Subjective ratings are also difficult to make because of the continuous variation expressed for this trait. Large numbers of people would need to rate a population of fruit to create a consistent average. Subjective rating scales may work well for one person's analysis but inherently vary with other raters. Manual measurements of fruit are impractical as a result of the large number of fruits needing to be tested in a population. However, to perform studies of the genetic markers for fruit elongation, the fruit shape must first be quantified. The discovery of these markers could assist in future breeding selections by allowing a breeder to determine a selection's ability to produce elongated fruit without waiting several years for a crop. With this population exhibiting continuous variation, it was thought that the genetic markers responsible for regulating fruit shape could be found. The resulting population exhibited large phenotypic variation, particularly for berry shape. The female parent was seeded and had very elongated berries. The male parent had large, round to oblong, seedless berries. In 2001, a cross was made at the University of Arkansas between the selections A-2315 and A-2659 (J.R. Overall, breeders routinely assess fruit shape however, those shapes that are odd or undesirable are often discarded or only kept as potential parental material rather than primary selections. Although it is rare for apples to be taller than wide, it is possible to use the height-to-width ratio of the parents to predict the progeny's ratio as well ( Janick et al., 1996). One article discusses flat versus oblong apple ( Malus domestica L.) shape ( Janick et al., 1996). No elongated cultivars have been released, but in the growing area of specialty fruits, these elongated berries could have a promising future in the marketplace.Īlthough fruit shape is an important characteristic in fruit breeding, few articles exist in the literature that discuss shape as a specific breeding objective. This elongated fruit shape trait has remained in the Arkansas grape breeding program and subsequent crosses have been made to further express this trait. Moore believed that the elongated shape was attractive in a table grape, so he continued to intercross selections (J.N. This cultivar is unique for its elongated berry shape ( Clark, 2003). Moore performed some crosses with the cultivar Lady Patricia ( Clark, 2003), which was released by the University of Illinois in 1968 ( Clark, 1997). James Moore started the grape breeding program at the University of Arkansas ( Clark, 2003). Keywords: grape breeding small fruits fruit characterization This technology should be useful for shape characterizations in other fruits as well. This analysis method was a reasonably quick and simple way to quantify grape berry shape, yielding valuable phenotypic data in numerical form. When compared with the human ratings, results showed strong correlations of r = 0.941 for major:minor axis ratio, r = –0.804 for shape factor, and r = 0.744 for compactness. Computer findings were compared with data from human raters using a simple correlation. The program discriminately selected image pixels representing the fruit and determined the area and perimeter of a grape berry, which were subsequently used to calculate the major:minor axis ratio, shape factor, and compactness values. Each segregant of a population of table grapes ( Vitis spp.) with parents of wide shape variation was photographed and analyzed for shape using SigmaScan ® software. Therefore, a method was developed to analyze digital images containing multiple fruits to characterize fruit shapes. Subjective rating scales can also be used, but their effectiveness is questionable when done by multiple raters resulting from varying descriptive standards among individuals. Objective manual measurements can be performed on small samples of fruit, but this method is difficult and very time-consuming when dealing with larger samples or when shapes are complex or shape variations are slight. Quantifying fruit shape is challenging, particularly when measurements are made on segregating populations of plants.
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