Articles
BREEDING GREENHOUSE TYPE TOMATOES TOLERANT TO THE WHITEFLY-BORNE TOMATO YELLOW LEAF CURL VIRUS
Our breeding of indeterminate F1 hybrid tomato cultivars adapted to protected houses is based on tolerance derived from the wild tomato, Lycopersicon peruvianum. A BC3F6 line, designated M-60, is the source of tolerance.
Tolerance is controlled by five recessive genetic factors.
Selection for TYLCV tolerance in early segregating populations was made in an insect-proof greenhouse following inoculation with viruliferous whiteflies.
Field trials were performed with experimental TYLCV – tolerant tomato hybrids to test their reaction under severe natural infection.
Healthy plants were transferred from an insect-proof nursery to the field at the Bsor Experiment Station in the autumn season of 1991 and 1992. During the growing season plants were sprayed three times with insecticides to minimize direct whitefly damage.
Tolerant hybrids infected with TYLC showed a mild interveinal chlorosis on the leaves and their leaflets became slightly cupped.
These plants gave an acceptable yield in spite of the infection.
In contrast, infected plants of susceptible hybrids became markedly stunted, leaflets rolled upward and inward, and showed severe interveinal chlorosis.
Fruit set and yield were markedly reduced.
A series of experimental F1 hybrids tolerant to TYLCV were grown in single stem culture in a whitefly-proof protected greenhouse in the winter of 1991 and 1992. These hybrids produced fruit with very good color and shape, but fruit were relatively small (70–80 g) and not firm enough.
Additional breeding effort is, therefore required to improve fruit characteristics.