Evaluation of dark jute SSR markers and morphological traits in genetic diversity assessment of jute mallow (Corchorus olitorius L.) cultivars

Abstract

The jute mallow (C. olitorius L.) is an important nutritious green leafy vegetable in the tropical region of Africa. This study assesses the extent of genetic diversity and intra-specific relationships among 16 cultivated jute mallows of Nigeria (14), [Ghana (1) and Togo (1), used as checks, evaluating 16 dark jute SSR markers and 16 morphological traits (quantitative and qualitative). The study reveals moderate to high variation among the cultivars in the number of pods, pod yield and plant height traits. Based on the principal component (PC) analysis of the quantitative traits, the pod length, pod width, number of pods, pod yield and plant height are important traits composing PC1. On the other hand, the pod pedicel length and days of 50% flowering traits are highly correlated variables in PC2. Pod length, pod width, pod pedicel length and plant height account for the total diversity. Two main groups (I and II) and an outgroup are identified among the 16 cultivars based on the quantitative traits. among the cultivars, leaf shapes identified are ovate (38% of cultivars), lanceolate (6%), oblanceolate (25%) and palmately lobed (31%). Three markers which have monomorphic alleles are excluded and thirteen markers are used to analyse the genetic diversity. A total of 41 alleles are amplified using the 13 polymorphic markers with an average of 2.75 per locus. The mean polymorphism information content (PIC) value is 0.42, ranging from 0.06 to 0.73. The mean gene diversity or expected heterozygosity = 0.05 (from 0.06 to 0.76). The observed heterozygosity (Ho) ranges from 0.00 to 0.88, with a mean of 0.60. The mean genetic dissimilarity is 0.35. Thus, the SSR data indicate a moderate genetic dissimilarity within jute mallow under study. Clustering using the neighbour-joining dendrogram predicated on the SSR data separates the cultivars into three major groups in which the two cultivars from Ghana and Togo show distinctiveness from the cultivars from Nigeria. Principal coordinate analysis of SSR data is consistent with neighbour-joining groupings. The study based on a set of dark jute markers and morphological traits reveals that the extent of genetic diversity of cultivated jute mallow and could be used in germplasm evaluation. In addition to the knowledge of the high genetic variability observed in the number of pod and the yield of some of the studied cultivars, further efforts are needed to characterise the cultivar pods’ nutritive values for human health.