EFFECT OF THE VRN1-FR1 INTERVAL ON COLD-HARDINESS LEVELS IN NEAR-ISOGENIC WHEAT LINES

We investigated the feasibility of cold hardiness manipulation in whea t, Triticum aestivum L., with the Vrn1-Fr1 interval on chromosome 5AL. The interval contains a gene(s) that has influenced vernalization req uirements and cold hardiness levels. We conducted LT50 tests (lethal t emperature of 50% of plants) on wheat NILs (near-isogenic lines) that differed for alleles at the Vrn1-Fr1 interval, to determine the effect s of the interval on cold hardiness levels between hardy and nonhardy wheat. The Mts were derived from five backcrosses between a spring whe at recurrent parent,'Marfed', and two winter wheat donor parents, 'Suw eon 185' and 'Chugoku 81', hardy and nonhardy, respectively. The devel oped populations were Suweon 185/6Marfed and Chugoku 81/6*Marfed spri ng and winter NILs. Results showed that the winter NILs could tolerate a 4.3 degrees C colder LT50 store than the spring NILs, and that the Suweon 185/6Marfed winter Mts could tolerate a 0.5 degrees C colder L T50 than Chugoku 81/6Marfed winter Mts. Results indicate that the Vrn 1-Fr1 interval explained between 71 and 91% of the variation for LT50 scores between these genotypes. The Mts were analyzed with the probe X wg644 to confirm linkage with the Vrn1-Fr1 interval and to determine i ts utility as a marker for vernalization requirement and cold hardines s. EcoRI-digested DNA of the winter and spring Mt wheat, probed with X wg644, showed that a 9.7-kb band co-segregated with the winter growth habit. Results indicate that differences in cold hardiness levels betw een winter wheat cultivars may be explained by this interval and that the interval may be manipulated through plant breeding to improve the cold hardiness of cultivars.