Determination of aneuploids in hop (Humulus lupulus L.) using flow cytometry

In order to study the possibility that high-resolution flow cytometry can be used for determination of aneuploids, different genotypes of Humulus lupulus were analyzed. Triploid cultivars are bred by hybridization between diploid and tetraploid lines, and as the result of this process, some aneuploids are occasionally also formed. We analyzed eight triploid cultivars and seven putative aneuploids. Triploid cultivars Cerera, Cicero, Celeia, Cekin, Blisk, Mt. Hood, Huller Bit. and Willamette (3x = 30) were measured for nuclear DNA content using Trifolium repens as reference. No significant differences among peak positions of triploid cultivars (having an average CV value per peak of 1.94%) were found. Measurement of nuclear DNA content was also performed for seven lines: 175/75, 89/113, 89/154, 91/215, 175/17, 89/87 and 91/74 previously determined by chromosome counting to be aneuploids (CV per peak was 1.41%). A statistically lower DNA content was found for line 175/75 and higher values were measured for lines 89/154, 89/113 and 91/215. Repeated chromosome counting revealed that the number of chromosomes in line 175/75 was 29, while lines 89/154, 89/113 and 91/215 possessed 31 chromosomes. The other lines were identified as triploids. We conclude that flow cytometry can be efficiently used for determination of aneuploidy in Humulus lupulus.