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82.
In a comparison of four potato varieties, in-soil hatch of the golden potato cyst nematode (Globodera rostochiensis) was positively correlated to in vitro hatch in response to potato root leachate (PRL). The in-soil hatch of cysts of G. rostochiensis to two of the four varieties was significantly less than that of the control (cysts in gravel without potato plants) in the first 2 wk after plant emergence, suggesting the production of hatching inhibitors (HIs) by young potato plants. The hatching factor: hatching inhibitor ratio of PRL was positively associated with the net hatching activity of the PRL. Four zones of HI activity were resolved following gel permeation chromatography of PRL on Sephadex G-10. Hatch-inactive chemicals, which stimulated the activity of hatching factors (HFs) in PRL (hatching factor stimulants, HSs), were also isolated from PRL, hatch levels induced by individual HFs responding differently to the same HS preparation. The complex interactions between individual HFs and other hatching chemicals in PRL was illustrated when addition of the hatch-active potato glycoalkaloid α-solanine caused both inhibition and stimulation of PRL-induced hatch, depending on the α-solanine concentration. 相似文献
83.
In glasshouse tests, sap from plants infected with 15 different isolates of tomato spotted wilt tospovirus (TSWV) from three Australian states was inoculated to nine genotypes of tomato carrying TSWV resistance gene Sw-5 or one of its alleles. A further two resistant tomato genotypes were inoculated with four isolates each. The normal response in resistant genotypes was development of necrotic local lesions in inoculated leaves without systemic invasion, but 22/752 plants also developed systemic reactions in addition to local hypersensitive ones. Using cultures from two of these systemically infected plants and following four cycles of subculture in TSWV resistant tomato plants, two isolates were obtained that gave susceptible type systemic reactions but no necrotic spots in inoculated leaves of resistant tomatoes. When these two isolates, DaWA-1d and ToTAS-1d, were maintained by repeated subculture for 10 successive cycles in Nicotiana glutinosa or a susceptible tomato genotype, they still induced susceptible type systemic reactions when inoculated to resistant tomato plants. They were therefore stable resistance breaking isolates as regards overcoming gene Sw-5. When resistance-breaking isolate DaWA-1ld multiplied together with original isolate DaWA-l in susceptible tomato, it was fully competitive with the original isolate. However, when DaWA-ld and ToTAS-ld were inoculated to TSWV resistant Lycopersicon peruvianum lines PI 128660R and PI 128660S and to TSWV resistant Capsicum chinense lines PI 152225, PI 159236 and AVRDC CO0943, they failed to overcome the resistance, producing only necrotic local lesions without systemic infection. Thus, although the ease of selection, stability and competitive ability of resistance breaking isolates of TSWV is cause for concern, L. peruvianum and C. chinense lines are available which are effective against them. The effectiveness of the resistance to TSWV in nine tomato genotypes was examined in a field experiment. Spread was substantial in the susceptible control genotype infecting 42% of plants. Resistance was ineffective in cv. Bronze Rebel, 26% of plants developing infection. In contrast, it held up well in the other eight resistant genotypes with only 1–3 or no plants of each becoming infected. Accumulated numbers of Thrips tabaci, Frankliniella occidentalis and F. schultzei were closely correlated with TSWV spread. 相似文献
84.
Six blackberry or hybrid berry cultivars and 19 raspberry cultivars were assessed for their infectibility with, and sensitivity to, graft inoculation with 10 distinct viruses found infecting Rubus in the UK. Cultivars were grafted with each of, two isolates of the pollen borne raspberry bushy dwarf virus (RBDV), five aphid borne viruses: black raspberry necrosis, raspberry leaf mottle (RLMV), raspberry leaf spot (RLSV), rubus yellow net and raspberry vein chlorosis (RVCV); and isolates of the nematode transmitted nepoviruses, arabis mosaic, raspberry ringspot, strawberry latent ringspot and tomato black ring. All tested cultivars were infectible with a resistance breaking isolate of RBDV but only about half of that number with the Scottish type isolate of the virus. The raspberry cvs Autumn Bliss, and occasionally Glen Garry and Glen Prosen, developed leaf yellowing symptoms following infection with RBDV, but none of the other infected cultivars showed obvious leaf symptoms when kept in a heated glasshouse during the growing season. All tested cultivars were infectible with each of the four viruses transmitted in nature by the aphid, Amphorophora idaei. Most were infected symptomlessly, but seven cultivars developed severe leaf spotting symptoms due to infection with RLMV or RLSV. All but one of the raspberry cultivars were infectible with RVCV, which is transmitted in nature by the aphid Aphis idaei, and almost all infected plants developed leaf symptoms; only one of the hybrid berry or blackberry cultivars tested was infected with RVCV. In tests with the four nepoviruses, all tested cultivars, except Tummelberry, were infectible with at least one or more of these viruses. However, cultivars responded differently to challenge inoculation with different isolates of individual nepoviruses. Several cultivars developed chlorotic leaf mottling following infection with some nepovirus isolates. The implications of these results for virus control are discussed in the light of the changing pattern of virus and virus vector incidence in the UK. 相似文献
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PHILIP W. ATKINSON ALLAN J. BAKER KAREN A. BENNETT NIGEL A. CLARK JACQUIE A. CLARK KIMBERLY B. COLE ANNE DEKINGA AMANDA DEY SIMON GILLINGS PATRICIA M. GONZÁLEZ KEVIN KALASZ CLIVE D. T. MINTON JASON NEWTON LAWRENCE J. NILES THEUNIS PIERSMA ROBERT A. ROBINSON HUMPHREY P. SITTERS 《Journal of Applied Ecology》2007,44(4):885-895
88.
Ecological,morphological and genetic divergence of sympatric North Atlantic killer whale populations
ANDREW D. FOOTE JASON NEWTON STUART B. PIERTNEY ESKE WILLERSLEV M. THOMAS P. GILBERT 《Molecular ecology》2009,18(24):5207-5217
Ecological divergence has a central role in speciation and is therefore an important source of biodiversity. Studying the micro‐evolutionary processes of ecological diversification at its early stages provides an opportunity for investigating the causative mechanisms and ecological conditions promoting divergence. Here we use morphological traits, nitrogen stable isotope ratios and tooth wear to characterize two disparate types of North Atlantic killer whale. We find a highly specialist type, which reaches up to 8.5 m in length and a generalist type which reaches up to 6.6 m in length. There is a single fixed genetic difference in the mtDNA control region between these types, indicating integrity of groupings and a shallow divergence. Phylogenetic analysis indicates this divergence is independent of similar ecological divergences in the Pacific and Antarctic. Niche‐width in the generalist type is more strongly influenced by between‐individual variation rather than within‐individual variation in the composition of the diet. This first step to divergent specialization on different ecological resources provides a rare example of the ecological conditions at the early stages of adaptive radiation. 相似文献
89.
Abstract. 1. Euedaphic collembola alter their soil distribution in response to above‐ground aphid herbivory of Poa annua L. Graminae, a host grass. 2. Two mechanisms potentially underpin this effect. Carbon‐rich aphid honeydew falling onto the soil surface may affect mycophagous collembola; alternatively aphid‐induced changes in root biomass may be necessary to produce changes in collembola abundance. 3. When compared to a plant‐only control, aphid herbivory increased the number of collembola in the top 5 cm of soil, reduced both foliar and root biomass, and increased shoot/root ratio. Honeydew addition had no effect on collembola numbers or any recorded host‐plant parameter. 4. Honeydew deposition is not responsible for the increased numbers of collembola found in the upper soil after aphid herbivory; aphid‐induced reductions in root biomass may be the most important factor explaining knock‐on effects of aphid herbivory on soil fauna. 相似文献
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