Identification and differentiation of soft rot and blackleg bacteria from potato using nested and multiplex PCR

Journal of Plant Diseases and Protection - The bacterial genera Pectobacterium, Dickeya and Enterobacter are plant pathogens that cause soft rot and blackleg of potato. In the present study, 25...     

Additive and interactive effects of functionally dissimilar soil organisms on a grassland plant community

The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF.In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms.     

Hybrid zones as a tool for identifying adaptive genetic variation in outbreeding forest trees: lessons from wild annual sunflowers (Helianthus spp.)

The identification and study of adaptively important genes in forest trees represents a formidable challenge because of their long generation spans. In annual or perennial herbs, formal genetic studies can be employed to identify the quantitative trait loci (QTLs) and/or candidate genes that underlie important traits, and the segregating populations can be transplanted into natural populations to measure the strength and direction of selection. However, the application of these methods to forest trees is difficult, because the creation of appropriate genetic material is extremely time-consuming in long-lived, woody plants, and lifetime fitness estimates are difficult or impossible to obtain. Although QTL mapping should in principle be feasible in wild intraspecific populations (as an alternative to artificial crosses), this approach is less likely to be successful in trees because LD (linkage disequilibrium) will decay quickly in large outbreeding plant populations. Within the present paper, we discuss a modified approach based on natural hybrid zones. We describe the use of wild annual sunflowers (Helianthus spp.) as a model for exploring the hybrid zone approach. Transplanted experimental hybrids allowed us to assess the adaptive value of individual chromosomal blocks in nature, and data on natural Helianthus hybrids suggest that similar approaches are possible in natural hybrid zones. Our results allowed us to test the role of hybridization in the origin of ecological divergence in wild sunflowers. In addition, they have practical implications for identifying adaptively important genes or QTLs in trees. This is exemplified by three temperate forest taxa, Populus (poplars, aspens, cottonwoods), Fraxinus (ash), and Quercus (oak). All three are diploid and important genomic tools are under development. Moreover, all three offer extensive hybrid zones whose likely age can be inferred from fossil data. Age data enables estimates of the size and frequency of chromosomal blocks in hybrids, thereby providing guidance in designing marker-based experiments. We predict that natural hybrid zones will be valuable tools for identifying the QTLs and/or candidate genes responsible for adaptive traits in forest trees.     

阿拉伯胶和香精油对香蕉及番木瓜贮藏过程中炭疽病及品质的控制效果

严格控制由刺盘孢属(Colletotrichum spp.)真菌引起的炭疽病对减少热带水果工业的经济损失十分重要。本文主要研究了阿拉伯胶(GA)(10%)、柠檬香草精油(LG)(0.05%)、肉桂精油(CM)(0.4%)及其复合组分在试验条件下对离体与活体香蕉和番木瓜炭疽病菌的抑制活性。结果表明,0.05%的LG和0.4%的CM对于引起香蕉和番木瓜炭疽病的两种病原菌Colletotrichum musae和Colletotrichum gloeosporioides分别具有抑制活性;单独GA处理并未表现出抑菌活性,但将0.05%LG、0.4%CM与10%GA混合处理则具有较大的抑菌活性;在各处理中,以PDA培养基中加入10%GA及0.4%CM的处理对C.musae和C.gloeosporioides这两种病原菌抑制活性最显著,对于两种病原菌菌丝生长抑制率分别为73.4%和70.0%,对孢子萌发抑制率分别为88%和85%。活体试验结果也表明,10%GA结合0.4%的CM处理具有最佳的作用效果,对C.musae和C.gloeosporioides的抑制方面表现出较强的增效作用,对人工接种的香蕉和番木瓜炭疽病导致的腐烂抑制率分别为80%和71%。品质评价的试验结果也表明,10%GA结合0.4%CM的涂膜处理具有良好效果,果实失重率、硬度、可溶性固形物和可滴定酸含量的变化均表明该处理可显著推迟果实的成熟。上述结果表明,10%阿拉伯胶结合0.4%肉桂精油处理可以作为控制诸如香蕉和番木瓜等常见热带水果采后炭疽病的生物杀菌剂。     

Does Age Matter? The Influence of Age on Response Rates in a Mixed-Mode Survey

The appeal of cost savings and faster results has fish and wildlife management agencies considering the use of Internet surveys instead of traditional mail surveys to collect information from their constituents. Internet surveys, however, may suffer from differential age-related response rates, potentially producing biased results if certain age groups respond to Internet surveys differently than they do to mail surveys. We examined this concern using data from a mixed-mode angler survey conducted in South Dakota following the 2011 fishing season. Results indicated that young anglers (16–18) had the lowest return rates and senior anglers (65+) had the highest, regardless of survey mode. Despite this consistency in response rates, we note two concerns: (a) lower Internet response rates and (b) different age groups represented by the Internet and mail survey samples differed dramatically. Findings indicate that constituent groups may be represented differently with the use of various survey modes.     

Genetic diversity and population structure assessed through simple sequence repeat markers in Saccharum spp. hybrids from Pakistan and Sri Lanka

Genetic Resources and Crop Evolution - The Saccharum species members are extremely complex allopolyploids. In this study, sixty Saccharum spp. hybrids were analyzed using simple sequence repeat...     

Genotypic variability and phenotypic plasticity of cavitation resistance in Fagus sylvatica L. across Europe

Xylem cavitation resistance is a key physiological trait correlated with species tolerance to extreme drought stresses. Little is known about the genetic variability and phenotypic plasticity of this trait in natural tree populations. Here we measured the cavitation resistance of 17 Fagus sylvatica populations representative of the full range of the species in Europe. The trees were grown in three field trials under contrasting climatic conditions. Our findings suggest that the genotypic variability of cavitation resistance is high between genotypes of a given population. By contrast, no significant differences were found for this trait across populations, the mean population cavitation resistance being remarkably constant in each trial. We found a significant site effect and a significant site?×?population interaction, suggesting that cavitation resistance has a high phenotypic plasticity and that this plasticity is under genetic control. The implications of our findings for beech forest management in a context of climate change are discussed.