How variable characteristics of bean cropping systems affect Fusarium and Rhizoctonia root rot epidemics?

Abstract

Fusarium root rot (FRR) and Rhizoctonia root rot (RRR) are potential threats to bean production worldwide. Disease incidence, severity and index, and yield were assessed at vegetative, flowering–podding and maturity stages in 122 commercial bean fields. Area under the disease progress curve (AUDPC), linear and quadratic coefficients of disease-time regressions were also used as epidemiological descriptors. From factor analysis, development of FRR and RRR epidemics were characterized mainly by AUDPC. Using redundancy analysis, 30 agricultural indicators accounted for 69% variations in FRR- and RRR–AUDPC, and bean production. Severe FRR and RRR epidemics and less pod and seed production corresponded with deep seeding, dense weed, low soil organic matter, planting White bean, mechanical cultivation, planting in Abhar region, frequent irrigation, growing continuous bean, lack of herbicide application, fungicidal treatment of soil, urea application, flat seedbed, short initial-drought period, unfertilized planting and early planting. Such epidemiological information assists with improving disease control programs.