Agro-morphological and genetic characterization of advanced potato (Solanum tuberosum L.) breeding lines in Mahikeng, South Africa

Abstract

One of the most important strategies for increasing crop productivity and improvement in potato yield output is the development and introduction of new cultivars. Phenotypic characteristics are the first aspects to consider in crop improvement and breeding as it demonstrates the relationship among genotypes. The study aimed to characterize advanced potato breeding lines (genotypes) using agronomic and morphological traits under Mahikeng growing conditions. Thirty-three potato genotypes obtained from the ARC-VIMP breeding programme were evaluated for agronomic and morphological traits under field conditions using a randomized complete block design with three replications across two seasons. The genotypes were planted during the 2019/2020 and 2020/2021 summer cropping seasons. Data were collected on 15 quantitative traits. The analysis of variance for 12 of the traits revealed a highly significant (P<0.0001) differences among the genotypes and it was not significant for 3 traits. Relatively high genotypic and phenotypic variance values were obtained for emergence percentage, plant height, number of leaves, leaf area, chlorophyll content, individual tuber weight and yield per plant. Plant height, number of leaves, branches and tubers, stem diameter, chlorophyll content, individual tuber weight, tuber length and yield per plant had a heritability of more than 80%. For the morpho-agronomic characters evaluated, cluster analysis revealed that there was variability among the 33 potato genotypes. The genotypes were classified into three primary clusters. Each cluster was subdivided into two sub-clusters: 1 and 2. The grouping helped to identify genotypes that share the same characteristics and that are closely related. Plant height, the number of stems, stem diameter and individual tuber weight had a strong positive correlation with the yield per plant. The first five principal components explained 71.21% of the variation, indicating that there are significant genetic differences between the genotypes which can be utilized for breeding purposes to improve these features. Characteristics such as tuber shape, size and colour are important for the fresh market and are the key factors considered for the processing industry. The genotypes exhibited high diversity in growth habit, leaf texture, tuber shape, tuber colour, flesh colour, tuber distribution and tuber eye depth. The growth habit was placed into three groups, erect (21.2%), semi-erect (45.5%) and spread (21.2%). There was a wide

variation in leaf texture, 3% was coarse- hairy, 3% was smooth/glossy, 12.1% was fine and hairy, 30.3% were fine and 51.5% were coarse. Tuber shape also showed wide variation as 3% was compressed-oblong, 6.1% was oblong, 6.1% long-oblong, 9.1% was round, 12.1% was obovate, 15.2% was compressed and 48.5% was elliptic. Genotypes showed variation in tuber colour, 6.1% was slightly dark cream, 15.2% dark cream, 39.4% was cream and 39.4% was light cream. Flesh colour also showed high variation, 3% was light cream, 6.1% was dark cream, 9.1% was yellow, 24.2% was white, 24.2% was light yellow and 33.3% was cream. There was a slight variation in tuber distribution with 12.1% being evenly distributed and 87.9% predominantly apical. Tuber eye depth showed moderate variation, 3% was deep, 24.2% were medium, 36.4% were protruding and 36.4% were shallow. The genotypes studied showed a great genetic variability which can be considered for crop improvement and breeding.