摘要:

Thirty-one sorghum hybrids were evaluated for ergot ‘escape’ resistance at Bethlehem and Potcherstroom during the 1996/97 and 1997/98 seasons. Trials were designed so that flowering and artificial inoculation occurred over a range of flowering dates and thus, ergot potentials Non-linear regression analysis was applied to determine the relationship between ergot potential of a flowering date and observed ergot severity in a hybrid. Ergot potential of a flowering date was calculated from weather data and is defined as the expected ergot severity in a genetically broad-based sorghum population. Ergot resistance was quantified using the Ergot Breakdown Point which is the ergot potential required to induce disease, arbitrarily taken as 5% observed ergot severity (5%EBP), Sixteen hybrids showed various degrees of resistance with 5% E BP'S which ranged from 5.2–34.6%, Most 5% EBP's tended towards the lower end of the scale. Similarly hybrids differed in the rate of resistance breakdown. The relationship between pollen viability and ergot potential was quantified in five hybrids and in all cases the relationship between weather induced reductions in pollen viability and increased ergot susceptibility was highly significant, Results suggest that hybrid resistance to ergot is relatively low and can be significantly improved.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634857

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Among other disadvantages, low hullability of sunflower seed results in oil cake with a high fibre and low protein content. Hullability is known to increase with increased seed size. Seed size generally decreases with an increase in plant density. The objective of this experiment was to determine the effect of plant density on hullability other physical trails and chemical seed composition of three sunflower cultivars. In a field trial at Potchefstroom the cultivars HV 3037, PAM 7392 and SNK 37 were planted in rows 0.9 m apart at densities of 20 000, 35 000 and 50 000 plants per ha in a randomised complete block, design with two replicates. Yield and seed trails differed among cultivars. Seed oil and protein content was not affected by plant population. Grain yield and hull content were significantly higher for the 20 000 than for the 35 000 and 50 000 populations. The thousand seed weight, a measure of seed size, decreased for all cultivars with increased plant population, The hullability of HV 3037 and SNK 37 declined with increased plant population, while it changed relatively little for PAH 7392. Higher hullability for the 20 000 population resulted in a higher protein content of the kernel rich fraction. Indications are that plant populations lower than the recommended 35 000 plants ha−1will maximise hullability and minimise losses due to fine material.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634858

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Eriocephalus punctulatus, also known as, ‘Kapok Bos’, belongs to the Asteraceae family. It is an attractively scented woody shrub, that reaches a height of about one metre. It produces a highly priced essential oil with a dark blue colour and an attractive fresh fruity fragrance. The most profitable time to harvest this crop in the Eastern Cape is during the months of October and November when the plants have reached the full flower/seed set stage. However, there is a major reduction in oil yield, per kilogram of vegetative material, during transportation from the cultivation fields to the extraction facility, particularly if the wind speeds exceed 50 km/h. Oil yield was increased if the material was processed a few days after harvest.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634859

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The first phase in the domestication programme ofEriocephalus punctulatusinvolved establishing how this crop could be harvested without adversely affecting plant vigour and longevity. The second phase of the domestication programme was the development of harvesting schedules that would result in high yields of oil without affecting the longevity of the plants. Highest oil yield occurred in mature plants once they had reached the flowering stage. For optimum oil recovery, harvested material must be processed within seven days. Other post- harvesting management practices such as the effect of drying plant material before distillation were also evaluated.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634860

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Wheat crops produced under dryland conditions in the winter rainfall region of South Africa often experience periods of water stress. It is, therefore, important to identify spring wheat cultivars that can withstand these conditions. The multitude of factors potentially involved in drought resistance make it unlikely that a single measurement will provide an all-encompassing test of drought tolerance. The aim of this study was to determine whether total ear water potential, relative water content (RWC), leaf diffusive resistance (LDR), transpiration rate and the accumulation of free proline could be used to distinguish between drought tolerant and drought sensitive spring wheat cultivars. The withholding of water and the use of polyethylene glycol (PEG) imposed stress at different physiological growth stages. It was shown in this study that these physiological parameters could be used to identify drought tolerance in spring wheat cultivars. Although genetic differences, as measured by the above-mentioned parameters, do exist between cultivars, the effect of water stress on plant growth and harvest data should also be taken into account in deciding whether these differences are of any commercial benefit.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634861

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Approximately 90% of the annual wheat crop produced in the Republic of South Africa is milled into flour for bread-baking purposes. The percentage of flour extracted, as well as the dough development properties, determine the milling and dough mixing characteristics. In an increasingly deregulated market environment, these quality characteristics largely determine the price of the wheat. The ability of cultivars and localities to produce high quality wheat grain must, therefore, be classified. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995. Similar production practices were followed at all localities. AMMI (Additive Main Effects and Multiplicative Interaction) analyses were used to describe the effect of cultivar, environment and their interaction on flour extraction yield, Falling Number, gluten, as well as Mixograph dough development time, peak height and band width. Environment was found to be the most important contributor to variance for all characteristics determined. No significant cultivar × environment interaction was found for flour extraction yield. Cultivar as a main effect contributed only 2.5% to the variation in flour extraction, while that of environment was 68.7%. Significant cultivar × environment interactions were found for Falling Number, gluten content, dough development time, peak height and band width. Interactions were particularly strong for cultivars such as Palmiet and Adam Tas in the case of Falling Number and gluten content, indicating a lack in stability in these properties. Nantes, SST 55 and to a lesser extent SST 16 and SST 66, showed considerable sensitivity with regard to dough development time, peak height and band width. Cultivar reaction over years may, therefore, vary considerably at the same locality. It is thus almost impossible to classify cultivars and localities according to these characteristics.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634862

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Protein content and quality determine flour quality, as well as the success of bread-baking. The stability of wheat quality characteristics is of great importance to the milling and baking industry, who have to produce an end product of acceptable and consistent quality to the consumers. It is, therefore important to classify cultivars and production regions according to their ability to produce high quality wheat grain. Seven spring wheat cultivars were grown at nine localities for the period 1992 to 1995 for the purpose of this study. The effect of cultivar, environment and their interaction on water absorption, Alveograph characteristics and loaf volume were described by AMMI (Additive Main Effects and Multiplicative Interaction) analyses. Environment was found to be by far the most important contributor to variance for all the characteristics determined. Except for water absorption, where the effect of cultivar was not significant, cultivar, environments, as well as cultivar × environment interaction, significantly affected all these characteristics. SST 16 showed considerable cultivar × environment interaction for water absorption, Alveograph W-value and loaf volume, indicating a lack in stability for these parameters. Adam Tas, on the other hand, showed sensitivity for the Alveograph characteristics. This tendency may be ascribed to the effect of cultivar × environment interaction on grain protein content. Cultivar reaction may, therefore, differ from year to year at the same locality.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634863

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Clivia miniataRegel is widely cultivated as a garden ornamental and a pot plant. It occurs in many attractive shades of orange, red, yellow and pink but little information exists regarding its use as a cut flower. The possibility of picking cut flowers when all the flowers on the inflorescence are still closed and forcing flowers to open in distilled water and in Chrysal AKC™ was examined. A forcing temperature of 21 ± 2°C and an irradiance of 22 ± 3 μmol photons m2s−1was used. After 190 hours, in both distilled water and Chrysal AKC™, more than 90% of flowers had opened and developed normal coloration. However, after 96 hours, 90% of inflorescences held in distilled water and 10% of those in Chrysal had developed peduncle splitting. The mechanism involved in the prevention of splitting is unknown but it is suspected that sucrose may have caused this.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634864

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Transient transformation was optimised for bread wheat,Triticum aestivum L.cv Kariega, using a particle inflow gun constructed at ARC-Roodeplaat. Excised immature embryos, culturedin vitrofor 5 to 7 days, were bombarded with pAHC25 and analysed for the presence of the β-glucuronidase reporter gene. Three bombardment variables were optimised and most blue spots were obtained with a helium pressure of 600 kPa, 20 mm particle flight distance and 0.4 Mosmoticum in the bombardment medium. Furthermore, the maize ubiquitin promoter was shown to be functional in Kariega.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634865

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Aqueous ammonia was used to determine its effectiveness as a soil steriliser for use in glasshouses and to see if it can be used as an alternative sterilising method. A sandy soil was used to examine the effect of aqueous ammonia on the numbers of weeds, nematodes and microbes. The aqueous ammonia was applied to 1 kg of soil in doses of 2, 4, 6 and 8 ml with three contact periods of 24,48 and 72 hours for each dose. The application of ammonia water to the soil produced a clear decline in the numbers of weeds, nematodes and microbes. There was a direct correlation between the decline in numbers with an increase in dosage and time.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634866

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor