HERITABLE IMPROVEMENT OF FROST TOLERANCE IN WINTER-WHEAT BY IN-VITRO SELECTION OF HYDROXYPROLINE-RESISTANT PROLINE OVERPRODUCING MUTANTS

In a previous study (Dorffling et al., J. Plant Physiol. 142, 222-225, 1993) in vitro-selection and regeneration of hydroxyproline (Hyp)-res istant lines of winter wheat (Triticum aestivum cv. Jo 3063) with incr eased frost tolerance and increased proline contents was reported. In this study the heritability of these traits was investigated. The F-1 progenies derived from the pollination of regenerated plants with poll en from wild type plants developed higher mean frost tolerance (lower LT(50) values) and higher proline levels compared with in vitro-contro ls and wild type plants. In the F-2 generation, which was obtained by self-pollination, segregation of the Hyp-lines in a 3:1 phenotypic rat io with regard to the traits frost tolerance and proline content was o bserved. Subsequent selection of extremes in the F-2 yielded homozygou s plants in the F-3 generation. Lower LT(50) values and increased prol ine contents in those F-3 plants were significantly correlated. Furthe rmore, improved frost tolerance of one of the selected mutants was als o observed in studies with whole plants in the F-4 generation. These r esults, which are similar to results of parallel studies on winter bar ley, provide strong evidence for the heritability of the traits 'incre ased frost tolerance' and 'increased proline content' obtained by this in vitro-selection procedure. The mutation seems to be due to a singl e incompletely dominant gene. A comparison of frost tolerance values f rom F-3 Hyp-progenies with those of seven standard varieties differing in frost tolerance indicates a considerable improvement of frost tole rance by the described in vitro-selection method.