Chromosome doubling has been widely explored as a bridge to help gene introgression between different ploidy levels both between and within species for crop improvement (Hayward et al., 1993; Meru, 2012; Wu et al., 2011). Both fruit and seed are often larger after chromosome doubling (Campos et al., 2009; Wu et al., 2012; Ye et al., 2010). However, very little information has been available on the effects of increasing ploidy level on other attributes of fruit quality considered important in crop improvement.
Actinidia Lindl. (kiwifruit) species have only relatively recently been introduced into cultivation and grown as commercial crops. Most kiwifruit produced are consumed fresh (Ferguson, 2009), so returns to producers depend on the prices obtained for the fresh fruit. Factors influencing fruit price include total supply, season of supply, cultivar and, most important, fruit quality.
Fruit quality in kiwifruit has many components such as fruit size, shape, flesh texture, color, flavor, firmness, DM, SSC, vitamin C content, core size, and skin color and thickness. Further expansion of the kiwifruit industry will require the development of new cultivars with enhanced sweetness, flavor, and storage life and a variety of flesh colors (Ferguson and Seal, 2008) as well as optimum fruit quality with easy handling during field management and harvesting, packing, storage, and marketing.
In this article, we compare some aspects of fruit quality in some diploid selections of Actinidia chinensis with those of fruit from autotetraploids produced by colchicine-induced chromosome doubling. Our aim was to determine the effects of increasing the number of genomes on fruit quality and development using a number of easily measured attributes. During fruit development, SSC at harvest is an indicator of fruit maturity, and DM content reflects the potential SSC at eating ripeness once starch reserves have been converted to sugar (Burdon et al., 2004; Feng et al., 2011). Flesh firmness can also be used to assess fruit maturity and storage ability. One of the selections studied was ‘Hort16A’ and autotetraploids derived from it. As fruit of ‘Hort16A’ mature, the flesh color changes from green to yellow, and flesh hue angle (ho) is one of the key parameters used to determine the quality and maturity of its fruit because the color appeals greatly to consumers. The three other selections studied came from a program to develop kiwifruit with red flesh: the extent and intensity of red pigmentation are important parameters for assessing quality in these selections. These various quality attributes were used to assess the possible commercial potential of the different selections and the autotetraploid plants derived from them.
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