THE EFFECTS OF SELECTION FOR SODIUM-TRANSPORT AND OF SELECTION FOR AGRONOMIC CHARACTERISTICS UPON SALT RESISTANCE IN RICE (ORYZA-SATIVA L)

A multiple cross was constructed with the aim of combining component t raits for the complex salinity resistance character. The aim was to co mbine donors for physiological traits with the agronomically desirable semi-dwarf/intermediate plant type and with the overall salinity resi stance of the traditional tall land races. We report a study of select ion strategies in the resulting breeding population. The effects of ea rly selection for agronomic traits and early selection for low sodium transport were compared with a control population in which minimal sel ection was practised. Conventional selection for agronomic characters at early generations selected against low sodium-transporting (and thu s potentially salt-tolerant) genotypes. In contrast, mild early select ion for low sodium transport enriched the population in potentially sa lt-resistant genotypes but did not select against agronomic (semi-dwar f/intermediate) genotypes. It is concluded that selection for agronomi c traits should be made after selection for salt resistance and, ideal ly, should be delayed until the population has reached near-homozygosi ty.