VARIABILITY IN MORPHO-PHYSIOLOGICAL TRAITS OF COMMON BEAN UNDER TERMINAL DROUGHT

Abstract

Terminal drought leads to severe reductions in the dry matter and development of the canopy of common bean plants (Phaseolus vulgaris L.). The aim of this study was to determine the effect of terminal drought on the expansion of the foliar area (AF), the accumulation of dry weight in the aerial section (PSPA) and roots (PSR), and transpiratory efficiency (ET) under controlled conditions. The hypothesis was that terminal drought reduces the accumulation of the biomass in the above ground section (shoot) but increases the root weight and transpiratory efficiency. In a random complete block design with three repetitions in irrigation (R) and three under terminal drought (S), 12 genotypes were included. One 80-40-00 dose of fertilization was used. The terminal drought condition reduced AF 17-24%, 40-59% and 63-79% in flowering, seed-filling period and physiological maturity (MF). The S also reduced PSPA and total plant biomass (BM) by 33 and 26%, whereas the total dry weight of roots (PSTR), the root/shoot ratio and ET were 53, 67 and 58% higher in drought than in irrigation. The highest proportion of roots was produced in the 0-20 cm layer (R=50.6% y S=54.7%). PSR decreased in the lower levels of the soil: 20-40 (R=29.5%; S=26.4%), 40-60 (R=14.1%; S=11.9%), 60-80 (R=5.8%; S=5.2%) and 80-100 cm (only in S=1.8%). Varieties FM M38, FM Sol and FM RMC showed a better behaviour in most of the traits evaluated in plants. Therefore, they can be used as parental lines in plant breeding programs.