مسح حقلي لمرض الطرف الأسود على القمح و تطوره تحت ظروف التخزين في محافظة الرقة-سورية

الملخص EN

The study was carried out to survey the occurrence of black point disease on wheat kernels in Raqqa province, Syria during the 1998/1999 and 1999/2000 growing seasons, and to evaluate storage influence on disease development.

The survey included 184 fields grown with durum and bread wheat cultivars, in eight major growing areas, from which randomized grain samples at harvesting time were collected in both seasons.

Samples from two different sites as well as at two different directions and depths (15 and 25 cm) were taken from grain heaps stored at El-Baleakh purchasing center, Raqqa.

Grain samples were tested to determine the percentage and severity of infection, and the pathogens involved in this disease.

This sampling process was replicated at four dates with two months interval.

Results showed that Bohouth 5 (durum wheat) was the most affected cultivar in terms of percentage and severity of infection, in both seasons compared with bread wheat cultivars, and this was more clear in 1999/2000 compared to 1998/1999 season.

Alternaria alternata (Fr.) Keissler and Fusarium spp.

was found to be the most frequent fungi (94%) associated with affected kernels, but Cladosporium herbarum Link, Cochiliobolus sativus Drechsler and Curvularia sp.

were less frequent (6%).

According to storage period, grains showed significant increases in percentage and severity of infection, and the most affected kernels were from the fourth sampling date.

Moreover, these differences were highly significant in the central part of the heap, in the southeastern compared with the northeastern site, and at depth 25 cm compared with 15 cm.

Isolation from the stored grains at different dates showed that gradual decrease in the frequency of field fungi, and increase in the storage ones such as Penicillium spp.

and Aspergillus niger Van Tiegh did occure