| Crown rot, caused by multiple pathogens in wheat, has been a serious threat to wheat production in Huang-Huai flood plain in China with the increasing severity recent years. Because crown rot as a soil born disease is hard to prevent and control, planting resistant varieties was a safe and effective ways. At present, the domestic study on crown rot disease on wheat is rare. To screen wheat cultivars with the stable resistance to crown rot disease, we conducted indoor pot experiment and actual field test with inoculation of the dominant pathogens of Fusarium pseudograminearum and F. graminearum of wheat crown rot disease, combined with the optimization of condition on toxin production and susceptibility test of wheat varieties to the toxin produced by F. pseudograminearum for 88 wheat cultivars in the Huang-Huai flood plain and 21 foreign germplasm materials. The main results were as follows:The results of greenhouse pot tests for the total cultivars and foreign germplasm materials tested showed that there were no immunity and resistant varieties while all the cultivars were susceptible to the crown rot caused by F. pseudgraminearum Wz2-8A. The investigation and comparison of two test results found that the resistant performance of 8 cultivars was inconsistent, including Tanshan 24, Jimai 5 and BATAVIA.3 ect., witch showed suceptibel to highly susceptible（S-HS） with a proportion of 7.34% the total cultivars tested. Most of the tested had similar resistant permformance, In which a total of 7 cultivars（Yujiao 5, Zhoumai27, IRN 497, SUNCO/2*PASTOR, etc.） was susceptible（S）, accounting for 6.24%, and the other 94 cultivars were highly susceptible（HS） accounted for 86.24%. All of the candidates were susceptible or highly susceptible to F. graminearum 072-7 strain in the twice pathogenic tests. For example, only IRN 497 performed moderate resistance-susceptibility（MR-S）, which had an average disease index of 19.30 and 26.67 in the two experiments with a proportion of 0.92%; Six cultivars（Yanzhan 9433, Feng Decun 1, SABUF/3/BVN/CETA/AE., SOOTY 9Rascon-37, ect.） was susceptible（S） with the proportion of 5.50%; fifty-seven cultivars and germplasms（Zhoumai 27、Fanmai 5、BATIVIA, etc.） were susceptible –highly susceptible in a rate of 52.29%, while the other 45 cultivars showed high sensitivity（HS） with the proportion of 41.28%.The results of seedling experiments in field indicated that the total cultivars and foreign germplasm materials tested were no immunity to F. pseudograminearum Wz2-8A strain, i.e., most cultivars were susceptible or highly susceptible. The analysis of data from twice experiments showed that the cultivar Yumai 8, for instance, was susceptible to resistant（S-MR） performance, accounted for 0.92%, with the average disease index of 27.97 and 20.00; eight cultivars（Jiaomai 266, Jinmai 8, Yumai 70-36, ect.） ect., were susceptible（S）, accounting for 9.09% of the total cultvars tested; a total of 39 varieties, such as fanmai 5, Lankao 906, SUNCO/2*PASTOR, ect., had susceptible to high susceptible performans（S-HS）, accounted for 35.78%, while the other 61 samples were highly susceptible（HS） with the proportion of 55.68%. As to F. graminearum 072-7 strain, there was no immunity and resistant varieties found during the twice tests, except that the cultivar MACKELLER was susceptible to resistant（S-MR） performance, accounted for 0.92%, with the average disease index of 28.00 and 18.75. A total of 11 cultivars, such as Zhoumai 24, Taishan 24, 2-49, etc., were consistant with susceptibility（S）, accounted for 10.09%. We still noticed that many samples had the variable resistance performance from susceptible-highly susceptible（S-HS）, which contained 49 cultivars, e.g., Yumai 58, Taishan 22, BATIVIA, etc., accounted for 44.95%. The other 48 cultivars showed high sensitivity（HS） with the proportion of 44.04% between the two independent tests.The results of adult tests showed that for the total cultivars and foreign germplasm materials tested was no immunity varieties, i.e., most cultivars were susceptible or highly susceptible to F. pseudograminearum Wz2-8A. Investigation and comparison of two trials found that only the cultivar Xuke718 and BATIVIA, for instance, was moderate resistant（MR） performance, accounted for 1.83%. A total of 13 varieties, including Zhoumai 27 and Zhoumai 18, 2-49, SUNCO/2*PASTOR, etc., accounted for 11.93%, was moderate resistant to susceptible（MR-S）. A total of 50 varieties, such as Jiaomai 266, Zhongyu 6, GATCHER, etc., was susceptible-highly susceptible（S-HS） with the proportion of 35.78%. The cultivar Yumai 49-986, for instance, was highy susceptible to moderate resistant（HS-MR） performance, accounted for 0.92%. Of 17 varieties, such as Xi’nong 979, Pin’an 3, SUMAI 3, GOLVER, etc., accounted for 15.60%, were susceptible（S）. The other 26 cultivars showed high sensitivity（HS） with the proportion of 23.85%. There were still no immunity varieties coming out to F. graminearum 072-7. Investigation and comparison of two trials found that of 12 varieties, such as the cultivar Yumai 34, Yanzhan4110, SUNCO/2*PASTOR,ect., were moderate resistant to susceptible（MR-S） performance, accounted for 11.01%. Of 17 cultivars such as Lankao 198, Zhoumai 23, SUNR23, ect., were susceptible（S） between two independent test, accounting for 15.60%. Of 49 varieties, such as Yumai 18-64, 2-49, IRN 497, etc., accounted for 44.95%, were susceptible- highly susceptible（S-HS）. A total of 25 cultivars, such as Kaimai 18, Yujiao 5, SOOTY9Rascon-37 and so on, showed highly susceptible（HS） with the proportion of 22.94%. The 6 samples, including Luomai 18, Huaimai 16, SABUF/3/BVN/CETA/AE and so on, were highly susceptible to moderate resistant（HS-MR） with the proportion of 5.50%.The results of the conditions of toxin production of F. pseudograminum showed that the suitable conditions for the toxin production were with PS medium at p H 8 at 20℃ for 25 d. When light application time and the condition of culture were changed, the virulence of liquid culture filtration had no significant difference, i.e., time of light application and culture condition just slightly affected the ability of toxin production, whereas with dark incubation and interrupted shaking, the toxin exhibited a highest inhibition rate to wheat root growth.The results of crude toxin measurement of F. pseudograminearum on different wheat varieties in Huang-Huai flood plain revealed that the wheat varieties showed big difference of susceptibility in which the radical growth of variety China-Spring was the most sensitive with the growth rate of up to 72.63% inhibited, while Zhoumai 27 had the weakest susceptibility with only that of 24.59%.The similar results was found in the foreign germplasm materials, e.g., SN1081/AE.SQUARROSA（222） was most sensitive while 2-49 variety had the weakest susceptibility with the radical growth inhibition rate of 74.10% and 40.75%, respectively. Compared with the rate of radical growth inhibition and germ growth for the same variety, the former one was higher than that of the latter. |
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