultivars with durable PBS resistance traits is an important research objective for improving pear germplasm. The Deshengxiang is a popular pear variety in China and resistant to PBS. This study aimed to detect quantitative trait loci (QTL) associated with PBS resistance trait in pear and determine closely linked molecular markers by specific locus amplified fragment sequencing (SLAF-seq). F1 population resulting from a cross between "Deshengxiang" (female) and "Guiguan," a susceptible (male) variety, was developed and evaluated in 2016 and 2017. SLAF technology was used to discover SNPs in the F1 individuals and subsequently a high-density genetic linkage map for PBS resistance was constructed which contained 17,604 SNP markers. Based on the linkage map, the markers were distributed into 17 linkage groups, spanning 1548.48 cM, with a mean marker distance of 0.09 cM, representing the densest genetic map of the genus Pyrus. QTL analysis of PBS resistance identified a locus strongly related to PBS resistance at 77.68 ~ 112.99 cM on linkage group 15, which was further narrowed down to 93.79 ~ 112.99 cM. Two markers, Marker94293 and Marker94206, located at 97.47 and 102.93 cM, were closely associated with PBS resistance, with a Δ (SNP index) value of 0.46. Co-localization of QTL interval, bioinformatics analysis, and functional annotation revealed PBS putative candidate genes. Overall, the high-density pear linkage map is a suitable reference for mapping PBS resistance trait, QTL, and genes identified in this study contribute information that could be useful for PBS improvement in pear.

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most destructive diseases that pose a great threat to wheat production. Wheat landraces represent a rich source of powdery mildew resistance. Here, we report the map-based cloning of powdery mildew resistance gene Pm24 from Chinese wheat landrace Hulutou. It encodes a tandem kinase protein (TKP) with putative kinase-pseudokinase domains, designated WHEAT TANDEM KINASE 3 (WTK3). The resistance function of Pm24 was validated by transgenic assay, independent mutants, and allelic association analyses. Haplotype analysis revealed that a rare 6-bp natural deletion of lysine-glycine codons, endemic to wheat landraces of Shaanxi Province, China, in the kinase I domain (Kin I) of WTK3 is critical for the resistance function. Transgenic assay of WTK3 chimeric variants revealed that only the specific two amino acid deletion, rather than any of the single or more amino acid deletions, in the Kin I of WTK3 is responsible for gaining the resistance function of WTK3 against the Bgt fungus., Powdery mildew is a major threat to world wheat yields. Here the authors describe the map-based cloning of Pm24, a gain-of-function powdery mildew resistance allele that encodes a tandem kinase-pseudokinase protein with a deletion in a kinase domain that is endemic to certain wheat landraces.

Pepper root rot is a serious soil-borne disease that hinders pepper production, and efforts are being made to identify biological agents that can prevent and control pepper root rot. Our group recently discovered and produced a biological agent, named G15, which reduces the diversity and richness of fungi and bacteria when applied to pepper fields. In the soil of the G15-treatment condition, the pathogenic fungus Fusarium was inhibited, while the richness of beneficial bacteria Rhodanobacter was increased. Also, the ammonia nitrogen level was decreased in the G15-treatment soil, and the pH, total carbon, and total potassium levels were increased. Compared to the control condition, pepper yield was increased in the treatment group (by 16,680 kg acre−1). We found that G15 could alter the microbial community structure of the pepper rhizosphere. These changes alter the physical and chemical properties of the soil and, ultimately, improve resistance to pepper root rot and increase pepper yield.

Background: Wheat root rot disease due to soil-borne fungal pathogens leads to tremendous yield losses worth billions of dollars worldwide every year. It is very important to study the relationship between rhizosphere soil fungal diversity and wheat roots to understand the occurrence and development of wheat root rot disease. Results: A significant difference in fungal diversity was observed in the rhizosphere soil of healthy and diseased wheat roots in the heading stage, but the trend was the opposite in the filling stage. The abundance of most genera with high richness decreased significantly from the heading to the filling stage in the diseased groups; the richness of approximately one-third of all genera remained unchanged, and only a few low-richness genera, such as Fusarium and Ceratobasidium, had a very significant increase from the heading to the filling stage. In the healthy groups, the abundance of most genera increased significantly from the heading to the filling stage; the abundance of some genera did not change markedly, or the abundance of very few genera increased significantly. Physical and chemical soil indicators showed that low soil pH and density, increases in ammonium nitrogen, nitrate nitrogen and total nitrogen contributed to the occurrence of wheat root rot disease. Conclusions: Our results revealed that in the early stages of disease, highly diverse rhizosphere soil fungi and a complex community structure can easily cause wheat root rot disease. The existence of pathogenic fungi is a necessary condition for wheat root rot disease, but the richness of pathogenic fungi is not necessarily important. The increases in ammonium nitrogen, nitrate nitrogen and total nitrogen contributed to the occurrence of wheat root rot disease. Low soil pH and soil density are beneficial to the occurrence of wheat root rot disease. Keywords: Rhizosphere soil, Fungal diversity, Community structure, Wheat root rot disease

In this investigation of the efficacy of the natural product physcion for the control of gray mold of tomato in the field and possible modes of action, physcion was significantly less effective in in vitro antifungal tests than synthetic fungicides pyrimethanil and boscalid. However, in greenhouse tests, physcion dramatically reduced the severity of gray mold on tomato plants. We further found elevated activity of several enzymes associated with the synthesis of phenolic compounds and plant defense reactions, including phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase. Physcion also significantly increased plant growth, indicating that it can also act as a growth promoter in tomato. The results from two consecutive years of field trials revealed that the application of physcion at a rate of 9 g a.i./ha reduced disease incidence between 63.44 and 69.79%, comparable to the fungicide pyrimethanil. Together, these results indicate that although physcion had little direct effect on the growth of B. cinerea, it increased tomato performance by stimulating an endogenous plant defense response and acting as a growth promoter. The study therefore provides strong evidence that physcion provides an alternative treatment for the management of gray mold in organic and low input tomato production and in traditional integrated pest management programs.

Powdery mildew, a fungal disease caused by Blumeria graminis f. sp. tritici (Bgt), has a serious impact on wheat production. Loss of resistance in cultivars prompts a continuing search for new sources of resistance. Wild emmer wheat (Triticum turgidum ssp. dicoccoides, WEW), the progenitor of both modern tetraploid and hexaploid wheats, harbors many powdery mildew resistance genes. We report here the positional cloning and functional characterization of Pm41, a powdery mildew resistance gene derived from WEW, which encodes a coiled-coil, nucleotide-binding site and leucine-rich repeat protein (CNL). Mutagenesis and stable genetic transformation confirmed the function of Pm41 against Bgt infection in wheat. We demonstrated that Pm41 was present at a very low frequency (1.81%) only in southern WEW populations. It was absent in other WEW populations, domesticated emmer, durum, and common wheat, suggesting that the ancestral Pm41 was restricted to its place of origin and was not incorporated into domesticated wheat. Our findings emphasize the importance of conservation and exploitation of the primary WEW gene pool, as a valuable resource for discovery of resistance genes for improvement of modern wheat cultivars.

Background: Wheat root rot disease due to soil-borne fungal pathogens leads to tremendous yield losses worth billions of dollars worldwide every year. It is very important to study the relationship between rhizosphere fungal diversity and wheat roots to understand the occurrence and development of wheat root rot disease. Results: A significant difference in fungal diversity was observed between the diseased and healthy groups in the heading stage, but the trend was the opposite in the filling stage. The abundance of most genera with high richness decreased significantly from the heading to the filling stage in the diseased groups; the richness of approximately one-third of all genera remained unchanged, and only a few low-richness genera, such as Fusarium and Ceratobasidium, had a very significant increase from the heading to the filling stage. In the healthy groups, the abundance of most genera increased significantly from the heading to the filling stage; the abundance of some genera did not change markedly, or the abundance of very few genera increased significantly. Physical and chemical soil indicators showed that low soil pH and density, increases in ammonium nitrogen, nitrate nitrogen and total nitrogen contributed to the occurrence of wheat root rot disease. Conclusions: Our results revealed that in the early stages of disease, highly diverse rhizosphere fungi and a complex community structure can easily cause wheat root rot disease. The existence of pathogenic fungi is a necessary condition for wheat root rot disease, but the richness of pathogenic fungi is not necessarily important. The increases in ammonium nitrogen, nitrate nitrogen and total nitrogen contributed to the occurrence of wheat root rot disease. Low soil pH and soil density are beneficial to the occurrence of wheat root rot disease.

H62 copper alloy is a commonly used material in engineering, and stress cracking of copper alloys has always been concerned. In this paper, a two-dimensional model of H62 copper alloy was established by COMSOL electrochemical module, and the stress corrosion of H62 copper alloy was analyzed by using measured engineering stress-strain curve. The results show that the tensile stress has a serious effect on the stress corrosion, and the excessive tensile stress will lead to the fracture failure of the contact.

Many medicinal plants possess antimicrobial activities, and have antagonistic endophytic fungi that help them protect from pathogen attack. The aim of this study was to examine endophytic fungi in traditional Chinese medicinal plants, and understand if these organisms have antimicrobial activities and they can be potentially used for biological control of plant diseases. A total of 208 endophytic fungal isolates were collected from stems (83), leaves (121) and flowers (4) of 26 medicinal plant species. The majority of the isolates belonged to Alternaria, Phomopsis, Colletotrichum, Phoma and Acremonium as well as several species allocated to Mycelia sterilia. A detached leaf assay was conducted by testing these isolates on wheat powdery mildew (Blumeria graminis f. sp. tritici, or Bgt). Fifteen isolates of endophytic fungi inhibited Bgt, exhibiting control efficacies ranging from 65.4% to 100%. Of these isolates, LPS-1, SCS-6 and 16-6, exhibited significant inhibition of Bgt proliferation (>90%). Isolate LPS-1 isolated from the stem of Ilex cornuta Lindl. ex Paxt. had the highest efficacy, resulting in 100% inhibition of Bgt growth on detached leaf segments. Based on morphological characteristics and phylogenetic analyses of the ITS rDNA sequences and translation elongation factor 1-alpha (TEF-1α) gene regions, LPS-1 was identified as Lasiodiplodia pseudotheobromae. A range of culture conditions for LPS-1 were examined and the results indicated that optimal antifungal activity resulted from static cultures in PDB (pH 7.0) inoculated with three mycelial plugs and incubated at 30 °C for 6 days. With further study, LPS-1 can be a candidate for biological control.

Blumeria graminis f. sp. tritici (Bgt) is an obligate parasite that only infects living tissues of wheat (Triticum aestivum L.). Long term preservation of Bgt is useful for genetic studies but it is challenging due to difficulty of artificial cultivation. In this study a simple protocol was developed in which desiccating the conidia using crystals (3–6 mm in diameter) of silica gel allowed viable storage for 12 months. The conidia were mixed with silica gel, dried for 5 h at 23 °C, and then stored at −80 °C. The preserved Bgt isolates still maintained their viability after 12 months and successfully infected detached leaves of wheat seedlings. Analysis of 20 Bgt isolates revealed that the cryopreservation process had no effect on two key phenotypic variants: virulence against 12 near-isogenic wheat cultivars and their sensitivity to the fungicide triadimefon. DNA sequencing analysis confirmed that the nucleotide sequences of the 1.4 α-demethylase inhibitor (cyp51), chitin synthase 1 (chs1), and β-tubulin (tub2) genes had not changed and still contained the corresponding single nucleotide mutations. These results indicate that the silica gel-based desiccation protocol is suitable for the long term preservation of large numbers of Bgt isolates.

A secreted mucin-like protein in the rice brown planthopper (Nilaparvata lugens) enables insect feeding and induces plant immune responses.

Deployment of cultivars with genetic resistance is an effective approach to control the diseases of powdery mildew (PM) and yellow rust (YR). Chinese wheat cultivar XK0106 exhibits high levels of resistance to both diseases, while cultivar E07901 has partial, adult plant resistance (APR). The aim of this study was to map resistance loci derived from the two cultivars and analyze their effects against PM and YR in a range of environments. A doubled haploid population (388 lines) was used to develop a framework map consisting of 117 SSR markers, while a much higher density map using the 90K Illumina iSelect SNP array was produced with a subset of 80 randomly selected lines. Seedling resistance was characterized against a range of PM and YR isolates, while field scores in multiple environments were used to characterize APR. Composite interval mapping (CIM) of seedling PM scores identified two QTLs (QPm.haas-6A and QPm.haas-2A), the former being located at the Pm21 locus. These QTLs were also significant in field scores, as were Qpm.haas-3A and QPm.haas-5A. QYr.haas-1B-1 and QYr.haas-2A were identified in field scores of YR and were located at the Yr24/26 and Yr17 chromosomal regions respectively. A second 1B QTL, QYr.haas-1B-2 was also identified. QPm.haas-2A and QYr.haas-1B-2 are likely to be new QTLs that have not been previously identified. Effects of the QTLs were further investigated in multiple environments through the testing of selected lines predicted to contain various QTL combinations. Significant additive interactions between the PM QTLs highlighted the ability to pyramid these loci to provide higher level of resistance. Interactions between the YR QTLs gave insights into the pathogen populations in the different locations as well as showing genetic interactions between these loci.