Cassava: Difference between revisions

Cassava undergoesdeteriorates after post-harvest, physiologicalwhen deterioration (PPD) oncethe the tubers are separatedfirst from the main plantcut. The tubers, when damaged, normally respond with a healing mechanism. However, the same mechanism, which involvesproduces [[coumaric acid]]s, startswhich about 15 minutes after damage,oxidizes and failsblackens to switch off in harvestedthe tubers., Itmaking continuesthem untilinedible theafter entirea tuber is oxidized and blackened within two to threefew days. afterThis harvest, rendering it unpalatable and useless. PPDdeterioration is related to the accumulation of [[reactive oxygen species]] (ROS) initiated by cyanide release during mechanical harvesting. Cassava shelf life may be increased up to three weeks by overexpressing a cyanide-insensitive alternative oxidase, which suppressed ROS by 10-fold.<ref>{{cite journal |last1=Zidenga |first1=T |display-authors=etal |year=2012 |title=Extending cassava root shelf life via reduction of reactive oxygen species production |journal=[[Plant Physiology (journal)|Plant Physiology]]|volume=159 |issue=4 |pages=1396–1407 |doi=10.1104/pp.112.200345 |pmc=3425186 |pmid=22711743}}</ref> PPDPost-harvest deterioration is onea ofmajor theobstacle mainto obstaclesthe preventingexport farmersof from exporting cassavas abroad and generating incomecassava. Fresh cassava can be preserved like potato, using [[thiabendazole]] or bleach as a fungicide, then wrapping in plastic, coatingfreezing, inor waxapplying ora freezingwax coating.<ref>{{cite web |title=Storage and processing of roots and tubers in the tropics |url=http://www.fao.org/docrep/x5415e/x5415e04.htm |access-date=4 May 2016 |publisher=[[U.N. Food and Agriculture Organization]] |archive-date=22 April 2016 |archive-url=https://web.archive.org/web/20160422120308/http://www.fao.org/docrep/x5415e/x5415e04.htm |url-status=live }}</ref>

While alternative methods for PPDcontrolling controlpost-harvest deterioration have been proposed, such as preventing ROSreactive oxygen species effects by use ofusing plastic bags during storage and transport, coating the roots with wax, or freezing roots, such strategies have proved to be economically or technically impractical, leading to [[plant breeding|breeding]] of cassava varieties more tolerant to PPD and with improved durability after harvest, achieved by different mechanisms.<ref name="gmr">{{cite journal |last1=Venturini |first1=M. T |last2=Santos |first2=L. R |last3=Vildoso |first3=C. I |last4=Santos |first4=V. S |last5=Oliveira |first5=E. J |year=2016 |title=Variation in cassava germplasm for tolerance to post-harvest physiological deterioration |journal=[[Genetics and Molecular Research]] |volume=15 |issue=2 |doi=10.4238/gmr.15027818 |pmid=27173317 |doi-access=free}}</ref> Plant breeding has resulted in different strategies for cassava tolerance to PPD.<ref name="gmr" /><ref name="cs">{{cite journal |last1=Morante |first1=N. |last2=Sánchez |first2=T. |last3=Ceballos |first3=H. |last4=Calle |first4=F. |last5=Pérez |first5=J. C. |last6=Egesi |first6=C. |last7=Cuambe |first7=C. E. |last8=Escobar |first8=A. F. |last9=Ortiz |first9=D. |last10=Chávez |first10=A. L. |last11=Fregene |first11=M. |year=2010 |title=Tolerance to Postharvest Physiological Deterioration in Cassava Roots |journal=[[Crop Science (journal)|Crop Science]]|volume=50 |issue=4 |pages=1333–1338 |doi=10.2135/cropsci2009.11.0666}}</ref> One wasapproach induced by [[mutagen]]ic levels ofused [[gamma ray]]s, whichto putativelytry silencedto onesilence of thea genesgene involved in PPDtriggering genesis, whiledeterioration; another wasstrategy aselected groupfor ofplentiful high-[[carotenecarotenoid]] clones in which thes, [[antioxidant]]s propertieswhich ofmay [[carotenoid]]s are postulatedhelp to protectreduce theoxidization rootsafter from PPDharvest.<ref name="cs" />