New faba bean genotypes resistant to chocolate spot caused by Botrytis fabae [Vicia faba L. - Tunisia]

English. The response of 67 genotypes of faba bean (Vicia faba) to the virulent isolate IBf24 of Botrytis fabae was studied under field conditions. Five of these genotypes (LPF39, LPF113, LPF44, LPF237 and LPF05) were moderately resistant to chocolate spot according to their MDI (mass disease index). Ten lines (LPF38, LPF41, LPF64 LPF95, LPF106, LPF132, LPF225, LPF228, LPF23, LPF233) were moderately susceptible and 15 lines (LPF54, LPF61, LPF66, LPF89, LPF124, LPF129, LPF131, LPF134, LPF138, LPF152, LPF173, LPF174, LPF190, LPF274, BPL710) were susceptible, as shown by their MDI values, but with low AUDPC (area under disease progress curve) values, and were believed to have an overall tolerance to the disease. Fourteen of the genotypes tested in the field, as well as the resistant BPL710 and the susceptible Rebaya 40 controls, were further screened under greenhouse conditions in order to confirm the field evaluation. In both the field and the greenhouse trials, the 4 lines LPF44, LPF237, LPF05 and LPF113 showed the highest level of resistance to the disease. These trials also revealed that genotypes with only overall tolerance may yet constitute interesting sources of resistance. Genotype BPL710, with known resistance to B. fabae races in the Mediterranean region, was found to be susceptible in the field but moderately susceptible in the greenhouse, suggesting the appearance of new races of this pathogen

Italian. [E' stata studiata la risposta di 67 genotipi di fava (Vicia faba) all'isolato virulento IBf24 di Botrytis fabae in condizioni di campo. Cinque di questi genotipi (LPF39, LPF113, LPF44, LPF237 and LPF05) erano moderatamente resistenti alla macchia color cioccolata in base al loro MDI (indice di massa della malattia). Dieci linee (LPF38, LPF41, LPF64 LPF95, LPF106, LPF132, LPF225, LPF228, LPF23, LPF233) erano moderatamente suscettibili e 15 linee (LPF54, LPF61, LPF66, LPF89, LPF124, LPF129, LPF131, LPF134, LPF138, LPF152, LPF173, LPF174, LPF190, LPF274, BPL710) risultavano suscettibili, come evidenziato dai loro valori di MDI, ma con bassi valori di AUDPC (area sotto la curva di progresso della malattia), ed erano ritenute in possesso di una tolleranza complessiva alla malattia. Quattordici dei genotipi valutati in campo, unitamente ai controlli BPL710 resistente e Rebaya 40 suscettibile, sono stati ulteriormente verificati in condizioni di serra per confermare i dati ottenuti in campo. Sia nelle prove di campo, sia in quelle in serra, le 4 linee LPF44, LPF237, LPF05 e LPF113 hanno evidenziato la resistenza piu' elevata alla malattia. Queste prove hanno anche messo in luce che i genotipi con solo una tolleranza complessiva possono rappresentare comunque fonti interessanti di resistenza. Il genotipo BPL710, caratterizzato da resistenza alle razze di B. fabae nella regione mediterranea, e' risultato suscettibile in campo ma moderatamente suscettibile in serra, facendo ritenere possibile la comparsa di nuove razze di questo patogeno]