Pesticidal compounds from higher plants

Higher plants offer an excellent source of biologically active natural products. Over the centuries numerous plants have been exploited as sources of insecticides, but nowadays traditional botanical insecticides play only a minor role in world agriculture. Nevertheless, plant natural products still have enormous potential to inspire and influence modern agrochemical research. Few plant natural products will ever reach the market as products per se, but others will provide lead structures for programmes of synthetic chemistry and hopefully follow the success story of the synthetic pyrethroids. Structurally complex compounds, which are not amenable to synthetic chemistry programmes, may also have a role to play by validating new modes of action for pesticides. Examples are presented of compounds exhibiting insecticidal, fungicidal and herbicidal effects. Consideration is also given to the development of screening programmes to detect new compounds with interesting biological properties. Careful experimental design and thorough recording of procedures and data are crucial to success. Badly designed programmes afford only weakly active compounds or show effects which cannot be reproduced at a later date. Natural product chemistry, whether based on higher plants, micro-organisms or other sources, is a very difficult science, but there is little doubt that dedicated research will eventually be rewarded with exciting new lead structures for industrial application.     

Effect of fungal pathogens on digestibility and chemical composition of Italian ryegrass (Lolium multiflorum) and tall fescue (Festuca arundinacea)

Slight infection by Drechslera siccans or Rhynchosporium spp. significantly reduced in vitro dry matter digestibility, water-soluble carbohydrate and the total amino acid content of Italian ryegrass (Lolium multiflorum) foliage. The concentration of all 15 amino acids detected was reduced, with arginine reduced significantly more than the others. Total nitrogen was either increased or not changed, and the amino acid composition was not altered. Limited work with Drechslera festucae on tall fescue (Festuca arundinacea) gave similar results. Small samples of healthy and diseased grass leaves at three different physiological stages were used to detect these changes.
Limited leaf spotting by D. siccans caused metabolic changes of the same magnitude as extensive leaf blotching by Rhynchosporium. Impaired photosynthesis and growth of the fungi within the leaf tissues are possible causes of these changes. Decreased digestibility and increased dry matter content of diseased grass foliage could be of great practical importance.     

A survey of ryegrass swards for the presence of fungal pathogens in relation to management

Surveys of perennial and Italian ryegrass swards (Lolium perenne L. and L. multiflorum Lam.) at regular intervals in 1977 and 1978 in Berkshire, Wales and Devon confirmed that leaf infection by Drechslera spp. was the most frequently occurring foliar fungal disease. Rhynchosporium spp. and Puccinia coronata Corda were also recorded but in contrast to Drechslera spp., which caused damage throughout the year, attacks by these two fungi were only sporadic.
The incidence of Drechslera was greater in 1977 than in 1978 and was greater in Berkshire where most fields were infected in both years than in Wales and Devon. Both perennial and Italian ryegrasses were infected. The number of leaves damaged increased with leaf age. Damage was greater on fields managed for conservation than those which were grazed. Infection increased from February onwards and was greatest in autumn. It is concluded that Drechslera might be controlled by removing infected herbage in autumn by cutting.
Rhynchosporium spp. were prevalent only in Berkshire and more Italian ryegrass fields ( ca , 50%) were infected than perennial ryegrass fields ( ca , 10%). Infection was confined to the period March to May. This pathogen caused more leaf area damage than Drechslera .
Puccinia coronata occurred only once in Devon and Wales. In Berkshire incidence was confined to 1978 and was common from September to November, when 60–70% of both Italian and perennial ryegrass fields were infected. Some difference between perennial ryegrass cultivars was observed.     

Major bacterial contribution to marine dissolved organic nitrogen

Next to N2 gas, the largest pool of reduced nitrogen in the ocean resides in the enormous reservoir of dissolved organic nitrogen (DON). The chemical identity of most of this material, and the mechanisms by which it is cycled, remain fundamental questions in contemporary oceanography. Amino acid enantiomeric ratios in the high molecular weight fraction of DON from surface and deep water in three ocean basins show substantial enrichment in D enantiomers of four amino acids. The magnitude and pattern of these D/L enrichments indicate that peptidoglycan remnants derived from bacterial cell walls constitute a major source of DON throughout the sea. These observations suggest that structural properties of specific bacterial biopolymers, and the mechanisms for their accumulation, are among the central controls on long-term cycling of dissolved organic nitrogen in the sea.     

大豆新品种陇黄2号选育报告

陇黄2号是由甘肃省农业科学院旱地农业研究所和农业生物技术国家重点实验室(香港中文大学)于2008年从山西省农业科学院经济作物研究所引进的以晋豆23为母本、鲁豆4号为父本常规杂交的F3代群体中,采用系谱法选育而成的大豆新品种。2013 — 2014年参加甘肃省大豆品种(系)区域试验,2 a 10点(次)平均折合产量为2 572.28 kg/hm2,比对照品种陇豆2号平均增产9.17%。2015 年参加甘肃省大豆品种(系)生产试验,平均折合产量2 501.70 kg/hm2,比对照品种陇豆2号增产6.09%。陇黄2号田间表现高抗花叶病毒病和大豆黑斑病。籽粒含粗蛋白(干基)385.3 g/kg、粗脂肪(干基)204.2 g/kg,品质优良。陇黄2号适用于机械化作业的间套作带状复合种植。该品种适宜在甘肃省河西灌区、中部沿黄灌区、陇东旱塬区及生态条件相近地区种植。