The inheritance of resistance to blue mold (Peronospora tabacina Adam) in two cultivars of tobacco (Nicotiana tabacum L.)

Abstract

Two blue-mold resistant cultivars of Nicotiuna tabacum L. were crossed with each other and with the susceptible Israeli local cultivar Mikhal. F1, F, and F3 progenies of these crosses, F1 and Fz of backcrosses and the parental varieties were grown in a series of experiments, in which the seedlings were exposed to heavy natural infection with Peronospora tabacina ADAM. The genetic basis of resistance was found to be identical in the two resistant strains Bel-61-10 and Chemical mutant. A single dominant major gene determined the segregation of resistance versus susceptibility in the crosses of these strains with Mikhal. The level of resistance of resistant segregates was shifted by environment and by quantitatively modifying genes. The index of resistance, which was calculated as a weighted mean of the degree of blue-mold expression of the resistant segregates, differed in the generations of cross progeny. This could be explained by the different expected levels of the modifying genes in these generations. Heritability of the index of resistance was calculated by parent-offspring regression and it was found to be 0.542 in the F3 and 0.227 in F, backcross progenies.

RAPD and SCAR Markers Linked to an Introgressed Gene Conditioning Resistance to Peronospora tabacina D.B. Adam. in Tobacco

“…These data suggest that resistance in Chemical Mutant may be due to alien gene introgression rather than induced mutation. Indeed, Marani et al (1972) found no segregation for blue mold resistance in progeny derived from the cross Bel 61‐10/Chemical Mutant, a result suggesting that genetic factors conditioning resistance in these two lines were identical. As noted by Rufty (1989), it is unlikely that a resistance allele derived via mutation breeding would occur at the same genome position as that which possesses a gene introgressed from a wild Nicotiana relative.…”

“…Our marker data suggest that N. debneyi may be the true donor of resistance in Ovens 62 as well as in Sirone, Sirogo, ZA 684, ZA 692, Sota 6505, and Bel 6‐10. It was interesting that all 12 coupling phase RAPD markers linked to a factor controlling blue mold resistance in Ovens 62 were also present in lines with resistance supposedly achieved via induced mutation (Marani et al, 1972). These data suggest that resistance in Chemical Mutant may be due to alien gene introgression rather than induced mutation.…”

“…As noted by Rufty (1989), it is unlikely that a resistance allele derived via mutation breeding would occur at the same genome position as that which possesses a gene introgressed from a wild Nicotiana relative. Marani et al (1972) noted the possibility that accidental mixing of seed may have occurred during the development of Chemical Mutant.…”

“…Eight of the cultivars/breeding lines reportedly carried blue mold resistance transferred from either N. goodspeedii , N. velutina , or N. debneyi (Rufty, 1989) (Table 2). Two were reported to possess resistance induced by chemical mutation (Marani et al, 1972; Rufty, 1989).…”

“…Resistance can be found within several Nicotiana species of Australian origin where blue mold is endemic and has reportedly been introgressed into cultivated tobacco from N. debneyi (Clayton, 1967; Clayton et al, 1967; Lea, 1963), N. goodspeedii Wheeler (Wark, 1963, 1970), and N. velutina Wheeler (Wark, 1963, 1970). Resistance induced by treatment of flue‐cured cultivar Virginia Gold with the mutagen triethylene iminotrazine has also been reported (Marani et al, 1972). Few resistant cultivars are available to growers worldwide, however (Shoemaker, 2004).…”