A survey of bacterial wilt in China collected 286 strains of Ralstonia solanacearum from 17 plant species in 13 Chinese provinces to investigate genetic diversity using the biovar (bv.) and phylotype classification schemes. A phylotype-specific multiplex-PCR showed that 198 isolates belonged to phylotype I (bv. 3, 4 and 5) and 68 to phylotype II (bv. 2 and bv. 1). A phylogenetic analysis examined the partial sequence of the egl and hrpB gene of all strains and the genetic diversity of 95 representatives was reported, demonstrating that Chinese strains are partitioned into phylotype I (Asia) and II (Americas). Phylotype I strains (historically typed bv. 3, 4 and 5), had considerable phylogenetic diversity, including 10 different sequevars: seven previously described sequevars 12 to 18 and three new sequevars: 34, 44 and 48. Chinese strains Z1, Z2, Z3, Z7, Pe74 and Tm82 were not genetically distinguishable from the edible ginger reference strain ACH92 (r4-bv. 4) for sequevar 16. This is believed to be the first report of this ginger group in China. All Chinese bv. 2 strains falling into the genetically and phenotypically diverse phylotype II were placed into phylotype IIB sequevar 1 (historically the Andean race3-bv. 2 potato brown rot agent). In both the egl and hrpB sequence-based trees, strains isolated from mulberry were present in two distinct branches found in sequevars 12 and 48 (reference strains R292 and M2, respectively).
Turnip mosaic virus (TuMV), the only potyvirus known to infect brassicas, is a devastating virus threatening many economically important brassica crops, including cabbage, Chinese cabbage, oilseed rape and mustard. TuMV disease, which was first discovered in the United States, is now found worldwide, especially in Europe, Asia and North America. TuMV results in a yield loss of up to 70% and has a wide host range, infecting most cruciferous plants, as well as many non-cruciferous species. This virus is also characterized by high pathotype diversity because of its highly variable genome structure and has been divided into 12 pathotypes. These characteristics, as well as its nonpersistent transmission mode by as many as 89 aphid species, mean the disease is difficult to prevent through traditional methods such as the application of chemicals, prompting researchers to seek host resistance for effective control. During the last decade, extensive studies have been conducted to investigate inheritance, mapping and cloning of the TuMV resistance genes, and several NB-LRR-or eIF-encoding loci with divergent molecular mechanisms have been uncovered. These studies have greatly facilitated resistance breeding for brassica crops and have advanced our understanding of virusÀhost interactions.
In recent years increasing demands and the relatively low-care cultivation of the crop have resulted in an enormous expansion of the acreage of maize in China. However, particularly in China, Fusarium ear rot forms an important constraint to maize production. In this study, we showed that members of both the Fusarium fujikuroi species complex (FFSC) and the Fusarium graminearum species complex are the causal agents of Fusarium ear rot in the main maize producing areas in China. Fumonisin producing Fusarium verticillioides was the most prevalent species, followed by fumonisin producing Fusarium proliferatum and 15-acetyldeoxynivalenol producing F. graminearum. Both Fusarium temperatum and Fusarium boothii were identified for the first time in the colder regions in China, extending their known habitats to colder environments. Mating type analysis of the different heterothallic FFSC species, showed that both types co-occur in each sampling site suggestive of the possibility of sexual recombination. Virulence tests with F. boothii (from maize) and F. graminearum from maize or wheat showed adaptation to the host. In addition, F. graminearum seems to outcompete F. boothii in wheat-maize rotations. Based on our findings and previous studies, we conclude that wheat/maize rotation selects for F. graminearum, while a wheat/rice rotation selects for F. asiaticum. In contrast, F. boothii is selected when maize is cultivated without rotation. A higher occurrence of F. temperatum is observed on maize in colder climatological regions in China, while Fusarium meridionale seems restricted to mountain areas. Each of these species has their characteristic mycotoxin profile and deoxynivalenol and fumonisin are the potential threats to maize production in Northern China.
Taken together, our results demonstrate that overexpression of miR-203 sensitizes MM cells to TMZ by targeting GLS, providing new insights into the development of anti-tumour agents for patients with chemotherapy-resistant MM.
A total of 129 wheat cultivars collected from local breeders in four ecological regions in China was evaluated for Fusarium head blight resistance after natural infection under epidemic conditions. The disease index was scored and seven toxins concentrations were determined by UPLC-MS/MS. The disease index ranged from 6.3 to 80.9% and a strong correlation was found between the regions from which the cultivars originate and disease index. The middle and lower reaches of Yangtze River Region showed the highest disease resistance, followed by the upper reaches of the Yangtze River Region. FHB resistance of cultivars from northern and southern Huanghuai Region was lowest and all cultivars in these regions are highly or moderately susceptible. Disease index was significantly correlated with toxin accumulation on nation scale, but no clear correlation was found within most ecological regions. The toxin accumulation was also not well correlated with resistant levels. As the incidence of FHB has increased dramatically over the last decade, improved FHB resistance in cultivars is urgently needed. We recommend that besides scoring for disease index also mycotoxin accumulation in cultivars is incorporated in breeding procedures and the evaluation of cultivars.
In China, several diseases of maize (Zea mays L.) including ear rot are caused by Fusarium spp., leading to significant yield losses and potential risk of mycotoxin contamination (2,3). In 2013, a survey was conducted to determine the population composition of Fusarium species on maize ears in Jilin Province. Symptomatic maize ears with pink or white mold were collected and surface disinfested with 70% ethanol and 10% sodium hypochlorite, followed by three rinses with sterile distilled water and placed onto potato dextrose agar (PDA). After 3 days of incubation at 25°C in the dark, newly grown-out mycelia were transferred onto fresh medium and purified by the single-spore isolation method (4). Fusarium spp. were identified by morphological characteristics (2) and sequence analysis of translation elongation factor-1α (TEF) gene (1). A large number of Fusarium spp. were found including F. graminearum species complex and F. verticillioides. In addition, a new species, F. temperatum, recently described in Belgium (2), was also identified. F. temperatum was originally described as F. subglutinans, but a robust polyphasic approach proved it to be a new biological species closely related to F. subglutinans (2). Previous studies had reported ~15% of Fusarium maize ear rot in Jilin was F. subglutinans. In this study, we found both F. subglutinans s. str. and F. temperatum in the proportion of 16.3% and 9.2%, respectively. Similar to previous studies (2), colonies of our strains on PDA were initially white cottony mycelium that become pinkish white. Conidiophores formed abundantly on SNA that were erect, branched, and terminated in 1 to 3 phialides. Microconidia were abundant, hyaline, 0 to 2 septa, obovoid to oval, and not produced in chains. Chlamydospores were absent. Typically macroconidia were falcate, 3 to 5 septate (mostly 4 septate), hyaline with a curved and blunt apical cell and a distinct foot-shaped basal cell. In order to validate this result, partial translation elongation factor (TEF-1α, 629 bp) gene sequences of isolates were generated (GenBank Accession No. KJ137018) (1). BLASTn analysis revealed 100% sequence identity to F. temperatum (HM067690). A pathogenicity test was performed on maize cv. Zhengdan958. Four days after silk emergence, 2 ml conidial suspension (105 macroconidia/ml) of each isolate was injected into each of 10 maize ears through silk channel. Control plants were inoculated with sterile distilled water. Twenty days after inoculation, typical Fusarium ear rot symptoms (reddish-white mold) was observed on inoculated ears and no symptoms were observed on water controls. Koch's postulates were fulfilled by re-isolating the same fungus from the infected seeds. Although F. temperatum was reported to attack maize kernels in southern China where the annual average temperatures are moderately high (3), to our knowledge, this is the first report of F. temperatum causing Fusarium ear rot in northern China, where the winter is long and very cold, the annual average temperature is 4 to 5°C, and the lowest temperature is lower than –35°C. This indicated that F. temperatum was widely distributed in different ecological regions in China. Furthermore, the northeast spring corn region that includes Jinlin is the most important corn belt, with corn production of this region accounting for 42% of the total corn production in China. Therefore, we should pay more attention to the new species in this region and consider them in the development of maize cultivars with broad-based resistance to the pathogens. References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) J. Scauflaire et al. Mycologia 103:586, 2011. (3) J. H. Wang et al. J. Phytopathol. 162:147, 2014. (4) L. Yang et al. Phytopathology 98:719, 2008.
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