摘要:

Apices only (wounding) or apices plus seeds (seed removal) were removed from fruit of 18-year-old apple trees (Malus domesticaBorkh.) of the cultivars ‘Paulared’ and ‘Golden Delicious’ at 2–6 dates between the end ofJune drop and harvest over a 3-year period, to determine the effects of these treatments on fruit abscission in the field. Between 33 and 96% of ‘Paulared’ fruit abscised within 2 weeks if deprived of seeds at 4–7 weeks after petal fall. In the same period 0–14% of control and 3–44% of wounded fruit abscised. When the apex of the fruit was removed c. 8–12 weeks after petal fall, almost all fruit abscised whether seeds were removed or not. At the same time abscission of untreated fruit remained low (< 3%). Fruit wounded at 10 or 12 weeks after petal fall and then immediately sprayed with a 1 mMsolution of silver thiosulphate abscised less than fruit wounded only. ‘Golden Delicious’ fruit did not abscise prematurely when either wounded or when the seeds were removed early (June-July). Wounding at the time of fruit maturity (September-October) increased ethylene evolution significantly only if performed before the climacteric.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421784

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Hydrogen cyanamide use was investigated as a means of improving flowering and fruit set in nashi (Asian pear,Pyrus serotinaRehder var.cultaRehder) cultivars. The onset of flowering and shoot extension were advanced, and the length of the flowering period was shortened in all cultivars tested. Most response was shown by the later-flowering cultivars ‘Shinseiki’ and ‘Nijisseiki’, Best results were achieved at application rates of 3% a.i. Applications of hydrogen cyanamide at 6 and 9% a.i, caused serious bud and wood damage, regardless of time of application. Application at 3% a.i. caused damage only if applied within 3 weeks of natural flowering. At 1.5%, no damage occurred, but the effects on flowering were uneven and the results inconsistent. For the pollinator, ‘Shinseiki’, best results were achieved with a single application of 3% a.i. at c. 30–50 days before natural flowering, substantially improving overlap with the flowering periods of the other nashi cultivars. Early applications were sometimes associated with reduced flower and fruit numbers and an increased level of bud and wood damage, apparently in response to an adverse reaction between hydrogen cyanamide and the earlier applied copper sprays. Later applications of the chemical were generally associated with reduced levels of bud damage, or “bud jump”.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421785

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Harvest method had a consistent and significant effect on fruit quality parameters (acidity, berry integrity, and colour) for anyone cultivar irrespective of the season. At any picking date, machine-harvested fruit were always less acidic and had lower berry integrity than comparable handpicked fruit. For the cultivars ‘Skeena’ and ‘Glen Clova’, hand-picked fruit always had more intense red coloration than machine-harvested fruit. There were less marked differences in Brix levels between hand-picked and machine-harvested fruit. The results suggest fruit colour and Brix levels are not suitable as the only guides to fruit quality. Measures of acidity and possibly also fruit firmness should be used to complement these tests if an accurate assessment of raspberry quality is to be gained. Biennial bearing, when compared with annual cropping, had no discernable effect on fruit quality in the season investigated.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421786

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The tamarillo,Cyphomandra betacea(Cav.) Sendt. (Solanaceae), is a minor fruit crop grown in New Zealand and in subtropical climates elsewhere around the world. There is little genetic variation in the cultigen, but characters of commercial importance have been observed in related wild species.Cyphomandra betaceawas crossed with nine otherCyphomandraspecies. Generally, fruit set was poor and no viable seed was set in the crosses attempted. The use of polyploid forms ofC. betaceain some species crosses did not enhance the success of interspecific hybridisation. Various stages of cross failure were identified, most of which were post-zygotic. The data would suggest that incongruity, rather than the S locus, is governing interspecific compatibility in this genus. Suggestions are made for the future genetic improvement of the tamarillo by interspecific hybridisation.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421787

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Axillary buds of Japanese persimmon (Diospyros kakiThun. cv. ‘Hiratanenashi’) were decontaminated, their budscales removed aseptically and placed in modified Murashige and Skoog (MS) medium containing 4.5 μMzeatin. Over 60% of the buds initiated shoots in 6 weeks. A multiplication rate of over 10-fold could be achieved in 6–8 weeks by two transfers (shoot proliferation and shoot elongation) in the same medium. Attempts to initiate shoots from meristem tips were unsuccessful. Using shoots that are > 25 mm long, c. 85% rooting was accomplished over a 6-week period in diluted (nitrogen content, 1/4 strength; other nutrients, 1/2 strength) MS medium containing 2% activated charcoal and 4.9 μMindole-3-butyric acid (IBA) with a liquid overlay of the undiluted medium containing 4.5 μMtrans-zeatin (t-Z). Techniques are also described for the regeneration of whole plants from leaf segments (from in vitro propagated plants) using a combination of t-Z (10 μMand anyone of three auxins tested—indole-3-acetic acid, IBA or (α-naphthalene acetic acid (0.001-0.01 μM). The presence of auxins was not essential but slightly accelerated the organogenic callus formation and organogenesis. Rooted plantlets were planted into a mixture of peat, perlite, and CaCO3and acclimatised in a fog tent for 4–8 weeks.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421788

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The fungicides iprodione, vinclozolin, and procymidone were compared for the control of onion white rot in two trials in the Pukekohe (South Auckland) district of New Zealand during the 1984–85 and 1985–86 crop years. Neither iprodione nor vinclozolin was effective as a seed treatment or as a combination of seed treatment and foliar sprays. Procymidone was highly effective when used in a combination of seed treatment (5.0 g a.i./kg seed) and foliar sprays (0.75 kg a.i./ha monthly × 4). In the year of higher disease incidence (1984–85) plant losses were reduced from 58 to 20% using a combination of procymidone seed treatment and foliar sprays. In-furrow applications of procymidone (3.0 kg a.i./ha) at planting were highly effective in controlling the disease but were severely phytotoxic to young plants. Highest yields were obtained in procymidone-treated plots. Seed treatment with iprodione gave higher yields than did untreated controls (captan 8 g a.i./kg seed) despite the failure to control white rot. The failure of both iprodione and vinclozolin to control disease in these trials, whereas both were effective in previous trials, suggests that these chemicals may have succumbed to the phenomenon of enhanced degradation in the soil.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421789

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Various methods of application of the fungicide procymidone were evaluated for the control of onion white rot (Sclerotium cepivorumBerk.) in field trials carried out in the 1986–87 and 1987–88 crop seasons. The conventional method of seed treatment followed by foliar sprays (monthly × 4) reduced disease incidence by 71 and 95% (of untreated control) in the respective seasons. When applied as a dispersible granule to the soil surface above the seed immediately after planting, disease incidence was reduced by 89 and 95% respectively. Application of procymidone to the soil surface as a spray gave similar control but induced transient symptoms of phytotoxicity in the young seedlings. A slow release formulation of procymidone applied as a seed dressing was more effective than the conventional formulation for seed dressing, and, when followed by foliar sprays, an 85% reduction in disease incidence was obtained. Iprodione applied as a seed treatment followed by four foliar sprays gave a moderate reduction in disease incidence (42%, 60% in respective trials). Procymidone granular formulations are convenient to apply and highly effective against the disease and offer good commercial prospects.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421790

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Light intensity, photoperiod, relative humidity, and temperature during fern growth and fernage at timeof inoculation, and wetnessduration, light intensity, and temperature during infection period were examined to establish their effect on severity ofStemphyliumleaf spot on asparagus. Plants were inoculatedwith a conidialsuspension of two isolates ofStemphyliumsp. from asparagus. Disease assessments based on percentage stem area necrosis,percentagediebackof stem,and percentage infection of cladode tissue were made 10–14 days after inoculation. Asparagus fern grown under conditions of low light (particularly a reduced photoperiod), high relative humidity, and temperature became severely infected. Disease severity decreased with increasing age of fern at time of inoculation. Two days of wetness following inoculation were sufficientfor maximum diseasedevelopment; plants held at low temperature (14°C) had higher levels of infection than those held at 20 or 26°C. Light intensityduring the infection period had no effect on disease severity levels. Of the three methods of disease assessment, cladode infection provided the most reliable measure of disease severity levels. The method of assessing percentage of cladode infectionon a group of seedlingsin a pot was more reliable than the assessments made on individual seedlings.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421791

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Fusariuminfection of barley, maize, oats, and wheat was determined in a total of 362 samples of grain harvested in New Zealand during 1987, 1988, and 1989. The incidence of other fungi with toxigenic potential such asMicrodochium nivale, Diplodia maydis, andPenicilliumandAlternariaspecies was also recorded. The amount ofFusariuminfection varied with grain type and region of origin. Samples from the South Island had a lower levelof infection than samples from the North Island. Maize had the highest level of infection.F. graminearumandF. crookwellensewere the Fusarium species most frequently recovered from maize, whereasF. graminearumandF. culmorumwere the most common species isolated from barley and wheat grown in regions showing a high level of infection. A number of potentially toxigenicPenicilliumspecies were recovered from maize.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421792

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Fusariuminfection in field and stored maize from the Waikato region of New Zealand was determined in 1988 and 1989.F. crookwellense, F. graminearum, andF. semitectumwere the most common species isolated from leaf pieces, field kernels, and stored maize. The proportion ofF. semitectumwas greatest on stored maize. Levels ofFusariuminfection on leaf pieces and field kernels were high in both years, as was the level of insect damage. Other potentially toxic fungi were also recorded, namely,Alternaria, Aspergillus, Diplodia, andPenicilliumspecies. Field maize yieldedPenicilliumspecies of low toxicity, but 22 isolates ofP. crustosum, a potential mycotoxin producer, were isolated from the 1988 and 1989 crop of stored maize, as well as 17Diplodia maydisisolates and 53 non-toxigenicAspergillusisolates.

ISSN:0114-0671    

DOI:10.1080/01140671.1991.10421793

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor