In recent years, Fusarium head blight (FHB) outbreaks have occurred much more frequently in China. The reduction of burning of the preceding crop residues is suggested to contribute to more severe epidemics as it may increase the initial inoculum. In this study, a large number of Fusarium isolates was collected from blighted wheat spikes as well as from rice stubble with perithecia originating from nine sampling sites in five provinces in Southern China. Fusarium asiaticum dominated both wheat and rice populations, although rice populations showed a higher species diversity. Chemotype analysis showed that rice is the preferred niche for NIV mycotoxin producers that were shown to be less virulent on wheat. In contrast, 3ADON producers are more prevalent on wheat and in wheat producing areas. The 3ADON producers were shown to be more virulent on wheat, revealing the selection pressure of wheat on 3ADON producers. For the first time, members of the Incarnatum-clade of Fusarium Incarnatum-Equiseti Species Complex (FIESC) were found to reproduce sexually on rice stubble. The pathogenicity of FIESC isolates on wheat proved very low and this may cause the apparent absence of this species in the main wheat producing provinces. This is the first report of the Fusarium population structure including rice stubble as well as a direct comparison with the population on wheat heads in the same fields. Our results confirm that the perithecia on rice stubble are the primary inoculum of FHB on wheat and that cropping systems affect the local Fusarium population.

Carbendazim resistance was detected using 4,701 Fusarium graminearum species complex isolates collected from major wheat-producing regions in China from 2018 to 2020. A total of 348 carbendazim-resistant isolates were identified. The majority of carbendazim-resistant isolates were detected in Jiangsu and Anhui Provinces. In total, 227 and 88 isolates were obtained from each of the Jiangsu and Anhui Provinces, with a high resistance frequency of 41.12 and 20.56%, respectively. The predominant resistant isolates harboring point mutations were F167Y (79.31%), followed by E198Q (16.38%) and F200Y (4.31%). Compared with F. graminearum, F. asiaticum isolates were more likely to produce carbendazim resistance. In this study, we first detected carbendazim-resistant isolates in Hebei, Shaanxi, Sichuan, and Hunan Provinces. In Jiangsu, Anhui, and Zhejiang, the frequency of carbendazim-resistant isolates maintained a high level, resulting in stable carbendazim-resistant populations. We also found the dynamic of carbendazim-resistance frequency in most provinces showed similar trends to the epidemic of Fusarium Head Blight (FHB). Our results facilitate the understanding of the current situation of carbendazim resistance of FHB pathogens and will be helpful for fungicides selection in different wheat-producing areas in China.

Ralstonia solanacearum phylotype I mulberry strains are causative agent of bacterial wilt of mulberry. Current diagnostic methods are not adopted to the mulberry wilt disease. In this study, we developed a rapid method, loop-mediated isothermal amplification (LAMP), to detect R. solanacearum phylotype I mulberry strains. A set of six primers was designed to target the clone MG67 sequence in this LAMP detection which can be completed in 20 min at 64 °C. The results of the LAMP reaction could be observed with the naked eye due to magnesium pyrophosphate precipitate produced during the reaction or the color change after adding SYBR Green I. The specificity of the LAMP was confirmed using DNA from 46 representative strains of R. solanacearum and 7 other soil-borne bacteria strains. This method was also of high sensitivity and could be used to detect the presence of less than 160 fg genomic DNA or 2.2×102 CFU/ml of bacterial cells per 25 μl reaction volume, moreover, the presence of plant tissue fluid did not affect the sensitivity. Since it does not require expensive equipment or specialized techniques, this LAMP-based diagnostic method has the potential to be used under field conditions to make disease forecasting more accurate and efficient.

Corrigendum: Loop-Mediated Isothermal Amplification Method for the Rapid Detection of Ralstonia solanacearum Phylotype I Mulberry Strains in China

Erwinia amylovora is the bacterial pathogen that causes fire blight and is considered one of the most important plant pathogenic bacteria in the world, posing a serious threat to pear and apple production. However, majority of the current risk assessment studies have focused primarily on the potential geographic distribution of E. amylovora , with less focus on its dispersal patterns, dispersal risk areas, and economic impacts. Here, species distribution models, the minimum cost arborescence approach, the MigClim package, and Monte Carlo stochastic simulations were integrated to comprehensively assess the global establishment risk, the local dispersal patterns, the dispersal risk areas, and the economic losses for E. amylovora . The results showed that E. amylovora is primarily distributed in North America, southern South America, Europe, northern and southern Africa, western and eastern Asia, and southern Oceania under near-current climatic conditions. In addition, the overlapping area between the distribution area of E. amylovora and the host production area is 1,897.62 × 10 ⁴ km ² , mainly located in central North America, southern South America, Europe, northern Africa, eastern and western Asia, and southern Oceania. Its global distribution and the overlapping areas are expected to expand further under future climatic conditions. Erwinia amylovora shows a primarily “leap-frog” long-distance spread in China, and the dispersal risk area is mainly in northwestern China. The economic losses caused by E. amylovora to the host industry amounted to 5,603.66 million dollars without any control measures; however, 2,390.13 million dollars can be saved after control measures. Such comprehensive risk assessments provide global guidance for the monitoring and control of E. amylovora in host production areas while also helping to formulate management priority strategies in local dispersal risk areas, thereby reducing economic impacts.