Study On The Occurrence Rule Of Sclerotinia Sclerotiarum In Sunflower And Induced Disease Resistance In Xingjiang

Researching of 10 S.Sclerotiorum's biological characters in Xingjiang,the result showed, hyphae of S.Sclerotiorum could grow between 5～30℃and the optimum temperature was 20～25℃.The optimum Ph for mycelial growth was 5～7.The effect of light on S.Sclerotiorum wasn't prominent to the mycelial growth. The S.Sclerotiorum strains grew better on PDA and PSA medium than others. The ability of producing toxin-oxalic acid by some strains had positive relation with the growth ability. All strains have high pathogenicity. There were some difference among the growth speed of mycelial, sclerotinia production and the ability of oxalic acid production. In addition, researching on the production of apothecia of S.sclerotorium indicated that after the low-temperature inducing produced more apothecias.Through investigating and researching to the occurrence regulation of S.sclerotiorum of sunflower ,the results indicated that the root rot disease is dominant in Xingjiang,its occurrence is very close relation to sowing dates, irrigation, meteorological factor, sunflower varieties. The S.sclerotiorum of sunflower is serious when seedtime is earlier .The more sowing later, the more light of sunflower S.sclerotiorum .Its disease index reach sick peak after irrigation. Disease of the seeding period had a positive relation with the temperature. Disease of the growth period had not relation with the relative moisture. resistance of 35 sunflowers varieties were identified in disease field, the results showed that all of them were sensitive or high sensitive. There were sensitive varieties of 10 and high sensitive varieties of 15. So it is very important to cultivate disease-resistant material in today.The study on the induced resistance to S.sclerotiorum in sunflower by Oxalic acid showed that the media having low concentration of Oxalic acid (1.0～3.0mmol/L) had a low relati- on with on germination rate of sunflower,which is 52.5%～97.5%. when exceeding 4.0 mmol/L ,the germination rate of sunflower decrease .meanwhile the root and hypocotyl was restricted. Response of seedling with oxalic acid resistance to S. sclerotiorum showed that seeding had high disease frequency. Oxalic acid is a suitable selective agent for resistance screening in vitro, which results indicated that oxalic acid concentration high induced but lesion diameter more little. After the induced resistance Sandaomei'seeds were identified in disease field showed that oxalic acid concentration high induced disease index low. Directional selection in disease field is a effective method that improve resistance of sun- flower. Previous experiment only one year need study further more.