Assessment of mycorrhizal association of a threatened medicinal plant Clerodendrum indicum (L.) O. Kuntze (Verbenaceae) in different ecological variations

Abstract

Mycorrhizae association is reported to enhance the survivability of the host plant under adverse environmental conditions. The present study aims to explore the mycorrhizal association in the roots of different ecotypes of a threatened medicinal plant, Clerodendrum indicum (L.) O. Kuntze (Verbenaceae), collected from W.B., India, which correlates the degree of root colonization to the nutritional status of the native soil. Ten ecotypes of C. indicum having diverse morphological variations were collected. The mycorrhizae were characterized by both morphological and molecular methods. The nutritional status of the native soils was estimated. The study revealed that all the ecotypes have an association with mycorrhizal forms like hyphae, arbuscules, and vesicles. The molecular analysis showed Glomus intraradices and Rhizophagus irregularis as the associated arbuscular mycorrhizal fungi (AMF). A significant variation in arbuscule and vesicle formation was found growing in the varied nutritional statuses concerning soil parameters. The arbuscule was found negatively correlated with pH, conductivity, and potassium and positively correlated with organic carbon, nitrogen, and phosphorus. The vesicle was found positively correlated with pH, organic carbon, and potassium and negatively correlated with conductivity, nitrogen, and phosphorus. The interaction between conductivity: nitrogen, conductivity: phosphorus, organic-carbon: nitrogen, and pH: conductivity was significant in influencing vesicle formation. However, none of the interactions between parameters was found significant in influencing arbuscule formation. Thus, the study concludes that G. intraradices and R. irregularis are the principle mycorrhizae forming the symbiotic association with the threatened medicinal plant, C. indicum. They form vesicles and arbuscules based on their soil nutritive factors. Therefore, a large-scale propagation through a selective AMF association would help in the conservation of this threatened species from extinction.

Keywords: Arbuscular mycorrhizal fungi; Glomus intraradices; Rhizophagus irregularis; Soil nutritional content.

Fig. 1

Box plots showing data distribution and variation in Arbuscule % (a), Vesicle % (b), pH (c), electrical conductivity (d), Organic carbon % (e), nitrogen (f), potassium (g), and phosphorus (h) of the host ecotypes

Fig. 2

Phylogenetic tree was prepared by the maximum likelihood method. Amplicon sequences of this study are marked with the GenBank Ac. No. MN134340, MN134341, MN134343.

Fig. 3

Correlation matrix showing the correlation between all the parameters, the scale indicate positive (+1) and negative (−1) correlations, significance of the correlation between parameters is indicated by stars (“*”) mark (***p < 0.001, **p < 0.01, *p < 0.05)

Fig. 4

Scree plot (a) showing the percentage of explained variables by the principal components. Variable-PCA-biplot (b) showing the contribution of variables in data variation. Individual-PCA-biplot (c) showing the overall correlation of the parameters (grouped by the ecotypes)

Fig. 5

Scatter plots aided with linear regression line (a1 to a4) showing correlations between parameters and slope of the models, the shaded area around the blue regression line indicating the confidence (0.85) interval. Response surface plots (b1 to b4) aided by contours at the base of the plots, showing the interaction effect of parameters on vesicle formation