Screening tomatoes (Lycopersicon spp) for powdery mildew (Leveillula taurica (Lev. Arnand) resistance in the
Sudan.
Mohamed Y.F.1 and ElJack A.E2
Departments of Plant Pathology1 and Horticulture2, Gezira University, Wad Medani PO Box 20,. Sudan
Tomato is one of the most important vegetable produced in the Sudan. Its production faces many disease
problems, along which is the powdery mildew which in the recent years had resulted in significant crop losses,
particularly during the relatively cool winter season. In many surveys, the disease was found to be very serious in
eastern and central parts of Sudan (Mohamed Y.F., unpublished). The disease was reported to be caused by
Leveillula taurica and Oidium lycopersici (Kozik, 1993).
In this study, commonly grown tomato varieties, hybrids and some lines obtained from INRA; France and
from different seed companies were tested for powdery mildew resistance. The plants were subjected to natural
infection in the field. Four samples of diseased leaves from each entry were examined using the microscope.
Evaluation for powdery mildew resistance, was done twice, the first was at flowering stage and the other one month
later. A rating scale of 9 (resistance), 7 (high intermediate resistance), 5 (intermediate resistance), 3 (low
intermediate resistance) and 1 (susceptible) was used, and the average of the two evaluations was taken as shown
in table (1):
Microscopic examination proved that the causal agent of the disease was L. taurica and none of the
samples showed the presence of Oidium lycopersici. Field results showed that none of the lines, varieties and
hybrids was immune. The only line that showed resistance was a Lycopersicon pimpinellifolium (Acc. LA1478). The
tomato varieties Calev and Belev which were developed at INRA as resistant to the disease showed only high
intermediate level of resistance. This could be attributed to either a different race of the pathogen or more
conducive environmental conditions for infection and disease development, thus they could not be utilized as a
good source of resistance to be transferred in the susceptible commercial varieties grown in Sudan. The rest of
Lycopersicon esculentum collection tested which contain F1 hybrids, varieties and lines was mostly in the
susceptible group. This made it necessary to go for interspecific crosses to transfer resistance into commercial
varieties of tomatoes.
No navigation control above? Click here!
