Post-harvest physiological deterioration (PPD) is a major cause of food losses in cassava value chains, that renders cassava roots useless few days after harvest. PPD is a self-inflicted oxidative process triggered by the harvest, that results in large economic losses or increased marketing costs. This manuscript describes how both the environment and genotypic diversity influence the severity of PPD, based on the results of two major experiments.

In Experiment 1, PPD was assessed three consecutive years in roots from five genotypes through seven post-harvest storage days. PPD, scopoletin and dry matter content (DMC) were recorded during storage. PPD increased with duration of storage period, DMC and scopoletin content. High ambient moisture and temperature during storage also resulted in higher PPD, highlighting the importance of controlled storage conditions during post-harvest logistics and distribution.

In Experiment 2, seven genotypes were planted every two weeks during 15 months (30 consecutive biweekly plantings), in order to investigate the effect of the season of planting. Roots were harvested exactly 10 months after planting. In 13 harvests (out of 30), roots from plants pruned six days earlier were also evaluated. Results indicated large seasonal variations across genotypes. Roots harvested during the cooler season were less sensitive to PPD. Pruning reduced PPD, but also DMC.

Both experiments confirmed that PPD is a complex process, and that environmental conditions during plant growth play a major role. Therefore genetic differences can be reliably detected only by assessing several roots (at least 10) and no less than three different harvesting batches (at different seasons). This is critical for varietal improvement, one of the aims of the RTBfoods and RTB projects, in order to reliably identify progenitors with PPD tolerance and include them in breeding cycles and selection of improved progeny.