Different levels of resistance in blue mould resistant tobacco

Abstract

Seedlings of resistant tobacco lines were assessed for leaf reaction to blue mould infection at normal transplanting size and grouped in four levels of reaction. Segregation ratios from heterozygous plants confirmed the presence of a single major gene for resistance and suggested the presence of additional minor genes. Selection based on seedling reaction has accumulated minor genes for resistance in the presence of the major gene and has resulted in a very high level of resistance to the strain APT1 in both seed bed and field. The relation between the resistance levels was similar in the parent and two subsequent selfing generations. The relative disease expression at the different levels of resistance in seedlings and field plants was positively correlated.