The disease caused by Sclerotinia sclerotiorum has traditionally been difficult to control, resulting in tremendous economic losses in oilseed rape (Brassica napus). Identification of important genes in the defense responses is critical for molecular breeding, an important strategy for controlling the disease. Here, we report that a B. napus mitogen-activated protein kinase gene, BnaMPK3, plays an important role in the defense against S. sclerotiorum in oilseed rape. BnaMPK3 is highly expressed in the stems, flowers and leaves, and its product is localized in the nucleus. Furthermore, BnaMPK3 is highly responsive to infection by S. sclerotiorum and treatment with jasmonic acid (JA) or the biosynthesis precursor of ethylene (ET), but not to treatment with salicylic acid (SA) or abscisic acid. Moreover, overexpression (OE) of BnaMPK3 in B. napus and Nicotiana benthamiana results in significantly enhanced resistance to S. sclerotiorum, whereas resistance is diminished in RNAi transgenic plants. After S. sclerotiorum infection, defense responses associated with ET, JA, and SA signaling are intensified in the BnaMPK3-OE plants but weakened in the BnaMPK3-RNAi plants when compared to those in the wild type plants; by contrast the level of both H2O2 accumulation and cell death exhibits a reverse pattern. The candidate gene association analyses show that the BnaMPK3-encoding BnaA06g18440D locus is a cause of variation in the resistance to S. sclerotiorum in natural B. napus population. These results suggest that BnaMPK3 is a key regulator of multiple defense responses to S. sclerotiorum, which may guide the resistance improvement of oilseed rape and related economic crops.

No abstract

Here, we report the complete genome sequence of Xanthomonas arboricola pv. juglandis DW3F3, a strong pathogenic strain isolated from blighted walnut immature fruit (Juglans regia L. cv. Qingxiang). The genome consists of a single chromosome (5,144 kb).

iopbores (2). Conidia ranged from 15 to 60 |jm (mean 25.5 |jm) long and 10 to 25 ¡im (mean 13.6 pm) wide {n = 50) with I to 6 transverse and 0 to 1 longitudinal septa per spore. To identify botb isolates to tbe species level, genomic DNA was extracted from mycelial plugs and gene specific primers (ALT-HIS3F/R) were used via conventional PCR to amplify a portion of tbe histone gene (357 bp) (Jurick II, unpublisbed). Amplicons were sequenced using tbe Sänger metbod, and tbe forward and reverse sequences of eacb amplicon were assembled into a consensus representing 2x coverage. A megaBLAST analysis revealed tbat tbe isolates were 99% identical to Altemaria alternata sequences in GenBank (Accession No. AE404617), wbicb was previously identified to cause decay on stored apple fruit in Soutb Africa. To prove pathogenicity, Kocb's postulates were conducted using organic 'Gala' apples. Tbe fruit were surface disinfested with soap and water and sprayed witb 70% etbanol to runoff. Wounds, 3 mm deep, were done using a sterile nail and 50 pi of a conidial suspension (1x10* conidia/ml) was introduced into eacb wound per fruit. Fruit were tben stored at 25°C in 80 count boxes on paper trays for 21 days. Water only was used as a control. Ten fruit were inoculated with eacb isolate or water only (control) and the experiment was repeated once. Symptoms of decay observed on inoculated were 'Gala' apple fruit were identical to tbe symptoms initially observed on 'Nittany' apples obtained from cold storage after 21 days. No symptoms developed on fruit in tbe controls. A. alternata was re-isolated 100% from apple inoculated witb tbe fungus, completing Kocb's postulates. A. alternata has been documented as a preand postharvest patbogen on Malus spp. (3). To our knowledge, tbis is tbe first report of postbarvest decay caused by A. alternata on apple fruit during cold storage in Pennsylvania.Worldwide, Japanese yew {Taxus cuspidata Sieb. & Zuce.) is a popular garden tree, witb large trees also being used for timber. In July 2012, leaf bligbt was observed on 10% of Japanese yew seedling leaves planted in a 5OO-m2 field in Andong, Gyeongsangbuk-do Province, Soutb Korea. Typical symptoms included small, brown lesions tbat were first visible on tbe leaf margin, wbicb enlarged and coalesced into tbe leaf becoming brown and bligbted. To isolate potential pathogens from infected leaves, small .sections of leaf tissue (5 to 10 mm'') were excised from lesion margins. Eight fungi were isolated from eight symptomatic trees, respectively. These fungi were bypbal tipped twice and transferred to potato dextrose agar (PDA) plates for incubation at 25°C. After 7 days, tbe fungi produced circular mats of wbite aerial mycelia. After 12 days, black acervuli containing slimy spore masses formed over tbe mycelial mats. Two representative isolates were furtber cbaracterized. Tbeir conidia were straigbt or sligbtly curved, fusiform to clávate, five-celled witb constrictions at tbe septa, and 17.4 to 28.5 x 5.8 to 7.1 \im. Two to four 19.8-to 30.7-|am-long byal...

Walnut bacterial blight caused by Xanthomonas arboricola pv. juglandis (Xaj) has serious repercussions for walnut production around the world. Between 2015 and 2017, disease samples were collected from six counties (Danjiangkou, Baokang, Suizhou, Shennongjia, Zigui, and Xingshan) in Hubei province, China. Fifty-nine Xaj strains were identified by morphology and specific PCR primers from 206 isolates. The genetic diversity of 60 Xaj strains (59 from Hubei plus one from Beijing) was evaluated by Multilocus Sequence Analysis (MLST), and their resistance to copper ion (Cu2+) treatment was determined. A Neighbor Joining phylogenetic dendrogram was constructed based on four sequences of housekeeping genes (atpD-dnaK-glnA-gyrB). Two groups of strains were identified whose clustering was consistent with that of glnA. The minimal inhibitory concentration of copper ion on representative Xaj strain DW3F3 (the first genome sequenced Xaj from China) was 115 μg/ml. Setting the copper resistant threshold value to 125 μg/ml, 47 and 13 strains were considered sensitive and resistant to Cu2+, respectively. Furthermore, five strains showed Cu2+ resistance at 270 μg/ml. Compared to the copB from sensitive strains, the copB gene in resistant strains had a 15-bp insertion and eight scattered single nucleotide polymorphisms. Interestingly, the clustering based on MLSA was distinct between Xaj copper ion resistant and sensitive strains.