摘要:

SummaryIn field trials conducted at Samaru, Nigeria in 1983, 1984 and 1985, damage todauromillet by the millet stem borer,Coniesta ignefusalisHampson (Lepidoptera: Pyralidae), varied between years and dates of planting. The crop was almost completely destroyed by the stem borer during 1984. Based on 1983 and 1985 data, the period between 10 July and 2 August appears to be best for plantingdauromillet at Samaru for least stem borer damage while planting between 11 and 30 July appears to be optimum for grain yields.The direct sown crop suffered more damage than the transplanted crops in all years but only in 1985 was the difference significant. There was no significant difference between slant and upright transplanting in terms of stem borer damage and grain yield. It is concluded, therefore, that the choice of planting method would depend on its convenience to the farmer.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04815.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryTechniques were developed for testing umbelliferous species against naturally‐occurring populations of carrot fly in the field. The most efficient technique involved exposure of plants to either first or second generations of the insect in the field, followed by caging of infested plots and trapping of emerged flies in water in yellow water dishes.In a series of field experiments between 1981 and 1989 inclusive, a total of 132 umbelliferous species and sub‐species were tested against carrot fly. Seventy‐eight of these proved to be new hosts, 27 were confirmed as hosts and 27 failed to support any carrot flies. Six non‐umbelliferous plant species failed to be colonised by carrot fly. Sources of variability in investigations of the host range of insects are di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04816.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryA leaf spot disease of melon caused byAlternaria alternataf.sp.cucurbitaewas recorded for the first time in Crete. Necrotic flecks surrounded by chlorotic halos developed on the cotyledons and the leaves of the middle and the upper part of the plants; the flecks enlarged and coalesced to form lesions of 2 cm or more in diameter with brown fructifications of the pathogen on their surface. Severely affected cotyledons and leaves became chlorotic and died. Of 16 species from eight botanical families that were inoculated, only those of the Cucurbitaceae were susceptible. Of four isolates ofA. alternatafrom tomato, sunflower, pear and cucumber, only the cucumber isolate was pathogenic to melon foliage.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04817.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryHelminthosporium oryzaetoxin induced electrolyte leakage from rice callus tissues and caused their browning and death. A virulent isolate of the pathogen invaded and colonised callus tissues rapidly, while a less virulent and a nonpathogenic isolate colonised calluses only weakly if at all. Addition of the toxin to calluses permitted colonisation of calluses by the nonpathogenic isolate. Four toxin‐resistant calluses were selected and plants regenerated from two of these resistant calluses showed resistance to the pathogen. This resistance was heritable and stability of resistance was observed in the R1, R2and R3generation

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04818.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThe spatial and temporal colonisation of tomato plants byPhytophthora cryptogeawas studied in rockwool nutrient culture. Root growth and the distribution and progress of infection were measured on dissected root fragments obtained from a detailed destructive sampling of the substrate. Dissected fragments of root or roots and fibres were plated on BNPRA agar, a selectivePhytophthoramedium. Roots colonised all parts of the rockwool substrate 60 days after planting with the exception of surface marginal and central areas of the slab which had a lower solution content. Most root biomass occurred in and immediately beneath the original growing block. The distribution ofP. cryptogeaclosely followed the pattern of root colonisation.An alternative, novel method for root analysis involved the dissolution of the mineral fibre and its formate bonding resin by digestion in 1mH3PO4for 45 min. Comparative recoveries ofP. cryptogeafrom plated fragments of dissected root and fibre or comminuted samples of acid‐released or dissected root showed that the acid treatment initially reduced the number ofPhytophthoracolonies in block and slab roots by 67% and 61% respectively. After 28 days, colony recovery from acid‐released roots in the rockwool slab increased and was between 4% and 13% lower than from other plating methods. Since 1mH3PO4was lethal to zoospores and surface sporangia, the colonies recovered were interpreted as originating exclusively from root lesions. Root fresh weight of healthy and inoculated plants declined during the initial period of fruit formation.P. cryptogeainfection led to a progressive reduction in root weight in the growing block and main slab and 28 days after inoculation, was approximately 50% of the controls.The acid digestion of rockwool fibre is proposed as a new approach to the problem of root and pathogen analysis in this substr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04819.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThe effect of root‐zone temperature onPhytophthora cryptogearoot rot was studied in tomato cv. Counter grown under winter and summer conditions in rockwool culture. A nutrient temperature of 25°C resulted in increased root initiation and growth, higher in winter‐grown than in summer‐grown plants. Rhizosphere zoospore populations were greatly reduced at 25°C and above.Growth ofP. cryptogea in vitrowas optimal between 20°C and 25°C and completely suppressed at 30°C. Encystment was enhanced by increased temperatures above 20°C. Zoospore releasein vitrooccurred in cultures maintained at constant temperatures in the absence of the normal chilling stimulus. Optimal release was at 10°C; no zoospores were released at 30°C.Inoculated, winter‐grown tomato plants maintained at 15°C developed acute aerial symptoms and died after 21 days. Comparable plants grown at a root‐zone temperature of 25°C remained symptomless for the 3‐months duration of the experiment. Summer‐grown infected plants at the higher root temperature wilted but did not die. Enhanced temperature was ineffective as a curative treatment in summer‐grown plants with established infection.Aerial symptoms ofPhytophthorainfection are seen as a function of the net amount of available healthy root. With high root zone temperatures this is determined by new root production and decreas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04820.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryA method of field screening groundnut seedlings for resistance to groundnut rosette virus (GRV), by means of which over 97% incidence was induced in rows of susceptible test plants, was developed at Chitedze Research Station in Malawi. Two GRV‐resistant Virginia cultivars (RG 1 and RMP 40) were crossed with three susceptible cultivars, one from each of the Spanish (JL 24), Valencia (ICGM 48) and Virginia (Mani Pintar) botanical groups. Twelve F1reciprocal crosses and their F2and backcross generations were produced and the material screened in nurseries in 1985/86 and 1986/87. Seedlings raised from plants which did not become infected in the field were inoculated in the glasshouse in order to eliminate susceptible escapees.The numbers of diseased and healthy individuals in each population were subjected to χ2tests. In the majority of the F2populations a good fit was obtained for a ratio of one resistant to 15 susceptible plants, a ratio to be expected if resistance to GRV were determined by a pair of independent complementary recessive genes. This was further supported by data from backcross generatio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04821.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryA method is described for the improved detection of bean yellow mosaic virus (BYMV) in gladioli leaves. Specific sequences of BYMV RNA, present in total RNA extracts of infected plants were detected following amplification by the polymerase chain reaction (PCR). The viral RNA was initially reverse‐transcribed into cDNA, then specific sequences were amplified by PCR using specific oligonucleotides as primers. Detectable amounts of virus RNA in BYMV‐infected plant tissue by PCR were approximately three to four orders of magnitude lower as compared with those detectable by ELISA and molecular hybridisation. Combining PCR with molecular hybridisation (using a32P‐labelled transcript of viral sequences as a probe), further increased the sensitivity of this method to a gain of four to five orders of magnitude as compared with direct molecular hybridisation, and enabled the detection of up to single picogram quantities of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04822.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThe flexuous filamentous particles of wineberry latent virus (WLV) were found to measure 620. 12 nm and not 510. 12 nm as previously reported. Analysis of dsRNA from infected plants detected a major species ofc.5.7. 106mol. wt and minor species of lower mol. wt. Purified virus particles formed a major and a minor buoyant density component in solutions of caesium salts with densities of 1.26 and 1.25 g cm‐3in Cs2SO4and 1.30 and 1.29 g cm‐3in CsCl. The particles contained a single nucleic acid species, presumably single stranded RNA, and a single polypeptide of estimated mol. wt 2.78. 106and 31 000 respectively. In indirect ELISA, purified particles of WLV and particles in plant sap failed to react specifically with antiserum to nine carlaviruses, 12 potexviruses, three capilloviruses or apple chlorotic leafspot closterovirus, nor was WLV found to react with several of these antisera in immunosorbent electron microscopy or immunoblots. In Marion and Olallie blackberry, WLV in mixture with raspberry bushy dwarf virus (RBDV), but not RBDV alone, induced veinal line‐pattern symptoms resembling those of calico disease reported from th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04823.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryEarlier attempts to discriminate serologically strains NL1, NL3 and NY15 of bean common mosaic virus (BCMV) and strain W of blackeye cowpea mosaic virus (B1CMV) had been unsuccessful. Antibodies directed towards N‐ and C‐, or N‐terminal peptide regions of the coat proteins of the above strains enabled the distinction between B1CMV‐W, BCMV‐NY15 and BCMV‐NL3 in electroblot immunoassay and in ELISA. The distinction was better with antibodies directed towards N‐termini than with those to N‐ and C‐termini. Strain NL1 of BCMV cross‐reacted with both B1CMV‐W and BCMV‐NY15, but not with BCMV‐NL3. Taxonomic implications of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1990.tb04824.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY