CHROMOSOMAL LOCATIONS OF GENES FOR ALUMINUM TOLERANCE, LEAF RUST, AND HIGH PROTEIN IN THE WHEAT CULTIVAR \u27ATLAS 66\u27 USING THE MONOSOMIC METHOD

Wheat breeders have observed a close association of high protein, leaf rust resistance, and aluminum tolerance in the wheat (Triticum aestivum L.) cultivar \u27Atlas 66\u27. In order to determine the cytogenetic basis for this association, Atlas 66 was crossed with \u27Wichita\u27 aneuploids and monosomics were chosen from the F(,1) hybrids. Disomic F(,2) plants were selfed to provide disomic F(,3) seed. An aluminum tolerance method was developed using 6.5 L pans of nutrient solution in a growth room. Seedlings were seven days old when measured and first exposed to aluminum, and were measured again after another seven days. Net root length (final minus initial root length) proved most useful in exploring gene action. Temperature seemed to affect aluminum tolerance, and the aluminum levels applied had a linear effect on root length with genotype by environment interaction. In one experiment, a 3:1 ratio of aluminum-tolerant to aluminum-susceptible plants was noted in the F(,2) generation. Under the conditions of a second experiment, tolerant and susceptible plants could not be classified as easily. A bimodal curve, though indicated, was not as clear, but chromosomes 5B and 7D could be eliminated as those carrying the primary gene for aluminum tolerance, while chromosome 5D may carry this gene. Further experiments must confirm these results. In a third experiment, no evidence of a bimodal curve was noted. When the grain of F(,3) progenies and the parental cultivars were grown in a greenhouse soil bed, a strong negative phenotypic correlation between yield and protein was noted. The parental cultivars did not show a significant difference in percent grain protein. Chromosomes 2B, 2D, 3B, 5D, and 6D of Atlas 66 conferred significantly (P = 0.05) less protein than Atlas 66. The existence of monosomic plants in one plot adversely affected grain protein. Awn length seemed a satisfactory trait for genetic studies. Seedlings were inoculated with leaf-rust culture PRTUS 1 and kept at 5(DEGREES)C. The reactions were observed six weeks later. Chromosome 2D appeared to carry a gene conferring leaf rust resistance in Atlas 66 according to F(,3) progeny tests; however, these results must be considered preliminary because of inconsistencies