Colletotrichum Corda is one of the most important plant pathogens that has a wide range of hosts including apple (Velho et al. 2016), coffee (Prihastuti et al. 2009), and many other species of plants. Meanwhile, anthracnose on tea plants (Camellia sinensis) caused by Colletotrichum spp. is one of the most severe diseases. During 2014 and 2015, a leaf and twig blight occurred with a disease incidence of 20 to 40% on tea plants in growing regions of Jiaoling County, in Guangdong Province. Symptoms began as small, water-soaked lesions on young leaves, and later became larger, semicircular or irregular, dark brown, reddish-brown at the margin. At later stages, the lesions became grayish white with black acervuli on surface. Six Colletotrichum-like isolates were isolated from symptomatic leaves on PDA, and pure cultures were obtained by single-spore isolation. All isolates initially produced white fluffy aerial hyphae and turned dark grayish with bright orange conidial masses. Ascomata 109.2 to 252.6 × 97.1 to...

Due to the natural destructiveness and persistence of the southern corn leaf blight (SCLB) fungus Bipolaris maydis (Nisikado et Miyake) Shoem, the characterization of B. maydis field isolates is essential to guide the rational distribution of resistant materials in corn-growing regions. In the present study, 102 field isolates collected from seven locations covering the entire region of Fujian Province, China, were assessed for mating type distribution, genetic diversity, and pathogenicity toward local sweet corn cultivars. Mating type detection via polymerase chain reaction indicated that 36.3 and 63.7% of isolates were MAT1-1 and MAT1-2, respectively; more than 80% of these isolates were confirmed using cross assays with known mating type isolates. Thirteen intersimple sequence repeat (ISSR) markers within and among two mating type populations revealed a high level of DNA polymorphism for all combined isolates and between MAT1-1 and MAT1-2 populations. The MAT1-2 population was more diverse based on DNA polymorphism than the MAT1-1 population. The value of G_STwas 0.0070, ranging from 0.0399 to 0.3044 based on analysis of combined isolates and individual regional populations, respectively, suggesting the presence of genetic differentiation in the two mating type populations from different locations. Pathogenicity assays revealed that both MAT1-1 and MAT1-2 populations were pathogenic to all 11 local sweet corn cultivars tested in this study. The potential of sexual reproduction, existence of genetic diversity in the two mating type populations, and pathogenicity suggest that B. maydis populations have independently clonally adapted under natural field conditions during corn cultivation.

The northern corn leaf blight (NCLB) pathogen Setosphaeria turcica (Luttrell) Leonard and Suggs is one of the main biotic constraints on sweet corn (Zea mays L.) yield and quality in Fujian Province, China. Currently, however, there is comparatively little information available regarding the distribution of mating types, population genetics, and reproductive strategies of this pathogen in Fujian. In this study, we investigated the distribution of mating types and population genetics of 117 isolates of S. turcica collected from seven of the main sweet corn-growing regions in Fujian Province, based on multiple polymerase chain reaction analyses using two mating type-specific primer pairs and 11 inter-simple sequence repeat markers. Furthermore, we examined the mode of reproduction of Fujian S. turcica populations. Both MAT1-1 and MAT1-2 mating types were detected throughout all seven sampling locations. The majority of MAT1-2 isolates were detected from Dongyou, Jian’ou, Pingnan, Songxi, and Longyan, whereas a large proportion of the detected MAT1-1 isolates were among those collected from Dongfeng and Nanjing. Furthermore, we detected five shared multi-locus haplotypes among S. turcica isolates from Dongyou, Jian’ou, Pingnan, Nanjing, and Songxi, whereas no shared haplotypes were observed between the Dongfeng (or Longyan) population and these five populations. Pairwise comparisons of the indices Φ_PT and Nm, and population structure and principal coordinate analyses indicated genetic differentiation between both the regional and the mating type populations of S. turcica in Fujian. The skewed mating type ratio associated with low a haplotypic diversity and evident linkage disequilibrium reveals a mixed reproductive strategy for S. turcica populations in Fujian Province. The findings of this study advance our current understanding of the genetic diversity, population structure, and reproductive strategies of S. turcica populations infecting sweet corn in Fujian Province, and will potentially contribute to further resistance breeding efforts.

Asparagus stem blight caused by Phomopsis asparagi is a major hindrance to asparagus production worldwide. Currently, fungicides are used to manage the disease in commercial production, but resistance to common fungicides has emerged in the wild population. In the present study, 132 isolates of P. asparagi collected from different provinces in China were tested for sensitivities to pyraclostrobin, tebuconazole, and fluazinam. We also determined the efficacies of six fungicides against P. asparagi. The frequency distributions of EC₅₀ values of the isolates tested were unimodal, but the curves for pyraclostrobin and tebuconazole had long right-hand tails. The mean EC₅₀ values for pyraclostrobin, tebuconazole, and fluazinam were 0.0426 ± 0.0029, 0.6041 ± 0.0416, and 0.0314 ± 0.0013 μg/ml, respectively. In addition, the EC₅₀ values for pyraclostrobin were very similar with or without salicylhydroxamic acid (SHAM), 20 μg/ml, indicating that SHAM is not needed to determine the sensitivity of P. asparagi to pyraclostrobin when using the mycelial growth inhibition assay. In greenhouse assays, Merivon (42.4% fluxapyroxad plus pyraclostrobin SC), Frown-cide (500 g/liter fluazinam SC), Cabrio (250 g/liter pyraclostrobin EC), and Nativo (75% trifloxystrobin plus tebuconazole WG) showed excellent preventive efficacy against P. asparagi. And these fungicides were more effective before inoculation than when they were applied after inoculation (P < 0.05). Therefore, these fungicides should be applied prior to infection to control stem blight. In field trials, Frown-cide, Merivon, Nativo, and Cabrio also performed good control effects, ranging from 75.2 to 86.0% in 2017 and 75.4 to 87.1% in 2018. We demonstrated that Frown-cide, Merivon, Nativo, and Cabrio had considerable potential to manage asparagus stem blight. In addition, rotations of these fungicides are essential for precluding or delaying the development of resistance and for controlling the disease.

Corn (Zea mays L.), especially sweet and glutinous maize, is one of the most economically important crops in Fujian Province, China. More than 60000 ha of corn are cultivated annually in the province. In the 2014 and 2015 field seasons, leaf spot symptoms were observed on maize starting in May. Blighted leaf areas on individual plants ranged from 10 to 20% in many fields and reached up to 50% in seriously diseased fields, with more than 5000 ha affected each year. Symptoms began as small, brown, water-soaked lesions on young leaves and later became larger, dark brown, necrotic lesions, 1 to 8 mm long on leaves. Finally, the most affected leaves became necrotic. To determine the causal agent, Small pieces of the symptomatic leaves were cut from the edges of lesions. Pieces were surface sterilized in 75% (v/v) alcohol for 2 min and then in 0.1% (w/v) mercuric chloride solution for 90 sec. Pieces were subsequently rinsed twice in distilled water, placed on potato dextrose agar (PDA), and incubated at 28°C in darkness for 3 days. The pure cultures were obtained by single conidia isolation. All isolates produced gray fluffy aerial hyphae and were dark on the underside of the plate. The typical hyphae were hyaline, branched, septate, and 2.5 to 8.8 µm (avg. 5.0 µm) in diameter. The mature conidia were nearly fusiform or long elliptical, straight or slightly curved, blunt round on both ends of the cell, non-transparent, dark brown, had 2- to 10-septatations, and were 25.0 to 92.5 μm (avg. 55.0 µm) in length and 7.5 to 17.5 μm (avg. 13.0 µm) in width (e-Xtra, Figure 1). The minimum temperature for mycelial growth in culture was above 5℃ with a maximum temperature of 35℃. Based on the morphological characteristics, these isolates were consistent with Cochliobolus heterostrophus (anamorph: Bipolaris maydis (Nisikado et Miyake) Shoem) according to Wen & Lu (1991) and Shoemaker (1959). Isolates FZ1509s, JO1503d, MH1505a, ZN1518a and LH1505b, which were isolated from symptomatic corn leaves in Fuzhou, Jian’ou, Minhou, Zhouning and Longhai, respectively, were selected as representatives for molecular identification. Genomic DNA was extracted from the isolates, and the nuclear ribosomal DNA internal transcribed spacer (ITS) regions were amplified with the universal rDNA-ITS primer pair ITS4/ITS5 (White et al. 1990). The resulting PCR products (GenBank Accession No. KU306341, KU306342, KU306343, KU306344 and KU306345) from five isolates were identical and shared 100% identity to the ITS sequences of strains ACCC38956 (GenBank Accession No. KT363892), CBS136.29 (GenBank Accession No. KJ909769) and CBS 573.73 (GenBank Accession No. HF934924) of C. heterostrophus, which were isolated from Z. mays in China, the USA and the Netherlands, respectively. Pathogenicity testing of the isolates was carried out by utilizing a conidial suspension inoculation method on the hybrid-type maize Shangpin (Fujian Nongfeng Agriculture Development Co., Ltd., susceptible) (Fang, 1998). Conidial suspensions (105 conidia ml–1) of each of the five isolates were sprayed on five leaves per plant on ten 30-day-old maize plants. Control plants were sprayed with distilled water. The inoculated corn seedlings were incubated at 28°C in a greenhouse with constant relative humidity of 90% and a 12-h photoperiod of fluorescent light. As a result, all inoculated plants exhibited similar symptoms as observed initially in the field, and C. heterostrophus isolates were re-isolated from the lesions (e-Xtra, Figure 2). Based on the morphological characteristics and rDNA ITS analysis, the isolates were identified as C. heterostrophus, which causes southern leaf blight. C. heterostrophus has been reported in other areas of China (Wei et al. 1988), but to our knowledge, this is the first report of C. heterostrophus causing southern leaf blight on Z. mays in Fujian Province, China. Southern leaf blight could have a significant impact on the establishment and productivity of this important cereal crop in open fields, especially under temperate, moist growing conditions. Therefore, there is urgency to determine the distribution of C. heterostrophus and develop maize hybrids which are resistant to C. heterostrophus in Fujian Province, to improve southern leaf blight control.