Study On The Health And Vigour Determination Of Tobacco Seeds

Tobacco（Nicotiana tabacum L.）is an important commercial crop in China.Tobacco seed,directly affecting the yield and quality of tobacco,is the most important production material in tobacco cultivation and production.Hence,the efficient determination on tobacco seed quality is an important guarantee for good yield and quality of tobacco.This study determined the fungi,bacteria and virus pathogens carried by 15different lots of tobacco seeds.According to the dominant pathogen species,suitable sterilizing agent were screened out,which provided theoretical basis and technical reference for prevention of tobacco seed-borne diseases.In addition,this study combined the controlled deterioration（CD）test and electrical conductivity（EC）to provide an efficient and fast method for the determination of tobacco seed vigour.The main research results were as follows:1.Among the 15 lots of tobacco seeds,12 lots were found to carry brown spot disease（Alternaria alternata（Freis）Keissler）and 14 lots were found to carry tobacco mosaic virus（TMV）.The two lost of tobacco seeds with severe infection,YY105-2015and YY97-2005,were seeded,and no brown spot disease or TMV were found in tobacco plants,indicating that the seeds carring brown spot disease or TMV did not mean that the plants would definitely get sick.In addition,the carbendazim had the best bactericidal effect against fungal pathogens,followed by mancozeb.For bacteria,kasugamycin had the best bactericidal effect,followed by zhongshengmycin.For TMV,0.2%KMnO₄ had the best disinfection effect,followed by 10%H₂O₂.2.The vigour of tobacco seeds could be determined fast and efficiently with the CD test followed by EC test.Eight lots of tobacco seeds were selected for the CD test,and that the results showed that the CD test had an extremely significant correlation with the field emergence percentage（FEP）（r=0.9608,P?0.001）.Meanwhile,the results of EC test on tobacco seed vigour indicated that the relative conductivity was significantly correlated with FEP（r=-0.7814,P?0.05）,but the correlation coefficient between absolute conductivity and FEP was not significant（r=-0.6796,P>0.05）.Because the CD test ultimatedly need to evaluate the difference of seed vigour level through the germination percentage measured by standard germination test,it takes much time,and is not conducive to the actual production and application.The EC test is more efficient and less time-consuming,but less accurate than the CD method.Therefore,this study explored the feasibility of CD test combined with EC to determine the vigour of tobacco seeds.The relative conductivity measured after CD is significantly correlated with FEP and germination percentage after CD,the correlation reached higher level at 30⁴8 h.It indicated that the EC test can replace the standard germination test after CD to rank quickly the vigour of tobacco seed lots.Compared with the traditional CD tes t,the CD+EC method saved time.Meanwhile it increased the precision of determination as compared with the EC test.Giving consideration to the efficiency and accuracy,the optimal soaking time was 36⁴2 hours.3.There was no significant correlation between field seedling emergence and the diseases-carrying rates（brown spot disease and TMV）of tobacco seeds in this study.The correlation analysis was made on the total carrying rate of brown spot disease in tobacco seeds,the carrying rate of brown spot disease in seed interior,the carrying rate of brown spot disease in seed outside,and the relative initial concentration of TMV with the field seedling emergence rate（one of the seed vigour index）.No significant correlations were found,indicating that the seeds of tobacco carried a little of brown spot disease and TMV virus had no significant effect on seed vigour.