Abstract

Higher levels of web blight
resistance is needed to increase common bean yield and seed
quality in the hot and humid regions of Central America and
the Caribbean. Only moderate levels of resistance have been
identified in common bean. Moreover, virulence patterns of
the web- blight pathogen, Thanatephorus cucumeris (Frank)
Donk, vary among geographic locations. Fields screening for
web-blight resistance is limited to seasons that favor the
development of the disease. In the field, it is also difficult to
separate disease avoidance due to plant architecture and
physiological resistance. Greenhouse and laboratory
techniques have been developed that facilitate the screening
of bean lines for physiological resistance. A recurrent
selection scheme is proposed to select beans with higher
levels of web-blight resistance. Inter-specific crosses may be
used to broaden the genetic base of resistance to web-blight.
P. coccineus lines with useful levels of resistance have been
identified. Transgenic bean plants with herbicide resistance
would be useful for minimum tillage. A cover of dead
vegetation on the soil surface could help to reduce the spread
of web-blight.