First Report of Powdery Mildew Caused by Golovinomyces bolayi on Veronica persica in Central China.

Veronica persica, Persian speedwell, is a flowering plant belonging to the family Plantaginaceae. Due to its showy flowers, this plant is widely planted in many home gardens, city parks and universities in China. From April to June 2021, signs and symptoms of powdery mildew were found on leaves of V. persica growing on the campus of Henan Normal University, Henan Province, China. Signs initially appeared as thin white colonies and subsequently white powdery masses were abundant on the adaxial and abaxial surfaces of leaves and covered up to 99 % of the leaf area. The infected leaves showed chlorotic, deformed or senescence features. About 150 V. persica plants were monitored and more than 90 % of the plants showed these signs and symptoms. Conidiophores (n = 20) were 108 to 220 × 10 to 13 µm and composed of foot cells, followed by short cells and conidia. Conidia were hyaline, doliiform-subcylindrical shaped, 21 to 37 × 15 to 22 µm, and showed distinct fibrosin bodies. Conidial germ tubes were produced at the perihilar position. No chasmothecia were observed. The observed morphological characteristics were consistent with those of previously documented Golovinomyces bolayi (Braun and Cook 2012). To further confirm the powdery mildew fungus, structures of the pathogen were harvested and total genomic DNA was isolated using the method previously described by Zhu et al. (2019, 2021). Using the primers ITS1/ITS4, the internal transcribed spacer (ITS) region of rDNA was amplified (White et al. 1990) and the amplicon was sequenced. The resulting sequence was deposited into GenBank under Accession No. MZ343575 and was 100 % identical (592/592 bp) to G. bolayi on Kalanchoe blossfeldiana (LC417096) (Braun et al. 2019). The additional phylogenetic analysis clearly illustrated that the identified fungus and G. bolayi were clustered in the same branch (Zhu et al. 2022a; Zhu et al. 2022b). To test pathogenicity, healthy V. persica plants were collected from the campus of Henan Normal University and leaf surfaces of three plants were inoculated by dusting fungal conidia from mildew-infested leaves using pressurized air. Three plants without inoculation served as a control. The spore-treated and non-treated plants were separately placed in two growth chambers (temperature, 18℃; humidity, 60%; light/dark, 16h/8h). Seven- to eight-days post-inoculation, pathogen signs were noticeable on inoculated plants, whereas control plants remained healthy. Similar results were obtained by conducting the pathogenicity assays twice. Therefore, based on the analysis, G. bolayi was identified and confirmed as the causal agent of the powdery mildew. This pathogen has been reported on V. persica in Iran (Golmohammadi et al. 2019). However, to our best knowledge, there is no report concerning the powdery mildew caused by G. bolayi on V. persica in China. Recently, G. bolayi was segregated from species clades of G. orontii complex (Braun et al. 2019). Our record of the molecular characterization of G. bolayi will support the further phylogeny and taxonomy analysis of the G. orontii complex. The sudden outbreak of powdery mildew caused by G. bolayi on V. persica may detract from plant health and ornamental value. The identification and confirmation of this disease expands the understanding of this causal agent and will offer support for future powdery mildew control.

Jasmonic acid pretreatment improves salt tolerance of wheat by regulating hormones biosynthesis and antioxidant capacity.

Salt stress is a severe environmental factor that detrimentally affects wheat growth and production worldwide. Previous studies illustrate that exogenous jasmonic acid (JA) significantly improved salt tolerance in plants. However, little is known about the underlying molecular mechanisms of JA induced physiochemical changes in wheat seedlings under salt stress conditions. In this study, biophysiochemical and transcriptome analysis was conducted to explore the mechanisms of exogenous JA induced salt tolerance in wheat. Exogenous JA increased salt tolerance of wheat seedlings by alleviating membrane lipid oxidation, improving root morphology, enhancing the contents of ABA, JA and SA and increasing relative water content. In the RNA-seq profiles, we identified a total of 54,263 unigenes and 1,407 unigenes showed differentially expressed patterns in JA pretreated wheat seedlings exposed to salt stress comparing to those with salt stress alone. Subsequently, gene ontology (GO) and KEGG pathway enrichment analysis characterized that DEGs involved in linoleic acid metabolism and plant hormone signal transduction pathways were up-regulated predominantly in JA pretreated wheat seedlings exposed to salt stress. We noticed that genes that involved in antioxidative defense system and that encoding transcription factors were mainly up- or down-regulated. Moreover, SOD, POD, CAT and APX activities were increased in JA pretreated wheat seedlings exposed to salt stress, which is in accordance with the transcript profiles of the relevant genes. Taken together, our results demonstrate that the genes and enzymes involved in physiological and biochemical processes of antioxidant system, plant hormones and transcriptional regulation contributed to JA-mediated enhancement of salt tolerance in wheat. These findings will facilitate the elucidation of the potential molecular mechanisms associated with JA-dependent amelioration of salt stress in wheat and lay theoretical foundations for future studies concerning the improvement of plant tolerance to abiotic environmental stresses.

First report of Podosphaera fusca Causing Powdery Mildew on Coreopsis lanceolata in China.

Coreopsis lanceolata, known as lance-leaf coreopsis, is a perennial plant with high ornamental value. It is widely grown in many public parks and home gardens in China due to its showy flowers. From May to June 2020, typical powdery mildew-signs and symptoms were seen on leaves of C. lanceolata cultivated in the east campus of Henan Normal University, Henan Province, China. Abundant white powder-like masses in spot- or coalesced-lesions were on ad- and abaxial surfaces of plant leaves and covered up to 50 % of the leaf area. The infected leaves were deformed and eventually prematurely senescent. Approximately 80 % of observed C. lanceolata plants showed these signs and symptoms. Unbranched conidiophores (n = 25) were 90 to 200 × 12 to 20 µm and showed a foot cell, followed by 1 to 3 short cells and conidia. Ellipsoid-ovoid shaped conidia (n = 30) were 22 to 36 × 15 to 23 µm, with a length/width ratio of 1.4 to 2.4. No chasmothecia were detected. The powdery mildew fungus was initially identified as Podosphaera fusca based on the morphological characteristics. Total genomic DNA of the pathogen was extracted and the rDNA internal transcribed spacer (ITS) region was amplified and sequenced using the primers ITS1/ITS4 (White et al. 1990; Zhu et al. 2019). The obtained sequence was deposited into GenBank under Accession No. MT899186 and was 100 % identical to P. fusca (JX546297) from Herba eupatorii (Ding et al. 2013). To perform pathogenicity assays, leaf surface of three healthy plants was inoculated with fungal conidia according to a previously described method (Zhu et al. 2021). As a control, three non-inoculated plants were used. The control and inoculated plants were placed separately in two growth chambers (light/dark, 16 h/8 h; humidity, 65 %; temperature, 20 ℃). Fourteen- to sixteen-days post inoculation, powdery mildew signs were noticed on inoculated plants, whereas control remained asymptomatic. Similar results were found by performing two repeated pathogenicity assays. Therefore, based on the morphological and molecular analysis, the pathogen was identified and confirmed as P. fusca. This fungus has been reported on C. lanceolata in Korea (Park et al. 2010) and Italy (Garibaldi et al. 2007). This is, to the best of our knowledge, the first report of P. fusca on C. lanceolata in China. The sudden occurrence of this powdery mildew disease on C. lanceolata may adversely affect the health of valuable ornamentals in China. The precise identification of the causal agent of this powdery mildew of C. lanceolata is a preliminary step in developing effective disease management strategies.