The possibilities of GAIA method application for DUS examination in Ukraine

Purpose. To determine the applicability of the GAIA method for comparison of reference collection of maize lines based on weights of the difference for morphological characteristics and SSR markers. Methods. Field methods (descriptive plant morphology), molecular methods (PCR, capillary electrophoresis), and statistical methods (principal component analysis, correlation analysis). Results. The study examined 57 lines of maize reference collection to determine their differences based on phenotypic and molecular distances using the GAIA method. The comparison of maize lines, considering the difference for morphological characteristics, identified 12 lines classified as “Distinct Plus” compared to other studied maize lines. The obtained data indicate that most of the “Distinct Plus” lines were classified as distinct according to distinctness, uniformity, and stability (DUS) testing. However, three pairs of lines identified as “Distinct Plus” were classified by the DUS expert as similar or very similar. It was determined that the first two principal components explain 23.37% of characteristic variability. Principal component analysis revealed that the high level of variability attributed to the differences of grouping characteristics and traits which are not used for variety grouping during DUS testing. This suggests that to enhance the effectiveness of the GAIA method, it is advisable to increase weights of the difference for qualitative morphological characteristics. Based on the combination of phenotypic and molecular distances, an additional 35 pairs of maize lines were identified with a high degree of distinction, eliminating the need for side-by-side field comparisons in the next growing season. Conclusions. The application of the GAIA method for maize line analysis helps reduce the number of side-by-side field comparisons by integrating morphological traits and molecular markers.