The Quantity Index × Quality Index (Q×Q) Model for Ornamental Value Assessment in Garden Roses Based on Rose Hips, and the Evaluation of 704 Field-Grown Cultivars and Taxa.

A model was developed to calculate the rose-hip-based ornamental value (OVhip) of rose cultivars. In this "Quantity Index × Quality Index" (Q×Q) model, the Quantity Index refers to hip production, whereas the Quality Index refers to the epicarp color of the rose hip. The rapid determination of quantity under field conditions requires ranking, which provides only an approximate estimate; however, its precision can be improved. To replace ranking class numbers with production-based values, a sample of items was both ranked (Chip) and measured (Phip). A strong power-function relationship (Phip = 0.12792 × Chip3.00120) was found; therefore, the calculated Phip values can be used as the Quantity Index. To determine the Quality Index, the aesthetic value of 21 rose hip samples was scored, and the epicarp colors of the same samples were also measured. A strong linear correlation was found between the scores and the a* coordinate of the CIE color space, consequently; the CIE a* can be used as the Quality Index. In this Q×Q model, OVhip is calculated as the product of these two indices after normalization. Using this model, 704 items were evaluated in the Budatétény Rose Garden (Hungary), where the highest OVhip values were recorded for Rosa micrantha, Rosa canina 'Inermis', and the lucieae hybrid 'Fragezeichen' (Boettner, 1910). Among the hybrid tea roses, 'DELamo' (Delbard, 2004) and, among the floribundas, 'Méphisto' (Mallerin, 1951), had the highest OVhip.