Possible involvement of the phloem sealing system in the acceptance of a plant as host by an aphid

Possible reasons for the rejection of some lines ofTriticum monococcum (Tm44 and Tm46) by the aphidSitobion avenae were explored. In allT. monococcum lines studied, whether unfavourable (non-host/resistant plant) or favourable (host/susceptible plant), the concentrations of hydroxamic acids, a family of aphid-resistance factors in cereals, were significantly lower than the levels in the favourable host-plantTriticum aestivum cv. Therefore, hydroxamic acids did not account for the host/non-host patterns observed. Phloem sap was collected by stylectomy from young seedlings of favourable and unfavourable plants. In non-aphid-resistant genotypes, the success in stylectomy, the proportion of amputated stylets resulting in long (>1 min) exudations, the average duration of exudation, and the final volume of sap exuded, were higher than in the aphid-resistant genotypes. It is concluded that aphid interference with the phloem sealing system of the plant is a likely mechanism of rejection ofT. monococcum lines Tm44 and Tm46 as hosts byS. avenae.     

亚洲栽培稻7种生态型的聚类分析

本文根据酯酶、过氧化物酶同工酶的酶带数、Ｒｆ，累积值，以及籽粒糊化温度级别，对亚洲栽培稻７个生态型的５６个品种进行了ＷｏｒｄＭｅｔｈｏｄ离差平方和聚类分析，结果表明：５６个品种可分为２类８群：Ｉ类中以Ａｍａｎ，Ｔｊｅｒｅ，Ｂｕｌｕ生态型品种为Ⅱ类中以Ｂｏｒｏ，Ｇｕｎｄｉｌ，Ａｕｓ生态型品种为主．Ａｍａｎ，Ｂｕｌｕ，Ｂｏｒｏ，Ｇｕｎｄｉｌ因遗传分化程度较低，分布相对集中，基本上形成了以各生态型品种为主导的群，Ａｕｓ，Ｔｊｅｒｅ，Ｕｐｌａｎｄ生态型品种几乎散布于各个群中．根据类群的划分及生态型在类群中所占的品种数，可以推测：同一类的Ａｍａｎ，Ｔｊｅｒｅ与Ｂｕｌｕ，Ａｕｓ，Ｂｏｒｏ和Ｇｕｎｄｉｌ间的亲缘关系相对接近．     

蓝莓果汁饮料原花青素的热稳定性及降解动力学模型

【目的】研究蓝莓果汁饮料中原花青素的热稳定性及降解动力学特征,为蓝莓果汁饮料贮藏条件的优化及保质期预测提供参考。【方法】观察不同pH蓝莓果汁饮料中原花青素含量在有氧与充氮气条件下以不同温度处理时的变化情况,判断反应级数,运用动力学方程建立蓝莓果汁饮料原花青素降解模型。【结果】有氧条件下,蓝莓果汁原花青素在pH 5.8、4.6、2.2时降解反应活化能分别为25.34、18.77、16.80 kJ/mol,半衰期为1.91~4.58 d;充氮气条件下,蓝莓果汁原花青素在pH 5.8、4.6、2.2时降解反应活化能分别为56.70、26.35、19.36 kJ/mol,半衰期为1.90~15.79 d。【结论】在有氧或充氮气条件下,随着温度的升高和pH的降低,蓝莓果汁饮料原花青素的稳定性下降,原花青素降解反应的活化能和半衰期呈明显下降趋势;充氮气处理可以提高原花青素的稳定性,降解反应均符合一级反应动力学模型。通过验证试验发现:所建立的蓝莓果汁饮料原花青素降解动力学模型与实测值拟合程度较好(决定系数R²≥60.25%)。     

黑莓果实发育成熟期木质素合成CAD酶及其基因表达

【目的】比较黑莓高硬度品种‘Arapaho’和低硬度品种‘Boysen’果实发育成熟期木质素合成肉桂醇脱氢酶(CAD)基因表达,及其与CAD酶活性及总木质素含量的关系。【方法】对不同发育时期的黑莓果肉,利用半定量RT-PCR分析18个RuCADs基因成员的表达,利用比色法测定CAD酶活性,利用滴定法测定总木质素含量。【结果】在黑莓的18个RuCAD基因成员中,有8个CADs基因成员在2个品种发育早、中期果肉中表达量较高; 其中RuCAD16仅在‘Boysen’的早、中期果肉中表达,而在‘Arapaho’中不表达。‘Arapaho’和‘Boysen’果肉CAD酶活性均在着色前即花后9 d和花后21 d时最高,着色后呈下降趋势。‘Arapaho’和‘Boysen’果肉木质素分别在花后24 d和花后27 d含量较高。【结论】‘Arapaho’和‘Boysen’果实着色后,RuCADs基因成员表达呈多样化,且硬度与RuCAD酶及木质素含量关系表现出一定差异; 而在果实发育后期,RuCADs基因表达量降低。CAD酶活性降低及木质素含量下降,与黑莓成熟果实硬度下降具一致性,推测木质素合成与成熟果实硬度形成具有相关性。     

生防菌株A-29的鉴定及其活性成分分析

生防菌株A-29分离自山东省科学院中试基地内的番茄根际土中。利用通用引物27f和1492r扩增A-29的基因组DNA获得1492bp的16SrDNA序列片段,登录号为EU430264,同源性与直丝紫链霉菌（Strep-tomyces viridocyaneus）YIM30997（AF513223）达98.9%。生理生化特性测定中,除吲哚反应和木糖利用2项不同外,其它指标A-29与S.viridocyaneus完全相同,故将菌株A-29鉴定为S.viridocyaneus。菌株A-29的无菌发酵滤液具有广谱抗性,在PDA平板上对供试的8种植物病原真菌均有不同程度的抑制作用,其中对黑斑链格孢的抑制效果最好,抑菌圈半径为7.0mm。分别利用二氯甲烷和乙酸乙酯浸提法提取发酵上清液中的活性成分,采用气相色谱-质谱联用仪对提取液进行定性分析,菌株A-29各提取液中可检测到的化学成分种类主要有：有机酸类、酯类、苯及其衍生物、烷烃、酮类、杂环化合物等,结合文献报道：上清乙酸乙酯提取液中可能的活性成分为：（S）-（＋）-2′,3′-Dideoxyribonolactone、2-Vinyl-9-[3-deoxy-.beta.-d-ribofuranosyl]hypoxan-thine;上清二氯甲烷提取液中可能的活性成分为：2-（Phenyl-piperidin-1-yl-methyl）-cyclohexanol、10-Methoxy-nb-.alpha.-Methylcorynantheol。     

木霉粉剂对黄瓜病害防效和生长发育的影响

采用木霉菌（Trichoderma asperellum）和木霉粉剂,通过平板对峙培养法,进行了木霉菌对黄瓜枯萎病菌的体外抑菌活性（ECS0）测定和棚室小区试验对黄瓜猝倒病和枯萎病防效及生长发育的调查。结果表明,木霉菌对黄瓜枯萎病菌（Fusarium oxysporum f. sp．cucttmarirtttm）的致死中浓度约为535个孢予mL^-1,可见木霉对黄瓜枯萎病菌具有很强的抑菌能力;木霉粉剂对黄瓜猝倒病的防治效果为54．4％,对黄瓜枯萎病的防治效果最高可达89．5％。同时木霉粉剂对黄瓜有促进提早开花和增产作用。图3,表4,参13。     

Development of DNA probes for cytotoxin and enterotoxin genes in enteric bacteria

Summary DNA probes to identify the genes encoding toxins in enteric bacteria have been developed. Use of these probes reduces the number of animals required for toxicity testing, as suspect bacteria can be directly tested for the presence of toxin. We have augmented the gene probes available by developing probes against theEscherichia coli enterotoxin LTII and shiga toxin fromShigella dysenteriae 1.The LTII gene fromE. coli 357900 was identified and characterised and a suitable internal probe was obtained. The LTII gene was found not to be common among enterobacteriae from various geographical locations. Isolates predominately of animal origin from Nigeria and Thailand hybridized with the probe.The shiga toxin gene was isolated fromS. dysenteriae 1 by a combination of in vivo and in vitro methods. An internal probe was identified and used against different serogroups ofShigella andE. coli isolated. The probe was found to hybridize withS. dysenteriae 1 isolates and also someS. flexneri andS. sonnei strains. Representatives were tested for toxin production and found to produce toxin at low levels.     

盐田刚毛藻的营养成分分析

应用生化技术对盐田刚毛藻的营养成分进行分析，结果表明盐田刚毛藻是一种优良饲料．     

茶藨生柱锈重寄生木霉分生孢子萌发的生物学特性

3株茶藨生柱锈菌(Cronartium ribicola J.C.Fischer)重寄生木霉(Trichoderma spp.)(TR1、TR2、TR3)的分生孢子在水琼脂、葡萄糖、PDA、改良Fries、华山松树皮浸汁和锈孢子培养基上均能萌发,TR1在各种培养基上的萌发率最高,萌发速度最快,而TR2和TR3在水琼脂和葡萄糖培养基上的萌发则较差;3个菌株孢子萌发的最适温度范围为20～30℃,其中TR1的萌发温度范围最广,在15～35℃内均能较好地萌发;3种孢子萌发的最适pH范围为4～5,相对湿度范围35%～100%(50%以上较易萌发);黑暗和交替黑暗能刺激TR1孢子萌发,连续光照则有利于TR2和TR3孢子的萌发.     

水分胁迫对楸树苗木光合特性的影响

应用PEG处理人工模拟干旱胁迫环境条件,采用完全随机试验设计,在人工气候室研究了8个品种(类型)楸树1年生扦插苗在4种不同水分胁迫(CK、4%、8%和12%)下的光合特性.结果表明:水分胁迫下各品种(类型)楸树的净光合速率、蒸腾速率、气孔导度、胞间CO2浓度、Fv/Fm和Fv'/Fm'均降低.周2、光叶、梓树和南阳的净光合速率下降由气孔导度引起,而楸树、圆长、‘豫1'和金丝则由非气孔导度因素即叶肉细胞光合能力下降引起.综合表明,南阳、光叶、周2和金丝抗旱性稍强,其余4品种稍差.