Paul D. Legg

Effects of the Nicotiana debneyi black root rot resistance factor on agronomic and chemical traits in burley tobacco.

SummaryLines isogenic or near isogenic for traits other than resistance to black root rot from Nicotiana debneyi were developed in eight cultivar backgrounds of burley tobacco (N. tabacum L.). For each cultivar background, a resistant and susceptible selection from the seventh backcross generation plus the recurrent parental cultivar were evaluated for ten agronomic and chemical traits. Resistant selections were statistically different from the susceptible entries for days to flower, total nitrogen content, and total alkaloid content. Also, resistant selections were consistently lower in yield, but the differences were statistically nonsignificant. Resistant selections were also taller in three families and in two families the resistant selections had wider leaves. Linkage of genetic material from N. debneyi with the resistance factor was suggested as the possible reason for differences between resistant and susceptible selections.

Genetic parameters in aKy 14 xKy Ex 42 burley population ofNicotiana tabacum L.

SummaryIn the F2 generation of the cross between burley varieties,Ky 14 andKy Ex 42, estimates of additive genetic variance were significant for yield, days to flower, and number of leaves. All estimates of dominance variance, additive X additive variance, and interactions between genetic variances and years were smaller than twice their standard errors. The gain expected from selecting and recombining the best 10% of theF2 plants ranged from 4% for number of leaves to 8.6% for yield. Additive genetic correlations between pairs of agronomic characters were positive. Yield and number of leaves were negatively correlated with total alkaloids.