摘要:

SummaryThin layer agarose isoelectric focusing (IEF) was used to separate proteins from the larvae ofTipula oleraceaLinnaeus andTipula paludosaMeigen (Diptera, Nematocera). Silver staining revealed protein banding patterns which consistently distinguished these two species at any stage in their life cycles. Within the pH range 5–6Tipula paludosacontained one major protein band andT. oleraceatwo bands, with the pI value of theT. paludosaprotein being slightly higher than those ofT. oleracea. The IEF method is particularly useful for the larval stages of these species because they are often visually inseparable. Leather jackets obtained during a survey of Northern Ireland and north‐eastern and western Scotland were tested to determine the distribution and frequency of these species occurring in grassland. In each area surveyedT. paludosapredominated with only one field in Northern Ireland and north‐eastern Scotland found to containT. oleracea. In western ScotlandT. oleraceaoccurred in five fields each year of the survey, and was locally abundant on the Isle of Bute in the 1990/91 survey making up 15% of the total larvae t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04008.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryFirst instar nymphs and adults of the grain aphidSirobion auenaethat had been reared at 10°C and 20°C over a number of generations, were cooled to ‐5°C and ‐10°C for 1 h and 6 h and returned to 20°C to assess the effects of brief exposures to low temperatures (cold‐pulses) on their survival. rate of development, longevity and fecundity. A strong acclimation response was observed in first instar nymphs, with significantly less mortality in groups reared to 10°C compared to 20°C. Mean development time from first instar to adult was not significantly affected by low temperature exposure at the first nymphal stage. Longevity in all groups cooled as first instars was reduced by the sub‐zero cold‐pulses, and was also dependent on temperature and exposure time. Acclimated aphids survived longer than non‐acclimated individuals. Reproductive rate, in terms of the number of nymphs born per aphid per day, was unaffected by cold stress applied at the first instar stage. Total fecundity was however reduced, being a function of the number and longevity of the survivors.Adult aphids were less cold hardy than nymphs; mortality was higher at ‐10°C than ‐5°C increasing with duration of exposure from 1 h to 6 h. Mean fecundity was reduced significantly in aphids cooled at the adult stage, the number of aphids born per day decreasing as the exposure period of the cold‐pulse increased, suggesting that low temperature had affected embryogenesis. All the nymphs born to adults surviving exposure to ‐5°C for 6 h died within 48 h of birth, indicating that low temperature has a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04009.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe fungus gnat (Bradysia impatiens) was examined for its ability to transmitPythium aphanidermatumto cucumber plants. Larvae that had ingested oospores and mycelium, and then fed on the roots of young cucumber plants growing in rockwool readily introduced the fungus to them. Trans‐stadial transmission of oospores from the larval to the adult stage ofB. impatienswas demonstrated, although decreasing to a very low level (1.67%) in adults. However, external transmission ofP. aphanidermatumon the surface of adults could not be shown. These results suggest that the larval stages of fungus gnats play a role in the dissemination of the fungus between cucumber plants but that adults probably play only a minor rol

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04010.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryExperiments were conducted to study the progress of purple blotch disease of garlic caused byAlternuria porriin the field, to determine the relationship between garlic leaf age and susceptibility toAlternaria porri, and also to assess loss in bulb characters due to purple blotch of garlic. Per cent disease severity and number of purple blotch lesions on four garlic genotypes of known susceptibility, Sel‐10 (highly susceptible), G‐41 (highly susceptible), IC‐49382 (moderately susceptible) and IC‐49373 (moderate to less susceptible) were monitored from bulb formation to bulb maturity at weekly intervals. Lesions appeared early on highly susceptible cultivars, Sel‐10 and G‐41. Rapid progress of disease development was noticed during the last 3 wk before bulb maturity. Peak severity at the maturity of the crop was significantly higher on highly susceptible genotypes. No definite correlation could be established between number of lesions and disease severity. A logistic curve was fitted to predict the disease progress on different weeks before bulb maturity. Levels of leaf tissue found damaged byA. porriat weekly intervals from bulb initiation to bulb maturity were significantly lower on younger leaves than on older leaves. Leaves that emerged 7 wk before bulb maturity required more than a 5 wk period to reach 50% leaf damage, whereas leaves emerging 2, 3 and 4 wk before bulb maturity exceeded 50% leaf damage within a 2–3 wk period. Individual garlic leaves became more susceptible to purple blotch as they aged and emerging leaves were more susceptible the closer they emerged to bulb maturity. Per cent loss in bulb weight and bulb volume was found to be significantly higher on highly susceptible genotypes. No significant reduction in number of cloves/bulb was observed. We propose 4 wk before bulb maturity as the action threshold for initiation of fungicidal application to prevent damaging leve

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04011.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryFour isolates of pea seed‐borne mosaic virus (PSbMV) representing pathotypes P1 (isolates US and Q) and P4 (isolates S4 and S6), and groups III (US and Q) and V (S4 and S6) have been used in a study of the survival and partitioning of PSbMV under conditions of continuous seed transmission in the commercial pea cultivar Dundale.Assays suitable for detecting virus in small tissue samples were developed, and included dot‐immunobinding assay with antisera to both PSbMV and cytoplasmic inclusion body (CIB) protein, and dot hybridisation assay (DHA) with cDNA transcribed from virus RNA. Under the conditions of our experiments, seed transmission occurred at rates exceeding 90% for all virus isolates.Virus was detectable by serology and symptoms in inoculated plants, and in all vegetative tissue of second generation plants raised from seed of the inoculated plants. However, in the third, fourth and fifth sequential generations raised from seed, all plants were symptomless. Neither virus nor CIB were detectable in leaf, stem or roots by serology, but both were readily detectable in some floral parts, and in immature and mature seed. Mature seed contained virus and CIB antigen in the testa, cotyledon and embryo. Inoculum prepared from whole seeds was infectious. The testa was shown not to be involved in transmission between generations, thus implicating the embryo alone in vertical transmission. Virus antigen could not be detected in the emerging cotyledons of germinating seed and all true leaves by serology, but the leaves contained PSbMV RNA detectable by DHA.These results show that PSbMV infection can be transferred through the vegetative phase at a subliminal level, and reaches relatively high concentrations in floral parts and seeds. Thus PSbMV may be maintained at a high level of infection in seed in the absence of any apparent symptoms in the plant, and without a requirement for horizontal transmission between plants by vectors. Such a mechanism may explain the high levels of infection commonly reported in pea breeding li

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04012.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryA previous survey on pepper lines (Capsicum annuumL.) indicated that a susceptible cultivar, Yolo Wonder, reacted to cucumber mosaic virus (CMV) by producing a systemic yellow mosaic. By contrast, CMV caused no symptoms on lines Perennial and Vania. The virus is recoverable from the uninoculated leaves of Perennial, while in Vania CMV is restricted to the inoculated leaves. To interpret these phenomena, a comparative study on CMV multiplication rates, yield, specific infectivity and relative proportion of RNAs was made in the inoculated leaves of the three pepper varieties. The rate of CMV multiplication, as estimated by the double antibody sandwich form of enzyme‐linked immu‐nosorbent assay, was lower in Perennial than in Vania or Yolo Wonder. The yield of virus purified from Perennial was very low when compared with Vania or Yolo Wonder. The specific infectivity of the virus extracted from Perennial was less than that from Vania or Yolo Wonder. These results suggest that Perennial is resistant to CMV multiplication, while restriction of the virus in inoculated leaves of Vania is not due to the inhibition of the virus replication. However, polyacrylamide gel electrophoresis revealed that the RNA profiles of CMV purified from the three pepper lines were simi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04013.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe effectiveness of the synthetic pyrethroids deltamethrin and lambda‐cyhal‐othrin in preventing (i) aphid colonisation of four cowpea cultivars with different levels of aphid resistance and (ii) the introduction and subsequent spread of cowpea aphid‐borne mosaic virus and cucumber mosaic virus was investigated under tropical field conditions.Sprays of these pyrethroids eight days apart prevent aphid colonisation and within crop spread of virus by the colonisingAphis craccivora. However, neither deltamethrin nor lambda‐cyhalothrin prevented the initial introduction of virus into the cowpea crop and, when incoming alate incidence was high, virus incidence was higher in the sprayed than in the unsprayed plots. In addition, the degree of aphid resistance of each cultivar affected secondary virus spread within the crop, with greatest spread in the most resistant c

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04014.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryCluster analysis was used to classify cowpea cultivars developed for resistance toM. testulalisin Nigeria based on data collected on four damage parameters. The cultivars were grouped into classes for each of two locations under two protection regimes. Differences were observed in the groupings for the two locations while one cultivar, MR×6–84F was found to have wide adaptability in the presence or absence ofM. testulalisinfestation. This is particularly useful for the selection of breeding materials in cultivar improvement for specific or general ecological zon

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04015.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryUnder field conditions a wildDaucusspecies from Libya,D. capillifolius, supported less than one tenth as many carrot flies (Psila rosae) as the susceptible carrot cultivar Danvers Half Long 126. Breeding lines developed from crosses betweenD. capillifoliusand three different carrot types were grown in a series of field experiments at Wellesbourne between 1980 and 1989. Each year selections were made for agronomic quality and/or for increased resistance to carrot fly. The programme produced lines which for size, shape and colour represented most of the commercially‐important carrot types. Some of these lines were also significantly more resistant to carrot fly than selections from the partially‐resistant cv. Sytan. However, the best lines were not as resistant as the wild parent. The highest quality resistant lines were sold to seed companies for variety product

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04016.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe expansion of individual leaves was examined in 19 genotypes of potato (Sofunum tuberosumL.) grown either with irrigation or droughted from the time of plant emergence. Drought reduced the thermal time from emergence to leaf appearance in 10 genotypes but had no significant effect in the other genotypes. In all the genotypes, final size of leaves was reduced by drought, but the magnitude of the effect differed significantly (P<0.001) with genotype. In the droughted treatment, the final size of leaves was correlated (P<0.001) with the maximum rate of leaf expansion suggesting that reductions in final size of leaves were the result of reduced expansion rate rather than of effects on the duration of expansion.Both the constant and the slope of the relation between leaf expansion rate and soil moisture deficit differed between genotypes. Osmotic adjustment was limited, maximally 0.16 MPa, and did not correlate with the ability to maintain leaf expansion with increasing soil moisture deficit.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1993.tb04017.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY