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  • Author or Editor: R. J. Monroe x
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Abstract

Experimental results from horticultural field trials are obscured by the effect of systematic variation. This variation is directly related to the position of the plot in the field and is referred to as a fertility gradient(s). Trend analysis eliminates the effect of fertility gradients by fitting a polynomial regression equation (response surface model) to the systematic variability in the experimental units. Two cultivar trials of potato (Solanum tuberosum L.) conducted to compare results from trend analysis with that using the standard design analysis indicated that fertility gradients existed in the fields and were of a form that could be adequately fitted by a response surface model. A 3-dimensional plot of the response surface model indicated that the fertility gradients formed a very complex surface which could not be eliminated by experimental design. Of the 3 experimental designs used, the Latin square was the most efficient while the completely random was the least efficient. Trend analysis resulted in a large gain in relative efficiency over the standard analyses of completely random and randomized block designs. It also resulted in a substantial gain over that of a Latin square design. Adjusting the means using a response surface model in trend analysis also improved treatment estimates. Tests of significance using adjusted means were more precise and easier to interpret. Trend analysis proved to be the most efficient way to analyze the data, regardless of the experimental design used.

Open Access

Abstract

‘Nugget’, ‘Gem’, ‘Goldrush’ and ‘Centennial’ sweet potato cultivars were grown for 3 yr at 3 locations in North Carolina. Root samples were collected at peak harvest (about October 1) each year and examined for intercellular space (IS). At 1 location each year a collection was made 3 wk prior to peak harvest, at peak harvest, and 3 wk after peak harvest. Cultivars differed significantly from one another in IS at harvest and averaged 6.26, 7.32, 8.41 and 9.85 ml/100 ml of root for ‘Nugget’, ‘Gem’, ‘Goldrush’ and ‘Centennial’, respectively. Over the 3-yr period IS did not differ significantly due to location, time of harvest, or years.

Open Access

Abstract

Fruit of 104 clones and 75 seedlings of highbush blueberries were assayed for acidity, soluble solids, and keeping quality. From this group, 9 clones were selected to represent 4 extreme soluble solids and acid classes. These 9 clones were harvested over 2 years at 2 North Carolina locations. The previously reported relationships between high fruit acidity (Ac) or low soluble solids-to-acid ratio (SS/Ac) and high keeping quality (low DK) were extended from a few cultivars to a population of representative blueberry genotypes. Approximately 80% of the decay variability can be accounted for by various soluble solids and acid measures indicating that a soluble solids and acid measure would be useful to the breeder for segregating clones into those of poor, intermediate and good keeping quality. Suggested clonal discriminatory Ac, SS/Ac and pH x SS levels were proposed, and the possibility of field screening of blueberry clones for keeping quality potential was examined.

Open Access