The evergreen shrub
×
is a
×
hybrid belonging to the family Rosaceae that is widely used in ornamental landscaping. In March 2022, severe powdery mildew symptoms were observed on shrubs of
×
in Huaxi ...University Town, Guiyang, Guizhou Province, China. All observed
×
plants in the green belts of both roads and parks in University Town showed powdery mildew symptoms. Almost all young branches of each
×
individual was infected. Powdery mildew colonies covered twig tips entirely, including the stems, petioles, and the adaxial and abaxial surfaces of leaves. Infected leaves were rolled up and had irregular, dark red spots. Fungal hyphae were straight to flexuous, branched, septate, 3 to 6 μm in width, and had nipple-shaped appressoria. Conidiophores were erect, straight or somewhat flexuous, and measured 90 to 300 µm × 7 to 10.5 µm (n = 30). Foot-cells were cylindrical or subcylindrical, straight or somewhat flexuous, and measured 25 to 50 × 7 to 9.5 µm (n = 30). Foot-cells were followed by one to two shorter cells, these being 10 to 16 × 7 to 9.5 µm in size (n = 50). Shorter cells were followed by one to six conidia (most often five conidia). Conidia formed in chains, ellipsoid to ovoid in shape, having dimensions of 22.5 to 30 × 12.5 to 16 µm (n = 50), and containing fibrosin bodies. No chasmothecia (fruiting bodies) were observed. Based on these morphological characteristics, the pathogen was identified as
(Ellis & Everh.) E.S. Salmon (Braun & Cook 2012). To confirm this species-level identification, the ribosomal DNA internal transcribed spacer (ITS) was amplified using the primers ITS1/ITS4 (White et al. 1990). The resulting sequence was deposited in GenBank (Accession No. ON325389). When the query coverage is 100%, the obtained ITS sequence showed 99.8% identity with
(AB027231, MT180425, MZ298746, KX842350, and KY661036) and 100% with
(HM242221, KY661017, KY661028, KY661050, KY661076, KR048110, MW364489, MW364490, MZ343479, OM022112, ON073894, and ON325389), respectively. Based on the ITS sequences of
spp., phylogenetic tree was constructed with MEGA7.0 using the Maximum Likelihood method. The ML analysis supported our isolate's putative identification as
. To fulfill Koch's postulates, pathogenicity testing was conducted by gently pressing naturally diseased leaves onto young leaves of three healthy, potted 1-year-old
×
plants; three non-inoculated healthy plants served as control. Powdery mildew symptoms were observed on 100% inoculated
×
plants after 12 days (in a growth chamber at 21°C under a 12 h/12 h light/dark cycle), whereas the control plants remained symptomless. The powdery mildew colonies on inoculated leaves were morphologically identical to those observed on the original diseased leaves. It is known that
causes powdery mildew on
×
in Italy (Garibaldi et al. 2005). Moreover, this fungus reportedly infected
in New Zealand, Ukraine, Italy, the United States, Japan, and in East China's Shandong Province (Liang et al. 2012). To the best of our knowledge, this is the first report of powdery mildew caused by
on
×
in Southwest China's Guizhou Province. This finding is significant as
is the causal agent of powdery mildew on apple and pear (Strickland et al. 2021). The occurrence of said disease on
×
could pose a potential disease threat to these fruit crops if nearby ornamental shrubs were able to act as reservoirs for the fungus, and a means to escape agricultural management efforts.
The MLO (Mildew Locus O) gene family encodes plant-specific proteins containing seven transmembrane domains and likely acting in signal transduction in a calcium and calmodulin dependent manner. Some ...members of the MLO family are susceptibility factors toward fungi causing the powdery mildew disease. In tomato, for example, the loss-of-function of the MLO gene SlMLO1 leads to a particular form of powdery mildew resistance, called ol-2, which arrests almost completely fungal penetration. This type of penetration resistance is characterized by the apposition of papillae at the sites of plant-pathogen interaction. Other MLO homologs in Arabidopsis regulate root response to mechanical stimuli (AtMLO4 and AtMLO11) and pollen tube reception by the female gametophyte (AtMLO7). However, the role of most MLO genes remains unknown. In this work, we provide a genome-wide study of the tomato SlMLO gene family. Besides SlMLO1, other 15 SlMLO homologs were identified and characterized with respect to their structure, genomic organization, phylogenetic relationship, and expression profile. In addition, by analysis of transgenic plants, we demonstrated that simultaneous silencing of SlMLO1 and two of its closely related homologs, SlMLO5 and SlMLO8, confer higher level of resistance than the one associated with the ol-2 mutation. The outcome of this study provides evidence for functional redundancy among tomato homolog genes involved in powdery mildew susceptibility. Moreover, we developed a series of transgenic lines silenced for individual SlMLO homologs, which lay the foundation for further investigations aimed at assigning new biological functions to the MLO gene family.
Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs with more than 200 nucleotides in length, which play vital roles in a wide range of biological processes. Powdery mildew disease (PM) has ...become a major threat to the production of melon. To investigate the potential roles of lncRNAs in resisting to PM in melon, it is necessary to identify lncRNAs and uncover their molecular functions. In this study, we compared the lncRNAs between a resistant and a susceptible melon in response to PM infection.
It is reported that 11,612 lncRNAs were discovered, which were distributed across all 12 melon chromosomes, and > 85% were from intergenic regions. The melon lncRNAs have shorter transcript lengths and fewer exon numbers than protein-coding genes. In addition, a total of 407 and 611 lncRNAs were found to be differentially expressed after PM infection in PM-susceptible and PM-resistant melons, respectively. Furthermore, 1232 putative targets of differently expressed lncRNAs (DELs) were discovered and gene ontology enrichment (GO) analysis showed that these target genes were mainly enriched in stress-related terms. Consequently, co-expression patterns between LNC_018800 and CmWRKY21, LNC_018062 and MELO3C015771 (glutathione reductase coding gene), LNC_014937 and CmMLO5 were confirmed by qRT-PCR. Moreover, we also identified 24 lncRNAs that act as microRNA (miRNA) precursors, 43 lncRNAs as potential targets of 22 miRNA families and 13 lncRNAs as endogenous target mimics (eTMs) for 11 miRNAs.
This study shows the first characterization of lncRNAs involved in PM resistance in melon and provides a starting point for further investigation into the functions and regulatory mechanisms of lncRNAs in the resistance to PM.
Key message
New powdery mildew resistance gene
Pm68
was found in the terminal region of chromosome 2BS of Greek durum wheat TRI 1796. The co-segregated molecular markers could be used for MAS.
Durum ...wheat (
Triticum turgidum
L. var.
durum
Desf.) is not only an important cereal crop for pasta making, but also a genetic resource for common wheat improvement. In the present study, a Greek durum wheat TRI 1796 was found to confer high resistance to all 22 tested isolates of
Blumeria graminis
f. sp.
tritici
(
Bgt
). Inheritance study on the
F
1
plants and the
F
2
population derived from the cross TRI 1796/PI 584832 revealed that the resistance in TRI 1796 was controlled by a single dominant gene, herein designated
Pm68
. Using the bulked segregant RNA-Seq (BSR-Seq) analysis combined with molecular analysis,
Pm68
was mapped to the terminal part of the short arm of chromosome 2B and flanked by markers
Xdw04
and
Xdw12
/
Xdw13
with genetic distances of 0.22 cM each. According to the reference genome of durum wheat cv. Svevo, the corresponding physical region spanned the
Pm68
locus was about 1.78-Mb, in which a number of disease resistance-related genes were annotated. This study reports the new powdery mildew resistance gene
Pm68
that would be a valuable resource for improvement of both common wheat and durum wheat. The co-segregated markers (
Xdw05
–
Xdw11
) developed here would be useful tools for marker-assisted selection (MAS) in breeding.
Summary
Powdery mildew (PM) is a severe fungal disease of cultivated grapevine world‐wide. Proanthocyanidins (PAs) play an important role in resistance to fungal pathogens; however, little is known ...about PA‐mediated PM resistance in grapevine.
We identified a WRKY transcription factor, VqWRKY56, from Vitis quinquangularis, the expression of which was significantly induced by PM.
Overexpression (OE) of VqWRKY56 in Vitis vinifera increased PA content and reduced susceptibility to PM. Furthermore, the transgenic plants showed more cell death and increased accumulation of salicylic acid and reactive oxygen species. Transient silencing of VqWRKY56 in V. quinquangularis and V. vinifera reduced PA accumulation and increased the susceptibility to PM. VqWRKY56 interacted with VqbZIPC22 in vitro and in planta. The protein VqWRKY56 can bind to VvCHS3, VvLAR1, and VvANR promoters, and VqbZIPC22 can bind to VvANR promoter. Co‐expression of VqWRKY56 and VqbZIPC22 significantly increased the transcript level of VvCHS3, VvLAR1, and VvANR genes. Finally, transient OE of VqbZIPC22 in V. vinifera promoted PA accumulation and improved resistance to PM, while transient silencing in V. quinquangularis had the opposite effect.
Our study provides new insights into the mechanism of PA regulation by VqWRKY56 in grapevine and provides a basis for further metabolic engineering of PA biosynthesis to improve PM resistance.
The purpose of this study was to determine the virulence structure of oat powdery mildew (Blumeria graminis f. sp. avenae, Bga) populations in Poland collected in 2014 and 2015. Powdery mildew ...isolates were collected from 18 locations in Poland. In total, nine lines and cultivars of oat, with different mildew resistance genes, were used to assess virulence of 180 isolates. The results showed that a significant proportion of the Bga isolates found in Poland were virulent to differentials with Pm1, Pm3, Pm6, and Pm3 + Pm8 genes. In contrast Pm4, Pm5, Pm2, and Pm7 genes were classified as resistant to all pathogen isolates used in the experiment. Based on obtained results we can state that there are differences in virulence pattern and diversity parameters between sites and years, but clear trends are not deducible.
Powdery mildew is a major disease that causes great losses in soybean yield and seed quality. Disease-resistant varieties, which are generated by reducing the impact of susceptibility genes through ...mutation in host plants, would be an effective approach to protect crops from this disease. The Mildew Locus O (MLO) genes are well-known susceptibility genes for powdery mildew in plant. In this study, we utilized the CRISPR/Cas9 system to induce targeted mutations in the soybean GmMLO genes to improve powdery mildew resistance.
A dual-sgRNA CRISPR/Cas9 construct was designed and successfully transferred into the Vietnamese soybean cultivar DT26 through Agrobacterium tumefaciens-mediated transformation. Various mutant forms of the GmMLO genes including biallelic, chimeric and homozygous were found at the T0 generation. The inheritance and segregation of CRISPR/Cas9-induced mutations were confirmed and validated at the T1 and T2 generations. Out of six GmMLO genes in the soybean genome, we obtained the Gmmlo02/Gmmlo19/Gmmlo23 triple and Gmmlo02/Gmmlo19/Gmmlo20/Gmmlo23 quadruple knockout mutants at the T2 generation. When challenged with Erysiphe diffusa, a fungus that causes soybean powdery mildew, all mutant plants showed enhanced resistance to the pathogen, especially the quadruple mutant. The powdery mildew severity in the mutant soybeans was reduced by up to 36.4% compared to wild-type plants. In addition, no pleiotropic effect on soybean growth and development under net-house conditions was observed in the CRISPR/Cas9 mutants.
Our results indicate the involvement of GmMLO02, GmMLO19, GmMLO20 and GmMLO23 genes in powdery mildew susceptibility in soybean. Further research should be conducted to investigate the roles of individual tested genes and the involvement of other GmMLO genes in this disease infection mechanism. Importantly, utilizing the CRISPR/Cas9 system successfully created the Gmmlo transgene-free homozygous mutant lines with enhanced resistance to powdery mildew, which could be potential materials for soybean breeding programs.
Relevance.
Powdery mildew is one of the most common and harmful diseases of cucumber (
Cucumis sativus
L.) in open and protected ground. Moreover, in the closed ground, the harmfulness is higher than ...in the field. The yield of cucumber, due to the defeat of plants by powdery mildew, decreases by 30-50%, and in some cases by more than 70%. The creation of modern cucumber hybrids is impossible without the constant involvement in the breeding process of new sources of economically useful traits, including resistance to real powdery mildew. It is very important to combine in one line both a high degree of parthenocarpy, and the female type of flowering, and resistance to the most harmful diseases. We tried to solve this problem in our work.
Materials and methods
. The experience was laid in 2018-2022 in the Odintsovo district of the Moscow region on the basis of the head institution of the Federal State Budgetary Scientific Institution Federal Scientific Vegetable Center (FSBSI FSVC) in the conditions of a spring ground greenhouse of the Block type, on a natural infectious background. On the basis of the laboratory of breeding and seed production of pumpkin crops, 27 collectible and about 50 breeding samples of parthenocarpic cucumber were studied. The article presents an assessment of the resistance to this powdery mildew of 36 of the most aligned and most valuable cucumber breeding samples in terms of a complex of economically useful features. 2-3 families, 6 plants in each, were evaluated for each sample for 2 years. During the entire growing season, the intensity of powdery mildew damage was assessed on a four-point scale and the spread of the disease in %.
Results.
Among the collection samples of cucumber, on a natural infectious background, two hybrids of the agrofirm BEJO ZADEN B.V. were not affected by powdery mildew: Amur 1801 F1, Artist F1, a hybrid without a name of the agrofirm MONSANTO HOLLAND B.V., conventionally named – Semenis F1 and hybrid Kibria F1 of the agrofirm RIJK ZWAAN. To a small extent, less than one point, they were amazed: Orpheus F1, Merengue F1, Marinda F1, Masha F1, Othello F1, List F1, Adam F1, SV 4097 F1 and Krasotka F1. 11cucumber breeding samples selected in previous years of research on a complex of economically useful signs that were not affected by this disease during 2 years of research were identified. Work will continue to evaluate these lines for resistance to real powdery mildew on an artificial infectious background.
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