YIELD AND NUTRITIONAL QUALITY OF SNAP BEAN IN TWO ENVIRONMENTS

Abstract

In México dry bean (Phaseolus vulgaris L.) is traditional, but not of snap bean (fresh bean pods) despite its high contents of proteins, carbohydrates, fiber, calcium and vitamins. In the State of México, snap bean production does not satisfy the domestic demand, thus requiring importation. Since yield and nutritional quality of the fresh pods may be a function of cultivar and environmental conditions, the aim of this study was to elucidate the nature of this interaction in snap bean production. Three cultivars were tested, determinate growth habit varieties ‘Strike’ and ‘Black Valentine’, indeterminate climbing growth habit variety and ‘Hav-14’, in two contrasting environments (Montecillo, semiarid climate; and San Pablo Ixayoc, temperate climate) in the State of México. Sowing was done on May 7, 2008, under rainfed conditions. The experimental design was a randomized complete block for each environment. Variables recorded were: days to phenologic events, fresh pod weight (in g m^-2), number of pods per m², and nutritional quality. With regard to the environment, collected data included maximum and minimum temperatures, precipitation; evapotranspiration (ETc); and Heat Units (UC) were calculated. The time of occurrence of the phenologic stages of bean plants varied among cultivars and environments. In Montecillo cv. ‘Strike’ presented the shortest cycle (78 d from sowing to last harvest) and cv. ‘Hav-14’ the longest (102 d). In San Pablo cv.’Strike’ extended its cycle by 12 d and ‘Hav-14’ by 17 d. In Montecillo, the highest yield and number of pods (1.37 kg m^-2 and 307) corresponded to cv.’Hav-14’ with 782 UC, 175 mm of and ETc and 275 mm of precipitation, and the lowest values to cv. ‘Strike’ (0.195 kg m-2 and 57 beans, respectively) in San Pablo (567 UC, 151 ETc and 379 mm of precipitation). The pod nutritional quality showed differences between environments: in Montecillo cv. ‘Hav-14’ recorded the highest contents of proteins (22.3 %), minerals (8.8 %) and fiber (acid, -ADF- 24.3 %, and neutral, -NDF- 31.5 %); while at San Pablo, the opposite trend was observed, with lowest values in proteins (18 %), minerals (6.1 %), ADF (17.4 %) and NDF (24.4 %). A significant genotype x environment interaction was found, since variables yield, number of beans and nutritional quality varied depending on the test location.