Application of cluster analysis for grouping Brassica oleracea var. italica varieties for the difference test

Abstract

Purpose. To use cluster analysis of morphological cha­racters to simplify the identification of Brassica oleracea var. italica and form groups of similar varieties for the test of difference. Methods. Analytical, mathematical and statistical methods were used in the work. As input information for the statistical processing of the obtained results, information on the results of the examination for distinctness, uniformity and stability (DUS) from the database of the Automated Information System of the Ukrainian Institute for Plant Varieties Examination was used. Cluster modelling was carried out using the IBM SPSS Statistics “Statistical Package for the Social Sciences”. Results. A morphological description of broccoli varieties was carried out on the basis of 32 characteristics for the examination of distinctness, uniformity and stability. The morphological code formulae of the latter, composed of the corresponding codes for the manifestation of identifying characteristics of vegetative and generative organs of plants, served as a source of initial data. Out of 41 varieties described by 32 morphological characteristics, only two groups were found to be similar in terms of the identifying characteristics of the varieties. Two types of variables were used as parameters of the model: target – characteristic “Head: anthocyanin colour”, focal – “Head: colour”. The full list of characteristics was as follows “plant: by height (at harvest maturity)”, “leaf: position (at beginning of head formation)”, “leaf blade: wavy edge”, “leaf blade: blistering”, “petiole: by length”, “head: colour”, “head: anthocyanin colour”, “head: by density”, “flower: colour”, “flower: intensity of yellow colour”, “male sterility”. Using computer modelling, clusters of 17 similar broccoli varieties and 9 control objects (varieties) were formed, the identification of which involved eleven morphological characteristics. Conclusions. In order to search for distinguishing characteristics in the process of testing the difference of cabbage varieties, broccoli was grouped into clusters according to such morphological characteristics as the position of the leaf at the beginning of the formation of the head; waviness of the edge of the leaf blade; blistering of the leaf plate; petiole length; head colour; presence of anthocyanin and intensity of yellow colour.