Leaves of passion fruit with suspected virus symptoms were collected in Guangxi for RNA extraction, the small RNA library was constructed and sequenced by high-throughput sequencing. Bio-informatics was performed to identify the viruses. Primers were designed according to the sequencing results for identification the viruses in passion fruit.The result showed that 560 contigs were produced from the 20 921 061 clean reads by library sequencing and assembly. Among them, 99, 97, 69 and 12 contigs were annotated as telosma mosaic virus(TeMV), cucumber mosaic virus(CMV), East Asian passiflora virus(EAPV) and soybean mosaic virus(SMV), respectively. All the samples were confirmed positive by RT-PCR for TeMV, EAPV and CMV, but negative for SMV. During 2015 to 2018, a total of 385 passion fruit samples with virus-like symptoms were collected from the main producing areas in Guangxi. 284 out of the 385 samples (73.76%) were positively for TeMV, EAPV and CMV infection by DAS-ELISA and RT-PCR. Among these three viruses, TeMV show the highest detection rate of 64.16%, and then EAPV with 41.30%, CMV with 11.43%. Mixed infections rate of TeMV + EAPV was 24.94%, TeMV+CMV was 4.16%, and EAPV+CMV was 0.26%. Mixed infection rate of all the above three viruses was 4.94%.
Tibetan semi-wild wheat (Triticum aestivum ssp. tibetanum Shao), Yunnan hulled wheat (T. aestivum ssp. yunnanense King) and Xinjiang rice wheat (T. petropavlovskyi Udacz et Migusch) are unique germplasm resources and have specific geographical distribution in China. Morphological characteristics of them are obviously different from common wheat (T. aestivum L.). Besides, disease resistance and tolerance can be used for improvement of modern wheat variety under biotic and abiotic stress. In this study, 213 accessions of Chinese endemic wheat (including 117 Tibetan semi-wild wheat, 78 Yunnan hulled wheat and 18 Xinjiang rice wheat) were inoculated with mixed races of wheat stripe rust to evaluate the resistance during seedling and adult stage, respectively. Meanwhile, molecular markers linked to twelve known resistance genes were used to detect the resistance genes. The results showed that 18 accessions were resistant at seedling stage, as well as 89 accessions displayed stable resistance at adult stage. Moreover, these resistant accessions mainly derived from Yunnan hulled wheat. By integrating all information of the pedigree of these accessions, resistance to stripe rust races, and molecular detection, it showed that only 2 accessions carried Yr18 and the 213 accessions were not detected to carry Yr5, Yr9, Yr10, Yr15, Yr17, Yr24/Yr26, Yr30, Yr41, Yr48, Yr65 and Yr67. These results indicated that the resistant accessions may contain other known or new resistance genes. The results will provide the information for further effective utilization of stripe rust resistance germplasms of Chinese endemic wheat subspecies and discovery of their resistance genes.
Watermelon mosaic virus (WMV; genus Potyvirus) is an important viral pathogen infecting cucurbit crops in China. Breeding and planting resistant varieties are the most economical and effective strategy to control viral disease. In this study, WMV but not papaya ringspot virus (PRSV) was detected on fruits of zucchini exhibiting ringspot symptoms by RT-PCR and virus specific antibodies. Zucchini cultivar ‘LvYuanDongBao' plants inoculated with WMV infectious clone pCamWMV-GFP showed ringspots on fruits, suggesting WMV is an important pathogen causing ringspot symptoms on zucchini fruits. In total, 46 samples collected from watermelon, cucumber, melons, zucchini and pumpkin plants in Tai'an, Shandong, were tested by WMV specific antibody using Plate Trapped Antibody-Enzyme Linked Immuno Sorbent Assay (PTA-ELISA). Results showed that 33 samples were WMV positive (71.74%). Zucchini fruits displaying ringspot symptoms from Xuezhuang were all WMV positive. Resistance to WMV in 81 cucurbit crops germplasm resources from Shandong Province was identified. Results showed that zucchini cultivars ‘Wanshengfengbao' and ‘Shengfengjinzhu' were moderately resistant to WMV; watermelon cultivars ‘Lvbaoxinxiu' and ‘Langchao 1' were moderately resistant to WMV; melon cultivar ‘Huangpimian melon' was resistant to WMV; cucumber cultivar ‘Xingjun beibei' were moderately resistant to WMV; pumpkin cultivar ‘Aiwei 80 pumpkin' was highly resistant, and five cultivars including ‘Miben pumpkin', ‘traditional Miben pumpkin', ‘Qiye early pumpkin', ‘Linglong 2' and ‘Green beibei mini pumpkin' showed resistance to WMV. All tested bottle gourd cultivars were susceptible or highly susceptible to WMV. These results will be helpful to control WMV by utilizing resistance of different cucurbit crops.
There are no standards for grading Panax notoginseng root rot disease. To find disease-resistant germplasm resources and evaluate disease-control effects, a new system for grading P. notoginseng root rot disease in field was established. In total, 200 diseased samples of 3-year-old Sanqi ginseng (P. notoginseng) were collected from Wenshan country, Yunnan Province, China, and 98 samples with varying degrees of decay were evaluated further. These samples were clustered and analyzed using SPSS21 according to five indices: the decay area, the presence of cross-section rot, rot of branches and fibrous roots, bud rot, and Lutou rot. The developed grading system was as following: Grade 0, healthy, no symptoms; Grade 1, rot occurs only on the surface and decay area is ≤10%, or rot has spread to the interior and decay area is >5% and ≤10%; Grade 2, rot has spread to the interior and decay area is >10% and ≤40%, with no rotten branches or fibrous roots; Grade 3, rot has spread to the interior and decay area is >40% and ≤50%, with rot of branches and fibrous roots; Grade 4, rot has spread to the interior and decay area is >50% and ≤70%, with rot of branches and fibrous roots; and Grade 5, rot has spread to the interior and decay area is >70% or roots have rotted completely, with rot of branches and fibrous roots. The effects of soil treatments on controlling Sanqi root rot disease were examined using this grading system in 2016 and 2017, and the results showed that it could be used in practice. Compared with traditional grading systems, this new one was better for making evaluations and the results better reflect real conditions.
Ethylene (ET) signaling plays important roles in plant defense responses to various environmental stresses, but its role in regulation of rice sheath blight resistance remains to be studied systematically. In this study, a susceptible rice cultivar Lemont and a resistant rice cultivar YSBR1 were used to analyze the expression levels of marker genes in ethylene biosynthesis and signaling pathway after inoculation with R. solani. The results showed that the infection of R. solani significantly induced the expression levels of related genes and activated ethylene signaling pathway. Two chemicals were employed to activate and suppress ET signaling, respectively, on both cultivars. After inoculation with R. solani on both cultivars, we found that activation of ET signaling significantly enhance rice resistance to the pathogen, while suppress the ET signaling apparently reduced rice resistance. Further, we inoculated three ET receptor mutants, etr2, etr3, and ers2, with R. solani at the booting stage in greenhouse. As expect, we found that lesion lengths of the three mutants were all significantly longer than that of the wild type. Taken together, these data demonstrated that ET signaling played an important role in rice defense response or basic resistance to sheath blight. These results provide a theoretical basis for further elucidating the mechanism between "rice - R. solani” and establishing new strategies to prevent and control this disease.
As beneficial microorganisms, Enterobacter sp. not only promotes the growth of some plants, but also plays an important role in the control of harmful organisms. In this study, Biolog microbial physiological and biochemical analysis, co-culture and other means were used to study the nutritional and spatial competitiveness, colonization characteristics and the promoting effect on rice seedlings of Enterobacter cloacae MY01, Lysobacter antibioticus 13-6 and Xanthomonas oryzae pv. oryzicola RS105. The biocontrol effect of stripe disease was determined to determine the synergistic effect of E. cloacae and L. antibioticus on bacterial leaf streak (BLS). The results show that MY01 grows rapidly and can utilize most of the carbon and nitrogen sources, so it has strong nutritional competitiveness and limits the growth of other bacteria. When inoculated in the greenhouse, the control effect of MY01 on BLS is similar as 13-6 and MY01can enhance the relative control effect of 13-6 on BLS, and the control effect can reach 93.44%. As a potential strain, E. cloacae MY01 has certain control effects on BLS and promotes the prevention and controlof L. antibioticus 13-6 against BLS.
