Breeding for postharvest physiological deterioration in cassava: problems and strategies

Abstract

Cassava is a major food crop for millions of people in Africa, Asia and South America, forming an essential food-security and income generation commodity for small-scale or subsistence farming communities. The storage root is the most important component of the crop that provides more calories than cereals. Immediately after harvest, cassava storage roots undergo complex biochemical and physiological changes known as postharvest physiological deterioration (PPD), which is influenced by genotype, environmental and agronomic factors, resulting to spoilage, rendering the storage roots unpalatable and unmarketable. This problem has remained unresolved over the years. This review describes the innovative breeding technologies which could be used to prolong cassava storage root shelf-life. In this review, we discuss the available knowledge on (i) physiology and biochemistry of cassava storage root with regard to PPD (ii) strategies for minimizing PPD in cassava storage roots (iii) traits associated with PPD tolerance as essential targets for prolonging cassava storage root shelf life, and (iv) suggestions for novel genomic tools and modern genetic and breeding approaches for prolonging shelf-life in cassava storage roots. With its extensive genomic resources including the public release of cassava reference genome sequence assembly and other and resources, and innovative plant breeding technologies, the crop offers an excellent opportunity to serve as a model to address postharvest spoilage and improve food security. Continuous improvements based on the new plant breeding technologies (genome editing, speeding breeding and RNA-dependent DNA methylation) in cassava and innovations in postharvest handling and storage of the storage roots are expected to provide sustainable solutions for PPD constraints and make cassava an important food security and nutrition and industrial crop.

A method for rapid and homogenous initiation of post-harvest physiological deterioration in cassava storage roots identifies Indonesian cultivars with improved shelf-life performance

“…However, Baturaja was the only cultivar which showed a consistent PPD response over the two growing seasons. Our observations confirm the importance of environmental factors in the response to PPD as reported in previous studies [ 8 , 11 , 19 , 21 ]. It also highlights the importance of evaluating cassava cultivars for the PPD trait over several years and possibly in different environments [ 11 , 17 , 38 ].…”

Plant regeneration from leaf mesophyll derived protoplasts of cassava (Manihot esculenta Crantz)

“…(Table 1). Muchericheri had a substantially higher response of protoplast yield with 20.50×10 6 protoplast/g FW. The yield of TMS60444 and Karibuni was not significantly different with change in enzyme combination.…”

“…Cassava production and utilization is also impeded by short-postharvest shelf life of the storage roots due to post-harvest physiological deterioration (PPD), a physiological and biochemical process that is triggered by the unavoidable physical damage of storage roots during harvesting. PPD is characterized by initial blue/black discoloration and organoleptic changes in the storage roots within 24–72 hr of harvest, which severely renders the storage roots unpalatable and unmarketable [ 6 ]. Furthermore, cassava usage is impeded by potentially toxic quantities of cyanogenic glycosides, linamarin, and lotaustralin in all plant organs with exception of the seeds [ 7 ] and this demands the need for cassava storage roots to be processed before eating to remove or reduce their levels.…”