b'Andys Advice: Potato Tuber CrackingBy Andy Robinson, Extension Potato Agronomist, NDSU/UMNdevelopduringtuberdevelop- cracking,resultinginsignificant ment as a result of a physiologicaleconomic loss.responsetoanenvironment stress, herbicide injury, or diseaseTubergrowthcracksarecaused pressure.Airchecks,thumbnailwhentheinternalcoretissue cracks or shatter bruise are impact- growsfasterthanthesurfacetis-related cracking that occur whensueorperidermwhentubersare tubers are harvested and handled.enlarging. This often occurs when Tuber cracking in any form are notrelativelypoorgrowingcondi-desirable and can result in qualitytions are rapidly followed by rela-loss and disease entry. The quanti- tivelygoodgrowingconditions, tyandseverityoftubercrackingsuch as a period of low soil mois-willvarybasedonthecultivar,turefollowedbyexcessiveirriga-growingenvironment,diseasetionorrainfall,causingrapid Tubergrowthcracksareakintopressure, and handling. changesintuberturgidityand commonscabintheRedRivergrowth rate. Other rapid changes Valley.Theycomeandgo,oftenGrowthcracks,asthenameintubergrowthreportedto with no good explanation or rea- describes, are cracks that developencouragegrowthcrackscan soning.However,environmentalonthetuberswhilegrowing.come from poor nitrogen manage-conditionsareoftenthebiggestThesecrackscanvarytremen- mentduringbulking,planting culprit,causingstressedplantsdouslyinseverity,withsomecultivars that tend to have larger that are more susceptible to thesetubercracksbeingshallowandsized tubers, or low-density plant-problems. small that do not affect the grade,ing.Tubercrackingmostcom-whereasothersmaybedeepfis- monlyoccursatthebud-endof Tubercrackingisanexternalorsures that expand across the tuberthetuberandstretcheslength-surfacedisorder.Itisnoninfec- andaroundthebudend.Thewise,butcrackingcanhappen tious or often termed a physiolog- severity of growth cracks can varyanywhereonthetuber.Deeper ical disorder, meaning it does notbycultivar.Thesedifferencesaregrowth cracks are a result of stress spread to other tubers. There areoften manifest in an environmen- inearlybulking,whileshallow differenttypesoftubercrackingtally stressful growing season. Forcracking happens later in bulking. thatwilldiscussedinthisarticleexample,someyearsweseefewAstuberscontinuetodevelop, with a focus on growth cracks thattuberswithcrackingwhileothergrowthcrackswillsuberizeand are most common. Growth cracksyears there are many tubers withheal.12 POTATO GROWER NOVEMBER/DECEMBER 2022'