Attempt to Classify Petunia Species on the Basis of Corolla Shape.

Abstract

Four parameters, namely, corolla diameter (CD), corolla tube length (TL), corolla length (CL) and corolla tube diameter (TD) of Petunia were measured. These measurements and ratios of TL/CD, CL/CD and TL/TD were compared in order to study the possibility of using them as corolla shape indices in the classification of Petunia. The values of CD, CL, TD and ratios of TL/CD, CL/CD were affected by the temperature conditions controlled at 30/24, 25/19, 20/14°C (day/night). With the decrease of the temperature, the CD and TD values clearly increased. Since the changes in CD were drastic, the values of the TL/CD and CL/CD ratios tended to decrease with decreasing temperature. Measurements of CD, TL and CL were significantly different between whiteflowered species (P, axillaris and P. parodii) and purple-folowered P. inflata. Flowers of P, parodii and P. axiliaris resembled each other, whereas the values of TL and the three ratios at the same temperature were distinct. In P, inflata, all the measurements and ratios did not overlap with those of whiteflowered species, and the values of the ratios were the smallest among the species and lines investigated in this study. In the reciprocal F1 hybrids of P. axillaris and P. inflata, the measurements and ratios were intermediate between those of the parental species. Therewas no significant difference between the ratios of reciprocal Fl hybrlds. Moreover, the ratios of P. hybrida were intermediate between those of P. axillaris and P, inflata. In P. hybrida, the values of the measurements and ratios of 'W166K' were slightly larger than those of 'Rose'. The CL/CD ratio showed the largest differences among the species and lines. The results of the present study suggest that the three ratios are very useful as indices of the corolla shape for the classification of Petunia species.