Phenotypic diversity for agronomic traits in a collection of blackcurrant (Ribes nigrum L.) cultivars evaluated in Poland

Abstract

This paper presents an assessment of phenotypic diversity for forty blackcurrant (Ribes nigrum L.) cultivars, originating from different counties and maintained in an ex situ collection. The data of eighteen traits, describing phenology, plant morphology, yield, fruit quality and plant susceptibility to main diseases and pests, were recorded across 3 years, from 2007 to 2009. The data were analyzed using principal component analysis (PCA) and cluster analysis (CA) by the Ward's method and the square of the Euclidean distance. The six principal components (PC1–PC6) explained approximately 77% of the total variance among the blackcurrant cultivars tested, and the first two PCs accounted for approximately 37% of the multi-trait variation. Due to a substantially high correlation between PC1 and the three phenological traits (time of bud burst, time of beginning of flowering and time of fruit ripening), fruit size and firmness of the fruit skin, this principal component represents these inter-correlated blackcurrant traits to a large extent and could be called “Ripening time driving fruit size and skin firmness”. The second principal component, because of its correlations with the recorded traits, could be called “Plant susceptibility to diseases and pests affecting fruit productivity”. The third PC could be called “Plant size related to susceptibility to two-spotted spider mite”. Cluster analysis distinguished six homogenous groups. This study confirmed the outstanding differences among the genotypes from different geographic origins and those from similar geographic origins. It also suggests that the characterized blackcurrant collection has high potential for specific breeding goals. The cultivars included in the diverse clusters could be potential parents with complementary levels of the most discriminating traits for the assessed genotypes. These cultivars could be used for hybridization to obtain a high heterotic response and thus could substantially contribute to blackcurrant breeding programs.