Pathotype Identification Of Heterodera Avenae, Resistant Evaluation Of Wheat Materials And Determing Of Damage Threshold

Cereal cyst nematode Heterodera avenae is an economically important plant parasitic pest on cereal crops. It has been spread to 16 provinces in China and threatened the safety of domestic wheat production. The aims of this study were clarifying the pathotypes of H. avenae populations in Jiangsu Province, evaluating the resistance of wheat germplasms and cultivars, revealing the effects of initial population densities on nematode reproduction, wheat growth and determining the damage threshold. The study will provide informative support for designing control strategies.The pathotypes of H. avenae populations in Fengxian and Peixian County of Jiangsu Province, China, were identified using 23 different cultivars of international host differential sets (IHDS) by the optimized bioassay test under greenhouse condition. The results indicated that the resistance evaluation of all cultivars against two Jiangsu populations were the same. Only Varde and Dalmatische out of 13 barley cultivars, and the five wheat cultivars, including Capa, Loros, Iskamish K-2-light, AUS 10894 and Psathias were susceptible to H. avenae, while the rest of IHDS cultivars were resistant. The two H. avenae populations were identified as the same pathotype and classified as Group Hal. However, they were different from the 14 defined pathotypes.The resistance of 94 wheat germplasms and cultivars against H. avenae Peixian population were evaluated by inoculating with second stage juveniles under greenhouse conditions. The results revealed that no materials were found to be immune to H. avenae. Ten materials were evaluated as resistant aganist H. avenae, including 3 highly resistance Huamai No.1, Aizaoba No.15 and code W1074, and 7 medium resistance Jingzhouxingmai, Liangxing No.99, Yangfumai No.11, Huaimai No.29, Yunnan 011-12, Xumai No.99 and Taikong No.6 (Shangdong). The rest of 94 materials were susceptible to H. avenae and took 89.4% to the total evaluated materials. The single plant of cultivar Xifeng had the highest number of white females as 115.5. These screened resources can provide materials for breeding new resistant cultivars and support for integrated management of cereal cyst nematode.During two growing seasons of winter wheat in year 2011-2013, the effects of initial population densities (P,) of H. avenae on nematode reproduction and wheat growth were evaluated in pot experiments under natural conditions. The results showed that the reproduction factor (Rf) of H. avenae was decreased with the increasing densities of H. avenae. The reproduction factor was 8.7 when Pi was 0.5 egg/mL soil, while Rf was 1.5 when Pi was 128 eggs/mL soil. The plant height, aerial shoot dry weight, root dry weight and grain yield were also decreased, which elucidated the negative relationship with the initial population densities. Wheat growth and grain yield decreased significantly when Pi was higher than 8 eggs/mL soil. Therefore, control measures should be carried out in wheat field when nematode density become higher than this economic limit value. Using the Seinhorst model, the tolerance limit value (T) was calculated based on the above mentioned four parameters. The final tolerance limit of wheat to H. avenae was determined as 7.1 eggs/mL soil. The study provided the theoretical support for designing the integrated strategies for H. avenae disease.