Fungal response from oat (Avena sativa) plants and surface residue in relation to soil aggregation and organic carbon

Abstract

The influence of soil fungi on soil organic carbon (OC) from surface residue was tested in outdoor plots in southern Ontario, Canada, 2004. Fungal hyphal length, soil aggregation, OC and light and heavy fractions of organic matter were compared with factors of plant growth (with or without oat [Avena sativa]) and surface residue (no residue, oat straw (low C:N) or corn (Zea mays) stalks (high C:N)) in a factorial arrangement. Significant increases were observed in soil OC from the oat plants, and from corn stalks compared to straw residue, in the growing season with very moist, high OC, sandy soil. In treatments with corn stalk residue, fungal hyphal length was increased with interaction from the oat plants and residue and was positively correlated with the heavy fraction organic matter along with soil OC. Fungal hyphae, plant roots and high C:N residue were all factors in soil OC increases.     

转基因生物技术育种: 机遇还是挑战？

转基因生物技术是一项全新的育种技术, 也是当前国际上进展最快、竞争最激烈的研究领域之一。自20世纪90年代生物技术育种诞生以来, 转基因作物的商品化应用及由此引发的一系列问题就引起公众的广泛关注。该文就世界上转基因生物技术育种及产业化现状、几个主要转基因作物安全性案例及最终结果, 以及如何科学推进我国转基因作物的产业化等提出了自己的思考, 以期帮助公众科学地理解和面对转基因生物技术所带来的育种技术上的革命。     

Crop presence,but not genetic diversity,impacts on the rare arable plant Valerianella rimosa

Background: Intensive farming affects farmland biodiversity, and some arable plants in particular. Increasing crop genetic diversity can increase crop productivity or resilience and could also benefit rare arable plants.

Aims: We examined whether barley presence, sowing density and genetic diversity impacted the rare plant Valerianella rimosa and explored possible underlying mechanisms.

Methods: In a field study near Dundee, Scotland, we sowed plots of five single barley genotypes, and all five genotypes combined, at three densities; we also had barley-free plots. Valerianella seeds were sown into half of all plots. Measured responses included early-season cover and harvest biomass of barley and common weeds, abiotic parameters (soil moisture, light) and establishment, biomass and seed production by V. rimosa.

Results: Barley presence promoted V. rimosa establishment early in the growing season, but without barley density or genetic diversity effects. By harvest, the impact of barley presence on V. rimosa abundance was lost; there were no effects on Valerianella seed production. Barley negatively impacted common weeds, but V. rimosa did not benefit from any indirect facilitation by barley, being bigger without barley.

Conclusions: Early beneficial effects of barley on V. rimosa abundance appear offset by late-season competition. However, limited impacts of barley on V. rimosa reproductive success, and negative impacts on common weeds, indicate crops might play a role in conservation management of rare arable plants by creating space in the weed community.     

Effects of landscape and management on ground‐dwelling insect assemblages of farmland in Jeju Island,Korea

Granite‐derived soils are widespread in the farmland of Korea in general. In contrast, Jeju Island has mainly volcanic ash soils. Soils and weather condition in Jeju Island created a unique agricultural system. We identified the features of ground‐dwelling insects in farmlands of Jeju Island. This study was conducted in four areas (Samdal‐ri and Susan‐ri in Seogwipo city, and Dongmyeong‐ri and Suwon‐ri in Jeju city) in Jeju Island, Korea. Field surveys were carried out twice in summer (June) and autumn (September) in 2013. Ground‐dwelling insects were sampled quantitatively by using pitfall traps. As a result, in total 3322 individuals, 137 species, 48 families and 8 orders were investigated in farmlands of Jeju Island. Especially, members of Coleoptera and Hymenoptera accounted for a large proportion of ground‐dwelling insect communities. The numbers of species and individuals for major taxonomic groups showed significant regional and seasonal differences. This study implied that the seasonal and regional differences of ground‐dwelling insect communities were affected by surrounding land use patterns, life history patterns of each taxonomic group and farmland management.     

60份豇豆品种资源的耐盐能力评判

运用《豇豆基因型耐盐能力技术鉴定方法》(专利号ZL200810048423.5),对60份豇豆品种的耐盐能力进行了鉴定评判。试验材料经苗期培养和盐胁迫处理后,分别测定处理组和对照组的植株叶片叶绿素含量、过氧化氢酶活性、可溶性蛋白质含量、细胞伤害率以及单株鲜重等指标并计算其SRI值,运用专利技术的预测模型,得出各品种耐盐综合评价值(D值)。依据评判标准,紫魁、玉农农家宝特优、抗病芦花等11个品种的综合评价值D≥0.68,归为盐耐受型品种;之豇14、白皮、矮紫尾青等8个品种的综合评价值D≤0.48,归为盐敏感型品种;其余41个品种的D值介于0.48~0.68之间,属于中度耐盐品种。本研究结果扩大了豇豆种质耐盐能力鉴定评判份数,丰富了耐盐种质鉴定信息。     

15份多花黑麦草优良引进种质的表型变异分析

多花黑麦草(Lolium multiflorum Lam.)是世界栽培牧草中的优良禾本科牧草。为更好地利用多花黑麦草种质资源,本研究对引自国外的15份多花黑麦草种质的15个形态性状和农艺性状进行了变异系数、相关性分析、主成分分析和聚类分析。结果表明:15份材料间存在较大变异,除单株干重外,其余性状在供试材料间均表现出显著性差异,变异系数范围为10.28%~39.15%,变异系数平均值为19.49%,从小到大依次为小穗数小穗长株高分蘖数千粒重花序长倒二叶长小花数茎粗第一节间长倒二叶宽旗叶宽旗叶长单株干重单株鲜重。主成分结果表明,前5个主成分累积贡献率达到84.51%,第1主成分以株高为主要特征;第2主成分以旗叶和倒二叶长、宽为主要特征;第3主成分以花序长和小花数为主要特征;第4主成分以千粒重为主要特征;第5主成分以产草量为主要特征。15份种质材料经基于欧氏距离的UPGMA聚类分析被划分为3大类,类别间存在较显著的差异,其中第2类因其植株高大、叶片宽大的特点,具备选育高产种质的潜力。     

平榛种质资源坚果农艺性状鉴定与评价研究

平榛是我国重要的榛属植物资源,为鉴定、评价和保护平榛种质资源,提高其利用效率,采用主成分分析和聚类分析方法对99份平榛种质资源坚果的主要农艺性状进行了鉴定和综合评价。结果表明:平榛种质资源坚果的24个性状具有丰富的遗传多样性;10个数量性状的主成分分析确定了4类影响因子,反映了育种选择方向及潜力;基于各种质间形态性状的遗传差异,将99份平榛种质划分为5大类群,第Ⅰ类群可作为选育果面光滑品种的育种和候选亲本材料,第Ⅱ类群可作为选育大粒型、适宜机械化加工的育种和候选亲本材料,第Ⅲ类群具有作为市场产品的潜力,第Ⅳ类群可作为选育圆形、果面无条纹的育种和候选亲本材料,第Ⅴ类群可作为选育高丰产性品种的育种和候选亲本材料。上述研究为平榛种质资源的评价、保护和选优工作提供了基础数据。     

Balancing competition for resources with multiple pest regulation in diversified agroecosystems: a process‐based approach to reconcile diversification and productivity

Agroecosystem plant diversification can enhance pest biological regulation and is a promising alternative to pesticide application. However, the costs of competition for resources between plants may exceed the benefits gained by pest regulation. To disentangle the interactions between pest regulation and competition, we developed a generic process‐based approach that accounts for the effects of an associated plant and leaf and root pests on biomass production. We considered three crop–plant associations that differ in competition profiles, and we simulated biomass production under wide ranges of both pest regulation rates and resources’ availability. We analyzed outputs to quantify the pest regulation service level that would be required to attain monoculture yield and other production goals. Results showed that pest regulation requirements were highly dependent on the profile of resource interception of the associated plant and on resources’ availability. Pest regulation and the magnitude of competition between plants interacted in determining the balance between nitrogen and radiation uptake by the crop. Our findings suggest that productivity of diversified agroecosystems relative to monoculture should be optimized by assembling plants whose characteristics balance crops’ resource acquisition. The theoretical insights from our study draw generic rules for vegetation assemblage to optimize trade‐offs between pest regulation and production. Our findings and approach may have implications in understanding, theorizing and implementing agroecosystem diversification. By its generic and adaptable structure, our approach should be useful for studying the effects of diversification in many agroecosystems.     

The growth characteristics and yield potential of rice (Oryza sativa) under non‐flooded irrigation in arid region

The objectives of this field experiment were to study the growth characteristics and yield potential of rice plants under non‐flooded irrigation in arid area. Non‐flooded treatments included drip irrigation with plastic mulching treatments (DIs), furrow irrigation with plastic mulching treatment (FIM) and furrow irrigation with non‐mulching treatment (FIN). Conventional flooded cultivation (F) was check treatment (CK). The four drip irrigation treatments differed in the amount of water applied before and after panicle initiation. Root length density, leaf dry weight, shoot dry weight and root activity were generally higher in the non‐flood‐irrigated treatments (especially the drip‐irrigated treatments) than in the flood‐irrigated treatment at mid‐tillering. However, the growth and development of rice plants were limited after jointing in the non‐flooded irrigation treatments. Increasing the root/shoot ratio and root length density in the 20–40 cm depth and decreasing specific root length at 0–20 cm soil layer were important mechanisms for helping the rice plants to adapt to the non‐flooded environmental stresses. Finally, the grain yield in the non‐flooded irrigation treatments was lower than that in the F treatment. These low yields were mainly attributed to the low root length density at 0–20 cm depth and root activity. Generally speaking, the restricted degrees in the DIs were smaller than that in the FIM and FIN treatments. Among the DIs, both the highest grain yield (8223–8900 kg ha^?1) and the highest water use efficiency (WUE) (0.63) were observed when the soil water content was kept at ?30 kPa before panicle initiation and at ?15 kPa after panicle initiation (referred to as the DI2 treatment). The yield in the DI2 treatment was not significantly different than that in the flood‐irrigated treatment. However, WUE was 2.5 times higher in the DI2 treatment than in the F treatment. These results suggest that drip irrigation technology can be considered as a better water‐saving cultivation of rice plants in arid region.     

Triticum monococcum lines with distinct metabolic phenotypes and phloem‐based partial resistance to the bird cherry–oat aphid Rhopalosiphum padi

Crop protection is an integral part of establishing food security, by protecting the yield potential of crops. Cereal aphids cause yield losses by direct damage and transmission of viruses. Some wild relatives of wheat show resistance to aphids but the mechanisms remain unresolved. In order to elucidate the location of the partial resistance to the bird cherry–oat aphid, Rhopalosiphum padi, in diploid wheat lines of Triticum monococcum, we conducted aphid performance studies using developmental bioassays and electrical penetration graphs, as well as metabolic profiling of partially resistant and susceptible lines. This demonstrated that the partial resistance is related to a delayed effect on the reproduction and development of R. padi. The observed partial resistance is phloem based and is shown by an increase in number of probes before the first phloem ingestion, a higher number and duration of salivation events without subsequent phloem feeding and a shorter time spent phloem feeding on plants with reduced susceptibility. Clear metabolic phenotypes separate partially resistant and susceptible lines, with the former having lower levels of the majority of primary metabolites, including total carbohydrates. A number of compounds were identified as being at different levels in the susceptible and partially resistant lines, with asparagine, octopamine and glycine betaine elevated in less susceptible lines without aphid infestation. In addition, two of those, asparagine and octopamine, as well as threonine, glutamine, succinate, trehalose, glycerol, guanosine and choline increased in response to infestation, accumulating in plant tissue localised close to aphid feeding after 24 h. There was no clear evidence of systemic plant response to aphid infestation.