Abstract

Four

experiments were established at Isla and Cotaxtla, Veracruz,

Méxicoto determine the reactions of 56 common bean

genotypes to M. phaseolina under irrigated-rainfed conditions

and to identify resistant and stable-yielding germplasms under

water-stress conditions. The germplasm included different

origins, genetic races, seed coat colors and genetic status and

was randomized in 7x8 lattice experimental designs and then

grown under irrigated and rainfed conditions (no irrigation

throughout the reproductive stage). Water stress promoted

earlier physiological maturity and increased charcoal rot

severity; in addition, water stress reduced common bean grain

yields. Through the four experiments TLP20/NT81, NGO

99165, Negro Veracruz, A 774, and BAT 477 showed the

highest grain yields (more than 1000 kg ha-1) and the lowest

charcoal rot severity ratings, while Negro Otomí, 9457-43,

NGO 99176, CNC 2, and VAX 2 showed an inverse behaviour.

Drought Intensity Index varied through experiments although

the highest values were found at Isla (0.53 and 0.38 in 2000

and 2001, respectively). No clear association between Drought

Susceptibility Index and charcoal rot severity or grain yield

were found, but a negative relationship between grain yield and

charcoal rot severity was registered (r = -0.26*) en promedio.

Although no clear associations were found, the genotypes with

the lowest M. phaseolina damages and the highest grain yields

showed low values of drought susceptibility index.