First report of race composition and distribution of sunflower broomrape, Orobanche cumana, in China.
To identify the race composition of sunflower broomrape (Orobanche cumana) in China, a total of 18 sunflower broomrape samples were collected in August 2011, 2012 and 2013 from different provinces/locations in China, including Xinjiang (Xinyuan, Shihezi, Tekesi, Beitun, Urumqi and Yining), Nei Mongol (Linhe, Xixiaozhao, Wuqianqi, Tuzuoqi, Keyouqianqi and Aohanqi), Shanxi (Hunyuan, Shilou, Mizhi and Dingbian), Jilin (Tongyu) and Hebei (Xuanhua). The differential hosts were each inoculated with the seeds of each broomrape isolate that was recovered. Briefly, 2 parts of field soil and one part of vermiculite were mixed together and used as potting mix. The mix was inoculated with broomrape seeds at 10 mg of seeds per 100 g of potting mix. The inoculated mix was placed in a 7 cm (diameter) × 11 cm (height) plastic pot to fill two-thirds of the pot volume. Three sunflower seeds were placed on the surface of the mix at an even distance from each other and covered with additional mix. The pots were kept in a greenhouse under a 16 h photoperiod at 10 000 lux of illumination intensity, temperature of 20-25°C and 40% relative humidity. At 40 days after incubation, sunflower seedlings were taken out from the pot and the roots were washed with tap water. The number of tubercles was recorded on the root of each differential host. Race types were determined based on the reaction (tubercule formation on roots) of all the standard differential hosts to the test isolate. The results showed that races A, D, E, and G of O. cumana were present among the isolates. Race G was found in Wuqianqi, Xixiaozhao and Linhe in the western part of Nei Mongol. Race E was found only in Shihezi of Xinjiang. Race D was found in Aohanqi and Keyouqianqi (eastern part of Nei Mongol); Xinyuan, Tekesi, Beitun and Urumqi (northern part of Xinjiang); and Tongyu (northern part of Jilin). Race A was found in Mizhi, Shilou and Hunyuan of Shanxi and Xuanhua in Hebei. Additionally, race A was also found in Tuzuoqi, the middle region of Nei Mongol. Thus, races A, D, E and G were the main race types of O. cumana in China. Race D was the predominant race type and had the widest distribution. Race G was the highest level race type in this study, but was mainly limited to the western part of Nei Mongol. This is the first report of race composition and distribution of sunflower broomrape (O. cumana) in China.