Seed pod shattering in the genus Lotus (Fabaceae): A synthesis of diverse evidence

Birdsfoot trefoil (Lotus corniculatus L.) is a perennial dehiscent species with an indeterminate growth habit. Pod shattering has been a major problem as seed loss is high due to the continuous flowering and rime of pod maturity. The anatomy of the pod plays a role in pod shattering. 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 for dehiscence varies with genotypes between 35 and 49%. Pod dehiscence is uncorrelated with plants grown to maturity under green house conditions and the same plants grown in the field. Management practices (timing of the harvest, clipping early in the season, misting, mowing and turning the windrow during drying, desiccants) have not been successful to control pod shattering. Shattering resistance is a character of high heritability and in Lotus is considered to be controlled by more than one gene. Breeding to reduce shattering through recurrent selection has been unsuccessful. Attempts to transfer the indehiscent seed pod trait from distantly related indehiscent species via interspecific hybridization, diploid bridge species, amphidiploidy, and backcrossing to birdsfoot trefoil, or similarly by interspecific somatic hybridization, have shown promise. The molecular approach has so far not been attempted but since genetic transformation can be carried out in Lotus. this avenue should be investigated.