Histological and inheritance studies of partial resistance in the Brassica napus–Albugo candida host-pathogen interaction

Traditional and doubled haploid (DH) genotypes of oilseed Brassica spp. resistant, partially resistant, moderately susceptible, and susceptible to Albugo candida were compared for phenotypic development of host‐pathogen interaction and histology of host‐pathogen interaction. The partially resistant genotype showed pinhead‐size pustules, mainly on the upper surface of cotyledonary leaves. Relatively less mycelium was observed in the partially resistant genotype compared with the susceptible genotype. In resistant B. napus genotypes, there was neither pustule development nor any mycelial growth. In the moderately susceptible genotype, the pustules were similar to those in the partially resistant genotype in being of pinhead‐size and occasionally coalescing. However, ample mycelial growth in the mesophyll tissue in the moderately susceptible genotype was similar to that in the susceptible control B. rapa cv. ‘Torch’. The susceptible genotype B. rapa cv. ‘Torch’ also showed large coalescing pustules. In the non‐host B. juncea cv. ‘Commercial Brown’, no pustules were formed although some mycelial growth was observed beneath the epidermal cell layer and in the mesophyll cell layer of the cotyledonary leaf tissue. For inheritance studies, two partially resistant B. napus genotypes were crossed with a resistant B. napus genotype. Various generations viz., F1, F1(reciprocal), F₂, and DHs produced from the crosses were inoculated with a zoospore suspension of race 7v of A. candida. The partially resistant phenotype appeared to be controlled by a single recessive gene designated as wpr with variable expression. The simple inheritance of partial resistance has implications for disease resistance breeding against white rust, as this type of resistance can be easily incorporated into elite breeding lines through conventional and DH breeding methods.     

Inter- and intraspecific feeding selectivity of Folsomia candida (Willem) (Collembola,Isotomidae) on fungi

Summary Selective grazing of fungi by soil microarthropods may affect decomposition rates of litter materials and the structure of microarthropod and fungal communities. We developed laboratory methods to assay feeding selectivity and investigated the preferences of the collembolan Folsomia candida on three fungi: Acremonium sp., Paecilomyces varioti, and Penicillium citrinum. F. candida showed stronger preference for Acremonium sp. than for P. varioti and P. citrinum. Oviposition site selection followed the same pattern. Actively metabolizing hyphae of Acremonium sp. and P. varioti were preferred over senescent hyphae, while spores of P. citrinum were preferred over active hyphae. If microarthropod preference for active hyphae is extensive, microarthropod regulation of decomposition could be more important than their biomass indicates. Furthermore, as the P. citrinum results indicate, mechanisms of microbial dissemination may include selective grazing.Contribution in part to International Symposium on Faunal Influences on Soil Structure, Edmonton, Alberta, Canada (11–13 June 1984), organized by W. B. McGill; and the annual meeting of the Ecological Society of America, Minneapolis, Minnesota (17–21 June 1985)     

杨柳毒蛾幼虫发生期,发生量预测预报的研究

杨毒蛾(Leucoma candida S.)、柳毒蛾(Leuccma salicis)是杨树的主要食叶害虫。我们从1984—1987年对该虫的发生期、发生量预测预报进行了初步研究。杨、柳毒蛾幼虫的发生期是在寄主杨树,展叶后的第10 d或日平均温度达到13℃以上时,开始上树取食。该虫的发生量预报可采用越冬基数调查和回归预报式两种方法,其种群数量动态预报模型所筛选出的预报因子与虫情的复相关系数都很高,模型的显著性水平也很高。经过检验及初步预报实践,效果较好。     

钙对葱兰花粉萌发和花粉管生长的影响

通过5种不同Ca2 浓度的培养基,研究了Ca2 对葱兰花粉萌发和花粉管生长的影响。结果表明,适当浓度的Ca2 能促进花粉萌发和花粉管的伸长,但对花粉萌发率的影响不显著。当培养基中的Ca2 浓度达到1.0×10-3mo·lL-1时,可抑制花粉的萌发和花粉管生长,并且与低浓度的Ca2 相比,对花粉管的破损显著。     

桉树林内间种山毛豆试验初期生长效应

为改善桉树林地地力,开展了桉树间种山毛豆(Tephrosia candida)作绿肥试验。对在桉树林内间种山毛豆3种不同密度(10600、12500、16400株/hm^2)的植株产量、养分含量及桉树林分树高、胸径生长量进行了分析。结果表明,不同密度间山毛豆单位面积植株产量无显著差异,但以12500株/hm^2处理的产量最高,比产量最低的10600株/hm^2处理高137.3%;1年生的山毛豆植株贮藏的氮、磷、钾养分含量分别是34.9、2.0、11.3kg/hm^2;桉树林2.5年生时,无论是否间种山毛豆或不同山毛豆密度处理的桉树林分树高、胸径生长量均无显著差异。     

真菌性乳房炎病原菌的分离鉴定与流行病学调查

本研究对山东省济南、泰安、临沂三地区共386份乳房炎奶样进行了真菌的分离鉴定与流行情况调查。经鉴定其病原为白色念珠菌。调查结果表明真菌性乳房炎在不同地区均有发生。个体养殖户奶牛奶样的真菌阳性率（19．3％）明显高于规模化养殖场（7．62％）；临床型乳房炎的真菌阳性率（13．11％）高于隐型乳房炎（3．75％）。本文的调查结果为更好地了解真菌在我国奶牛业的感染情况和采取有效的防治措施提供了一定的依据。     

干旱胁迫下3树种苗木叶片相对含水量、质膜相对透性和脯氨酸含量的变化

以金沙江干热河谷主要造林树种坡柳、银合欢和山毛豆的苗木为实验材料,通过盆栽苗自然干旱胁迫,同时以浇水处理为对照,探讨了干旱胁迫下3树种苗木叶片的相对含水量、质膜透性以及脯氨酸含量的变化情况。结果表明,干旱胁迫后,3树种苗木叶片的相对含水量、质膜相对透性以及脯氨酸含量都发生了变化,只是变化的幅度和进程不同。经三项生理指标的综合分析并结合3树种的自然表现,得出坡柳具有较强的抗旱能力,其次为银合欢,最后是山毛豆。     

核桃叶提取物对杨毒蛾生物活性的研究

核桃叶提取物对杨毒蛾具有较强的胃毒作用,不同浓度处理对死亡率的影响达极显著水平.致死中时(LT50)以稀释5倍液处理最短,杀虫效果与原液无显著差异.研究结果还表明,核桃叶提取物对杨毒蛾无拒食和触杀作用,但有一定的抑制发育的作用.     

Attraction to prey and prey-associated odours by the predatory mite Hypoaspis aculeifer in a soil experimental system

In terms of food searching and trophic interactions among soil organisms volatile signalling plays a crucial role. Still, volatile-based foraging decisions are poorly understood, especially as the dispersal and perception of cues is more restricted within the soil pore space than in simple laboratory approaches where volatiles disperse freely in the air. Focusing on the tritrophic interaction between the soil fungus Trichoderma viride, the fungivorous collembolan Folsomia candida and the predatory mite Hypoaspis aculeifer, we tested the effect of prey and prey-associated volatile signals on the food choice decision of the predatory mite in a laboratory experiment under soil conditions as well as the possible occurrence and relevance of grazing-induced indirect defence signals. The mites showed a clear preference for ungrazed and grazed fungal mycelium. However, we found no evidence of induced indirect defence as ungrazed mycelium was preferred to grazed fungus.