Establishment of a core collection of &lt;i&gt;Cynodon&lt;/i&gt; based on morphological data

C.Q Huang,J Tang,G.D Liu,C.J Bai,W.Q Wang,T Long

doi:10.17138/tgft(8)203-213

Abstract

In a field plot study conducted in Danzhou, Hainan province, China, a total of 537 wild Cynodon accessions from 22 countries and classified into 11 groups according to taxonomy and origin, were characterized in terms of 11 phenotypic traits in order to construct a core collection. For this, the optimal strategy was developed by screening within the following method levels: (i) 7 sampling proportions (5, 10, 15, 20, 25, 30 and 35%); (ii) 3 sampling methods (preferential sampling, deviation sampling and random sampling); (iii) 5 clustering methods [single linkage, completed linkage, median linkage, unweighted pair-group average (UPGMA) and Ward’s method]; (iv) 3 genetic distances (Euclidean distance, Mahalanobis distance and principal component distance); and (v) 3 sampling proportions within groups (simple, logarithmic and square root proportions). Mean difference percentage, variance difference percentage, coincidence rate of range and variation coefficient changing rate were the criteria adopted for evaluating how well the core collection represented the original collection. The correlation between the original and core collections was determined for comparison. The core collections were validated with the sample distribution diagram of the main components. Results showed that the optimal sampling method for constructing a Cynodon core collection was preferential sampling, the optimal sampling proportion being 20%. The optimal sampling proportion within groups was the square root proportion, the optimal genetic distance was Mahalanobis distance and the optimal clustering method was UPGMA. The proposed core collection of Cynodon is composed of 108 accessions; it was constructed following the optimal sampling strategy identified and retained the original collection´s phenotypic diversity, phenotypic trait correlations and phenotypic group structure. Thus, this collection could be considered a representative sample of the entire resource.

Highlights

Cynodon Rich., a C4-type herbaceous genus of the family Poaceae, subfamily Chlorioideae, tribe Cynodonteae, is one of the main 3 warm-season turf grasses as well as a fine pasture (Harlan and de Wet 1969) that can be divided into 9 species and 10 varieties (Taliaferro 1995)
Most Cynodon species originated from the African region; they are mainly distributed in warm and humid tropical or subtropical regions, with some in temperate regions (Rochecouste 1962; Harlan et al 1970; Wofford and Baltensperger 1985)
C. dactylon var. dactylon is a cosmopolitan species with a latitudinal distribution range of 53° N–45° S

Summary

Introduction

Cynodon Rich., a C4-type herbaceous genus of the family Poaceae, subfamily Chlorioideae, tribe Cynodonteae, is one of the main 3 warm-season turf grasses as well as a fine pasture (Harlan and de Wet 1969) that can be divided into 9 species and 10 varieties (Taliaferro 1995). Most Cynodon species originated from the African region; they are mainly distributed in warm and humid tropical or subtropical regions, with some in temperate regions (Rochecouste 1962; Harlan et al 1970; Wofford and Baltensperger 1985). C. transvaalensis, often referred to as African Bermuda grass, is indigenous to only the Transvaal region of South Africa (Harlan et al 1970). Domestic and foreign scholars have made progress in the collection and genetic diversity evaluation of Cynodon germplasm resources (Wu et al 2004, 2006; Wang et al 2009; Tiwari et al 2016; Zheng et al 2017). These studies provided a good basis for the construction of a core collection of Cynodon

Methods

Results

Conclusion