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

Early reports on new, nutritionally superior, white-flowered (zero-tannin) faba bean cultivars indicated that they may show poor emergence under field conditions. The field emergence of 23 winter and spring type 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 emergence under controlled environmental conditions. The emergence of lines near-isogenic except for flower colour (the coloured line SCI v. the white 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 (waterlogged)) 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 to -0.24 MPa in both lines, depending on temperature. Any decrease or increase in SWP beyond this range resulted in a substantial reduction and delay in emergence in both lines. Emergence of SWI was more adversely affected than SCI when the temperature decreased from 22 to 5 degrees C. The emergence of six winter and six spring lines/cultivars was tested in relation to fungicidal seed dressing using wet soil (-0.06 MPa) at 5 OC under controlled environmental conditions. White-flowered winter lines (WWI, Polar and WD) and the spring line, SWI, had poor emergence (56-85%) compared to coloured types (86-98%). In some lines there was a slight improvement when using a fungicidal seed dressing. However, white types with emergence equal to or better than the coloured types were also present (e.g. Glacier, Albatross and SVPW). The results of these experiments suggest that poor emergence in white types of faba bean is only a problem in some genotypes when soil conditions at sowing are unfavourable.