Distribution of the cereal cyst nematodes (Heterodera spp.) in wheat and barley fields in north-eastern regions of Syria

Cereal cyst nematodes (CCN) are important plant-parasitic nematodes of wheat and barley, and exist in most of the cereal growing regions of the world. As there is limited information on the nature and distribution of CCN species in Syria, a survey was conducted in north-eastern Syria to assess the distribution of CCN in the main wheat and barley growing areas. In the summer of 2009, a total of 167 composite soil samples were collected from 167 wheat and barley fields. Cysts were extracted from soil using the Fenwick can technique, then quantified and identified up to the species level by using both morphological and molecular methods. The study revealed that 62% of the fields were infested with the three Heterodera species: H. avenae, H. filipjevi and H. latipons. However, the most prevalent species was H. latipons, which was present in 76% of the infested samples, while it occurred alone in 67% of those samples. Heterodera avenae was detected singly in 20% of the samples, while 11% consisted of mixed populations with other species. Heterodera filipjevi was never detected alone; it was found mixed with H. avenae and/or H. latipons in 9% of the samples. The high number of extracted cysts (up to 116 cysts x 200 g(-1) of soil) is most likely related to the monoculture practiced in that region and the fact that growers are unaware of the existence of resistant varieties