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Zhanao Deng and Brent Harbaugh

Caladiums (Caladium×hortulanum) are ornamental aroids often forced in containers or grown in the landscape for their colorful leaves. The aesthetic value of caladium plants is largely determined by their leaf characteristics. Caladium breeding can be traced back to the mid-1800s when Gregor Mendel conducted his plant hybridization experiments, but information on the inheritance of caladium traits has been rather scant. To understand the mode of inheritance for three typical leaf shapes and three main vein colors in caladium, controlled crosses were made among commercial cultivars and breeding lines, and segregation of leaf shape and/or main vein color in the progeny was analyzed. The observed segregation ratios indicated that a single locus with three alleles seemed to determine the main vein color in caladium. The white vein allele was dominant over the green vein allele, but recessive to the red vein allele, which was dominant over both white and green vein alleles. The three leaf shapes (fancy, lance, and strap) in caladium seemed to be controlled by two co-dominant alleles at one locus. Leaf shape segregation was skewed in some crosses, which might imply the existence of other factors involved in caladium leaf shape development. Chi-square tests revealed that leaf shape and main vein color were inherited independently in caladium.

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Xiaohe Song and Zhanao Deng

Gerbera (Gerbera hybrida) is an important floricultural crop in the United States and worldwide. Powdery mildew (PM) caused by Podosphaera xanthii is the most common and destructive disease in gerbera production and landscape use. Gerbera breeding line UFGE 31-19 is one of the few sources of resistance to PM in gerbera and has contributed its resistance to new gerbera cultivars. To determine the mode of inheritance for PM resistance in UFGE 31-19, one of its PM-resistant (PM-R) progeny, UFGE 4033, was crossed with PM-susceptible (PM-S) cultivar, Sunburst Snow White, and their progeny were evaluated for PM severity. Distribution of PM severity ratings among the progeny was continuous but with two peaks, suggesting that the PM resistance in UFGE 4033 and UFGE 31-19 is a quantitative trait, likely controlled by major genes. Bulked segregant analysis (BSA) identified 17 molecular markers present in UFGE 4033 and the PM-R bulk but absent in ‘Sunburst Snow White’ and the PM-S bulk. Eleven of the molecular markers were mapped to one genetic linkage group, and two regions on this linkage group together explained 71.1% of the phenotypic (PM severity rating) variance in the segregating population. It was proposed that the two regions be named Rpx1 and Rpx2 (resistance to P. xanthii). Conidia of P. xanthii inoculated on the leaf surface of UFGE 4033 germinated, formed secondary germ tubes, and formed appressoria at high percentages, similar to those on the leaf surface of ‘Sunburst Snow White’. However, P. xanthii hyphae branched significantly less, were significantly shorter, and produced substantially fewer conidia on the leaf surface of UFGE 4033 and its PM-R progeny than on the leaf surface of ‘Sunburst Snow White’. These results should provide a sound foundation for use of UFGE 31-19 and progeny UFGE 4033 in gerbera disease resistance breeding and facilitate further investigation and understanding of the genetic bases of PM resistance in gerbera.

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Zhanao Deng and Brent K. Harbaugh

Cultivated caladiums (Caladium ×hortulanum Birdsey) are valued for their bright colorful leaves (Evans et al., 1992). They can be broadly classified into three groups based on leaf shape: fancy, lance, and strap (Deng and Harbaugh, 2006; Wilfret, 1986). Fancy-leaved caladiums have heart-shaped leaves with three main veins, petiole attachment peltate, and they have two large basal lobes. Strap-leaved caladiums have narrow, linear leaves with one main vein and no obvious basal lobes. Lance leaves are intermediate between fancy and strap types with leaf blades that are broad sagittate to cordate–lanceolate.

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Zhanao Deng and Brent K. Harbaugh

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Zhanao Deng and Brent K. Harbaugh

Caladiums (Caladium ×hortulanum Birdsey, Araceae Juss.) are tropical ornamental aroids. They are often forced as potted plants and grown in the landscape to provide color (Evans et al., 1992). A great majority of caladium plants in the floriculture trade are propagated from tubers. More than 95% of the caladium tubers used in the world comes from central Florida (Bell et al., 1998; Deng et al., 2008). Many existing commercial caladium cultivars show attractive coloration patterns but have poor pot or landscape performance and/or poor tuber yield. ‘Marie Moir’ is an

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Zhanao Deng and Brent K. Harbaugh

As a common pot and landscape plant, caladium (Caladium ×hortulanum Birdsey, Araceae Juss.) is valued for its colorful leaves and low maintenance requirements (Evans et al., 1992). Commercial caladium plants are grown from tubers. Central Florida growers produce greater than 95% of the tubers for the worldwide market (Bell et al., 1998; Deng et al., 2005). Tuber yield is one of the primary factors determining a caladium cultivar's production value and whether the cultivar will be acceptable to growers and viable in commercial production. Poor tuber yield has been one of the

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Zhanao Deng and Brent K. Harbaugh

Caladiums (Caladium ×hortulanum Birdsey, Araceae Juss.) are often used to provide color and a tropical ambiance to container gardening or the landscape (Evans et al., 1992). Approximately 95% of the caladium tubers used in the United States and worldwide are produced in Florida. Red fancy-leaved cultivars accounted for 23% of the acreage planted by Florida caladium growers (Bell et al., 1998). ‘Freida Hemple’ (33%) and ‘Postman Joyner’ (13%) accounted for nearly half of the red fancy-leaved cultivars commercially grown. ‘Florida Cardinal’, released from the University of Florida caladium breeding program in 1988 (Wilfret,

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Zhanao Deng and Brent K. Harbaugh

Cultivated caladiums (Caladium ×hortulanum Birdsey) are valued as important pot and landscape plants because of their bright, colorful leaves. Improving leaf characteristics or generating new combinations of these characteristics has been one of the most important breeding objectives in caladium. A major leaf characteristic in caladium is leaf blotching, the presence of numerous irregularly shaped color areas between major veins on leaf blades. This pattern of coloration in combination with bright colors has resulted in the popularity of a number of caladium cultivars. In this study, controlled crosses were made among three blotched and six nonblotched caladium cultivars. Their progeny were analyzed to understand the mode of inheritance of leaf blotching and its genetic relationship with the color of main leaf veins. Progeny of selfing nonblotched or crossing nonblotched cultivars were all nonblotched; selfing blotched cultivars (Carolyn Whorton, White Christmas, and Florida Blizzard) or crossing ‘Florida Blizzard’ and ‘Carolyn Whorton’ resulted in a 3:1 ratio (blotched:nonblotched); and progeny from crosses between blotched and nonblotched cultivars segregated in a 1:1 ratio (blotched:nonblotched). These results indicate that leaf blotching is controlled by a single nuclear locus with two alleles (B and b). χ2 analysis of the joint segregation between leaf blotching and vein color (V) in five crosses showed that the blotching allele B is linked to the green vein allele V g. ‘Carolyn Whorton’, ‘White Christmas’, and ‘Florida Blizzard’ are heterozygous for leaf blotching, and their genotype for leaf blotching and vein color (V r, V w, and V g for red, white, and green veins, respectively) are V r b//V g B, V g b//V g B, and V w b//V g B, respectively. This information will be valuable for planning crosses and breeding populations to develop new blotched caladium cultivars. The information gained in this study may be helpful for understanding the inheritance of similar traits in other aroids.