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  • 1
    Electronic Resource
    Electronic Resource
    Locating a resistance mechanism to the cabbage aphid in two wild Brassicas (1994)
    Springer
    Entomologia experimentalis et applicata 71 (1994), S. 23-31 
    Details
    ISSN: 1570-7458
    Keywords: Brassica fruticulosa ; B. spinescens ; Brevicoryne brassicae ; host-plant resistance ; EPG ; glucosinolates ; artificial diets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding behaviour of the cabbage aphid,Brevicoryne brassicae, was monitored electronically on two resistantBrassica species,B. fruticulosa andB. spinescens, and compared with a susceptible controlB. oleracea var.capitata cv. Offenham Compacta. Aphids, monitored for 10 h on the under side of leaves, performed recognizable feeding behaviour on all species. Electrical Penetration Graphs (EPGs) of aphids on resistant and susceptible plants showed no difference in behaviour for aphids on resistantBrassica species compared to susceptible until stylets penetrated the phloem sieve elements when a large reduction in the duration of passive phloem uptake (E2 pattern) onB. fruticulosa was indicated. Although feeding behaviour on 6 week-old plants ofB. spinescens was similar to the susceptible controls, behaviour on 10 week-old plants was similar to that recorded forB. fruticulosa. The mechanism of resistance is thought to be located in the sieve element as the normal sieve element salivation (E1) signal was either quickly terminated by withdrawal of the stylets from the sieve element or continued as a disrupted E2 pattern. Analysis of secondary plant compounds in the threeBrassica species only identified significant differences in the glucosinolate profile. No reproducible differences were detected in the concentration of phenolics or anthocyanins. The major glucosinolate component ofB. fruticulosa andB. spinescens was gluconapin rather than glucobrassicin and glucoiberin as found in the susceptible host plant. However, both pure glucosinolates and glucosinolate extracts from all three species did not reduce aphid survival on chemically-defined artificial diets. These results suggest that the mechanism of resistance may be a mechanical blocking of the sieve element or stylets rather than a difference in the secondary plant chemistry of glucosinolates and phenolics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02380566
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The relative importance of glucosinolates and amino acids to the development of two aphid pests Brevicoryne brassicae and Myzus persicae on wild and cultivated brassica species (1997)
    Springer
    Entomologia experimentalis et applicata 85 (1997), S. 121-133 
    Details
    ISSN: 1570-7458
    Keywords: Brevicoryne brassicae ; Myzus persicae ; Brassica fruticulosa ; B. spinescens ; B. juncea ; B. nigra ; B. carinata. B. macrocarpa ; B. villosa var drepanensis ; B. oleracea ; B. napus ; B. campestris ; host-plant resistance ; glucosinolates ; amino acids ; leaf water potential ; generalist ; specialist ; aphids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes an experiment to investigate the relative importance of glucosinolates and the availability of free amino acids in the phloem to the feeding behaviour and development of the specialist brassica aphid, Brevicoryne brassicae (L) (cabbage aphid) and the generalist, Myzus persicae, (Sultzer) (peach potato aphid). Aphid development was determined on brassica species and cultivated brassica varieties. Analysis of individual glucosinolates in the wild brassica species identified significant differences in their profiles and in their concentrations present in freeze dried leaves. Multiple regression analysis showed a significant correlation ( $$\left( {r = 0.83} \right)$$ ) between the intrinsic rate of increase of B. brassicae and glucosinolate concentrations; four glucosinolates, 2-OH-3-butenyl, and 2-propenylglucosinolate, 3-methoxyindolyl and 4-pentenylglucosinolates accounted for 79% of the variation. The intrinsic rate of increase of M. persicae was less correlated, though still significant ( $$\left( {r = 0.5} \right)$$ ); 3-indolyglucosinolate and 3-butenylglucosinolate accounted for 47% of the variation. Regression analysis also showed a correlation between phloem amino acid concentrations and the intrinsic rate of increase of B. brassicae ( $$\left( {r = 0.48} \right)$$ ) but not of M. persicae. The concentration of the important amino acids tyrosine, alanine, leucine and glutamic acid, accounted for 43% of the variation in intrinsic rate of increase. Leaf water potential of the Brassica species showed no relationship with the intrinsic rate of increase of either B. brassicae or M. persicae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003049105464
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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