摘要:

The causes of genotype interaction with the environment was investigated using AMMI (Additive Main Effects and Multiplicative Interaction)analysis. AMMI quantified environments by means of E_IPCA1 (first principal component analysis for environment) such that it was highly significantly correlated (r = -0.79) with accumulated growing degree units (GDUs) during the growing season. G_IPCA1 (first principal component analysis for genotype) scores were highly significantly correlated with growth rate related observations, such as days to 50% pollen shed (-0.77), days to physiological maturity (-0.81), and grain moisture at harvest (-0.87). Multiple linear regression analysis of data led to the conclusion that GJPCA1 scores can be explained with R2= 0.80 accuracy from a combination of grain moisture at harvest and either days to physiological maturity, or days to pollen shed. The AMMI required that E_IPCA1 and G_IPCA1 scores should, both be either positive or negative in order to increase AMMI1 yield estimates. This means that hybrids with a slower growth rate will be better adapted to environments with more GDUs during the growing season, and hybrids with a faster growth rate will be better adapted to environments with less GDUs during the growing season. This conclusion suggests that temperature, especially minimum night temperature, which determines the rate of development between physiological stages in the maize plant, may be a major contributor to genotype by environment interaction.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634888

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Identification of cowpea varieties with superior grain yield and high nitrogen fixing potential is crucial to increasing productivity of the crop among small-scale farmers in the Northern Province. A field experiment was established during the 1997/98 growing season to evaluate six cowpea varieties for their grain yield, protein content, yield components and proportion of seed N derived from symbiotic fixation (%Ndfa) through the natural abundance technique. The varieties evaluated were PAN311, Glenda, Bechauana white, Chappy, Encore and NWK. PAN311 produced the highest grain yield of 1635 kg ha−1which was 90% higher than the average across varieties. The lowest yielding variety was Glenda with an average of 368 kg ha−1. The high grain yield of PAN311 could be attributed to its high number of pods per plant, seed mass as well as harvest index. Seed protein concentration ranged from 237–275 g kg−1but did not differ among the varieties. Estimates of %Ndfa in seed ranged from 23.02–28.80% with Bechuana white showing the highest dependance and PAN311 the least. PAN311 is clearly the highest grain yielding variety, though several of the other varieties have the potential of improving farmers yield which is estimated to be about 400 kg ha−1.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634889

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The response of sunflower (Helianthus annuusL.) seed yield and seed processing quality to the amount and timing of nitrogen were studied in a field trial. Nitrogen application rates were 20, 70 and 120 kg ha−1with limestone ammonium nitrate as the nitrogen source. Timing of application treatments were all nitrogen applied at planting and split in ratios of 1:1 and 1:3, applied at planting and at the beginning of flowering. Timing of nitrogen application had no effect on seed yield or any of the seed quality characteristics. Seed yield increased on average by 22% per 50 kg of nitrogen applied per ha. Hullability was not affected, while seed oil content declined and the seed protein content increased moderately with increased amounts of nitrogen, leading to a decline in the amount of recoverable oil, an increase in the potential oil cake yield, an increase in the protein and decrease of the crude fibre content of the expected oil cake. The changes in seed quality characteristics were equal or less than 10% per 50 kg of nitrogen applied per ha.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634890

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Aluminium toxicity was investigated by analyzing the reaction of hydroponically-grown plants of two ecotypes ofT. triandrato Al (0, 25, 50, 100 μM; pH 4.1; for 28 days). The Al-tolerant 'Berg ecotype responded to the Al treatments by increasing root extension growth, D.M. production and they also controlled water-use over the full range of Al stresses. In contrast, Al inhibited root growth and D.M. production in the Al-sensitive Zululand ecotype and they also failed to control water-use at 100 μM Al. Microscopical investigation showed that the root cells of both ecotypes were generally resistant to Al with cellular disorganization being confined to the Zululand plants at the highest Al stress. The root caps of both ecotypes responded to Al in ways (amyloplast numbers, cap volume, secretions) which coincided with the contrasting growth responses observed in 'Berg and Zululand plants. Aluminium tolerance involved the accumulation of Al in the roots of 'Berg plants and was coincident with increases in root P and K concentrations. Consistent differences in water-use existed between ecotypes and control over water-use was linked to root growth. These findings are used to develop a theory covering the regulatory mechanisms involved in controlling root extension growth, Al tolerance and water-use.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634891

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Fourteen spring and winter hard red South African wheat (Triticum aestivumL.) cultivars were compared for their regeneration and transient anthocyanin expression efficiencies. Embryonic and non-embryonic callus, as well as plantlets, were obtained from all the cultivars cultured on a modified Murashige and Skoog basal medium supplemented with 5 mg l−16-Benzylaminopurine. Gamtoos and TugelaDn1were the best cultivars for the development of both roots and shoots. None of the cultivars produced callus or plantlets on ML3 medium. Transient anthocyanin expression was obtained in winter, as well as spring, hard red wheat cultivars. Using the nondestructive anthocyanin reporter-gene, it was established that the spring wheat cultivars PalmietDn1, PalmietDn2and PalmietDn5were the most suitable cultivars for future transformation studies, determined by the percentage bombarded calli expressing anthocyanin after two to three weeks.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634892

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Genetic engineering is an important tool which can be used together with conventional breeding methods in transferring certain economically important traits into cultivated varieties of almost any crop species. One of the methods for gene transfer is the particle bombardment technique. Several primary explants can be used with this technique for the transformation of groundnut. This study explored the use of mature embryo axes as explants for somatic embryogenesis, and determined the effect of medium composition on four South African genotypes. A modified Murashige and Skoog-medium was used with various concentrations of picloram. Mature embryo axes were found to be a suitable explant for induction of somatic embryogenesis. A significant difference was found in the response of the different genotypes to medium composition.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634893

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The morphological traits that are traditionally used to identify potato cultivars are not always reliable, especially when dealing within vitroplants. Various molecular marker techniques have been described for cultivar identification, but the Simple Sequence Repeat (SSR) technique has certain qualities that render it highly suitable for this application. In this study five SSR primer sets were used to characterize twenty-four commercially important potato cultivars. All profiles were found to be reliable and no variation was found between clones of the same cultivar. The number of polymorphisms detected with each of the markers varied, but none of the primers yielded only monomorphic fragments. The multilocus primer, STIIKA produced unique profiles for each of the 24 primer sets. However, the complicated nature of the profiles limits its use for routine diagnostic purposes. The use of the markers STS and STU 69633 the fact that they can be analysed simultaneously on one gel, saves time and costs. The present study thus confirms that SSRs can be employed in a routine profiling system to provide highly discriminative and standardized profiles for South African potato cultivars.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634894

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A study to assess the effectiveness of some zucchini [Cucurbita pepo(L.)] cultivars in limiting the effects of virus disease in zucchini crops was conducted at Bayne's Drift, KwaZulu-Natal. The severity of disease was assessed using a visual rating scale. No yield data was collected. ‘SQ 229’, ‘Puma’, ‘SQ 228’ and ‘Gemma’ offered some control. These cultivars may be useful in increasing production in areas severely affected by the virus diseases considered in the study.

ISSN:0257-1862    

DOI:10.1080/02571862.2000.10634895

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor