Screening techniques and sources of tolerance to extremes of moisture and air temperature in cool season food legumes

Breeding for resistance to extremes of temperature and moisture in cool season food legumes is limited by the lack of adequate screening techniques. The success of each technique depends upon the representativeness and reproducibility of the type of stress created. Descriptions of successful techniques are presented for frost and terminal drought. Development of new screening tests designed to select for specific adaptive traits require a better knowledge of the mechanisms of resistance in these crops, especially to drought. Rooting depth, early vigor, reduced branching, and osmotic adjustment are discussed. Other mechanisms of resistance to drought, heat, freezing, or chilling have been proposed but need to be studied jointly by crop physiologists and plant breeders.