Exploring genetic diversity of local avocado (Persea americana Mill.) germplasm from the bamboutos highlands diversity centre in western cameroon: a comprehensive multivariate and phylogenetic analyses based on phenotypic descriptors

Abstract

Abstract Background Avocado (Persea americana Mill.) is a tree of economic importance mostly grown for its fruit in home gardens and farms all over Cameroon. Plant germplasm resources are the basis for crop improvement. Analysis of complex traits and research on diversity on those resources is the first step leading to the exploration and creation of new plant varieties. The objective of this study was to assess the phenotypic variation of 206 avocado genotypes collected in ten villages across four altitude ranges in the Bamboutos highlands in western Cameroon. Results Cross tabulation and Chi-square tests revealed differential distribution of traits variants among villages and altitude ranges. Various phenotypic features were observed among trees, pointing out the existence of several avocado races in Cameroon. For all the 46 qualitative traits, 162 phenotypic classes were detected, giving an average of 3.52 phenotypic classes per trait. The diversity index varied significantly between traits, populations and altitude ranges with a mean value of H’= 0.90 for qualitative traits and H’=1.31 for quantitative traits. The top five traits with higher diversity indices were fruit shape (H’=2.04), ripe fruit skin colour (H’=1.75), seed shape (H’=1.75), Tree shape (H’=1.74) and colour of flesh next to seed (H’=1.47). Bangang and Batcham populations were found to be more diverse. The lowest altitude range, 1100–1300 m above sea level (MASL) displayed smallest diversity when comparing altitude ranges. The partitioning of the diversity revealed more variation within population and within altitude ranges. Although this study revealed extensive variation between trees at the village and altitude range levels, no clear groupings of genotypes was identified based on geography. Dendrogram revealed that avocado trees from the same village and even from the same altitude ranges differ substantially. Altitude was negatively associated seed length, time from ripeness to deterioration and time from maturity to deterioration of fruits. Seventeen traits were significantly associated with the two main principal components of the PCA. Cluster analysis revealed four distinct clusters, associated to the existing avocado races. Conclusion The significant morphological variations combined with the high diversity observed in the avocado genotypes are likely to help in planning germplasm management, conservation, and improvement. Clinical trial number Not applicable.

Keywords

• Avocado
• Cameroon
• Diversity index
• Genetic improvement
• Multivariate analysis
• Phenotypic variant