柑桔溃疡病菌存活期的研究

本文对鄂东南地区生态条件下柑桔溃疡病菌在不同场所的存活期进行了研究 ,并对其能否作为侵染源进行了评价。证实在病株病斑内的病菌存活时间可达一年以上 ,是此病发生最主要的侵染源。病菌在田间条件下的土壤、落叶、落果、果皮及自然水中的存活期均相当有限 ;其中以冬季病落叶中的病菌存活期最长 ,也不超过 3个月 ;故年前存在于这些场所的病菌均不能成为第 2年的初侵染源     

SSR-based genetic linkage analysis of resistance to crown rust (Puccinia coronata f. sp. lolii) in perennial ryegrass (Lolium perenne)

Crown rust (caused by Puccinia coronata f. sp. lolii) is a serious foliar disease of the pasture and turfgrass perennial ryegrass (Lolium perenne). Previous genetic studies have detected both qualitative and quantitative resistance mechanisms, and interpretation of the genetic system is complicated by variation within the sexually reproducing pathogen. Resistant and susceptible parental genotypes of ryegrass were identified using a composite urediniospore population collected from three geographically distinct locations. A two-way pseudo-testcross mapping population was obtained as the F₁ progeny of the pair-cross between ryegrass parental genotypes Vedette₆ and Victorian₉. Both parents showed intermediate resistance against a pathogen population collected in a single geographical zone (Hamilton, Victoria), but in the F₁ population, significant variation for a range of resistance-associated characters was detected. Statistical analysis of phenotypic data suggested a major gene effect, hence bulked segregant analysis with map-assigned simple sequence repeat (SSR) markers was used to scan the genome. A marker showing strong association with resistance was assigned to linkage group (LG) 2 of perennial ryegrass. Analysis of 11 LG2 SSR markers defined an interval between loci xlpssrh03f03 and xlpssrk02e02 as containing the gene or genes (LpPc1) conferring crown rust resistance. Resistance gene determinants were inherited from both parents, with up to 80% of the total phenotypic variation explained by markers segregating from Vedette₆ and up to 26% of the variation explained by markers segregating from Victorian₉. The two contributions together resulted in an additive increase in effect, with fully resistant individuals requiring determinants from both parents. A conserved syntenic relationship was observed with linkage group B of Avena strigosa, which is the location of a cluster of resistance genes to the oat form of crown rust. The implications of this study for marker-assisted selection of disease resistance in perennial ryegrass are discussed.     

甘肃陇南小麦不同品种类型抗条锈性变化特点分析

 1973~2002年的30年间,在我国小麦条锈病常发易变区的陇南,对小麦主要生产品种的抗条锈性变化动态进行了系统的观察,选择具垂直抗性、慢条锈性、高温抗性和持久抗性等不同类型的7个品种的观测数据进行了分析,认为里勃留拉和N.斯特拉姆潘列长期保持了稳定的抗锈性。里勃留拉的抗性可能由多对微效基因控制,N.斯特拉姆潘列的抗性可能由主效基因控制,兰天12号所具有的慢锈性和兰天1号的高温抗性以及抗条锈基因的合理布局对延长品种抗性也有一定作用。     

云南省稻瘟病,小麦锈病预测专家系统

基于稻瘟病、小麦锈病预测领域专家知识,以及借助模式识别势函数法实现的自学习、自提取的知识,采用正向和反向精确推理控制策略,首次建立云南省水稻穗瘟病、小麦条锈病预测专家系统,1994～1995年预测结果与实际情况基本一致。系统创造性地采用全屏幕编辑树图的知识输入法和森林表示技术对知识库进行管理,便于知识库的扩充和维护。推理结果、推理路径及知识查询以彩色图形方式显示,对于学习领域专家的实践经验具有独特优点。     

牛奶子锈病及其重寄生菌

2002年在四川省宝兴县蜂桶寨国家自然保护区和天全县喇叭河自然保护区牛奶子上发现了牛奶子锈病,经鉴定,该锈病为牛奶子春孢锈菌Aecidiumelaeagni-umbellatae Diet.其病株率100%、病叶率26%,叶片枯斑、脱落和削弱树势.在牛奶子锈病菌上采集到自然重寄生菌,经鉴定为Tuberculina sp.,该重寄生菌为国内外首次发现.重寄生菌寄生于牛奶子锈菌春孢子器出口处,阻碍春孢子的释放,具有潜在的生防应用价值.笔者对牛奶子锈病的症状特点、病原形态特征及牛奶子锈病菌的重寄生现象与重寄生菌的形态特征等进行了研究.     

基于GIS的中国小麦条锈病菌越夏区气候区划

 基于多年的气象数据(1980~2001年),首次从制约小麦条锈病菌越夏的温度因子入手,结合寄主小麦因素,利用地理信息系统(Geographical Information System,GIS),对我国小麦条锈病菌越夏区进行较详细的气候区划。本研究从温度条件上明确了全国适合小麦条锈病菌越夏的范围。研究表明,在我国小麦种植区适合小麦条锈病菌越夏的范围很广。其中甘肃、四川、云南、陕西境内适合越夏的地区是连成一片的,甘肃东部除了西边的几个县外其它地方7、8月份最高一旬均温在20~23℃,条锈病菌越夏困难;西藏、青海境内的小麦种植区几乎都适合小麦条锈病菌越夏;贵州境内适合越夏的地区可能和云南越夏区是一个整体。云南适合越夏的地区甚广,且地形复杂,需要进一步调查研究。     

以Taichung29为背景的小麦抗条锈病近等基因系转育进展

自1988年起,系统开展了以Taichung29为背景的小麦抗条锈病近等基因系转育及其基础性研究。采用回交法和系谱法相结合的转育方法,以春性品种Taichung29为轮回亲本作母本,分别与25个抗性供体即中国小麦条锈病菌鉴别寄主和国际上重要的抗条锈基因载体品种杂交、回交和自交。通过基因推导分析、单体分析和SSR标记技术检测目的基因,选育抗条锈近等基因系,现已获得重要进展,成功选育出8个以Taichung29为背景的抗条锈病单基因近等基因系,即Taichung29*6／Yr1、Taichung29*6／Yr2、Taichung29*6／Yr5、Taichung29*6／Yr7、Taichung29*6/Yr9、Taichung29*6／Yr10、Taichung29*6/YrSpP、Taichung29*6/YrKy2。另有9个组合转育获得343个抗性稳定株系,正检测其目的基因,3个组合转至BC₆F₃,自交纯合筛选抗性稳定株系,5个组合转至BC₅,继续回交转育。     

云南省小麦条锈病流行体系的研究现状

对云南省小麦条锈病的发生危害、流行特点、条锈菌越夏规律、品种及小种变异、环境因素等流行体系作 了较为详细的叙述,并针对各个环节提出综合防治策略。     

Combining competition from Lolium perenne and an insect–fungus combination to control Rumex obtusifolius seedlings

Although adult Rumex obtusifolius are problematic weeds, their seedlings are poor competitors against Lolium perenne, particularly in established swards. We investigated the possibility of using this weakness to augment control of R. obtusifolius seedlings with combinations of Gastrophysa viridula (Coleoptera: Chrysomelidae) and the rust fungus Uromyces rumicis. Rumex obtusifolius seedlings were grown in competition with L. perenne sown at different rates and times after R. obtusifolius: they competed successfully with L. perenne when sown 21 days before the grass. Sowing both species at the same time resulted in a dominant grass sward, with R. obtusifolius becoming dominant when sown 42 days prior to L. perenne. Grass sowing rate had no effect on R. obtusifolius growth or biomass. A second experiment investigated how competition from L. perenne sown 21 days after R. obtusifolius combined with damage from G. viridula and/or U. rumicis (applied at either the 3–4‐ or 10–13‐leaf stage, or at both stages) affected the growth and final biomass of R. obtusifolius. Beetle grazing at the latter leaf stage was the only treatment that reduced R. obtusifolius biomass, although rust infection at the earlier application led to an increase in shoot and root weight. The results are discussed in terms of the potential for use of these agents in the field.     

Growth- and leaf-temperature effects on photosynthesis of sweet orange seedlings infected with Xylella fastidiosa

The effects of growth and leaf temperature on photosynthesis were evaluated in sweet orange seedlings ( Citrus sinensis cv. Pera) infected with Xylella fastidiosa (the bacterium that causes citrus variegated chlorosis, CVC). Measurements of leaf gas exchange and chlorophyll  a fluorescence were taken at leaf temperatures of 25, 30, 35 and 40°C in healthy and infected (without visible symptoms) seedlings submitted to two temperature regimes (25/20 or 35/20°C, day/night), not simultaneously. The CO₂ assimilation rates ( A ) and stomatal conductance ( g _s) were higher in healthy plants in both temperature regimes. Values for A and g _s of infected and healthy plants were higher in the 35/20°C regime, decreasing with leaf temperature increase. In addition, differences between healthy and infected plants were higher at 35/20°C, while no differences in chlorophyll  a fluorescence parameters were observed except for potential quantum efficiency of photosystem II, which was higher in infected plants. Low A values in infected plants were caused by low g _s and probably by biochemical damage to photosynthesis. The high alternative electron sink of infected plants was another effect of reduced A . Both high growth and high leaf temperatures increased differences in A between healthy and infected plants. Therefore this feature may be partially responsible for lower growth and/or productivity of CVC-affected plants in regions with high air temperature.