Effect of chitin on biological control activity of Bacillus spp. and Trichoderma harzianum against root rot disease in pepper (Capsicum annuum) plants

Two bacterial isolates and one strain of Trichoderma harzianum were tested alone and in combination with chitin for efficacy in control of root rot disease caused by Phytophthora capsici and Rhizoctonia solani in pepper plants under greenhouse conditions. These bacteria (Bacillus subtilis HS93 and B. licheniformis LS674) were isolated from repeatedly washed roots of pepper plants. In in vitro assays, HS93, LS674 and T. harzianum were antagonistic against P. capsici and R. solani and produced high levels of chitinase. Seed treatment and root drenching with bacterial suspensions of HS93 with 0.5% chitin was more effective against Phytophthora and Rhizoctonia root rot than addition of the organisms without chitin. LS674 and T. harzianum reduced Rhizoctonia but not Phytophthora root rot. In two greenhouse tests, seed treatment and root drenching with HS93 amended with chitin enhanced its biocontrol activity against P. capsici but not on R. solani. The effects of LS674 and T. harzianum against R. solani were significantly enhanced when they were used as suspensions with 0.5% chitin for root drenching, but this had no effect on P. capsici. In both greenhouse experiments, the use of 0.5% chitin alone for root drenching reduced Rhizoctonia root rot. Reduction of root rot disease was accompanied by increased yield. These results show that the antagonistic activity of HS93, LS674 and T. harzianum may be stimulated by chitin resulting in significant improvements in their effectiveness against pathogens.     

Non-structural plum pox potyvirus proteins detected by immunogold labelling

Plum pox potyvirus (PPV) induces in infected Nicotiana clevelandii cells characteristic crystalline inclusions known as nuclear inclusions (NI) when located in the nucleus and as dense material (Dm) when located in the cytoplasm. Crystalline inclusions contain protease (NIa) and RNA-dependent RNA polymerase (NIb) proteins. It is now well established for all potyviruses that cylindrical inclusions contain CI helicase ATPase protein (Martin et al., 1992). The intracellular location of other non-structural PPV proteins remains unknown. Using Escherichia coli expression vectors, specific antibodies were obtained against P1, P3, 6K2 and NIb PPV proteins for which antibodies were not yet available. As expected, NIb antiserum labelled crystalline inclusions. P1, P3 and 6K2 proteins were present in both types of crystalline inclusions found in the nucleus and in the cytoplasm of PPV-infected leaves of N. clevelandii, suggesting that nuclear inclusions and dense material were composed of the same proteins. This composition is discussed.     

甲壳素对连作平邑甜茶生长、光合及抗氧化酶的影响

以苹果连作土盆栽的平邑甜茶幼苗为试材,探讨了0、0.5、1.0和2.5 g·kg-1不同施入量的甲壳素对其光合速率、活性氧含量及抗氧化酶活性的影响。结果表明,1.0 g·kg-1的甲壳素处理能显著促进幼苗株高、地径,干样质量和根冠比的增加,根冠比为对照的1.51倍;明显提高了幼苗叶片光合色素含量、净光合速率和蒸腾速率,其中光合速率为对照的1.30倍;同时提高了幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性,分别为对照的1.10倍、1.85倍、1.77倍和1.43倍;减少了叶片丙二醛(MDA)、过氧化氢(H2O2)和超氧阴离子的积累,分别为对照的73%、62%和34%,降低了脯氨酸(Pro)和可溶性糖含量。当甲壳素施用量为2.5 g·kg-1时则显著抑制平邑甜茶幼苗生长,降低幼苗叶片光合速率和抗氧化酶活性,并使超氧阴离子和脯氨酸含量明显上升。因此,适宜用量的甲壳素能减轻苹果的连作障碍。     

Nanostructured liquid crystalline particle assisted delivery of 2,4-dichlorophenoxyacetic acid to weeds,crops and model plants

Routine agricultural practices are heavily dependent on the use of surfactants, many of which are toxic to humans and detrimental to the environment. In proof of concept work we have previously shown the potential of nanostructured liquid crystalline particles (NLCP) to safely interact with plant leaf cuticular surfaces with minimal impact on epicuticular waxes. Here we demonstrate the use of NLCP to effectively deliver the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) to plant leaves in laboratory and field studies. In the laboratory, the physiological stress responses of lupin, Lupinus angustifolius (L.) (Fabaceae) towards NLCP spray applications were shown to be much reduced in comparison with application of two common surfactants. Phytotoxicity assays of 2,4-D loaded NLCP were used to validate the herbicidal effects on Arabidopsis thaliana (L.) Heynth. (Brassicaceae) and established a similarity with that of surfactant assisted 2,4-D delivery when tested at a concentration of 0.1%. Field trials were conducted to test the efficacy of NLCP-assisted delivery of 2,4-D in comparison with commercial surfactants for the control of the invasive weed wild radish, Raphanus raphanistrum (L.) (Brassicaceae), in wheat, Triticum aestivum (L.) (Poaceae) crop fields. Compared against Estercide 800, a commercially available 2,4-D formulation, NLCP assisted delivery of 2,4-D was effective at low concentrations of 0.03% and 0.06%. The crop yield remained similar for all the tested concentrations and formulations of 2,4-D loaded NLCP and Estercide 800. This is the first report to directly show that, as an alternative to conventional methods, NLCP can be used under both laboratory and field conditions to successfully delivery an agrochemical.     

几种高分子有机肥原料对土壤生物学性质的影响

通过室内模拟培养的方式,研究不同用量(折合有机质含量0.05,0.10 g/kg)的甲壳素、腐殖酸钠和造纸黑液对土壤微生物数量和土壤酶活性的影响.结果表明:与不施加有机肥原料的处理相比,甲壳素能促进土壤脲酶、过氧化氢酶、蔗糖酶、中性磷酸酶活性,且高量较低量处理分别增加了13.32％,4.20％,9.63％,21.88％;腐殖酸钠能抑制土壤脲酶活性,促进另外3种酶的活性,且高量处理较低量处理分别增加了6.57％,21.04％,9.82％;黑液处理能显著抑制土壤脲酶和中性磷酸酶活性,而对土壤蔗糖酶活性影响不大,对于过氧化氢酶活性只有高量黑液处理出现显著抑制作用.各有机肥添加剂均能显著增加土壤微生物量碳、氮含量,效果以腐殖酸钠最佳,其次为甲壳素,造纸黑液最小;甲壳素和腐殖酸钠均能显著提高土壤放线菌数量,抑制土壤真菌数量,且作用效果强度均为腐殖酸钠高量＞甲壳素高量＞腐殖酸钠低量＞甲壳素低量,造纸黑液对土壤放线菌和真菌的作用刚好与其相反;甲壳素对土壤细菌数量无明显作用,腐殖酸钠出现显著促进作用,而造纸黑液处理在培养初期(5～25 d)出现显著抑制作用.     

用丰年虫卵壳制备甲壳素和壳聚糖

介绍了用丰年虫卵壳制备甲壳素及壳聚糖的方法及过程,通过傅立叶变换红外光谱仪的检测并与美国标准谱图库检索出的用蟹壳制备的壳聚糖光谱图对照,证实丰年虫卵壳制备的壳聚糖。     

几种霉菌产甲壳素脱乙酰酶活力比较及部分酶学性质

比较了几种霉菌(毛霉、根霉、曲霉和青霉)在对数生长末期和稳定期末期的胞内和胞外甲壳素脱乙酰酶的活力。研究结果表明:(1)各霉菌的胞内和胞外都具有甲壳素脱乙酰酶活力,而且胞外酶的活力普遍大于胞内酶的活力;(2)处于对数生长期末期的毛霉菌株产甲壳素脱乙酰酶活力最高,其胞外酶活力达到了97.2±4.2 U/g干菌丝体。酶学特性研究表明:该酶的最适温度为50℃,最适pH约为7.2,低温保存稳定性较差,每24小时酶活力下降30%以上。     

亚洲玉米螟幼虫膜结合海藻糖酶基因RNAi效应

海藻糖是昆虫的血糖,为昆虫提供能量;海藻糖酶催化海藻糖分解为葡萄糖,是几丁质生物合成的原料。围食膜（peritrophic membranes,PMs）是昆虫消化道特有结构,对昆虫消化食物、保护肠道表皮细胞具有重要作用;几丁质是PMs的重要组分。海藻糖酶（trehalase,Tre）和几丁质合成酶（chitin synthase,CHS）是几丁质合成途径的第1个和最后1个酶。本研究通过饲喂亚洲玉米螟（Orstrinia furnacalis,Asian corn borer,ACB）膜结合海藻糖酶（OfMT）基因特异的干扰dsRNA,研究RNAi对ACB幼虫中肠CHSB（OfCHSB）基因表达及幼虫发育的影响。发现处理48 h后,OfMT基因和OfCHSB基因表达量分别下降了52%和53%,幼虫发育迟缓。通过对处理及对照ACB幼虫中肠石蜡切片进行苏木精-伊红染色（hematoxylin-ethanol,HE染色）和几丁质标记,发现血腔内脂肪体组织减小、中肠围食膜组织中几丁质含量减少。推测OfMT基因有可能成为ACB的生物防治的靶标基因。