甘蔗花叶病毒福建分离物外壳蛋白基因的克隆及序列分析

 A fujian isolate of Sugarcane mosaic virus named SCMV-FJ was isolated from infected sugarcane. Cloning and sequence analysis of the coat protein gene of this isolate was carried out. A pair of primers was designed and synthesized based on the nucleotide sequences of coat protein genes of sugarcane mosaic viruses reported. The coat protein gene of SCMV-FJ was amplified from the extracted total RNA of the infected sugarcane by using RT-PCR, and cloned into the pMD18-T vector. The sequencing result indicated that the cloned segment included a 1137 bp open reading frame(ORF) and a 228 bp 3' untranslated region, in which the ORF comprised the whole coat protein and part of the nuclear inclusion b. The nucleotide and the deduced amino acid sequences of the coat protein gene were compared with those of the other isolates or strains of SCMV subgroup reported in GenBank. The result showed that it shares 56.8%-97.1% and 55.3%-99.4% homology in nucleotide and the putative amino acid sequences, respectively, with the highest amino acid homology of 99.4% with SCMV-D. Thus it was identified as a SCMV-D. This experiment provided a rapid, sensitive and relatively inexpensive method for RT-PCR detection of SCMV. At the same time, the cloning of SCMV-FJ coat protein gene provided the foundation for plant gene engineering against SCMV.     

江西甘蔗花叶病病原的分子鉴定

 Sugarcane mosaic disease, caused by Sugarcane mosaic virus (SCMV), Sorghum mosaic virus (SrMV), Maize dwarf mosaic virus (MDMV) or Johnsongrass mosaic virus (JGMV) in Potyvirus, is one of the most important viral diseases of sugarcane. In the study, four primer pairs specific to SCMV, SrMV, MDMV and JGMV, respectively, were designed and used to detect 29 sugarcane leaf mosaic samples collected from 9 locations in Jiangxi province. The representative RT-PCR products were sequenced. The results showed that 22 samples were infected by SCMV, three by SrMV, and four were mix-infected by SCMV and SrMV. MDMV or JGMV were not identified in all samples. The result indicates that SCMV is the major pathogen of sugarcane mosaic disease in Jiangxi province, and SrMV is also a pathogen for the disease.     

云南甘蔗宿根矮化病调查及种茎温水处理脱菌效果检测

 Based on the specific primer from the nucleotide sequences between 16S-23S rDNA, Polymerase chain reaction (PCR) approach for detecting Leifsonia xyli subsp. xyli (Lxx) was established. The approach was applied to detect Lxx from 30 cultivars collected from two main sugar cane producing areas in Yunnan and 10 hot-water treatment samples. The results showed that 80% of the cultivars were infected by Lxx and hot-water treatment was proved to be an efficient measure to control but not completely eliminate Lxx in sugar cane tissues. The PCR products amplified from six infected cultivars were cloned and sequenced, six sequences were acquired and analyzed. It indicated that the six sequences were identical and showed 100% similarity with the isolates from Brazil, Australia and Fujian, and 99.54% with the isolate from Louisiana.     

土壤处理对西洋参根际线虫数量动态的影响及对防治茎线虫根腐病的效果

 Root rot of American ginseng (Panax quinquefolium) caused by Ditylenchus destructor is a novel disease found recently in Beijing area. The effects of three soil treatments (fumigating with chloropicrin, chloropicrin + lvfeng organic manure and nematicide fosthiazate) on the number of rhizospheric nematodes, survived plants, root yield and root rot of 3-year ginseng plant were compared. The effects were also investigated at the second year after treatment. The results indicated that the number of parasitic nematodes in rhizosphere of treated soil reached the peak value in late June to early July as the soil temperature raised in the growing season. Compared with the regular treatment, the number of plant parasitic nematodes was reduced while non-plant parasitic nematodes increased. The number of non-plant parasitic nematodes in the soil treated with chloropicrin + lvfeng organic manure was 2 times than that treated with chloropicrin only. The ratio of non-parasitic to parasitic nematodes of three treatments was higher than the control. Percent of survived plants was 94.8%-96.4% and diseased root was decreased obviously. The control efficacy was more than 89% at the first year after treatment. The survived plants and plot yield of ginseng increased significantly and the control efficacy was around 40% at the second year. The best of the three treatments was by chloropicrin + organic manure.     

广东番茄上检测到Tospovirus病毒

 Some tomato samples possibly infected by tospovirus in Guangdong were detected with indirect ELISA and RT-PCR. The results showed that the virus infected tomato did not react with the antiserum of Tomato spotted wilt virus (TSWV), but about 500 bp fragment of RT-PCR shared 83%-84% nucleotide identities with N gene of those reported tospoviruses. The phylogenetic tree of the N gene fragment compared with those of other tospoviruses indicated that the virus infected tomato was belonged to Tospovirus.     

Combined effects of snow depth and nitrogen addition on ephemeral growth at the southern edge of the Gurbantunggut Desert, China

Water and nitrogen(N) inputs are considered as the two main limiting factors affecting plant growth.Changes in these inputs are expected to alter the structure and composition of the plant community,thereby influencing biodiversity and ecosystem function.Snowfall is a form of precipitation in winter,and snow melting can recharge soil water and result in a flourish of ephemerals during springtime in the Gurbantunggut Desert,ChinaA bi-factor experiment was designed and deployed during the snow-covering season from 2009 to 2010.The experiment aimed to explore the effects of different snow-covering depths and N addition levels on ephemerals.Findings indicated that deeper snow cover led to the increases in water content in topsoil as well as density and coverage of ephemeral plants in the same N treatment;by contrast,N addition sharply decreased the density of ephemerals in the same snow treatment.Meanwhile,N addition exhibited a different effect on the growth of ephemeral plants:in the 50% snow treatment,N addition limited the growth of ephemeral plants,showing that the height and the aboveground biomass of the ephemeral plants were lower than in those without N addition;while with the increases in snow depth(100% and 150% snow treatments),N addition benefited the growth of the dominant individual plants.Species richness was not significantly affected by snow in the same N treatment.However,N addition significantly decreased the species richness in the same snow-covering depth.The primary productivity of ephemerals in the N addition increased with the increase of snow depth.These variations indicated that the effect of N on the growth of ephemerals was restricted by water supply.With plenty of water(100% and 150% snow treatments),N addition contributed to the growth of ephemeral plants;while with less water(50% snow treatment),N addition restricted the growth of ephemeral plants.     

茄科蔬菜立枯丝核菌的融合群鉴定

 Sixty-five samples were collected from rhizosphere soil, hot pepper and tomato plants showing damping-off, root rot and stem rot in Taian, Shouguang of Shandong province and Zhouzhi, Taibai of Shaanxi province. Thirty-nine Rhizoctonia solani isolates were obtained from these samples. The results of anastomosis group (AG) identification and sequence analysis of 5.8S rDNA-ITS of the isolates showed that thirty-six isolates (92.3%) belonged to AG-4, while only three (7.7%) belonged to AG-5. The isolates of AG4 could further be divided into two subgroups of AG4-HG-Ⅰ and AG4-HG-Ⅲ. The 5.8S rDNA-ITS sequences of the selected isolates of the two subgroups had the 99%-100% identity with standard isolates of AG4-HG-Ⅰ and AG4-HG-Ⅲ (from GenBank). Among the analyzed isolates, AG4-HG-Ⅰ subgroup was the dominant with the frequency of 79.5%. Subgroup AG-4-HG-Ⅲ with the frequency of 12.8% was the second. This is the first report that subgroup AG4-HG-Ⅲ of R. solani isolated from Solanaceae vegetable crops in China.     

Tolerance to Zn deficiency and P-Zn interaction in wheat seedlings cultured in chelator-buffered solutions

Zinc deficiency is a common constraint for wheat production in the regions with limited precipitation,particularly in the regions with high levels of available phosphate (P) in soil.Two experiments were conducted using chelator-buffered nutrient solutions to characterize differences in tolerance to Zn deficiency among three winter wheat (Triticum aestivum L).genotypes and to investigate the relationship between P and Zn nutrition in wheat species.Four indices,Zn efficiency,relative shoot-to-root ratio,total Zn uptake in shoot,and shoot dry weight were used to compare the tolerance to Zn deficiency among three wheat genotypes.The results indicated that the four indices could be used in breeding selection for Zn uptake-efficient genotypes.The genotype H6712 was the most tolerant to Zn deficient,followed by M19,and then X13.Specifically,H6712 had the highest Zn uptake efficiency among the three genotypes.The addition of P to the growth medium increased Zn uptake and translocation from roots to shoots.Total Zn content of the wheat plant was 43% higher with 0.6 mmol/L P treatment than that of control with 0 mmol /L P treatment.The Zn translocation ratios from roots to shoots were increased by 16% and 26% with 0.6 mmol/L P treatment and 3 mmol/L P treatment,respectively,compared with 0 mmol/L P treatment.In contrast,high Zn concentrations in the growth medium inhibited P translocation from roots to shoots,but the inhibitive effects were not strong.Sixty-six percent of P taken up by wheat plants was translocated to the wheat shoots at 0 μmol/L Zn treatment,while the percent was 60% at 3 μmol/L Zn treatment.The result may be due to the fact that the wheat plants need more P than Zn.     

进境玉米种子携带玉米褪绿斑驳病毒的检测与鉴定

 Imported maize seeds were planted in a quarantine greenhouse and two seedlings with chlorotic mottle symptoms were observed. The ELISA results showed that the two seedlings reacted positively with antibody against Maize chlorotic mottle virus (MCMV). The positive samples were further identified by RT-PCR method and the 711 bp size target bands were amplified specifically. The similarity range of nucleotide sequence of both RT-PCR product and six MCMV coat protein genes was 97%-99%. The amino acid sequence homology was 97.88%-99.89%. Based on the above results, the virus was identified as MCMV. It was the first time that MCMV was intercepted from imported maize seeds.     

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.     

甘蔗绵蚜为害损失研究

甘蔗绵蚜Ceratovacuna lanigera Zehntner是现今广泛分布于我国各甘蔗种植区,严重影响甘蔗产量和品质的叶部害虫。为探明现有生产水平条件下甘蔗绵蚜对甘蔗实测产量及糖分的为害损失和对新植宿根出苗的影响情况,给甘蔗绵蚜的科学有效防控提供理论依据和翔实的实测数据。本研究于2014—2016年,选择主栽品种,同田设立为害区和未为害区,调查评估绵蚜为害对新植宿根出苗的影响,甘蔗成熟期分别收砍称量和测定分析甘蔗产量及糖分含量,并计算甘蔗实测产量及糖分损失。研究结果显示,甘蔗实测产量减少2 503~4 123kg/667m~2,平均3 079kg/667m~2;产量损失率为28.5%~45.7%,平均35.9%;出汁率减少2.4%~4.13%,平均3.01%;甘蔗糖分降低5.48%~8.16%,平均6.38%;蔗汁锤度降低6.95~9.05°BX,平均7.66°BX;蔗汁重力纯度降低8.43%~19.97%,平均12.35%;而蔗汁还原糖分则增加1.01%~1.3%,平均1.21%;新植出苗率降低24.7%~27.3%,平均26.0%;宿根出苗数减少3 829~5 083株/667m~2,平均4 456株/667m~2,相对出苗损失率为57.6%~58.0%,平均57.8%。可见,目前云南蔗区甘蔗绵蚜为害造成的甘蔗产量及糖分损失十分严重,甘蔗绵蚜为害已成为现阶段严重影响甘蔗产量和品质的主要挑战之一。研究结果对加强甘蔗绵蚜的科学有效防控和支持中国蔗糖产业的可持续发展具有重要意义。     

低纬高原甘蔗白叶病植原体传播方式测定分析

Sugarcane white leaf (SCWL) is a new destructing disease of sugarcane that has rapidly expanded in low latitude plateau of Yunnan in recent years, and it is extremely harmful to sugarcane production. In order to study and clarify the transmission mode of SCWL phytoplasma in low latitude plateau, the samples were collec-ted from Gengma sugarcane-producing area of Lincang City, Yunnan Province. This area had the most severe SCWL disease from 2018 to 2019. The nested-PCR results showed that five susceptible mainly sugarcane varieties grown from diseased-seedcane were all infected in five treatments of new planting and ratoon sugarcane, and the disease incidence were 11.7% to 72.9%. While the disease incidence in plants grown from disease-free seedcane was 0%. Moreover, the disease incidence in plants grown from disease-free seedcane + insect-proof netting was also 0%. It observed that the primary transmission mode of SCWL phytoplasma was infected seedcane in Gengma sugarcane area (having serious disease prevalence) in Lincang City, Yunnan Province, and there was no insect vector transmission. The results of this study enriched the relevant theoretical and technical foundations of sugarcane phytoplasma disease, and provided theoretical guidance and scientific basis for the effective prevention and control of SCWL in low-latitude plateaus.     

Molecular detection of sugarcane striate virus and sugarcane white streak virus and their prevalence in the Miami World Collection of sugarcane and related grasses

Viruses in the genus Mastrevirus (family Geminiviridae), including those infecting sugarcane, have natural geographical ranges almost exclusively restricted to Africa and the Indian Ocean islands off the African coast. Only sugarcane white streak virus (SWSV) in Barbados and sugarcane striate virus (SStrV) in Florida and Guadeloupe are known to infect a few sugarcane varieties in the Western Hemisphere. In this study, PCR assays were developed to detect these two viruses in sugarcane. Five hundred and seventy-one DNA samples from Saccharum species and interspecific hybrids from the Miami World Collection of sugarcane and related grasses were tested for the presence of SStrV and SWSV by PCR. No variety was found infected by SWSV but SStrV was detected in 19 varieties. PCR data were confirmed by sequencing amplified fragments (248 bp). These fragments shared 93%–100% nucleotide identity with SStrV sequences from the GenBank database. SStrV isolates were distributed in six phylogenetic groups, including the four strains of the virus. Most varieties infected by SStrV originated from Asia, thus confirming a previous hypothesis stating that this virus originated from this continent. Absence of SStrV in commercial sugarcane in Florida also suggested that this virus has not been spread in this location, while infected plants have been present for several decades.     

宿根矮化病菌对甘蔗品质及茎、叶超微结构的影响

 甘蔗宿根矮化病(Ratoon Stunting Disease, RSD)是由Leifsonia xyli subsp.xyli (Lxx)引起的,是目前世界所有植蔗地区危害性极大的病害之一。本实验以甘蔗品种新台糖22号(ROC22)健康植株为对照,感染RSD植株为处理,观察和测定RSD侵染甘蔗引起的蔗株农艺性状、蔗糖分以及茎、叶超微结构的变化。结果表明:(1)感染RSD种茎的出苗率比对照减少2.94个百分点;株高比对照下降28.85 cm;茎径比对照减少0.28 cm;节间长度比对照减短3.50 cm;单茎重比对照低0.36 kg。(2)感染RSD植株的蔗糖分低于对照0.9个百分点(绝对值)。(3)利用透射电镜技术对感染RSD植株茎、叶细胞超微结构进行观察表明,叶片叶肉细胞、维管束鞘细胞及茎细胞内的细胞器及细胞核都发生了明显的病理变化。与健康叶片相比,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离。线粒体形态异常,有的肿大、内嵴模糊,严重者内嵴消失并空泡化,仅剩未被消解的残骸;细胞核形态变为不规则,核膜破裂,染色质分布不均匀,呈降解状态。在感染RSD甘蔗茎维管束导管细胞内积累有大量的电子致密物质,细胞壁有不同程度的溶解和断裂,这可能和RSD病原细菌侵染有关。以上结果表明:RSD侵染甘蔗后,可能导致光合效率下降,对水分和营养物质的运输能力降低,从而导致甘蔗品质和产量的降低。     

Impact of sugarcane yellow leaf virus (ScYLV) on the carbohydrate status of sugarcane: Comparison of virus-free plants with symptomatic and asymptomatic virus-infected plants

The carbohydrate concentration of old and young sugarcane plants, either virus-free or infected by sugarcane yellow leaf virus, was compared. Internode lengths and fresh weights of symptomatic plants were reduced, but not the sucrose concentrations. Starch and sucrose concentration in green leaf tops of mature (18 months old) was the highest in asymptomatic plants followed by symptomatic, and then by virus-free plants. Carbohydrates increased during daytime by 5–20%. The carbohydrate concentration in leaves of young, 6 months old plants was much lower than in mature plants and it increased to 500% during daytime. Asymptomatic leaves had a higher level of carbohydrates, especially starch, from late afternoon until the end of the night, suggesting a reduction of assimilate export.     

广东甘蔗黄叶病田间调查及病原病毒的分子检测

 广东省粤北和粤西蔗区多个县市的田间甘蔗上观察到甘蔗黄叶病(Sugarcane yellow leaf disease,SYLD)典型症状,目前该病仅局部分布,但部分田块病株率为5%~80%,发病品种有青皮果蔗、黑皮果蔗、新台糖系列品种、粤糖79/177和粤糖93/159等。采集发病田间显症叶片、无症叶片和在病叶上取食的甘蔗绵蚜(Ceratovacuna lanigera)样品,抽提总RNA,以基于甘蔗黄叶病毒(Sugarcane yellow leaf virus,SCYLV) CP基因序列的特异引物进行一步RT-PCR和巢式PCR扩增,并对扩增产物进行核苷酸序列测定和BLAST比对。结果显示,RT-PCR及巢式PCR产物核苷酸序列与分离自巴西的SCYLV B1株系相应区段同一率为100%;一步RT-PCR可从约70%的显症叶片样品中检测到SCYLV,而病田中的无症叶片样品以及在病叶上取食的单头甘蔗绵蚜样品需经巢式PCR扩增方可检测到SCYLV,阳性率分别为1%~5%和83%。本研究表明,广东省栽培甘蔗已受到SCYLV侵染,甘蔗绵蚜携带SCYLV。     

氯虫苯甲酰胺在甘蔗及土壤中的残留消解动态

建立了氯虫苯甲酰胺在甘蔗和土壤中残留的高效液相色谱检测方法,应用该方法对氯虫苯甲酰胺在甘蔗和土壤中的残留消解规律进行了研究。样品用乙腈提取,经Florisil固相萃取柱及N-丙基乙二胺(PSA)净化,紫外检测器检测,外标法定量。结果表明:当添加水平为0.05~2 mg/kg时,氯虫苯甲酰胺在甘蔗植株地上部分(包括茎秆和叶片)、茎秆(去除叶片后的地上至肥厚带部位)和土壤中的平均回收率为77%~97%,相对标准偏差(RSD)为3.4%~11.6%。氯虫苯甲酰胺在3种基质中的最小检出量(LOD)均为0.2 ng,最低检测浓度(LOQ)均为0.05mg/kg。两年两地的田间残留试验结果表明:0.4%氯虫苯甲酰胺颗粒剂在甘蔗下种时一次沟施后覆土,以有效成分用量120和180 g/hm2施药时,在土壤中的原始沉积量在1.18~3.57 mg/kg之间,半衰期为12.4~18.2 d;成熟时采收,甘蔗茎秆中氯虫苯甲酰胺的残留量低于0.05 mg/kg。参照我国制定的甘蔗上氯虫苯甲酰胺的临时最大残留限量(TMRL)值0.05 mg/kg,按照推荐剂量及推荐剂量的1.5倍分别施药1次,成熟时采收甘蔗是安全的。     

Susceptibility of sugarcane, plantation weeds and grain cereals to infection by Sugarcane yellow leaf virus and selection by sugarcane breeding in Hawaii

Hawaiian commercial sugarcane cultivars (Saccharum spp.), noble canes (S. officinarum), robust canes (S. robustum) and wild relatives of sugarcane (S. spontaneum and Erianthus arundinaceus) were tested by tissue blot immunoassay to determine whether they were infected by Sugarcane yellow leaf virus (SCYLV). Two-thirds of the commercial hybrids and noble canes were infected and therefore classified as SCYLV-susceptible, in contrast to the wild cane relatives where less than one third of the varieties were infected. The pedigree list of commercial, registered cultivars showed that 80% of cultivars were SCYLV-susceptible and that also 75–90% of the progeny of resistant (female) parents were susceptible (male parents are mostly unknown because of polycross breeding). In contrast, a cross between a resistant S. robustum and a susceptible S. officinarum cultivar yielded 85% resistant progeny clones, which indicated that SCYLV-resistance is a dominant trait. It is concluded that the breeding program selected against SCYLV-resistance with the result that 80% of the newly bred cultivars were susceptible. Exceptional was the period between 1950 and 1970, in which 50% of the newly-bred clones were resistant. This is the period in which SCYLV had entered Hawaii. Weed grasses and cereal grasses which grew in or next to sugarcane fields were not infected by SCYLV. Thus SCYLV does not spread from infected sugarcane plants to adjacent grasses or cereals under field conditions, although cereal grasses can be infected experimentally.