Identification of Colletotrichum Species Associated with Anthracnose Disease of Strawberry in Sichuan Province, China.

Strawberry anthracnose, caused by Colletotrichum species, is a major fungal disease threatening the strawberry industry in Sichuan Province of southwestern China. However, research on identification of Colletotrichum species associated with strawberry anthracnose in Sichuan remains scarce. In this study, 73 representative Colletotrichum strains were isolated from diseased leaves, stolons, petioles, and crowns of 11 major strawberry-planting localities in Sichuan Province. Based on morphological characteristics and multiloci phylogenetic analysis, the Colletotrichum strains were identified as three distinct species: Colletotrichum fructicola (53 strains, 72.60%), Colletotrichum siamense (17 strains, 23.29%), and Colletotrichum gloeosporioides sensu stricto (3 strains, 4.11%). Among them, C. fructicola was the most ubiquitous and dominant species, whereas C. gloeosporioides sensu stricto was restricted to Chongzhou. Importantly, our pathogenicity tests showed that C. fructicola and C. siamense can infect both leaves and stolons, whereas C. gloeosporioides sensu stricto was only pathogenic to leaves. Interestingly, although the sexual stage of C. siamense was not observed in this study, it still exhibited the strongest virulence to strawberry compared with C. gloeosporioides sensu stricto and C. fructicola. This is the first study to characterize Colletotrichum species causing strawberry anthracnose and evaluate their pathogenicity in Sichuan Province of southwestern China, which will provide a better strategy for accurate diagnosis and management of anthracnose disease in strawberry.

Symptoms and pathogens diversity of Corn Fusarium sheath rot in Sichuan Province, China.

To elucidate the symptoms and pathogens diversity of corn Fusarium sheath rot (CFSR), diseased samples were collected from 21 county-level regions in 12 prefecture-level districts of Sichuan Province from 2015 to 2018 in the present study. In the field, two symptom types appeared including small black spots with a linear distribution and wet blotches with a tawny or brown color. One hundred thirty-seven Fusarium isolates were identified based on morphological characteristics and phylogenetic analysis (EF1-α), and Koch's postulates were also assessed. The results identified the isolates as 8 species in the Fusarium genus, including F. verticillioides, F. proliferatum, F. fujikuroi, F. asiaticum, F. equiseti, F. meridionale, F. graminearum and F. oxysporum, with isolation frequencies of 30.00, 22.67, 15.33, 7.33, 6.00, 5.33, 3.33 and 1.33%, respectively. Fusarium verticillioides and F. proliferatum were the dominant and subdominant species, respectively. Two or more Fusarium species such as F. verticillioides and F. proliferatum were simultaneously identified at a mixed infection rate of 14.67% in the present study. The pathogenicity test results showed that F. proliferatum and F. fujikuroi exhibited the highest virulence, with average disease indices of 30.28 ± 2.87 and 28.06 ± 1.96, followed by F. equiseti and F. verticillioides, with disease indices of 21.48 ± 2.14 and 16.21 ± 1.84, respectively. Fusarium asiaticum, F. graminearum and F. meridonale showed lower virulence, with disease indices of 13.80 ± 2.07, 11.57 ± 2.40 and 13.89 ± 2.49, respectively. Finally, F. orysporum presented the lowest virulence in CFSR, with a disease index of 10.14 ± 1.20. To the best of our knowledge, this is the first report of F. fujikuroi, F. meridionale and F. asiaticum as CFSR pathogens in China.

Assessment of genetic diversity in chinese hulless barley accessions for qualitative traits

Cultivated barley (Hordeum vulgare L.) has been proven to be an economically important model plant and having large genetic diversity among the species. The effective exploitation of qualitative characters in barley can be measured by its genetic diversity and interrelationship. This study aims to determine the assessment of genetic diversity in Chinese hulless barley accessions for qualitative traits. Presently, in this study, the genetic diversity of 208 Chinese hulless barley from different Provinces of China, 111 genotypes were from the Tibet plateau, 30 Sichuan, 2 USA, 1 Canada, 12 Gansu, 51 Qinghai, 1 Yunnan was investigated; collected. Almost all the qualitative traits including crude protein, fiber, starch, neutral detergent fiber, and acid detergent fiber exhibited significantly high variability (p≤0.0001) among the cultivars. The data were analyzed using Statistics 8.1. In this study, significantly high variation was observed between starch content and neutral detergent fiber (23.64% and 11.54%). However, the highest diversity is based on the magnitude of the coefficient of variation exhibited in crude protein (13.82%), starch (12.87%), and fiber (12.17%). There was a significantly positive correlation between fiber, acid detergent fiber, and neutral detergent fiber except for starch content with crude protein and fiber that exhibited a significant negative correlation (r= -0.38*** and r= -0.92***). A large genetic diversity was observed through cluster analysis among all the 208 barley accessions, distance coefficient ranging between 0.28 and 75.86. The histogram revealed that frequency distributions of 208 different genotypes of hulless barley crop with all five different characters, crude protein, fiber, starch, neutral detergent fiber, and acid detergent fiber, showed normal distribution. It is concluded that this hulless barley study showed genetic diversity among the accessions and confirmed genetic diversity in various traits used.

Identification of Colletotrichum Species Associated with Blueberry Anthracnose in Sichuan, China.

Anthracnose caused by Colletotrichum spp. is an important disease of blueberries and results in large economic losses for blueberry growers. Samples of anthracnose were collected from six main blueberry cultivation areas in Sichuan Province. In total, 74 Colletotrichum isolates were obtained through a single-spore purification method and identified to the species through morphological characteristics and phylogenetic analyses based on partial DNA sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), internal transcribed spacer (ITS) regions, and the ß-tubulin (TUB2), actin (ACT) and calmodulin (CAL) genes. Among all species, Colletotrichum fructicola was the most dominant species, with an isolation percentage of up to 66.2% in Sichuan, followed by Colletotrichum siamense (17.6%), C. kahawae (5.4%), C. karstii (5.4%), C. nymphaeae (2.7%) and C. sichuaninese (2.7%). Pathogenicity tests showed all species were able to cause typical anthracnose symptoms on blueberry leaves and stems. Colletotrichum fructicola was the predominant species with strong aggressiveness. Moreover, C. fructicola, C. kahawae, C. sichuaninese and C. nymphaeae are first reported here to cause blueberry anthracnose. This study provides a comprehensive reference for the association of different Colletotrichum spp., which may support the sustainable management of blueberry anthracnose.

Maize/Soybean Relay Strip Intercropping Reduces the Occurrence of Fusarium Root Rot and Changes the Diversity of the Pathogenic Fusarium Species.

Fusarium species are the most detrimental pathogens of soybean root rot worldwide, causing large loss in soybean production. Maize/soybean relay strip intercropping has significant advantages on the increase of crop yields and efficient use of agricultural resources, but its effects on the occurrence and pathogen population of soybean root rot are rarely known. In this study, root rot was investigated in the fields of the continuous maize/soybean strip relay intercropping and soybean monoculture. Fusarium species were isolated from diseased soybean roots and identified based on sequence analysis of translation elongation factor 1 (EF-1α) and RNA polymerase II second largest subunit (RPB2), and the diversity and pathogenicity of these species were also analyzed. Our results showed that intercropping significantly decreased soybean root rot over monoculture. A more diverse Fusarium population including Fusarium solani species complex (FSSC), F. incarnatum-equiseti species complex (FIESC), F. oxysporum, F. fujikuroi, F. proliferatum and F. verticillioides, F. graminearum and F. asiaticum was identified from intercropping while FSSC, FIESC, F. oxysporum, F. commune, F. asiaticum and F. meridionale were found from monoculture. All Fusarium species caused soybean root infection but exhibited distinct aggressiveness. The most aggressive F. oxysporum was more frequently isolated in monoculture than intercropping. FSSC and FIESC were the dominant species complex and differed in their aggressiveness. Additionally, F. fujikuroi, F. proliferatum and F. verticillioides were specifically identified from intercropping with weak or middle aggressiveness. Except for F. graminearum, F. meridionale and F. asiaticum were firstly reported to cause soybean root rot in China. This study indicates maize/soybean relay strip intercropping can reduce soybean root rot, change the diversity and aggressiveness of Fusarium species, which provides an important reference for effective management of this disease.

Comparison of Transcriptome Differences in Soybean Response to Soybean Mosaic Virus under Normal Light and in the Shade.

Shading in the intercropping system is a major abiotic factor which influences soybean growth and development, while soybean mosaic virus (SMV) is a biotic factor that limits the yield and quality of soybean. However, little is known about the defense response of soybean to SMV in the shade. Thus, in the current study, both intensity and quality (red:far-red, R:FR) of the light were changed to simulate the shaded environment and comparative transcriptome analysis was performed. Morphologically, plant growth was inhibited by SMV, which decreased 35.93% of plant height and 8.97% of stem diameter in the shade. A total of 3548 and 4319 differentially expressed genes (DEGs) were identified in soybean plants infected with SMV under normal light and in the shade. Enrichment analysis showed that the plant defense-related genes were upregulated under normal light but downregulated in the shade. Pathways that were repressed include plant-pathogen interaction, secondary metabolism, sugar metabolism, and vitamin metabolism. In addition, genes associated with signaling pathways such as salicylic acid (SA), jasmonic acid (JA), and ethylene (ETH) were also downregulated in the shade. A qRT-PCR assay of 15 DEGs was performed to confirm transcriptome results. According to our knowledge, this is the first report on soybean response to dual stress factors. These results provide insights into the molecular mechanisms in which soybean plants were infected with SMV in the shade.