Cultivated caladiums (Caladium ×hortulanum Birdsey) are members of the aroid family and have been important pot and landscape plants (Evans et al., 1992). They are known for their bright and colorful leaves, adaptation to tropical and subtropical environmental conditions, and low landscape maintenance requirements. Caladiums are believed to have resulted from intra- or interspecific hybridization among several species that originated from the New World's tropical regions, including C. bicolor (Aiton) Vent., C. marmoratum Mathieu, C. picturatum C. Koch, and C. schomburgkii Schott (Birdsey, 1951; Hayward, 1950; Wilfret, 1993). They are diploids with 2n = 2x = 30 chromosomes (in Darlington and Wylie, 1955) and are propagated asexually through tuber division in the trade. Central Florida growers produce greater than 95% of the tubers used in the world for pot plant forcing and landscape planting (Bell et al., 1998; Deng et al., 2005).
The ornamental value of caladiums used as pot or landscape plants is determined primarily by leaf characteristics. Improving leaf characteristics or generating new combinations of them has been one of the most important objectives in caladium breeding and cultivar development (Wilfret, 1993). To increase breeding efficiency, efforts have been made in recent years to gain a better understanding of the inheritance of foliar traits. These efforts have resulted in a number of findings. For example, it has been found that the three main leaf shapes in caladium (fancy or heart-shaped, strap or linear-shaped, and lance, an intermediate between fancy and strap) are controlled by a single locus with two codominant alleles (F and f) (Wilfret, 1986). The three main vein colors (red, white, and green) are determined by a single locus with three alleles (Vr, Vw, and Vg) that are independent from the leaf shape locus (Deng and Harbaugh, 2006; Wilfret, 1986). The presence of leaf spots is controlled by a single locus with two alleles that are inherited independently from leaf shape but closely linked with the color of the main vein (Deng et al., 2008).
Another major foliar trait in caladium is leaf blotching, the occurrence of numerous irregularly shaped color areas between major veins on leaf blades. Leaf blotches may appear singly or coalesce to large areas of coloration, up to several inches on mature leaves. This pattern of coloration in combination with bright colors has resulted in attractive, highly valued and desired caladium cultivars, including Carolyn Whorton and White Christmas. With large pink or white blotches, ‘Carolyn Whorton’ and ‘White Christmas’ have been the most popular fancy-leaved pink or white cultivars (Bell et al., 1998; Deng et al., 2005). Interest in incorporating this coloration pattern into new cultivars has been strong, but information on the inheritance of this trait has been lacking.
Leaf blotches as well as color bands or stripes are common in several aroids and have resulted in diverse and intriguing foliar coloration patterns in these plants (Henny, 1988). These coloration patterns have been a major contributing component to the ornamental and/or economic value of a number of important ornamental aroids (Henny and Chen, 2003). For example, the occurrence of white bands, silvery light gray or gray–green blotches, and silvery stripes in various portions of leaves has resulted in a number of distinct coloration or variegation patterns in several aglaonema species (Aglaonema Schott) (Henny, 1986). Dieffenbachia (Dieffenbachia Schott) cultivars often have leaf areas in different shades of green, yellow, cream, and white or combinations of these colors. Controlled crosses and segregation analysis in aglaonema and dieffenbachia have shown that the inheritance of some of these patterns is controlled by nuclear loci with multiple alleles (Henny, 1982, 1983, 1986).
The objectives of this study were to understand the mode of inheritance of leaf blotching in caladium, to determine the genetic relationship between leaf blotching and vein color, another important foliar trait for caladium, and to infer the genotype of important caladium cultivars for leaf blotching.
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