Compendium of Potato Diseases - (PDF, 101 mb) - USAID

?(1
Fig. 13 Second growth as gemmation (left) and as a sprout (right) on an abnormally early tuber. (Left, courtesy W. M. Iritani)
adequate irrigat on, and foliage protect ion by pesticides).
3) )o not permit tubers to remain long in the soil alter vintes
ha e died.
Selected References
IR .Al \. II )(', I ic I ieNtillcckitkcit dci Kait,,dlel . Ilannekr.
Pllan/enchu. X542 541)
I1RII )M.A\. It A 1955 .socialiron (i internal bro\t spot ofpolato
tinher. \tlth hol. dr% \ cathl . Plant )is. Rep..39l37-44.
IARSON. R If.. and \. R. \tlH1 R I. '145. 'h siolhogical internal
if lot itt,, tiiCi, III ICOHiii s .1 A\arlr. RC, (Wlirihlngloir.
1)() 71 4,7-505.
/IM 1:RI \.(Vt I I S. S. 1964. Ilie occurrence ot potato healnecrosis
,, inproms ini Israel and Ihe toe ofitfected tub.rs as seed.
Fur. Po(tatio .1. 7:112-I 18.
(Prepared by W. .1. [looker)
Second Growth and Jelly End Rot
Second growth may he of se\cral types: II deftorrmed tubers
wit h protruding eves. lateral buds (knobby tubers), or apical
buds (dumbbells or elongated tubers) ( Fig. 12); 2)
gennimation sectondarv tubers on a1solon externsion of tire
otriginal tuber (Fig. 13 lcft; or 31 recently f'ormed tubers that,
before normal har\¢st. produC. either a sproultt or a leafy
aho~egrtiun( plant (I-ig. 13 right),
Second grolth is coiniiotinl attributed to high field
tetmperatures aind drought. I nav.i hiwe\er, result from
regeneration ftollo\wing ain\ condition causing irregular rates of
12
404
tuber development, such as uneven availability of' nutrients or
moisture. extrenies in temperat tire. or vine defoliation from hail
or frost. Positive separation of heat effects from drought effects
is difficult because high field iliperatures are ustiallv
accompanied hy drought and i conconitant reduction or
cessation of thuber gro\tII. When growing conditions improve.
resumption ol tuber growth becoies evident as second growth.
Second growth is usually' stimulated by soil temperatures of
270C and above, although sonic develops at lower
temperatures. IInder controlled condition.s subjecting plants to
32'C tor seven days wIs sufficiCit to initiate second growth.
Seerit\ \was greater \\ith longer periods of exposure and higher
tenperat tires. Second growth %%'iws not initiated by varying tie
water supply altmne.
Second growth and jelly end rot are interrelated because jelly
end rot is prevalent in abnormally shaped tubers, particularly
those with second growth. felly end or glassy end rot is highly
seasonal in occurrence, has been reported from many potato­
growing areas, and tnay involve 10-50"i or iiore of the crop.
l.osses due to reduced tuber quality are high.
"Iranslucent end" or "sugar end" refers to incipient
svnptonis visible at harvcst or developing in storage. Tubers
with such symptons frequently develop jelly end rot later.
Reducing sugars in translucent end or sugar end tubers cause
dark color in potato chips (Fig. 141)).
Symptoms
Stiloin etnds oftubers with.ielly end rot become translucent to
glassy, lack normal starch content, have reduced specific
gra\ity. slri\el. and collapse into a wet.jellylike substance (Fig.
14A)..Iell\ end rot tissue dries down to a leathery layer in dry
storage (IFig. 1411). )eiarcation between healthy and affected