Techniques to Evaluate Caladium Cultivars for Host Resistance to Fusarium Tuber Rot

Abstract

<jats:p>Caladiums, widely used in containers and landscapes as ornamental plants for their bright colorful leaves, are generally forced or grown from tubers. Commercial production of these tubers in central Florida is through dividing “seed” tubers and growing them in fields. Tuber quality is therefore of critical importance to success in container forcing, landscape use, and tuber production. Fusarium tuber rot (<jats:italic>Fusarium solani</jats:italic>) has been recognized as the most-destructive disease that affects caladium tuber quality. There is anecdotal evidence from growers indicating the existence of resistance in commercial caladium cultivars. To identify and confirm the source of fusarium tuber rot resistance in caladium, <jats:italic>F. solani</jats:italic> isolates have been collected from rotting tubers grown under different soil conditions and from different locations. The pathogenecity of these isolates has been tested through artificial inoculation of fresh harvested and/or stored tubers, and a number of highly virulent isolates have been identified. These isolates have been used to refine inoculation and disease evaluation techniques. Two techniques, spraying a conidial suspension onto fresh cut surfaces and inserting <jats:italic>Fusarium</jats:italic>-infested carnation leaf segments into artificial wounds, have proven to yield consistent resistance/susceptibility ratings among cultivars of known difference in resistance to fusarium tuber rot. Appropriate incubation temperatures and humidity seem to be very critical for disease development and evaluation. The two techniques have been used to evaluate 35 cultivars. Several cultivars, including `Candidum', showed a high level of resistance to fusarium tuber rot, and may be good breeding parent for developing new resistant cultivars.</jats:p>

Assessment of Genetic Diversity and Relationships Among Caladium Cultivars and Species Using Molecular Markers

“…The 45 cultivars included in this study represented a high level of phenotypic diversity in morphological, physiological, or horticultural traits such as leaf shape, color, coloration pattern (Wilfret and Hurner, 1982), tuber yield (Wilfret, 1983), sun tolerance (Bates-Cantwell, 2001), cold tolerance , resistance to pythium root rot (Pythium myriotylum Drechs.) (Deng et al, 2005a(Deng et al, , 2005b, resistance to fusarium tuber rot (Goktepe et al, 2006), and resistance to root-knot nematodes [Meloidogyne incognita (Kofoid and White) Chitwood] (Dover et al, 2005;McSorley et al, 2003) (Table 1). However, only 44.4% of the DNA markers detected in cultivars were polymorphic among cultivars, the average similarity coefficient among cultivars was >0.8, and all cultivars were highly concentrated in the PCoA plot (Fig.…”