土传真菌病害拮抗菌的筛选及其生防效果研究

为了获得对主要粮食作物水稻、小麦和经济作物大豆常见土传病害具有防治效果的生防菌,本研究从土壤中筛选到一株对所选6种病原真菌均有较好拮抗效果的菌株。基于形态学、生理生化特性及16S rDNA序列分析进行菌种鉴定,利用菌丝生长速率法对其无菌滤液和挥发性气体的抑菌效果进行验证,同时研究了其无菌滤液的热稳定性、酸碱稳定性和对蛋白酶K的稳定性。结果表明:本研究筛选到一株贝莱斯芽孢杆菌Bacillus velezensis CX-2,其无菌滤液对6种病原真菌的抑菌率在71%～95%之间,对小麦纹枯病菌、小麦全蚀病菌的抑菌率分别高达90. 13%、94. 34%;挥发性气体对6种病原菌的抑菌率在45%～80%之间;无菌滤液中的抗菌活性物质具有较强的热稳定性和对蛋白酶K的稳定性;无菌滤液pH在5～9之间时具有稳定的抑菌活性。该菌株可作为作物土传真菌病害生防菌剂较为理想的功能菌株。     

土壤几丁质酶对土传性真菌病害的防治作用

针对生物防治在无公害农业生产中的重要性,对土壤几丁质酶的来源,几丁质酶对其真菌性病害的防治,土壤几丁质酶对土传性真菌病害的防治等的理论与应用前景进行了论述,认为可以通过人工调控的方法发挥土壤几丁质酶的生物防治作用。     

根际真菌对黄瓜土传病害的抑制作用

为了了解根际真菌对黄瓜土传病害的影响,通过平板对峙试验和温室人工接种盆栽试验,对分离自根际土的16株真菌开展了对土传病原真菌的拮抗作用和黄瓜土传病害的抑制作用研究.结果表明: 有4株真菌对一种或多种供试病原真菌表现有拮抗作用,其中经鉴定为土曲霉的菌株JCL143对黄瓜枯萎病菌、立枯病菌和菌核病菌3种供试病原真菌均有较强的拮抗作用.在温室盆栽试验中,接种菌株JCL143对黄瓜3种病害的相对防效均在74%以上;而在不灭菌育苗基质的盆栽试验中,接种菌株JCL143对立枯病和菌核病的防效均在85%以上.在用自然土进行的温室盆栽试验中,接种菌株JCL143对伸蔓期黄瓜枯萎病的相对防效平均达84.1%.菌株JCL143的发酵液对3种供试病原真菌菌落生长都有不同程度的抑制作用,对菌核病菌的菌落生长抑菌率达63.3%.发酵液的抑菌活性随处理温度的升高而下降,对碱性pH值比酸性pH值敏感,而对蛋白酶处理不敏感.说明土曲霉是土壤中抑制植物土传病害的重要因素,菌株JCL143的抑病效果稳定,具有潜在的生防应用价值.     

植物根际促生菌对3种土传真菌病害病原的抑制作用

【目的】获取促生同时可防治3种土传真菌病害(Fusarium oxysporum、Sclerotinia sclerotiorum和Rhizoctonia solani)的生防菌,并明确其抑菌效果。【方法】利用前期研究获得的17株促生菌,采用平板对峙法测定其对病原真菌的拮抗作用及对菌丝生长的抑制作用。【结果】可有效拮抗立枯丝核菌的生防菌有6株,其中促生菌株FX2和LM4-3的抑制率达73.82%;拮抗尖孢镰刀菌的生防菌有7株,其中FX2的抑制率达到66.81%;拮抗油菜菌核病菌的生防菌有4株,其中菌株LHS11的抑制率高达85.71%。菌株LHS11和JM170通过次生代谢物抑制病原真菌。所有的生防菌对病原菌的菌丝生长均有一定的抑制作用。【结论】筛选得到对3种真菌病害病原具有较好生防作用的菌株LHS11和FX2。     

6种杀菌剂对金线莲病害及生长的影响

以福建产金线莲Anoectochilus roxburghii为材料,研究不同杀菌剂对金线莲病害防治及生长指标动态的影响。结果表明,多菌灵和甲基托布津对金线莲病害的防治效果较好,相对防治效果达到55.3%和47.1%;而百菌清和叶枯唑对病害的相对防治效果虽只有26.9%和5.3%,但二者处理对金线莲的茎粗和叶面积的增长有明显的促进作用。精甲霜·锰锌和乙蒜素在病害防治及促进生长指标方面无突出表现。     

三种甲氧基丙烯酸酯类杀菌剂拌种对花生幼苗生长及生理作用的影响

研究了不同温度和不同土壤湿度条件下,三种甲氧基丙烯酸酯类杀菌剂吡唑醚菌酯、醚菌酯、嘧菌酯以1 g a.i.·kg-1(种子)的处理剂量对花生幼苗生长及生理作用的影响。结果表明:湿度一定时,随温度的升高,花生幼苗的株高、主根长、地上鲜重和地下鲜重等生物学性状和保护酶(SOD、POD、CAT)等生理生化指标提高,25℃下花生生长状态最佳;60%湿度下,花生幼苗的株高等生物学性状和保护酶、转氨酶等生理生化指标,均好于40%和80%湿度条件下。三种药剂拌种处理后可以促进花生幼苗的生长,提高叶片保护酶(SOD、POD、CAT)和转氨酶(GPT、GOT)活性,增加叶绿素和叶片可溶性蛋白含量,提高根系活力。     

一株拮抗多种土传病害病原菌的芽胞杆菌筛选鉴定及发酵工艺优化

为减少化学农药的使用量,从土壤中筛选出一株可拮抗多种土传病害病原菌菌株,编号为BSK-12。通过生理生化、形态学特征和16S rDNA序列分析,鉴定菌株BSK-12为地衣芽胞杆菌(Bacillus licheniformis)。采用单因素试验、Plackett-Burman试验和最陡爬坡试验确定BSK-12培养成分和发酵条件的主要影响因素及其取值范围;再通过Box-Behnken试验对其主要因素进行优化,通过回归分析得出最佳发酵条件为发酵温度37℃、摇床转速180 r/min、初始pH值7,在该发酵条件下,芽胞数达到7.6×10～9 cfu/mL。BSK-12对五种土传病病原菌有较好的拮抗效果,可为研制生物农药提供优质菌种资源。     

三种药剂对早稻二化螟的防效及施药适期探讨

试验结果表明,氯虫苯甲酰胺、氯虫·噻虫嗪有对二化螟Chilo suppressalis(Walker)有较好的防效和较长的持效,一次施药可兼治多个峰次。20%氯虫苯甲酰胺150mL/hm2、40%氯虫·噻虫嗪120g/hm2和2.15%甲氨基阿维菌素苯甲酸盐750mL/hm2在二化螟2龄幼虫高峰期施药,药后8d对幼虫防效分别达94.7%、91.2%和91.0%;药后18d的防效依次为99.0%、98.0%、73.2%,氯虫苯甲酰胺、氯虫·噻虫嗪处理防效仍高于药后8d,但甲氨基阿维菌素苯甲酸盐处理防效明显下降;药后18d对主峰保苗效果(枯心)氯虫苯甲酰胺和氯虫·噻虫嗪分别为99.0%、98.0%,甲氨基阿维菌素苯甲酸盐处理偏低,为73.2%。对后峰保苗效果(枯鞘)氯虫苯甲酰胺为84.9%好于氯虫·噻虫嗪处理的69.3%,甲氨基阿维菌素苯甲酸盐的防效仅为7.1%。氯虫·噻虫嗪不同时期施药处理后,主峰卵孵高峰后14d考查,防治效果和保苗效果以卵孵高峰施药最好,其次为2龄幼虫高峰期施药;主峰卵孵高峰后24d考查,主峰卵孵高峰至3龄幼虫高峰施药对主峰均有较好的防效,但对后峰的防效,随着施药时间推迟而提高,但在螟虫重发地区施药过迟,前期的大量枯鞘会影响稻苗生长与分蘖。因此作者建议在二化螟发生量大、后峰数量多地区,采用主峰卵孵高峰和后峰卵孵高峰2次防治对策,在螟虫发生较轻、后峰数量较少或全代发生较为集中地区,可根据当地虫情发生情况,适当推迟施药,达到一次用药,解决全代螟害。甲氨基阿维菌素苯甲酸盐持效期较短,可根据螟虫发生峰次施用。     

高羊茅和多年生黑麦草内生真菌的分子检测

根据GenBank上报道的内生真菌Neotyphodium coenophialum和N.lolii的Nc25基因序列,设计了2对特异性引物FM1/R1和F3/R652,建立了一套适合于从高羊茅和多年生黑麦草种子中检测内生真菌N.coenophialum和N.lolii的常规PCR和巢式PCR方法。     

The Effect of Seed-Borne Pathogens on Emergence of Globe Amaranth, Calendula and Tagetes and the Methods of Control

Nimbya gomphrenae , Stemphylium vesicarium and Alternaria tagetica were isolated for the first time from seeds of diseased globe amaranth ( Gomphrena globosa ), pot marigold ( Calendula officinalis ) and marigold ( Tagetes erecta ), respectively, in Taiwan. The amount of seed-borne N. gomphrenae or Colletotrichum dematium was positively correlated (P=0.05) with the amount of the abnormal seedling and unemergent seed of globe amaranth. Similarly, the amount of seed-borne Alternaria alternata or S. vesicarium was negatively correlated (P=0.05) with the emergent rate of pot marigold. Treating the fungi-contaminated globe amaranth seeds with Bacillus megaterium [1.3 × 10⁹colony-forming units (CFU)/ml] or 1% NaOCl significantly (P=0.05) increased seed emergence over control whereas 10 p.p.m. pyrifenox could control N. gomphrenae on globe amaranth. Stemphylium -contaminated pot marigold seeds responded to 200 p.p.m. iprodione treatment by increasing significantly (P=0.05) in seed emergence over untreated control. For seed-borne A. tagetica , treating marigold seeds with Bacillus azotoformanis (1 × 10⁹CFU/ml) was found effective and mancozeb highly effective.     

A Clearing Technique for Detecting the Fungal Endophyte Acremonium sp. in Grasses

Leaf tissue of tall fescue Festuca arundinacea Schreb., hard fescue Festuca ovina L., red fescue Festuca rubra L. and perennial ryegrass Lolium perenne L. was stained with rose Bengal or aniline blue to detect the presence of the fungal endophyte Acremonium sp., Specimens were cleared using methyl salicylate, an optical clearing agent, and viewed using bright field microscopy. Tissue was presenred as dried tissue or stored in 70% aqueous ethyl alcohol before staining and clearing. Tissue was observed at 2, 4 and 12 weeks following clearing to check for stain retention. Staining with rose Bengal was inferior to aniline blue when followed by the clearing agent methyl salicylate. Fungal mycelia stained lighter with rose Bengal and were more difficult to detect than mycelia stained with aniline blue. The results illustrate the usefulness of combining staining and methyl salicylate clearing for detecting fungal endophytes.     

Effect of alternative treatments on seed-borne Didymella lycopersici in tomato

Aims:  To quantify the phytotoxicity and effect of alternative seed treatments based on acidified nitrite and elicitors of plant resistance (Tillekur and Chitosan) against seed-borne inocula of Didymella lycopersici .
Methods and Results:  Treatments tested were: nitrite [sodium nitrite in citric acid buffer (pH 2)] at 30, 100 and 300 mmol l⁻¹ and three exposure times (10, 20 and 30 min); Tillekur (in water) at 12·5, 25, 50, 100 and 200 mg ml⁻¹; Chitosan (in 0·05% acetic acid) at 2·5, 5, 10 and 50 mg ml⁻¹. Efficacy of treatments was determined in growth chamber experiments. Nitrite at 300 mmol l⁻¹ was completely effective, as was the fungicide, at controlling disease when applied for less than 20 min. Tillekur was as effective as the fungicide postemergence, but proved to be phytotoxic pre-emergence. Chitosan was significantly less effective than the other treatments.
Conclusions:  The high efficacy and low cost of acidified nitrite indicates that it is a suitable alternative to fungicides.
Significance and Impact of the Study:  There is currently a lack of effective seed treatments that can be used in organic and low-input crops. Treatments identified in this study can be considered as an effective alternative to chemical control against seed-borne fungal pathogens.     

The Hortega Silver Carbonate Method for Staining Pituicytes After Paraffin Embedding

In three papers published on pituicytes, of the ox by Bucy (1930), of the human by Shanklin (1940), and of the horse by Vazquez-Lopez (1942) the pituitaries were sectioned by the freezing method and stained by the Hortega silver carbonate technic. Since that time, as a routine procedure in our laboratory, frozen sections have been replaced by paraffin which in no way interferes with the Hortega silver carbonate staining.     

Regulation of leaf growth of grass by blue light

Changes in light quality occur naturally within a canopy when a plant grows from unshaded to shaded conditions, and the reverse occurs after a cut that reduces shading. These changes in light quality could be responsible for the variation in leaf elongation and appearance rates of grasses. The role of blue light in leaf growth was investigated in tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.). Leaf length was measured daily following a decrease or an increase in blue light to evaluate effects on duration of leaf growth, leaf elongation and the rate of leaf appearance rate. A reduction in blue light increased sheath length by 8 to 14% and lamina length by 6 to 12% for both species. These increases could be reversed by enrichment of blue light. With low blue light treatment, final leaf length was increased due to a greater leaf elongation rate. In tall fescue, but not in perennial ryegrass, this effect was coupled with a greater phyllochron and a longer duration of leaf elongation. Development of successive leaves on a tall fescue tiller were co-ordinated. A decrease in blue light increased the duration of elongation in the oldest growing leaf and also delayed the appearance of a new leaf, maintaining this co-ordination. We conclude that final leaf size and phyllochron for tall fescue can be significantly modified by blue light. Perennial ryegrass appeared less responsive, except for displaying longer sheaths and laminae in low blue light, as also occurred for tall fescue. We hypothesize that leaf length could be regulated by the quality of the light reaching the growing region itself.