HYBRIDIZATION OF TRITICUM AND AGROPYRON: V. DOUBLING THE CHROMOSOME NUMBER IN T. VULGARE AND F1 OF T. VULGARE × A. GLAUCUM BY TEMPERATURE TREATMENTS

Abstract

An apparatus was developed for applying heat treatments to spikes on plants growing in the field. This apparatus gave very satisfactory results on self-fertilized zygotes of Marquis wheat. Treatments at 42, 43, and 44 °C. for 20 min. induced chromosome doubling in 2% of the plants.A wide variety of temperature treatments was applied to more than 13,000 wheat florets 16 to 27 hr. after being pollinated with A. glaucum, in an attempt to produce fertile and stable F₁ hybrids. Chromosome doubling was induced in one F₁ plant of Kharkov × A. glaucum by exposure to alternating temperatures of 36° and 109° F. The resulting 84-chromosome plant grew slowly and failed to produce any spikes, as was the case with a number of 42-chromosome plants of this cross. Consequently there is uncertainty as to whether this plant is inherently abnormal aside from chromosome doubling, or whether the chromosome number is too high for normal development. It must be concluded from the results as a whole, that chromosome doubling by means of temperature treatments can be induced only with great difficulty in Triticum–A. glaucum hybrids.