Evaluation of components of partial resistance to black root rot in burley tobacco
1995
Wilkinson, C.A. | Shew, H.D. | Rufty, R.C.
Cultivars with moderate (KY 14), low (Burley 21), and no resistance (Judy's Pride) to black root rot, and the Fl of KY 14 X Burley 21 were evaluated for components of partial resistance to Thielaviopsis basicola. In addition, transgressive segregants from a previous generation mean analysis were intercrossed and progeny of the following crosses were evaluated: (KY 14 X Burley 21)F2 X (KY 14 X (KY 14 X Burley 21)F1), (KY 14 X Burley 21)F2 X (Burley 21 X (KY 14 X Burley 21)F1), and (KY 14 X (KY 14 X Burley 21)F1) X (Burley 21 X (KY 14 X Burley 21)F1). Five-week-old seedlings were transplanted into soil infested with 100 chlamydospores of T. basicola per gram of soil mixture and grown in the greenhouse at an average air temperature of 21 degrees C. Disease severity (percent root necrosis), number of lesions per root, lesion length, and population density of the pathogen were estimated 3 weeks after transplanting. Significant differences were observed among genotypes for each component of partial resistance measured. Significant positive correlations were observed between lesion number and disease severity and between lesion number and lesion length. However, a significant negative correlation was observed between lesion number and population density. Selection for components of partial resistance in burley tobacco should lead to increased levels of resistance to black root rot.
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