Effect of the absence of condensed tannins in faba beans (Vicia faba) on resistance to foot rot, Ascochyta blight and chocolate spot

Abstract

SUMMARYThe effect of breeding for the absence of condensed tannins in the testa ofVicia fabaL. on resistance to foot rot, Ascochyta blight and chocolate spot diseases was investigated in 1988–92 at Wageningen, The Netherlands. For this purpose the disease development in tannin-free and tannin-containing partners of six near-isogenic pairs was compared after exposure to causative pathogens. Except for one near-isogenic pair, in which both partner lines showed a relatively high resistance, the tannin-free lines were more susceptible to foot rot than the tannin-containing partners of the same pair. This observation indicates that the presence of condensed tannins in the testa prevents infection of the plant by the causative pathogens.Fusarium oxysporumandF. solani, isolated from faba bean tissues showing foot rot symptoms, were shown to be primary foot rot pathogens, whileF. avenaceumcaused wilting of young plantlets. No pathogenic isolates were obtained fromF. tabacinum. Resistance toBotrytis fabae(chocolate spot disease), scored on leaves and stems under glasshouse and field conditions in 1992, was not influenced by selection for the absence of condensed tannins which occur in the testa of mature seeds. Under the same environmental conditions, leaves, stems, pods and seeds of tannin-free lines showed similar levels of damage due toAscochyta fabae(Ascochyta blight) as the tannin-containing partner lines of the same near-isogenic pair. These results indicate that condensed tannins do not play a role in resistance to bothB. fabaeandA. fabae, probably because, except for the seeds, these polyphenols do not accumulate in the tissues affected by these pathogens.