小麦赤霉菌FGSG＿05656基因敲除及功能分析

小麦赤霉菌FGSG05656基因在MGV1敲除突变体中显著下调,为了进一步研究其生物学功能,本研究采用Split-Marker基因敲除技术,构建了含有潮霉素抗性基因(hph)的基因缺失盒。通过聚乙二醇(PEG)法转化野生型原生质体。潮霉素(Hygromycin)选择培养基筛选转化子后,PCR正负筛选鉴定敲除突变体。基于缺失突变体的表型和感染能力的变化来分析FGSG05656基因的生物学功能。与野生型PH-1相比,敲除突变体的生长速率和分生孢子数显著减少,表明FGSG05656基因可能参与菌丝体的生长和分生孢子的发生。植物感染试验显示缺失突变体与野生型之间没有显著差异。分生孢子是病原菌感染寄主的主要器官,它的减少可以显著减弱病原菌的扩散,FGSG05656基因敲除突变体分生孢子显著减少,这一结果对于进一步研究分生孢子发生的分子机理具有重要意义,同时为小麦抗病分子育种提供依据。     

香蕉枯萎病菌4号生理小种cat1基因敲除与表型分析

前期蛋白质组学研究发现尖孢镰刀菌古巴专化型4号生理小种(Foc4)中的过氧化氢酶1(cat1)基因受到巴西蕉诱导上调表达,为研究cat1基因在Foc4侵染香蕉过程中的作用,利用同源重组方法敲除Foc4的cat1基因,并对获得的敲除突变体开展表型分析和致病性测定。结果表明:cat1基因缺失对Foc4的菌丝、孢子形态、菌落生长、抗渗透压胁迫和细胞壁选择性压力等没有影响;但引起菌株抵抗外源氧胁迫、细胞壁穿透能力、纤维素利用能力减弱和对巴西蕉的致病性减弱。显示cat1基因的产物通过清除香蕉分泌的活性氧在Foc4对香蕉的致病过程中起作用,并参与病原菌对寄主纤维素成分的代谢。此结果为进一步深入研究香蕉枯萎病菌的致病机理奠定基础。     

玉米镰孢穗腐病发生条件及化学防治效果研究

通过人工接种筛选抗病品种资源,研究播期、种植密度对病害发生的影响,明确玉米镰孢菌穗腐病发生与品种资源、播期、种植密度的关系,分析棘孢木霉菌颗粒剂(TCF)和XDS种衣剂(40%毒死蜱乳油、20%辛硫磷和10%井岗霉素混剂)对玉米穗腐病的防效。结果表明,32个自交系中有6个抗病自交系,延迟播种玉米镰孢菌穗腐病发生严重,播种密度对病害发生程度无显著影响。人工接种条件下,TCF颗粒剂穴施、XDS种衣剂拌种2个处理表现为百粒重增加、秃尖长度降低,TCF颗粒剂穴施处理的防效最高,为48.69%。     

Biocontrol potential of Pseudomonas azotoformans,Serratia marcescens and Trichoderma virens against Fusarium wilt of Dalbergia sissoo

Wilt disease caused by Fusarium solani is a serious constraint to Dalbergia sissoo (shisham) plantations in northern India. In this study, the antagonistic potential of 40 bacterial isolates recovered from rhizophere soil of healthy shisham trees, and a well‐characterized Trichoderma species (Trichoderma virens) were tested for their possibility as biocontrol agents for F. solani. Two promising isolates (S1 and S15) were identified which inhibited pathogen growth, caused chitin degradation, produced siderophores and solubilized phosphate in vitro. Isolate S15 scored highest for hydrogen cyanide (HCN) production while isolate S1 was a non‐HCN producer. These two isolates were identified as Serratia marcescens (S1) and Pseudomonas azotoformans (S15) following sequence analysis of 16S rDNA. In dual culture assays, T. virens caused 80% inhibition of mycelial growth of the test fungus. The three selected antagonists when tested in planta in the glasshouse completely suppressed production of wilt symptoms on 12‐month‐old shisham plants. Further work is needed to ascertain the potential of these isolates to be used as biocontrol agents to manage shisham wilt under field conditions.     

Induction of Defense Gene Expression and the Resistance of Date Palm to Fusarium oxysporum f. sp. Albedinis in Response to Alginate Extracted from Bifurcaria bifurcata

In many African countries, the Bayoud is a common disease spread involving the fungus Fusarium oxusporum f. sp. albedinis (Foa). The induction of plant natural defenses through the use of seaweed polysaccharides to help plants against pathogens is currently a biological and ecological approach that is gaining more and more importance. In the present study, we used alginate, a natural polysaccharide extracted from a brown algae Bifurcaria bifurcata, to activate date palm defenses, which involve phenylalanine ammonia-lyase (PAL), a key enzyme of phenylpropanoid metabolism. The results obtained showed that at low concentration (1 g·L⁻¹), alginate stimulated PAL activity in date palm roots 5 times more compared to the negative control (water-treated) after 24 h following treatment and 2.5 times more compared to the laminarin used as a positive stimulator of plant natural defenses (positive control of induction). Using qRT-PCR, the expression of a selection of genes involved in three different levels of defense mechanisms known to be involved in response to biotic stresses were investigated. The results showed that, generally, the PAL gene tested and the genes encoding enzymes involved in early oxidative events (SOD and LOX) were overexpressed in the alginate-treated plants compared to their levels in the positive and negative controls. POD and PR protein genes selected encoding β-(1,3)-glucanases and chitinases in this study did not show any significant difference between treatments; suggesting that other genes encoding POD and PR proteins that were not selected may be involved. After 17 weeks following the inoculation of the plants with the pathogen Foa, treatment with alginate reduced the mortality rate by up to 80% compared to the rate in control plants (non-elicited) and plants pretreated with laminarin, which agrees with the induction of defense gene expression and the stimulation of natural defenses in date palm with alginate after 24 h. These results open promising prospects for the use of alginate in agriculture as an inducer that triggers immunity of plants against telluric pathogens in general and of date palm against Fusarium oxysporum f. sp. albedinis in particular.     

甜菜立枯病病原菌的分离和鉴定

旨在明确黑龙江大学呼兰校区甜菜立枯病的病原菌种类,为科学防治该病提供理论参考。以采自黑龙江大学呼兰校区的甜菜立枯病植株为试材,用形态学观察、致病性测定和分子生物学鉴定方法,依据柯赫氏法则,对病原菌进行分离和鉴定。结果表明,从发病甜菜幼苗根部上分离出的菌株L1,菌丝呈白色。大型分生孢子为镰刀型,有隔膜,小型分生孢子多为单细胞少数有隔膜。分子鉴定结果显示,该病原菌在基于ITS和tef1序列构建的系统发育树上与腐皮镰孢菌类群处同一分支。根据形态学和分子鉴定结果,确定引起黑龙江大学呼兰校区甜菜立枯病的病原菌为腐皮镰孢菌(Fusarium solani)。     

花椒根腐病病原鉴定和生物学特性研究*

 对云南省昭通市永善县黄华镇花椒根腐病的病原物进行鉴定并研究其生物学特性。结果表明,引起花椒根腐病的病原菌是茄形镰刀菌［Fusarium solani(Mart.)Sacc］,病菌的菌丝生长温度范围为5~40℃,最适温度为25~30℃,pH值范围为3~10,最适宜的pH值为5~7;分生孢子在相对湿度为90%以下不能生长,在相对湿度为100%(水滴)中才能很好的萌发;光照对其菌丝生长影响较小;60℃ 10 min为病原菌的致死温度;较适宜的碳氮源为蔗糖、乳糖和NaNO₃,(NH₄)₂SO₄。     

不同寄主尖孢镰刀菌培养滤液对黄瓜胚根萌发的影响

对不同寄主尖孢镰刀菌培养滤液对黄瓜胚根萌发进行了测定,结果表明,番茄(179,F-F.1.5-031017,番茄,福州福清)上分离的尖孢镰刀菌的发酵液处理的黄瓜种子的胚根重量最低,平均重量为85.00mg/10粒,黄瓜(120,F-H.6.5-030318-J4,黄瓜,漳州诏安)上分离的尖孢镰刀菌发酵液处理的黄瓜种子的胚根重量最高,平均为183.33mg/10粒。不同寄主发酵滤液对黄瓜胚根重量的影响大致可以分为3类:第一类为甜瓜(128,F-T.1.7-030514-03,甜瓜,福州永泰)、番茄(179,F-F.1.5-031017,福州福清)和班兜(107,F-B.1.1-030221,福州建新),第二类为西瓜(134,F-X.1.7-030320-03,西瓜,福州永泰)和网纹甜瓜(144,F-T2.1.1-030616-01,网纹甜瓜,福州义序),第三类为黄瓜(120,F-H.6.5-030318-J4,黄瓜,漳州诏安)。     

甘薯茎线虫与镰孢菌对甘薯的复合侵染

从甘薯茎线虫病的薯块中分离到茄病镰孢(Fusarium solani)和尖孢镰孢(F.oxysporum)2种真菌.通过苗期和薯块接种证实,尖孢镰孢与腐烂茎线虫(Ditylenchus destructor)能共同侵染甘薯引起复合侵染病害.     

木霉拮抗黄瓜枯萎病菌菌株的筛选

通过对峙培养、拮抗作用、耐性的测定,筛选出对黄瓜枯萎菌(Fusarium oxysporumf. sp. cucum erinum)拮抗作用强的木霉菌株(Trichoderma spp.)有13株,其中T55的拮抗作用最强。该菌株对峙培养对黄瓜枯萎菌抑菌率为80.16%,拮抗作用测定其圆盘滤膜法抑菌率大于50%,其它方法的抑菌率低于30%。该菌在5、10、35℃,pH4、9、10的条件下生长良好。