Studies on the tulip mosaic disease in Japan. VI

Abstract

Leaves of healthy tulip plants “William Pitt” (WP) in shooting stage (shoot-length 5-10cm above the ground) were inoculated with leaf- or petal-sap expressed from freeze-dried tissues of suspected tulip plants for the purpose of knowing if the latter is actually virus-infected. By the partial break (Fig. 1, left) that subsequently appear on the WP flower, it was judged whether unusual coloration in flower or foliage of the suspected plants was due to virus disease or of inherent nature.1. When leaf-sap from yellow (“Golden Harvest”) or white tulips (“Mrs. Grullemans” and “White Duchess”) bearing red lines or sprashes on petals was inoculated, no WP flowers showed partial-break. On the other hand, leaf-sap from these varieties showing leaf streaks produced partial-break on WP flower. Therefore, it seems unlikely that red lines or sprashes on petals of yellow or white varieties are due to virus disease.2. It was demonstrated that blotched or feathered flowers of dark purple tulips (“Queen of the Night” and “Van der Neer”) had been caused by virus infection, bacause WP flower showed partial-break by the inoculation of leaf-sap from these plants.3. It was also demonstrated that the flower symptom of bi-colored variety “Pink Beauty” in which ground color was visible in the pink area was due to virus disease.4. Leaf-sap from tulips of Parrot “Sunshine” and Double Late “Nizza” without leaf streaks did not produce partial-break on WP flower, suggesting that the flower variegations are not due to virus infection but due to the inherent nature of these varieties.5. It has been said that some “Rembrandt” tulips were derived from virus-infected Darwin tulip. In the present study, however, leaf-sap from “American Flag” plant bearing normal foliage did not cause flower breaking in WP, while leaf-sap from the plant bearing streaked foliage produced partial-break on WP flower. Therefore, it seems to assume that flower breaking of “American Flag” is not due to virus infection.6. “Gudoshnik”, one of the varieties of Darwin Hybrid, exhibits a wide range of variation in flower color. Leaf- or petal-sap from some individuals of this variety did not produce partial-break on WP flower upon inoculation. The color variation may be due to the inherent nature of this variety.7. With the exception of “Hydra”, leaf-sap from all varieties tested that are called “Variegated-Leaved” did not produce partial break on WP flower, irrespective of the variegation in leaf color is regular or irregular. They are “Cochinille”, “Peach Blossom”, “Purple Kroon”, “Rose Luisante”, “Yellow Prince”, and “William Pitt”. Of course, WP was readily infected by sap-inoculation from “Rose Luisante” plants that have either leaf streaks in green area other than leaf variegation or broken flowers. These facts may suggest that “Variegated-Leaved” might have been selected from genetical mutants.