烟草低头黑病病原菌的研究

 烟草低头黑病是烟草的主要病害之一,主要发生于山东潍坊一带烟区。经过对病原菌分离培养、形态特征观察、致病性和寄主范围测定,鉴定为辣椒炭疽菌(Colletotrichum capsici)的新变型——辣椒炭疽菌烟草变型(Colletotrichum capsici (Syd.) Butler & Bisby f. nicotianae G. M. Zhang & G. Z. Jiang f. nov)(烟草低头黑病菌)。     

棉铃疫病菌的鉴定及致病力的研究

通过对江西省棉铃疫病菌的培养性状、形态特征及生理生化特性等方面的研究，鉴定江西省棉铃疫病菌为ＰｈｙｔｏｐｈｔｈｏｒａｂｏｅｈｍｅｒｉａｅＳａｗａｄａ。致病力研究表明，棉铃疫病菌对棉铃的致病力强，对苎麻的致病力弱；不同的菌株对棉苗存在明显的致病力分化；棉铃疫病菌经反复接种棉苗和苎麻后，致病力会逐渐增强     

Sexual mating preferences in vitro and in planta among Japanese isolates of Phytophthora infestans

The sexual preferences of Japanese isolates of Phytophthora infestans were determined by mating on agar, in broth, or in plants. The influence of their sexual preference was confirmed in the host tissues. Three wild-type isolates and a -glucuronidase (GUS) transformant were co-cultured to identify the origin of antheridia and oogonia. Japanese A1 isolate had a unique sexual preference compared with foreign isolates. It produced self-fertile oospores with about 40% of total gametangia but tended to form antheridia on V-8 agar medium. In addition, oospores were formed in plants, but their sexual preference could not be reflected in vitro.     

Usefulness of the Detached Pod Test for Assessment of Cacao Resistance to Phytophthora Pod Rot

The detached pod test by spray method (DPT-SM) was developed to facilitate the screening of cacao genotypes for resistance to Phytophthora pod rot (PPR) caused by Phytophthora palmivora. The test has been adopted in many cacao research institutes, and it is imperative that its validity be assessed. In this study, 40 genotypes from various cacao groups were selected and screened for resistance to PPR by DPT-SM and field observations. Significant variation was observed in the reactions of the selected accessions based on the disease rating scale for DPT-SM and the percentage pod rot from field observations. A correlation coefficient of 0.68 (P<0.001) was observed between the results of year-1 and year-2 field observations. However, relatively lower correlation values were obtained between year-3 and year-1 (r=0.32; P=0.041) and year-3 and year-2 (r=0.35; P=0.025) field observations. A higher level of susceptibility was observed in the third year of field observations (63%) than in the first (15%) and second (25%) years. This suggests that the predisposing factors for PPR were unstable between the years of field observations. Data obtained from the Trinidad and Tobago Meteorological Services showed that the rainfall in November of the third year was higher than the amounts of rainfall in November of the first 2 years of field observations. This month marks the beginning of the main pod harvest season (November–February) and the high rainfall in November of the third year, and the presence of large number of mature pods may account in part for the increase in PPR in the third year of field observations than in the first 2 years. This shows that absolute reliance could not be placed on a single year of field observations in determining clonal resistance to PPR. A correlation coefficient of 0.59 (P<0.001) was obtained between the result of year-2 field observations and DPT-SM. Relatively lower correlation values were observed between DPT-SM and year-1 (r=0.55; P<0.001) and year-3 (r=0.44; P=0.005) field observations. The result of DPT-SM, however, shows a higher correlation (r=0.66; P<0.001) with the average of years 1–3 field observations. This suggests that a stronger association may exist between the result of DPT-SM and the cumulative data on field observations for a period longer than 3 years. The correlation (r=0.66; P<0.001) observed in this study confirms the usefulness of DPT-SM as an effective method of assessing clonal resistance to PPR and predicting field reaction in the long term. Since field observations are labour intensive and expensive to conduct on a yearly basis, the DPT-SM offers a cheaper and effective means of assessing clonal resistance to PPR. Being a non-destructive inoculation method, the DPT-SM provides a suitable option for cacao collections in genebanks to be assessed. It is also a cost-effective method for use in cacao breeding programmes. Based on its reliability, the DPT-SM has been adopted in the CFC/ICCO/IPGRI cocoa project ‘Cocoa Germplasm Utilization and Conservation: A Global Approach’ for the assessment of cacao resistance to PPR in several cocoa producing countries.     

Host Specialization not Detected Among Isolates of the EC-1 Lineage of <Emphasis Type="Italic">Phytophthora infestans</Emphasis> Attacking Wild and Cultivated Potatoes in Peru

To determine whether populations of Phytophthora infestans attacking wild and cultivated potatoes in the highlands of Peru are specialized on their hosts of origin, we characterized isolates using several neutral markers, metalaxyl resistance and for aggressiveness in a detached leaf assay. One hundred and fifty-three isolates were collected from the northern and central highlands of Peru from different potato cultivars (both modern and native cultivars) and from different species of wild, tuber-bearing potatoes. All the isolates analyzed belonged to one of four clonal lineages that had been described previously in Peru: EC-1, US-1, PE-3 and PE-7. The EC-1 lineage (n = 133) was dominant and present in similar frequencies on wild and cultivated potatoes. PE-3 (n = 14) was found primarily on cultivated potatoes, with only one isolate coming from a wild host. US-1 (n = 2) and PE-7 (n = 4) were rare; all but one (PE-7) occurred on wild potatoes. Isolates from the EC-1 lineage from modern cultivars were compared in three separate detached leaf inoculation assays with EC-1 isolates from the wild potato species S. sogarandinum, S. bill-hookerii or S. huancabambense, respectively. No significant interactions between isolate type (from wild or cultivated potato) and host type (wild or cultivated) were measured for any assay. It appears that the pathogen genotypes in the EC-1 lineage indiscriminately attack both wild and cultivated tuber-bearing solanaceous hosts in Peru, and breeders should be able to select for resistance using the common EC-1 lineage.     

Real-time detection of <Emphasis Type="Italic">Phytophthora nicotianae</Emphasis> and <Emphasis Type="Italic">P. citrophthora</Emphasis>in citrus roots and soil

Two primers, specific for Phytophthora nicotianae (Pn6) and P. citrophthora (Pc2B), were modified to obtain Scorpion primers for real-time identification and detection of both pathogens in citrus nursery soils and roots. Multiplex PCR with dual-labelled fluorogenic probes allowed concurrent identification of both species ofPhytophthora among 150 fungal isolates, including 14 species of Phytophthora. Using P. nicotianaespecific primers a delayed and lower fluorescence increase was also obtained from P. cactorumDNA. However, in separate real-time amplifications, the aspecific increase of fluorescence from P. cactorum was avoided by increasing the annealing temperature. In multiplex PCR, with a series of 10-fold DNA dilutions, the detection limit was 10 pg l^-1 for P. nicotianaeand 100 pg l^–1 for P. citrophthora, whereas in separate reaction DNA up to 1 pg l^-1 was detected for both pathogens.Simple and rapid procedures for direct DNA extraction from soil and roots were utilised to yield DNA whose purity and quality was suitable for PCR assays. By combining these protocols with a double amplification (nested Scorpion-PCR) using primers Ph2-ITS4 amplifying DNA from the main Phytophthora species (first round) and PnB5-Pn6 Scorpion and Pc2B Scorpion-Pc7 (second round), it was possible to achieve real-time detection of P. nicotianaeand P. citrophthora from roots and soil. The degree of sensitivity was similar to that of traditional detection methods based on the use of selective media. The analyses of artificially and naturally infested soil showed a high and significant correlation between the concentration of pathogen propagules and the real-time PCR cycle threshold.     

烟草黑胫病拮抗根际芽胞杆菌FB-16的筛选鉴定及其抑菌活性

为获得对烟草黑胫病有较强生防效果的拮抗细菌,从健康烟草根际采集30份土壤样品,分离纯化得到347株细菌,经病原真菌定向筛选后得到1株对烟草黑胫病菌等病原真菌拮抗活性较好的细菌FB-16,其对烟草黑胫病菌的抑菌带宽为23mm。采用菌丝生长速率法、作用机制试验、温室防病试验测定FB-16的抑菌作用,并通过形态学特征、生理生化特征及16S rDNA序列分析对菌株进行鉴定。结果显示,菌株FB-16发酵液对烟草黑胫病菌菌丝生长抑制率为95.96%;其代谢产物对烟草黑胫病菌菌丝有致畸作用;菌株FB-16为解淀粉芽胞杆菌Bacillus amyloliauefaciens(Gen-Bank登录号为JN245982);饱和度25%硫酸铵获得的抑菌物质对烟草黑胫病菌的抑菌活性较高,抑菌圈直径达42.00 mm;FB-16活性产物处理的烟草植株在接种烟草黑胫病菌7天后的防治效果为69.96%。表明菌株FB-16在烟草黑胫病生物防治中具有潜在的利用价值。     

福建省辣椒疫霉菌群体结构表型特征分析

为了明确福建省辣椒疫霉菌群体遗传结构的表型特征,对分离自福建省15个市(县)的300株辣椒疫霉菌的交配型、甲霜灵敏感性及生理小种进行了测定。结果显示,288株为A2交配型,12株为A1交配型,出现频率分别为96%和4%,以A2占优势,在各采集点均有分布。263株对甲霜灵表现敏感,28株为中间型,9株为抗性,分别占总体的87.67%、9.33%和3.00%,甲霜灵敏感菌株为主要菌系。根据菌株对辣椒疫霉菌生理小种鉴别寄主的致病性测定结果,可将辣椒疫霉菌划分为3个生理小种,其中168株为小种3,126株为小种2,6株为小种1,分别占56%、42%和2%,小种3为福建辣椒疫霉菌优势小种。     

枯草芽孢杆菌B006对黄瓜枯萎病菌和辣椒疫霉病菌的抑制作用及其抗菌组分分析

枯草芽孢杆菌菌株B006发酵液的甲醇提取物对黄瓜枯萎病菌Fusarium oxysporum f. sp. cucumerinum菌丝的抑制作用大于对辣椒疫霉病菌Phytophthora capsici菌丝的抑制作用;但对P. capsici游动孢子萌发的抑制作用明显大于对黄瓜枯萎病菌孢子萌发的抑制作用,提取物原液在5 min内可使辣椒疫霉的游动孢子全部崩解。提取物经60、90和120℃加热处理10 min后仍保持抑菌活性,其盐酸水解液在TLC层析板显现橙红色斑点,说明提取物具有环肽结构。HPLC-ESI-MS分析可得到m/z为995、1009、1023、1037、1051和1436、1450、1478和1492的质谱峰,与抗菌物质surfactin和fengycin的分子量大小一致。以终浓度为10^6 cfu·g^-1的接种量将B006菌剂施入无菌育苗基质中,在黄瓜和辣椒4～6片叶期时用固相萃取法提取根际的抗菌物质,并进行HPLC-ESI-MS分析,可从根际检测到surfactin和fengycin,但未从对照处理根上检测到脂肽类抗生素。本研究对理解枯草芽孢杆菌在田间状况下的防病机理有一定意义。     

辣椒抗疫病自交系的选育

为选育出抗疫病的辣椒新品种,利用引进的疫病抗源中间材料和自育辣椒自交系,采用回交转育的方法,筛选出系列抗疫病的辣椒自交系,并配制和筛选出1个较优抗病组合,命名为疫抗1号。该组合全生育期132d(青熟果),株高70cm,株幅62cm,分枝次数为6次,单株结果48个,果长22cm,果径1.6cm,平均单果鲜重17.8g,产量2 600kg/667m2;6叶苗期疫病病原混合接种鉴定表现为高抗。