STUDIES ON THE ESTABLISHMENT OF WHITE-FLOWERED FABA BEAN (VICIA-FABA)

Early reports on new, nutritionally superior, white-flowered (zero-tan nin) faba bean cultivars indicated that they may show poor emergence u nder field conditions. The field emergence of 23 winter and spring typ e white and coloured-flowered lines and cultivars was investigated in relation to fungicidal seed dressing in 1989/90 and 1990/91 in the UK. These trials showed no definite emergence problems in white-flowered faba beans, probably because of favourable soil and weather conditions . Further experiments were therefore conducted in relation to emergenc e under controlled environmental conditions. The emergence of lines ne ar-isogenic except for flower colour (the coloured line SCI v. the whi te line SWI) was investigated in relation to a range of soil moisture levels (soil water potential (SWP) ranging from - 1.02 to 0.0 MPa (wat erlogged)) and to three temperatures(22, 12 and 5 degrees C) in a clay loam soil. Emergence was rapid and high at the SWP range from -0.52 t o -0.24 MPa in both lines, depending on temperature. Any decrease or i ncrease in SWP beyond this range resulted in a substantial reduction a nd delay in emergence in both lines. Emergence of SWI was more adverse ly affected than SCI when the temperature decreased from 22 to 5 degre es C. The emergence of six winter and six spring lines/cultivars was t ested in relation to fungicidal seed dressing using wet soil (-0.06 MP a) at 5 OC under controlled environmental conditions. White-flowered w inter lines (WWI, Polar and WD) and the spring line, SWI, had poor eme rgence (56-85%) compared to coloured types (86-98%). In some lines the re was a slight improvement when using a fungicidal seed dressing. How ever, white types with emergence equal to or better than the coloured types were also present (e.g. Glacier, Albatross and SVPW). The result s of these experiments suggest that poor emergence in white types of f aba bean is only a problem in some genotypes when soil conditions at s owing are unfavourable.