ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635116

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The relative contribution of main stems and tillers, as well as the relative contribution of first, second and third kernels in spikeiets to grain yield and grain protein content, is seldom quantified. The grain yield of main stems, tillers and relative mass of kernels in the spikelet by floret position were determined in a long-term fertilization and irrigation experiment at the University of Pretoria. A randomized complete block design in a split-plot arrangement with three replicates was used. Main plots consisted of two different soil fertility levels and subplots were assigned to four cultivars. Mean grain yield of main stem (MS), first tiller (T1) and second tiller (T2) for the cultivar Kariega was 1.26 g, 0.98 g and 0.53 g respectively, 1.29 g, 0.78 g and 0.40 g for Carina, 1.63 g, 0.69 g and 0.09 g for Inia and 1.71 g, 1.10 g and 0.51 g for SST 86. Within a cultivar, the respective ears (MS, T1and T2) did not differ in mean grain protein content, but significant differences were observed among the cultivars with Kariega averaging 16.2% while SST 86 and Inia averaged 14.5%. Main stems contributed on average 68.6%, first tillers 24.8% and second tillers 4.4% of the mean yield per unit area. Main stems produced on average 44.1 grains, first tillers 28.9 grains and the second tillers 15.3 grains. Main stems constituted 51.7% of the total ear number per unit area, first tillers 30.3% and the second tillers 14.4%. First kernels were on average 9.3% larger than second kernels, and 26.5% larger than third kernels, but did not differ in grain protein content. Increasing soil fertility increased fertile ear number per unit area, grain yield of main stem and first tiller, decreased that of second tiller but did not affect grain number of main stem or first tiller, while kernel mass and grain protein content was increased slightly by relative position in the spikelet. Significant interactions between soil fertility and cultivar were observed for ear grain number and protein content, and grain protein content in different floret positions. Under the experimental conditions, grain yield was largely contributed to by main stems and first tillers, and especially first and second kernels in the spikelet.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635117

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Silking which coincides with the mid-summer drought in South Africa, could have a significant negative effect on maize yield. Errors in the prediction of silking date could contribute to errors in kernel number simulation, and consequently to errors in yield simulation. A field trial, comprising 21 planting dates and three cultivars representing short, medium and long growing season requirements was used to modify the crop growth model CERES3 (Maize) to improve its accuracy in the simulation of silking date by four days. The results were verified against a historical data set and showed an improvement in the simulation of silking date by two days.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635118

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A stem rust resistance gene, originally derived fromTriticum tauschiiaccession RL5289 and present in the germplasm line 87M66-2-1, is here designatedSr45. Sr45was found to be closely linked toSr33(9 ± 1.9 map units) and the centromere (21 ± 3.4 map units) on chromosome arm 1DS.Sr45is believed to be the same gene asSrX.The Russian wheat aphid resistance gene,Dn5, was loosely linked (32 ± 5 map units) toEp-D1b, which occurs on a translocation derived fromT. ventricosum, and to thecn?D1locus (37 ± 6.3 map units) on chromosome arm 7DL.Dn5derives fromT. aestivumaccession Pl294994 which was found to express two novelEp-1alleles (proposed designationsEp-A1dandEp-D1e).A gene (here designatedDn7) for Russian wheat aphid resistance that was derived from the rye accession, Turkey 77', mapped 14.5 ± 3.9 map units fromLr26on the 1BL.1RS translocation.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635119

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In the Western and Southern Cape the quality of wheat varies annually due to variable climatic conditions. This holds a commercial risk to the milling and baking industries in delivering the refined products to their respective clients. It is, therefore, important to classify cultivars and localities according to their ability to produce high quality bread wheat grain. In this study, similar production techniques were used to grow seven spring wheat cultivars at nine localities for the period 1992 to 1995. AMMI analyses were used to describe the effect of genotype, environment and their interaction on grain yield, kernel protein content and hectolitre mass. Environment was found to be by far the most important parameter of variance. No significant genotype × environment interaction was found for grain yield. Although cultivars differed in their yield potential, genotype as a main effect contributed only 1.3% to the variation in yield when compared to 90.7% for environment. Significant genotype × environment interactions were found for grain protein content and hectolitre mass. Cultivars such as Palmiet, Nantes, SST16 and to a lesser extent Adam Tas, showed considerable sensitivity to both high and low protein areas, indicating a lack-in stability for this parameter. Annual variation in rainfall during the grain filling period dominated environmental variation for hectolitre mass, making it almost impossible to classify cultivars and regions according to their ability to produce high hectolitre mass.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635120

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In forestry the need to manage plantations on a sustainable site-specific basis requires the understanding and management of any growth limiting factors. Soil water regime is a factor considered to be of prime importance with respect to explaining differences in tree growth. In research studies measurement of soil water content is carried out on a regular basis and due to theft and vandalism, soil water sensing equipment cannot usually be left on site. Other rapid methods to determine soil water content therefore have to be found. The ThetaProbe and Speedy Moisture Testèr were compared as alternative measures of soil water content determination in the top 10 cm of the soil to the more traditional gravimetric method. These methods were tested in KwaZulu-Natal on two contrasting soils in terms of clay content, organic carbon content and soil water content. Regression analysis performed to compare the two different methods with the gravimetric method as a reference, indicated that they were similar on a soil specific basis at theP< 0,001 level of significance. With calibration, they were found to be equally suitable for the purpose of taking the measurements. Results and problems encountered are discussed for each method.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635121

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Vigour of pre-emergent sunflower (Helianthus annuusL.) seedlings is reduced when daily peak soil temperatures exceed 44°C resulting in poor emergence. Seedlings of sorghum (Sorghum bicolorL. Moench) are known to acquire thermotolerance to temperatures of 45–50°C as a consequence of a brief pre-exposure of the imbibing seed to 40°C. The aim of this investigation was to determine whether sunflower seedlings can acquire heat tolerance. Seed of three sunflower cultivare was used to compare the response to heat shock of 2 hr at 50°C in untreated and thermotolerance induced incubated seed. Heat tolerance was induced by exposure of the imbibed seed to 40°C for I h, 24 h before the heat shock. The response was assessed by comparing germination percentages and hypocotyl lengths. Germination percentages and hypocotyl lengths of seedlings differed significantly for cultivars. Hypocotyls of seed pre-exposed to 40°C were shorter than untreated seed indicating the inability of sunflower to acquire thermotolerance.

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635122

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0257-1862    

DOI:10.1080/02571862.1998.10635123

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor