Research On Etiology And Occurrence Dynamic Of Cereal Cyst Nematode(heterodera Avenae) In Gansu Province

The survey was carried out over three years(2009-2012) in the main cerealgrowing areas of Gansu. samples were taken during cereal’s heading stage toflowering,especially where plants showed chlorotic, dwarfish and yellowing leaves,and therefore it has a stronger possibility they were attacked by cyst nematode. Eachsample was a composite of30subsamples collected with a small spade in the plantrhizosphere, and at a depth of5-15cm after removing the top5cm soil. At the meantime detailed information about samples should be recorded, such as host (wheat oroat), soil texture, Irrigation and other details. the samples were kept in plastic bagsand carried to laboratory.Samples were stored at6℃until they were processed. soilsample was thoroughly mixed and air dried When processing, then weighed200g soiland extract cysts with routine sieving-floating method. And cysts were counted underanatomical lens.451soil samples were collected from50counties or districts, cystswere extracted from261soil samples, so detection rates was57.9%, CCN occurred in85.7%counties in Gansu. Morphology identification and Rapid Molecular Diagnosiswere imployed in this test, H.avenae was identified as dominant population in Gansu.Internal transcribed spacers (ITS) region of ribosomal DNA in20cereal cystnematode (Heterodera avenae) populations were amplificated. The ITS sequence wasSequenced in Bio-chemical corporations and the length of20sequences were1045bp.sequences were blasted by microsoft DNAMAN and showed that similarity of20sequences was99.81%, there was no insertion,deletion of base in eachsequence,however there were substitutions in each sequence.phylogenetic trees ofrelated species and20tested populations was structured based on rDNA-ITSsequence using UPGMA method and the trees showed that tested populations andvalid species in avenae group were in the same class.Dynamic of H.avenae in filed of spring and winter wheat were observed bycollected samples regularly in one year. Rates of empty cysts and full cysts andhatchability ratio of second stage larva (J2) were recorded when processing soil samples each time, and each data has three repeat. In filed of winter wheat the rates ofempty cysts and full cysts keep higher in May, June, December and February infollowing year, hatchability ratio of J2keep highest in February and March infollowing year, at this time wheat is in seedling to reviving period and J2reachedpeak infection. In filed of spring wheat the rates of empty cysts and full cysts keephigher in May to July, December in the very year and October to November in nextyear, hatchability ratio of J2keep highest in June.Process of H.avenae parasitic on root of spring and winter wheat was observedby dying root with acid magenta, peak infection of J2in spring wheat appearedbetween May20th to June10th. Infection of J2in winter wheat appeared inbeginning of March, before winter the infection was not observed. The observationresults demonstrated that H.avenaeoccur annually in Gansu province no matter inspring or winter wheat field.