Evaluation of the resistance of some tobacco cultivars to fusarium wilt and root-knot nematode under natural field infection conditions

Fusarium wilt fungiFusarium oxysporum f.sp. nicotionae and root-knot nematodes (Meloidogyne incognita), are the most important soil-borne tobacco pathogens in Iran and over the world. Access to resistance genetic resources and cultivation resistant cultivars to these pathogens, are the most basic control methods to these pathogens and damage reduction come from epidemic disease, especially in the northern province of Iran. This research was studied in order to evaluate the resistance of 6 tobacco genotypes, including (BCE, HBT8, K17, Burley BB163, and Burley Geel 3) and Burley 21(as sensitive control) in a randomized complete block design (RCBD) with 3 replications during 2014-2015 under natural field infection. Fusarium wilt resistance evaluation based on Moorman et al with scale (0 - 4) evaluated on a weekly basis and resistance to root- knot nematode at the end of season based on number of galls, number of egg masses and the average number of egg per mass with scale 0 - 10 was performed. Evaluation the severity and progress of both diseases in the different cultivars showed that prevalence of these diseases by starting the heat season and air humidity has increased and these two pathogens have the synergistic effect together in the soil of field. The results of this research showed that Burley 21, Burley BB163, Burley Geel3 with sensitivity indexes 8,6,6 were respectively in groups susceptible, moderately susceptible, K17 with sensitivity indexes 4 are moderately resistant and BCE, HBT8 cultivars with sensitivity index 2 were in resistant groups to soil-borne pathogens. According to these results the BCE and HBT8 identified as a resistant cultivars and Burley 21 identified as a most sensitive cultivar under natural field infestation conditions.