SEED POD SHATTERING IN THE GENUS LOTUS (FABACEAE) - A SYNTHESIS OF DIVERSE EVIDENCE

Birdsfoot trefoil (Lotus corniculatus L.) is a perennial dehiscent spe cies with an indeterminate growth habit. Pod shattering has been a maj or problem as seed loss is high due to the continuous flowering and ri me of pod maturity. The anatomy of the pod plays a role in pod shatter ing. A change in the orientation of the cells in the pericarp in which unequal swelling and shrinkage occur and a lower lignification of the mesocarp have been considered as major causes. The relative humidity (RH) at the time of harvest is also a major factor. The critical RH fo r dehiscence varies with genotypes between 35 and 49%. Pod dehiscence is uncorrelated with plants grown to maturity under green house condit ions and the same plants grown in the field. Management practices (tim ing of the harvest, clipping early in the season, misting, mowing and turning the windrow during drying, desiccants) have not been successfu l to control pod shattering. Shattering resistance is a character of h igh heritability and in Lotus is considered to be controlled by more t han one gene. Breeding to reduce shattering through recurrent selectio n has been unsuccessful. Attempts to transfer the indehiscent seed pod trait from distantly related indehiscent species via interspecific hy bridization, diploid bridge species, amphidiploidy, and backcrossing t o birdsfoot trefoil, or similarly by interspecific somatic hybridizati on, have shown promise. The molecular approach has so far not been att empted but since genetic transformation can be carried out in Lotus. t his avenue should be investigated.