Molecular detection of Fusarium solani f. sp. glycines in soybean roots and soil

A polymerase chain reaction (PCR)-based method was developed to detect DNA of Fusarium solani f. sp. glycines , the cause of soybean sudden death syndrome. Two pairs of primers, Fsg1/Fsg2 designed from the mitochondrial small subunit ribosomal RNA gene, and FsgEF1/FsgEF2 designed from the translation elongation factor 1-α gene, produced PCR products of 438 and 237 bp, respectively. Primer specificity was tested with DNA from 82 F. solani f. sp. glycines , 55 F. solani non-SDS isolates, 43 isolates of 17 soybean fungal pathogens and the oomycete Phytophthora sojae , and soybean. The sensitivity of primer Fsg1/Fsg2 was 10 pg while that of FsgEF1/FsgEF2 was 1 ng when using F. solani f. sp. glycines total genomic DNA or down to 10³ macroconidia g⁻¹ soil. Nested PCR increased the sensitivity of the PCR assay 1000-fold to 10 fg using primers Fsg1/Fsg2, and 1 pg using primers FsgEF1/FsgEF2. F. solani f. sp. glycines DNA was detected in field-grown soybean roots and soil by PCR using either single pairs of primers or the combination of two pairs of primers. The occurrence of F. solani f. sp. glycines was determined using nested PCR for 47 soil samples collected from soybean fields in 20 counties of Illinois in 1999. F. solani f. sp. glycines was detected in soil samples from all five Illinois Agricultural Statistic Districts including 100, 89, 50, 92 and 50% of the samples from East, Central, North-east and West Districts, respectively.     

Variation in the response of melon genotypes to Fusarium oxysporum f.sp. melonis race 1 determined by inoculation tests and molecular markers

Screening of genotypes of melon ( Cucumis melo ) for resistance to wilt caused by Fusarium oxysporum f.sp. melonis is often characterized by wide variability in their responses to inoculation, even under carefully controlled conditions. The variability at the seedling stage of 17 genotypes susceptible to race 1 was examined in growth-chamber experiments. Disease incidence varied from 0 to 100% in a genotype-dependent manner. Using four combinations of light (60 and 90  µ E m⁻² s⁻¹) and temperatures of (27 and 31°C), only light intensity showed a statistically significant effect. Marker-assisted selection for fusarium resistance breeding using cleaved amplified polymorphic sequence (CAPS) and sequence-characterized amplified region (SCAR) markers were compared using a single set of genotypes that included 24 melon accessions and breeding lines whose genotype regarding the Fom-2 gene was well characterized. The practical value of the markers for discriminating a range of genotypes and clarifying the scoring of phenotypes was also tested using a segregating breeding population which showed codominant SCAR markers to be useful in marker-assisted selection.     

克萎星对棉花黄萎病的防治效果

克萎星可溶性粉剂是河南省濮阳农业科学研究所研制生产的防治棉花黄萎病的新农药，田间药效试验结果表明：克萎星防治棉花黄萎病，发病初期叶面喷施，防效71．7％～100％，最佳施用浓度500～1000倍液，间隔期7～10d,棉花安全。     

哈茨木霉对水稻恶苗病菌的拮抗作用

PDA平板拮抗试验表明 ,哈茨木霉对水稻恶苗病菌有强烈的拮抗作用 ,其孢子悬浮液的含孢量为 10⁶～10⁷个 /mL时 ,对恶苗病菌的抑制力达 92.33%。通过哈茨木霉菌液和 3种药剂对水稻恶苗病菌抑制效果的比较 ,哈茨木霉孢子悬浮液含孢量为 10⁷个 /mL与施保克质量浓度 1μg/mL的抑菌效果接近 ,分别为 76.7%、75.4%。显微摄影结果显示 ,哈茨木霉以附着胞附着在恶苗病菌菌丝上 ,然后穿透菌丝在其内生长 ,或与恶苗病菌的菌丝平行生长 ,然后再侵入病菌内寄生。     

O3对日光温室黄瓜病虫害的防治效果

通过室内与大田试验，明确O3对日光温室黄瓜病虫害的防治效果。研究结果表明，在病害发生初期，用O3发生器隔天施放O3，每天施放3次，每次40min，间隔20min，O3浓度维持约1mg／kg，施放后7天，对黄瓜霜霉病、白粉病、细菌性角斑病及灰霉病防治效果分别为63．4％、53．6％、68．7％和65．0％。室内施放O3 60s，间隔20min，持续12h，对温室白粉虱、南美斑潜蝇成虫杀伤力为100％。O3对黄瓜植株安全，但随着黄瓜生育期的推进，对O3的忍受能力依次减弱。苗期忍耐O3最大浓度为1～2mg／kg，结果期0．4～1mg/kg，后期0．2～0．4mg／kg。O3防治黄瓜病虫害新技术具有安全、有效、方便、无二次污染等特点，尤其在黄瓜定植前对棚室进行大剂量消毒，可不留死角，且有效地解决了硫磺等药物消毒所造成棚内一些设施的破坏及对生态环境污染的难题，具有广阔的推广应用前景。     

Biological and molecular characterization of Tomato spotted wilt Virus in Israel

Received April 24, 1997; received in final form June 29, 1997. Symptoms resembling tomato spotted wilt virus (TSWV) infections were documented among ornamental and vegetable crops in commercial greenhouses and open fields in Israel. Plants exhibiting these symptoms were collected from January 1992 to December 1996. Among cultivated plants analyzed for TSWV by enzyme-linked immunosorbent assay (ELISA), 19 species representing five families were found to be infected; natural infection was also recorded in six plant species of weeds. Virus identity was characterized by host range, serology and electron microscopy. Serological reaction with the isolates, found in Israel, using antisera from different sources as well as the sequence analysis of the nucleocapsid gene, demonstrated that the Israeli isolates of TSWV are a member of tospovirus serogroup I, type I (BR-01 strain). No virus transmission was found in seeds collected from virus-infected vegetable and ornamental crops. A non-radioactive molecular probe derived from the cloned nucleocapsid isolate enables specific detection of the virus in crude sap from infected plants. The detection of TSWV in Israel constitutes a severe potential threat to the ornamental and vegetable industry.     

玉米青枯病病原腐霉对其伴生镰刀菌的影响

 本试验以玉米青枯病病原肿囊腐霉(Pythium inflatum Malthews)与禾生腐霉(Pythium gramlnicola Subram)为材料,着重研究了两种腐霉的生长与代谢对其伴生病原禾谷镰刀菌(Fusarium graminearum Schw.)的影响,结果表明:1.腐霉的定殖生长能力弱于禾谷镰刀菌。在腐霉菌落上,禾谷镰刀菌仍可生长,而在禾谷镰刀菌菌落上,腐霉则不能生长。2.在伴生条件下,腐霉被镰刀菌覆盖的时间长短随接种间隔而有变化,接种间隔愈短,则覆盖愈快。3.两种腐霉的培养滤液均对禾谷镰刀菌的孢子萌发与芽管伸长及菌落扩展有明显的促进作用,表明滤液中含有对镰刀菌生长有利的活性成分。4.腐霉培养滤液对禾谷镰刀菌红色色素的产生有一定的抑制作用,其原因可能与腐霉的嗜糖性有关。5.田间结果表明,腐镰复合接种的发病率接近禾谷镰刀菌单菌接种,但低于腐霉单菌接种。     

几种化学物质诱导黄瓜对霜霉病的抗性

在黄瓜幼苗子叶期及第1真叶期用苯酚、水杨酸、无水对氨基苯磺酸和氯化钾进行诱导接种,可使黄瓜植株产生对霜霉病的抗病性。在自然病原激发病害的试验中,经上述4种化学物质诱导的植株,其病株率比CK分别降低30％、0％、20％和20％;病叶率发别降低20.61％、6.80％、31.62％和20.72％;相对免疫效果分别为21.73％、35.19％、59.61％和40.84％。在人工接种病原激发病害试验中,经上述4种化学物质诱导的植株,其病株率分别降低28.57％、42.86％、57.14％和28.57％;病叶率分别降低89.13％、63.13％、72.96％和82.75％;相对免疫效果分别为91.15％、33.33％、55.99％和52.81％。     

营养元素对木霉菌防治甜瓜枯萎病效果的影响

为明确各种营养元素在木霉菌防治甜瓜枯萎病生防体系中的作用,研究了9种营养元素铜、锌、铁、硼、钼、钙、锰、镁及钾对甜瓜枯萎病菌菌丝生长、木霉菌T23菌丝生长及产孢量、甜瓜种子萌发及根系生长的影响.结果表明:10～1000μg/mL的硫酸铜、硫酸锌、硫酸亚铁及硼酸对镰孢菌菌丝生长有较强的抑制作用,而对木霉菌的抑制作用远小于镰孢菌.适量加入钼酸铵、硫酸亚铁、硫酸钙及磷酸二氢钾有利于木霉菌菌丝生长及孢子形成,对甜瓜种子萌发及胚根生长也有较强的刺激作用.木霉菌结合钼酸铵、硫酸锰和硫酸钙处理土壤能显著降低甜瓜枯萎病的病情指数,相对防效分别为73.95%、73.77%和71.36%.     

草酸青霉菌果胶酶诱导黄瓜抗黑星病研究

 本文就草酸青霉菌(Penicillium oxalicum)的固态发酵提取产物--果胶酶粗酶液诱导黄瓜对黑星病(Cladosporium cucumerinum)的抗性进行了研究。以果胶酶粗酶液喷雾处理4个感黑星病黄瓜品种的黄化苗,48 h后挑战接种黑星病菌孢子悬液,其中"中农5号"黄瓜品种表现的诱导抗病效果最好,诱抗效果达62.51%。不同浓度果胶酶诱导处理黄瓜,发现果胶酶浓度在20 U/mL时,可导致黄瓜发病略高于对照;在40~200 U/mL浓度范围内,诱导效果较为明显。通过研究果胶酶诱导抗病的时效性,表明诱导处理前接种病菌或诱导处理后0、6 h接种的各处理病情指数与对照间没有差别,而诱导处理12~72 h后接种病菌的,果胶酶的诱导抗病效果均很明显,诱抗效果达29.64%~60.02%。实验还表明,随着挑战接种压力的增大,果胶酶的诱导抗病效果降低。果胶酶不能抑制黑星病菌孢子萌发,相反可以促进孢子萌发和芽管生长。