Relative Pathogenicity of Fusarium wilt isolates from various guava growing districts of Tamil Nadu in Guava (Psidium guajava L.) under in-vitro and in-vivo conditions

Several pathogens have been suspected in causing guava wilt disease, however F. oxysporum f. sp. psidii and F. solani are the most important pathogens to be associated with guava wilt disease (Psidium guajava L.). In the present investigation, the duration of symptom expression and relative pathogenic ability of ten F. oxysporum isolates obtained from several districts of Tamil Nadu was assessed under in-vitro and in-vivo conditions. Of these, every F. oxysporum isolates produced wilt symptoms either on all three replicates or on a single plant showing 80% wilt. It was noticed that different isolates caused wilting at a variable period of time indicating difference in their relative aggressiveness or virulence. Earliest symptom of wilt was recorded in isolates GF1 and GF4 of F. oxysporum f. sp. psidii. In both in-vitro and in-vivo conditions, the results concluded that the isolates GF1 obtained from Malumichampatti, Coimbatore and GF4 from Seethapatti, Tiruchirapalli were found to be highly pathogenic compared to that of all other isolates. Under in vivo conditions, the soil inoculation strategy has been demonstrated to be relevant and dependable for guava wilt replication (80 - 85%). Thus, the varying aggressiveness or virulence of different pathogenic isolates in the soil may explain the erratic distribution and prevalence of guava wilt in various geographic regions.