Possible peroxidase functions in the interaction between the parasitic plant, Orobanche aegyptiaca, and its host, Arabidopsis thaliana

The mechanism by which the flowering holoparasitic plant, Orobanche aegyptiaca , infects its host without evoking a defence mechanism is still poorly understood. In this work, we studied several mechanisms used by phytopathogenic fungi. We focussed on the possible role of peroxidases during O. aegyptiaca penetration into the roots of Arabidopsis thaliana . A convenient experimental system for studying the interaction under sterile conditions was developed. The formation of extracellular reactive oxygen species (ROS) was detected at the interaction site before, during, and after the parasite penetrated into the host. These extracellular ROS probably originated from the parasite. However, no intracellular ROS could be detected at the site of the interaction. Peroxidase activity was observed mainly at the apex of the root of the parasite and in the adventitious roots of the tubercle. Benzhydroxamic acid, a peroxidase inhibitor, was used to probe the possible role of peroxidase in the infection process. Peroxidase activity was observed in the root apex and adventitious roots of O. aegyptiaca, but no evidence was found for its participation in the actual infection process. Peroxidase activity was also found in the later stages of the interaction between the host and the parasite. We propose that peroxidases could have a role in generating extracellular ROS for loosening the cell wall of the host in order to facilitate penetration. Alternatively, the ROS could act in facilitating the root elongation of the parasite.     

Methyl jasmonate and methyl salicylate, but not cis-jasmone, evoke defenses against infection of Arabidopsis thaliana by Orobanche aegyptiaca

The mechanism by which some plant species develop resistance to the root parasite, broomrape ( Orobanche aegyptiaca ), is still not clear. Resistance to other pathogens can be induced by methyl jasmonate and systemic acquired resistance can be induced by treatment with salicylic acid, while cis -jasmone can act as a signaling molecule in plant–insect interactions. The three compounds studied, methyl jasmonate, cis -jasmone, and methyl salicylate, were applied to Arabidopsis thaliana seedlings that were then transferred to Nunc cell culture plates and exposed to the germinating seeds of O. aegyptiaca . The number of infections of the roots of single seedlings of A. thaliana was then quantified. Exposure for 24 h to very low concentrations of methyl jasmonate or methyl salicylate, which were then removed, effectively induced resistance to infection of A. thaliana by O. aegyptiaca , reducing attachment and tubercle formation by 90%. cis -Jasmone was far less effective in inducing a similar resistance to infection. These results support the view that methyl jasmonate can induce almost full resistance to infection by broomrape. The fact that such resistance is not observed under normal conditions of infection supports the idea that the root parasite does not evoke the full defensive response in the host plant.     

分枝列当种子萌芽生物学特性

以寄生于番茄的分枝列当种子为试验材料,研究预培养阶段温度、时间、渗透势以及培养阶段温度、萌发刺激物(独月却金内酯类似物GR24)的浓度和渗透势对种子萌发的影响,以期找到种子萌发的最适条件,从而可以人为创造控制分枝列当生长的环境,以达到有效防治的目的。结果表明:预培养阶段的最适培养温度为25℃,最适培养时间为6 d,最适的渗透势为0 MPa;培养阶段的最适培养温度为25℃,最适GR24浓度为1μmol/L,最适的渗透势为-1 MPa。     

新疆不同甜瓜品种对埃及列当的抗性鉴定

【目的】 研究从新疆收集的31个甜瓜品种对埃及列当的抗性程度和水平,为甜瓜抗列当育种和品种合理布局提供参考。【方法】 采用根室法、温室盆栽和田间小区测定,对31份甜瓜品种抗埃及列当寄生的能力进行评价。【结果】 抗性类型仅有金甜蜜17号,根室试验中接种列当生长停滞在第Ⅱ种寄生状态;室内盆栽与小区试验中埃及列当寄生率分别为33.33%和50.00%,寄生程度分别为0.33和1.67。耐寄生类型有亚洲密17号等 4个品种,根室试验中接种列当生长停滞在第Ⅲ种寄生状态;盆栽试验中列当寄生率在71.43%~75.00%,寄生程度在1.29~4.25。其余26个品种均属易感类型,根室试验中接种列当正常生长至第Ⅳ种寄生状态;室内盆栽与小区试验中埃及列当寄生率最高均为100%,寄生程度最高分别为13.00和17.50。【结论】 31个甜瓜品种中,1个为抗列当品种,4个为耐列当品种以及26个均为易感列当品种。目前,新疆栽培的甜瓜品种抗列当寄生的品种或材料较少,多为易感品种或材料,这是导致新疆甜瓜产区埃及列当危害严重的主要原因之一。     

Effect of rooting media and hormone concentrations on vegetative propagation of Balanites aegyptiaca

Vegetative propagation is widely used as a means of genotype preservation in clone banks and seed orchards but despite this, the possibility of vegetative propagation using hormones is not clear for many indigenous tree species, including Balanites aegyptiaca. This research is on the vegetative propagation of B. aegyptiaca as influenced by rooting media and growth hormones.Juvenile stem cuttings were obtained from 4 months old seedlings. Nodal stem cuttings 4–5 cm long from 3–5 mm diameter stems were treated with indole-3-butyric acid or indole-3-acetic acid at 50, 100 and 150 mg/L and sown in three different rooting media: top soil, river sand, and sawdust. The results reveal a significant effect(p \ 0.05)of rooting media and growth hormones on B. aegyptiaca cuttings. B. aegyptiaca can be propagated vegitatively without the use of hormones. The control was recommended for vegetative propagation of B. aegyptiaca.     

枯草芽孢杆菌DNKAS对加工番茄分枝列当的防治应用

分枝列当（Orobanche aegyptiaca）是一种根寄生植物,严重影响加工番茄的产量。为减轻其危害,首先通过皿内芽管生长试验,明确了枯草芽孢杆菌DNKAS对分枝列当芽管生长有显著抑制作用;并通过田间小区随水滴灌方式,设置清水对照（CK）、3 kg·hm^-2 DNKAS菌剂（D3）、4.5 kg·hm^-2 DNKAS菌剂（D4.5）、6 kg·hm^-2 DNKAS菌剂（D6）、9 kg·hm^-2 DNKAS菌剂（D9）、12 kg·hm^-2 DNKAS菌剂（D12）、7.5 kg·hm^-2黄腐酸钾（FA-K）、4.5 kg·hm^-2 DNKAS菌剂+7.5 kg·hm^-2黄腐酸钾(D4.5+FA-K) 共8个处理,研究不同处理对分枝列当的防治效果和增产效果;随后采用 Biolog-ECO微平板检测法,分析菌剂施用后土壤微生物群落的生态及代谢多样性变化,明确菌剂对作物及环境的影响。结果表明,纯菌剂施用条件下,D12处理的防治效果最佳,防效为52.33%,列当寄生数量最低为493个,寄生度为1.30,番茄产量为133 455 kg·hm^-2,增产56.48%。黄腐酸钾与菌剂混合施用效果明显优异于其单独施用,防治效果提高了14%,寄生度和寄生数降低约10%,番茄产量提高14%。不同处理的微生物代谢活性表现为：D4.5+FA-K > FA-K > D12> D9,不同处理间的碳源利用率差异不明显,Shannon多样性指数差异显著,表明生防菌DNKAS可增加土壤群落丰富度,生防菌KNKAS及其与黄腐酸复配可提高防效,适用于分枝列当防治。     

Evaluation of the pathogenicity of microorganisms isolated from Egyptian broomrape (Orobanche aegyptiaca) in Israel

Diseased Egyptian broomrape ( Orobanche aegyptiaca ) inflorescences were collected from a heavily broomrape-infested tomato ( Lycopersicon esculentum ) field in Israel. The microorganisms that were isolated from the diseased inflorescences were passed through Koch's postulates on Egyptian broomrape-parasitizing tomato roots in a polyethylene bag system and pots under greenhouse conditions. The fungi, Alternaria alternata , Macrophomina phaseolina , Rhizoctonia solani , and Fusarium solani , and the bacterium, Bacillus sp., were newly isolated from the diseased inflorescences of Egyptian broomrape and were found to be pathogenic to the parasite. Fusarium solani damaged all of the developmental stages of broomrape and prevented the damage that Egyptian broomrape causes to tomato plants. The level of pathogenicity and the damage of M. phaseolina , A. alternata , and Bacillus sp. to Egyptian broomrape in greenhouse experiments were relatively low. All the tested microorganisms are known as pathogens of tomato, yet none caused disease symptoms on the tomato plants grown in the inoculated polyethylene bags or in the pots. Fusarium solani demonstrated the highest potential for further development as a mycoherbicide for Egyptian broomrape control in tomato.     

分枝列当茎的发育解剖学研究

分枝列当茎的初生分生组织由原表皮、原形成层和基本分生组组织组成。在原形成层束分化为初生维管束的过程中,维管束可通过束内分化出１或几列薄壁细胞的方式分离形成２－４个维管束,使维管束的数目迅速增加。在初生生长过程中,部分髓射线薄壁细胞转变为异常形成层束,异常形成层束再分化产生新的维管束。     

小红瓢虫对埃及吹绵蚧的捕食功能的研究

运用普通生态学方法对埃及吹绵蚧的主要捕食性天敌小红瓢虫的捕食功能进行研究.结果显示,小红瓢虫对埃及吹绵蚧的密度反应为Holling Ⅱ型,圆盘方程拟合后的瞬时攻击率为0.577,处理时间为0.019;通过Hassell模型拟合,小红瓢虫自身密度增加导致的干扰效应为0.434;根据汪世泽提出的功能反应新模型,拟合后估计的...     

一株淡紫紫孢菌12ID-1的分离及其对埃及吹绵蚧的致病性

从埃及吹绵蚧虫（Icerya aegyptiaca）体中分离出一株虫生真菌菌株 12ID-1，对其进行了形态观察和 rDNA ITS 序列分析，同时优化了该菌株的产孢条件和测定了其不同浓度的孢子悬浮液对埃及吹绵蚧 2 龄若虫的致病性。结果表明：根据形态特征和分子鉴定结果，该菌株 12ID-1 为淡紫紫孢菌（Purpureocillium lilacinum）；菌株 12ID-1 在 SMAY 培养基、28 ℃和光暗交替（14 L : 10 D）的条件下产孢能力最强；致病性结果表明，当孢子浓度高于 1×106 孢子 /mL 时，随着 12ID-1 孢子浓度的增加，埃及吹绵蚧的校正死亡率越高，LT50 值递减，在孢子浓度为 1×108 孢子 /mL 时，第 7 天校正死亡率接近 100%， LT50 为 3.99 d；随着接种后时间的延续，LC50 值递减，在接种后 7 d，LC50 值为 1.3×106 孢子 /mL。可见淡紫紫孢菌 12ID-1 对埃及吹绵蚧具有较强的毒力，在埃及吹绵蚧生物防治中具有广阔的应用前景。