# Untargeted and targeted metabolomics approaches to characterise, select and advance cassava pre‐breeding populations with enhanced whitefly tolerance

## TL;DR

Researchers used metabolomics to identify chemical markers and pathways in cassava that help plants resist whitefly pests, which could improve breeding for more resilient crops.

## Contribution

The study identifies specific metabolite biomarkers and metabolic pathways associated with whitefly tolerance in cassava using bi-parental populations.

## Key findings

- Untargeted metabolomics identified the chemical feature 316.0924 as a significant marker for whitefly resistance.
- Targeted analysis revealed perturbations in cyanogenic glycosides, apocarotenoids, and phenylpropanoid pathways in tolerant cassava.
- The bi-parental population approach enabled the identification of quantitative metabolite markers and underlying resistance mechanisms.

## Abstract

Cassava (Manihot esculenta Crantz) provides food security for over 500 million people in Sub‐Saharan Africa (SSA). Whitefly (Bemisia tabaci) is a pest in this region that results in ca. 50% crop yield losses. Thus, it is important to develop approaches that will generate new varieties tolerant to this pest to advance food security in the region. Two parental cassava varieties, ECU72 tolerant to whiteflies and COL2246 a susceptible line, have been used to generate bi‐parental populations. The F1 generation has been screened for whitefly resistance, and progeny identified displaying enhanced tolerance. From designated F1 tolerant progeny, F2 families have been generated and phenotyped. The tolerance to whiteflies in the F2 population was further enhanced. Untargeted metabolomics was used to characterise whitefly susceptible and tolerant sub‐groups. PCA of the molecular features generated clustering of accessions into whitefly resistant and susceptible groups, and differentiating metabolite biomarkers were identified. The most significant metabolite marker for resistance is the chemical feature 316.0924. Although not consistent among all whitefly resistance sub‐groups, targeted LC–MS analysis revealed several pathways displaying perturbed levels. These include cyanogenic glycosides, apocarotenoids and the phenylpropanoid super‐pathway comprising hydroxycinnamic acids, flavonoids and proanthocyanidins. Thus, the generation of a bi‐parental population for whitefly tolerance/susceptibility enabled the identification of quantitative metabolite markers, the pathways contributing to tolerance, the underlying modes of action associated with resistance and the potential for the development of future high‐throughput low‐cost proxy markers. The approach also provides generic insights into future breeding strategies utilising bi‐parental progeny for the enhancement of traits.

A bi‐parental population has been created from cassava varieties ECU72 and COL2246, which are tolerant and susceptible to whitefly (Bemisia tabaci), respectively. Metabolomic characterisation of the F1 and F2 generations has revealed comparative metabotypes for whitefly tolerance, leading to metabolite biomarkers and sectors of metabolism contributing to underlying mechanisms of tolerance. These data provide a valuable resource for the incorporation of whitefly tolerance into cassava breeding programmes.