Insect growth regulating and antifeedant effects of neem extracts and azadirachtin on two aphid species of ornamental plants

Leaf disc choice test bioassay demonstrated that formulated neem seed extracts were highly deterrent and growth regulatory to rose aphid,Microsiphum rosae (L.) and Chrysanthemum aphid,Macrosiphoniella sanbornii (Gillete). Effective concentrations to produce 50% feeding deterrence was 0.80 and 0.84% respectively for 2nd instar nymphs irrespective of bioassay duration. The disruption of aphid feeding was related to the presence of azadirachtin concentration in the extract. The toxicity on contact from the leaf surface or via topical application due to azadirachtin was significantly different and topical treatment was at least 7 times more effective for both species. Thus growth regulatory effects of azadirachtin were influenced by the host plant and the stage of treatment. Field evaluation with formulated neem extracts revealed the effect to be more of growth regulatory nature thereby showing that azadirachtin is a physiological toxin for aphid species. Neem seed extracts reduced the population of aphid on respective host plants significantly, EC₅₀ values being 0.88 and 0.96% forM. rosae andM. sanbornii respectively.     

Insect growth regulating effects of neem extract and azadirachtin on aphids

Neem,Azadirachta indica (A. Juss.), seed oil (NSO) applied to leaf discs at a concentration of 1.0% resulted in 94% to 100% mortality of second instar nymphs of currant-lettuce aphid,Nasonovia ribis-nigri (Mosley), and green peach aphid,Myzus persicae (Sulzer), after nine days. The equivalent amount of pure azadirachtin (AZA) (≈40 ppm), the principle active ingredient of neem, was as effective as NSO. The survival of adult aphids was unaffected by NSO or AZA, but the survival of offspring from treated adultM. persicae andN. ribis-nigri was reduced significantly. The lethal concentration of AZA resulting in 50% mortality of second instar nymphs of nine species of aphids ranged from 2.4 ppm forM. persicae on pepper to 635.0 ppm for the strawberry aphid,Chaetosiphon fragaefolii (Cockerell), on strawberry. ForM. persicae, the growth regulating effect of AZA was influenced by the host plant and the nymphal instar treated.     

Insect antifeedant activity of clerodane diterpenes and related model compounds

A comprehensive compilation of all test results on the insect antifeedant activity of clerodane diterpenes and related model compounds is reported. To increase the compatibility of data from different sources, some of the results reported in the literature have been converted into a standardized form. The compounds were sorted into groups according to the different types of sidechain attached to C-9. Despite the wealth of information, collected in 15 tables, it remains difficult to assign importance to separate structural elements in relation to the observed antifeedant activity. A detailed analysis of the structure-activity relationships could not be presented, but some interesting trends can be distinguished based on the structures of the strongest antifeedants. The compilation covers the literature up to December 2001.     

The role of light in regulating seed dormancy and germination

Seed dormancy is an adaptive trait in plants. Breaking seed dormancy determines the timing of germination and is, thereby essential for ensuring plant survival and agricultural production. Seed dormancy and the subsequent germination are controlled by both internal cues (mainly hormones) and environmental signals. In the past few years, the roles of plant hormones in regulating seed dormancy and germination have been uncovered. However, we are only beginning to understand how light signaling pathways modulate seed dormancy and interaction with endogenous hormones. In this review, we summarize current views of the molecular mechanisms by which light controls the induction, maintenance and release of seed dormancy, as well as seed germination, by regulating hormone metabolism and signaling pathways.     

Antifungal activity of the carrot seed oil and its major sesquiterpene compounds

Carrot seed oil is the source of the carotane sesquiterpenes carotol, daucol and beta-caryophyllene. These sesquiterpenic allelochemicals were evaluated against Alternaria alternata isolated from the surface of carrot seeds cultivar Perfekcja, a variety widely distributed in horticultural practise in Poland. Alternaria alternata is one of the most popular phytotoxic fungi infesting the carrot plant. The strongest antifungal activity was observed for the main constituent of carrot seed oil, carotol, which inhibited the radial growth of fungi by 65% at the following concentration.     

Limonoids from the leaves of Soymida febrifuga and their insect antifeedant activities

Three new phragmalin-type limonoids (1–3) were isolated from the leaves of Soymida febrifuga together with thirteen known limonoids. The structures of these compounds were established on the basis of spectroscopic data. All these isolates were evaluated for their anti-feedant activities in tobacco caterpillar (Spodoptera litura) and castor semilooper (Achaea janata) using a no-choice laboratory bioassay. Among the tested, compounds 9 and 15 demonstrated the potent anti-feedant index (76.46 μg/cm², 66.61 μg/cm² against A. janata, and 61.69 μg/cm², 51.93 μg/cm²against S. litura).     

Toxicity of insecticides to obliquebanded leafroller, Choristoneura rosaceana, larvae and adults exposed previously to neem seed oil

Adult and sixth instar obliquebanded leafroller, Choristoneura rosaceana (Harris), exposed previously as fifth instar larvae to sub-lethal concentrations of neem, Azadirachta indica A. Juss., seed oil contained in artificial diet were more susceptible to topically applied pyrethroid, carbamate and organophosphate insecticides than C. rosaceana reared on control diets. Increased susceptibility to insecticides did not result from reduced vigour, as measured by reductions in adult or larval weights, but is instead correlated with previously demonstrated reductions in detoxication enzyme activities. The modest increases in susceptibilities, not exceeding ca. 4.5-fold, for C. rosaceana exposed to neem were achieved with subjects from a susceptible laboratory colony; a larger response could be expected for resistant field populations having elevated detoxication enzyme levels. Neem-based insecticides could be useful tools for the management of orchard pests that have developed resistance to synthetic neurotoxins. These findings also contribute to a better understanding of the numerous physiological changes that occur in larval Lepidoptera following exposure to neem extracts.     

Sulphur application improves the growth, seed yield and oil quality of canola

Sulphur (S) nutrition is very important for harvesting potential seed and oil yield of rapeseed. This study evaluated response of foliage applied thiourea on the performance of two canola cultivars Shiralee and Dunkeld. Sulphur was applied to soil (40 kg ha^?1) or foliage (500 and 1,000 mg L^?1) at rosette, bud initiation and flowering stages using elemental S or thiourea as source, respectively; no S application was taken as control. Among all the treatments, soil application of S improved the crop growth, yield and oil quality in both cultivars and was followed by foliar application of thiourea at 1,000 mg L^?1 compared with no application. Soil applied S and foliar thiourea (1,000 mg L^?1) delayed the flowering and maturity. Soil and foliar applied S significantly improved leaf area index, crop growth rate, net assimilation rate and chlorophyll contents. Plant height, number of branches, siliqua per plant, seed number per siliqua, 1,000-seed weight, biological and seed yield were also increased by soil applied S and foliage applied thiourea (1,000 mg L^?1). Nonetheless, improvement in harvest index, seed oil, protein and glucosinolate contents was only observed from foliage applied thiourea (1,000 mg L^?1). Response of cv. Shiralee to sulphur application was better than cv. Dunkeld. In conclusion, foliar applied thiourea (1,000 mg L^?1) can have potential to improve growth, yield and oil quality in canola and can be economically viable and attractive alternative source.     

昆虫种子捕食与蒙古栎种子产量和种子大小的关系

为了了解昆虫种子捕食者在栎类种群更新中的作用,于2006年秋季,在黑龙江省伊春市带岭区东方红林场研究了昆虫对蒙古栎Quercus mongolica在参园和东山两个种群的种子蛀食情况及其与蒙古栎种子产量和种子大小的关系。结果表明：(1)在参园和东山两个林分内,蒙古栎种子雨动态非常相似,种子雨成分中完好种子的平均密度仅为3.2±4.1个/m²（参园）和1.7±2.8个/m²（东山）,分别仅占种子产量的4.0％和3.2％,而虫蛀种子和败育种子的比例均在38%以上,以虫蛀种子的比例最高,分别为58.2％和57.7％;(2)柞栎象Curculio arakawai是蛀食蒙古栎种子的主要昆虫种类,在虫蛀种子中所占比例高达96.8％（参园）和97.1％（东山）,且象甲蛀食种子中所含虫卵数与种子大小有关,即种子越大,所含象甲的虫卵数就较多。本研究的结果说明2006年蒙古栎成熟种子多遭遇虫蛀,导致完好种子的数量极低,因而可能成为限制蒙古栎种群更新的重要因素。     

Bacillus thuringiensis and neem seed oil (Azadirachta indica) effects on the potato tuber moth Phthorimaea operculella zeller in the field and stores

A comparative evaluation for the efficacy of Bacillus thuringiensis and neem seed oil on Phthorimaea operculella has been carried out in the field and store. These two preparations were almost equally effective on the potato tuber moth infestation. The percentage of infestation was reduced through successive application of either preparations in the field up to harvest. No synergism was observed upon using combination of the two preparations. In the store, neem seed oil (500 ppm) was highly protective and was as effective as sevin. A combination of both neem and B.t. (Delfin) significantly protects the tubers. This suggests the possible use of either neem seed oil or B.t. in combating the insect pest in the field or during storage.     

CodY-regulated aminotransferases AraT and BcaT play a major role in the growth of Lactococcus lactis in milk by regulating the intracellular pool of amino acids

Aminotransferases, which catalyze the last step of biosynthesis of most amino acids and the first step of their catabolism, may be involved in the growth of Lactococcus lactis in milk. Previously, we isolated two aminotransferases from L. lactis, AraT and BcaT, which are responsible for the transamination of aromatic amino acids, branched-chain amino acids, and methionine. In this study, we demonstrated that double inactivation of AraT and BcaT strongly reduced the growth of L. lactis in milk. Supplementation of milk with amino acids and keto acids that are substrates of both aminotransferases did not improve the growth of the double mutant. On the contrary, supplementation of milk with isoleucine or a dipeptide containing isoleucine almost totally inhibited the growth of the double mutant, while it did not affect or only slightly affected the growth of the wild-type strain. These results suggest that AraT and BcaT play a major role in the growth of L. lactis in milk by degrading the intracellular excess isoleucine, which is responsible for the growth inhibition. The growth inhibition by isoleucine is likely to be due to CodY repression of the proteolytic system, which is necessary for maximal growth of L. lactis in milk, since the growth of the CodY mutant was not affected by addition of isoleucine to milk. Moreover, we demonstrated that AraT and BcaT are part of the CodY regulon and therefore are regulated by nutritional factors, such as the carbohydrate and nitrogen sources.     

Mouse sperm-egg interaction in vitro in the presence of neem oil

In vitro evidence is presented showing toxicity of neem oil on sperm-egg interaction in mouse. Cumulus oophorus-enclosed ova, inseminated with capacitated spermatozoa, were cultured in 1 ml of in vitro fertilization (IVF) medium and overlayered by 1 ml of different concentrations of neem oil (1, 5, 10, 25, 50 and 100%) for IVF duration of 4h. At the end of incubation, ova were allowed to grow in neem oil-free culture medium and assessed for fertilization, first cleavage (2-cell formation) and blastocyst formation in vitro at 4–14h, 24h and 108h post-insemination respectively. The study showed that the presence of neem oil at concentrations of 10, 25 and 50% caused inhibition of IVF in a dose-dependent manner. The toxic effect of exposure of 25 and 50% neem oil was further carried over to the first cleavage of the resulting fertilized ova and the toxic effect of 5, 10, 25, and 50% was carried over to the blastocyst formation from the resulting fertilized ova when grown in neem-oil free culture medium. A total of 94.1% inhibition of 2-cell formation and 100% inhibition of blastocyst formation from the inseminated ova was observed in 50 and 25% neem oil-treated groups respectively. Neem oil at 100% concentration caused 100% degeneration of ova at 1h of sperm-ova coculture. The study showed a direct toxic effect of neem oil on sperm-egg interaction in vitro and encourages research investigations of this herbal product as a pre-coital contraceptive.     

Chemical composition and antimicrobial,antioxidant, and anti-inflammatory activities of Lepidium sativum seed oil

Lepidium sativum (garden cress) seed oil was examined for its antimicrobial, antioxidant, and anti-inflammatory activities. The oil was obtained by hydrodistillation, where gas chromatography coupled with mass spectrometry that utilized to study its chemical composition. Microdilution method was used to test the antimicrobial effect of oil against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Klebsiella pneumoniae, and Candida albicans. The antioxidant activity was assessed by radical scavenging activity assay using 2,2-diphenyl-1-picrylhydrazyl radical. The major constituents found in the oil were 7,10-hexadecadienoic acid, 11-octadecenoic acid, 7,10,13-hexadecatrienoic acid, and behenic acid. The minimum inhibitory concentration (MIC) against all pathogens was 47.5 mg/ml, except for Salmonella enterica, which showed MIC of 90 mg/ml. The oil demonstrated antioxidant activity in a dose dependent pattern, with a half maximal inhibitory concentration (IC₅₀) value of 40 mg/ml, and exerted anti-inflammatory activity, wherein 21% protection was shown at a concentration of 300 μg/ml. Thus, L. sativum seed oil shows antimicrobial, antioxidant, and anti-inflammatory properties.     

The primary role of intracellular free Mg2+ in regulating cell growth

Comment on: Sahni J, et al. Cell Cycle 2010; 9:3565-74.     

The role of avian ‘seed predators’ as seed dispersers

Seed dispersal is a central process in plant ecology with consequences for species composition and habitat structure. Some bird species are known to disperse the seeds they ingest, whereas others, termed ‘seed predators’, digest them and apparently play no part in dispersal, but it is not clear if these are discrete strategies or simply the ends of a continuum. We assessed dispersal effectiveness by combining analysis of faecal samples and bird density. The droppings of seed dispersers contained more entire seeds than those of typical seed predators, but over a quarter of the droppings of seed predators contained whole seeds. This effect was further magnified when bird density was taken into account, and was driven largely by one frequent interaction: the Chaffinch Fringilla coelebs, a typical seed predator and the most abundant bird species in the area and dispersed seeds of Leycesteria formosa, a non‐native plant with berry‐like fruits. These results suggest the existence of a continuum between seed predators and seed dispersers.     

Evaluation of neem seed powder for Fusarium wilt and Meloidogyne control on tomato

Fusarium wilt and root-knot are important diseases of tomato. The use of chemical is becoming less appealing because of the health implications. Also, the chemicals required are often not within the reach of farmers in most of the developing part of the world. This research is aimed at finding an alternative mode of control. Tomato variety Roma VF inoculated with Meloidogyne and Fusarium were treated with 2 g/kg soil neem seed powder in the screenhouse and 2 Mg ha ^{? 1} in the field. An untreated and Furadan treated plot in the field served as control. Neem seed powder significantly reduced the disease severity of Fusarium and root-knot in both screenhouse and field. Results suggest the possible use of neem seed powder for control of the root-knot nematodes - Fusarium wilt disease complex.