SCREENING FOR DROUGHT RESISTANCE - EVALUATION OF DROUGHT SUSCEPTIBILITY INDEX OF LEGUME PLANTS UNDER NATURAL GROWTH-CONDITIONS

Eighteen cultivars of legume species (held bean, soybean, field pea, l upine) were screened for drought tolerance in 3 year-long held experim ents. The aim of the investigations was to evaluate the genetic variat ion of drought susceptibility of the tested varieties. The experimenta l plots were equipped with an installation which enabled the limitatio n of the water content in soil and soil irrigation The applied drought susceptibility index (DSI) considered the relations between seed yiel d of plants under drought conditions (Y-D) and that under conditions o f good soil watering (Y-IR) as well as their dependence on the drought severity index (D-S) The use of the index divided the cultivars into two groups of different drought tolerances. The group of drought resis tant cultivars characterized by mean values of the DSI index <0.31 com prised field bean cultivars Bourdon, Gobo and Nadwislanski soybean cul tivars Aldana, Polan and Progres, field pea cultivars Mike and Solara and lupine cultivars Popiel and Pac. To the drought sensitive cultivar s with DSI > 0.44 belonged Victor and Bronto of field bean species, Ba reness and Mige of field pea species and Emir of lupine species. In ge neral, the resistant cultivars when compared with the susceptible ones were characterized by lesser yield of seeds, which, however, was more stable both under conditions of drought and moistured plots. Any depe ndence of the degree of drought tolerance on the duration of the parti cular periods of plant growth was not observed in the experiments, how ever, both in drought susceptible and drought resistant cultivars ther e appeared the tendency to shorten the development phases under drough t and to prolong them under artificial irrigation. In general based on the results obtained, it can be concluded that legume plants belong t o the species sensitive to water supply. The observed decrease of plan t seed yield under moderate natural soil dryness in the year 1993 diff ered only a little from that found in experiments in the years 1994 an d 1995, when soil dryness was much more severe.