Variation of sweet potatoes with respect to source potentials and
sink capacities
L . Li' & C .H . Kao 2
1 Department of Horticulture, Chinese Culture University, Taipei, Taiwan, Republic of China;
2Department of Agronomy, National Taiwan University, Taipei, Taiwan, Republic of China
Received 11 July 1988 ; accepted in revised form 8 August 1989
Key words : Ipomoea batatas, sweet potato, grafting, sink capacity, source potential
Summary
By using four tester clones either as scions or stocks, source potentials and sink capacities of two groups of 13
and 20 sweet potato clones were measured in 1986 and 1987, respectively . Results obtained in the 1986 trial
were generally consistent with those in the 1987 trial, though different clones were used in both trials . There
were significant differences in source potentials and in sink capacities among tested clones . Responses of
source to sink and of sink to source were also estimated using a regression method . No significant correlation
was observed between source potential and response of source to sink . However, sink capacity showed
significant relationship with response of sink to source .
Introduction
Hozyo (1970) and Wilson (1967) suggested that
yield of sweet potato was determined primarily by
sink capacity rather than source potential . Hahn
(1977), on the other hand, has inferred that both
source potential and sink capacity can be rate
limit-ing to yield with the latter more important than the
former . In our previous work using reciprocal
grafts, we concluded that the source potential was
more
limiting
than sink in the first four months, but
they are equally important in determining tuberous
root yield at 6 months (Li & Kao, 1985a) .
Bouw-kamp & Hassam (1988) recently reported that
cul-tivars showing strong sink' effects were generally
low-yielding .
In a breeding program, it is much easier to
eval-uate and select for
sink
capacity (yield) than for
source potential (photosynthetic capacity) .
How-ever, evaluation for source potentials of sweet
po-tatoes is possible because source and sink can be
easily exchanged by reciprocal grafting for this
pur-pose . In the present investigation, four tester
clones were used as source and sink, respectively,
to evaluate source potentials and sink capacities of
various experimental sweet potato clones .
Materials and methods
All experiments were conducted in 1986 and 1987
in an experimental field of Chiayi Agricultural
Ex-periment Station, Chiayi, Taiwan, Republic of
China . The
soil
type was sandy loam .
Th four t st r clon s w r
C70-245, C70-200,
C70-311 and C70-105 which w r
us d in
our pr
vi-ous work (Li &
Kao,
1985a) . Thirt
n and tw nty
xp rim ntal clon s w r chos n for th 1986 and
1987 trials, r sp ctiv ly, to d t rmin th ir sourc
pot ntials and sink capaciti s . For th
1986 trial, 16
slips of
ach
xp rim ntal clon
w r
graft d to
ach of th four t st r clon s, and 16 slips of
ach
13 2
Z
N
F
1 .5
1 .3
0
1 .1
D
0
N
0.9
U
.
0
W
N
O .7
Z
0
W
0.5
0
.3
Y = 0 .5235 + 0 .0041 x
r = 0 .242
n = 13
13
12
11
10
8
9
-1/
1 I I I I I 1 1
75
85
95
105
115
125 135 145
7
6
4
5
SOURCE POTENTIAL (g/ plant)
Fig. 1 . R lation b tw n sourc pot ntial (x) and r spons of sourc to sink (y) for 13 xp rim ntal sw t potato clon s (1986 trial) . Th numb rs by points r f r to clon s ranking in Tabl 1 .
Tabl 1. Dry tub rous root yi lds (g/plant) of th 13 xp rim ntal clon s graft d to th four t st r sw t potato clon s (1986 trial)
2
1
*, ** M ans having sam l tt rs ar not significantly diff r nt at 5% and 1% l v l, r sp ctiv ly, by Duncan's Multipl Rang T st .
Ranking Clon t st d Stock M an scion
ff ct R spons of sourc to sink C70-245 C70-200 C70-311 C70-105 1 C68-220 177 .0 171 .1 162 .5 73 .1 145 .9a* 1 .10 2 C72-769 109.7 147 .9 230 .1 87 .7 143 .9a 1 .16 3 C69-27 146.3 160 .5 188 .1 44 .1 134 .8ab 1 .50 4 C66-51 133.0 120 .4 184 .1 54 .8 123 .1abc 1 .36 5 C66-24 152.1 170 .6 119 .1 50 .3 123 .Oabc 0.86 6 C70-244 150.2 141 .8 119 .2 77 .9 122 .3abc 0.60 7 C69-29 154.4 110 .9 120 .1 83 .8 117 .3abc 0.65 8 C67-249 145 .7 44 .6 166 .6 83 .9 110 .2abc 1 .15 9 C70-220 144.5 89 .8 108 .3 97.0 109 .9abc 0 .39 10 C67-59 152.9 78 .8 126 .7 68 .8 106 .8abc 0.95 11 C66-18 142.3 39 .4 166 .9 62 .7 102 .8abc 1 .39 12 C69-61 116.4 56 .9 139 .0 48 .0 90 .lbc 1 .13 13 C72-637 94.6 39 .3 119 .3 57 .9 77 .8c 0.77
M an stock ff ct 139 .9a** 105.5b 150 .Oa 68 .5c 116 .0
Y = - 0 .3035 + 0.0136 x
r = 0 .648 *
n=13
13
11
12
10
8
7
6
4
3
2
.
1
65
75
85
95
105
115
125
135
SINK CAPACITY
(g/plant )
Fig. 2 .
R lation b tw n sink capacity (x) and r spons of sink to sourc (y) for 13 xp rim ntal sw t potato clon s (1986 trial) . Thnumb rs by points r f r to clon s ranking in Tabl 2.
t st r clon w r
graft d to ach of th
13 xp
ri-m ntal clon s . In th
trial of 1987, 12 slips of ach
xp rim ntal clon w r graft d to ach of th four
t st r clon s as stock, and 12 slips of
ach t st r
clon us d as a scion w r graft d to ach of th
20
xp rim ntal clon s . About a month aft r grafting,
th grafts w r
plant d in th fi ld at a spacing of
100 cm b tw
n rows and 25 cm within rows in
August 1986 and August 1987 . A randomiz d
com-pl t block d sign was us d with four r com-plications .
Each plot consist d of four and thr
plants for th
1986 and 1987 trials, r sp ctiv ly . F rtiliz r was
appli d prior to planting (40 kg N, 40 kg P and 80 kg
K p r ha) and at 30 days aft r planting (40 kg N and
80 kg K p r ha) . Plants w r
harv st d 150 days
aft r planting and dri d in th
ov n at 90° C for 2
days . Data of dry tub rous root yi ld w r
ana-lyz d . Th
d gr
s of r spons s of sourc
to sink
and of sink to sourc
w r
d t rmin d by th
r
-gr ssion m thod propos d by Hahn (1977) .
In 1987, yi ld trial of 20
xp rim ntal clon s
without grafting w r
also conduct d simultan
-ously . All th
xp rim ntal conditions' and d sign
w r
similar to thos
of grafting
xp rim nt
con-duct d in 1987 .
1.55
w
1 .35
N
1 .15
O
Y
0.95
Z
U)
0
0,75
W
0
0
Q55
a
w
cc
0.35
0 .15
134
Tabl 2 .
Dry tub rous root yi lds (g/plant) of th four t st r clon s graft d to th 13 xp rim ntal sw t potato clon s (1986 trial)* M ans having sam l tt rs ar not significantly diff r nt at 1% l v l by Duncan's Multipl Rang T st .
R sults
r spons of sourc to sink m asur d by r gr ssion
co ffici nts for th
13
xp rim ntal clon s ar
1986 trial
shown in Tabl
1 . Th r
w r
significant diff
r-nc s at th 5% l v l among th sourc pot ntials
Th
sourc
pot ntial of a clon
is d fin d as its
of th 13 clon s . Th r w r significant diff r nc s
m an scion ff ct and th sink capacity is its m an
at th
1% l v l among th
sink capaciti s of th
stock
ff ct . Th sourc pot ntials and d gr
s of
four t st r clon s . Th r sults pr s nt d in Tabl 1
Tabl 3. Dry
tub rous root yi lds (g/plant) of th 20 xp rim ntal clon s graft d to th four t st r sw t potato clon s (1987 trials)* M ans having sam l tt rs ar not significantly diff r nt at 1% l v l by Duncan's Multipl Rang T st .
Ranking Clon t st d Stock M an scion
ff ct R spons of sourc to sink C70-245 C70-200 C70-311 C70-150 1 TN 64 268 .3 136 .3 84 .0 148 .3 159 .2a* 0 .11 2 C72-130 237 .1 163 .6 140 .6 86 .9 157 .1a 1 .29 3 C72-324 172 .4 132 .4 216 .9 101 .4 155 .8a 1 .53 4 C72-738 226.1 94 .5 240 .3 45 .9 151 .7ab 2 .95 5 C72-38 152.8 92 .8 221 .8 129 .4 149.2ab 1 .15 6 C72-769 105 .0 115 .8 178 .7 137 .4 134 .2abc 0 .27 7 C70-141 103 .6 193 .2 190.8 22 .9 127 .6abc 1 .81 8 TN 67 120 .7 138 .1 144.8 82 .7 121 .6abcd 0 .73 9 TN 66 156 .0 110 .5 125 .9 90.9 120 .8abcd 0 .71 10 TN 68 132 .9 112 .2 152 .5 62.6 115 .lbcd 1 .22 11 C68-106 87.1 155 .2 172 .2 40.7 113 .8bcd 1 .35 12 C68-220 122.2 73 .9 134 .7 106.9 109 .4cd f 0 .45 13 C72-554 106 .4 203 .0 81 .7 46.5 109 .4cd f 0 .38 14 C70-244 127 .8 80 .3 114 .9 32.7 88.9d f 1 .30 15 IN 57 99.3 54 .2 126 .7 60.4 85 .2d f 0 .92 16 C67-222 91 .3 26 .5 144 .4 54.8 79.3 f 1 .19 17 C72-277 113.1 66 .3 87 .5 24 .9 73 .Of 1 .08 18 C70-203 72.4 81 .2 84 .7 49 .0 71 .8f 0 .43 19 C71-66 66.6 45 .7 118 .2 55 .0 71 .4f 033 20 C70-220 64.7 60 .3 100 .0 59 .7 71 .2f 0 .43
M an stock ff ct 131 .3a* 106 .8b 143 .1a 72 .Oc 113 .3
R spons of sink to sourc 1 .46 0 .93 0 .91 0 .70
Ranking Clon t st d Scion M an stock
ff ct R spons of sink to sourc C70-245 C70-200 C70-311 C70-105 1 C69-27 188 .6 147 .3 129 .4 43 .1 127 .1a* 1 .56 2 C70-220 175 .3 177 .6 68 .2 76 .5 124 .4a 1 .54 3 C66-18 137 .8 126.8 137 .4 77 .3 119 .8ab 0.59 4 C70-244 129 .8 185.4 78 .8 46 .2 110 .1abc 1 .52 5 C67-59 119 .0 140.2 88 .3 71 .7 104 .8abcd 0.80 6 C72-637 174 .6 109.4 79 .8 44 .0 102 .Oabcd 1 .37 7 C69-29 144 .2 132.5 76 .4 45 .8 99 .7abcd 1 .28 8 C69-61 122 .6 112 .9 80 .5 23 .4 84 .9bcd 1 .20 9 C67-249 146 .0 75 .3 44 .5 61 .0 81 .7bcd 0.85 10 C68-220 79 .9 101 .7 112 .1 32 .5 81 .6bcd 0.55 11 C66-24 95 .3 99 .9 56 .3 40 .0 72 .9cd 0 .80 12 C66-51 71 .0 81 .9 53 .9 67 .9 68 .7d 0 .18 13 C72-769 75 .8 114 .4 31 .5 47 .8 67 .4 0.76
M an scion ff ct 127 .7a* 123 .5a 79.8b 52 .1c 95 .8
confirm d our arly finding (Li & Kao, 1985a), that
C70-311 and C70-105 had high and low sink
capac-iti s, r sp ctiv ly . No significant corr lation was
obs rv d b tw
n th
sourc
pot ntials and th
r spons s of sourc s to sinks (Fig . 1) .
Tabl
5 . Av rag dry tub rous root yi lds of 12 plants for 20 sw t potato clon s without grafting (1987 trial)* M ans having sam l tt rs ar not significantly diff r nt at 1% l v l by Duncan's Multipl Rang T st .
Th
sink capaciti s and d gr
s of r spons
of
sink to sourc
of th
13
xp rim ntal clon s ar
summariz d in Tabl 2 . Th r w r significant
dif-f r nc s at th
1% l v l among th sink capaciti s
of th 13 clon s t st d, and also among th sourc
pot ntials of th
four t st r clon s . C70-245 was
d monstrat d to b
a good sourc , wh r as
C70-105 a poor sourc . Th s r sults ar
in agr
m nt
with our
arly work (Li & Kao, 1985a) . Th
d
-gr
s of r spons s of sink to sourc w r plott d
against r sp ctiv sink capaciti s (Fig . 2) . In g n
r-al, clon s with high sink capaciti s show d high
r spons s of sinks to sourc s .
1987 trial
Th r sults of 1987 trial ar , in g n ral, consist nt
with thos
of 1986 trial, though diff r nt clon s
w r us d . Both sourc pot ntials and sink
capac-iti s w r significantly diff r nt among th
20
x-p rim ntal clon s at th 1% l v l (Tabl s 3 and 4) .
R sults also d monstrat d that C70-245 was a good
sourc wh r as C70-311 was a good sink . C70-105
1 C70-141 129 .8 253 .0 116 .6 93 .1 148.la* 1 .52 2 C70-203 208 .9 180 .9 58 .3 95 .1 135.8ab 1 .50 3 C72-738 108 .0 230 .5 118 .7 65 .8 130.8abc 1 .43 4 C68-106 216 .1 141 .6 80 .5 74 .2 128.labcd 1 .21 5 C70-244 117 .2 229 .3 94 .7 68 .4 127.4abcd 1 .57 6 TN 66 168 .6 169 .8 67 .9 99 .4 126.4abcd 1 .13 7 TN 67 147 .1 168 .4 90 .1 88 .8 123 .6abcd 0 .99 8 C72-554 144 .5 186.9 72 .0 89 .6 123 .3abcd 1 .24 9 C72-38 113 .8 160.0 147 .4 63 .4 121 .2abcd 0 .66 10 C72-277 176 .1 136.7 58 .4 82 .2 113 .4abcd 1 .05 11 C72-324 102 .1 160.7 83 .9 77 .3 106.Oabcd 0 .85 12 C71-66 133 .9 112.3 108 .4 67 .8 105 .6bcd 0 .48 13 TN 57 116 .2 154.8 75 .1 52 .1 99.6bcd 1 .11 14 C72-769 128 .9 108.3 92 .6 51 .8 95 .4bcd 0 .64 15 C70-220 116 .3 172.6 48 .4 39 .8 94.3bcd 1 .52 16 TN 64 109 .2 111 .1 107 .6 35 .5 90.9cd 0 .63 17 C72-130 127 .0 107.0 51 .4 72 .3 89.4cd 0 .68 18 C67-222 117 .5 79.4 100 .4 50 .8 87.Od 0 .28 19 C68-220 99 .5 138.4 59 .9 46 .2 86.Od 1 .02 20 TN 68 63 .2 137.7 38 .9 101 .5 85 .3d 0 .52 M an scion ff ct 132 .2b* 157.Oa 83 .6c 70 .8c 110.9
R spons of sourc to sink 1 .07 1 .82 0 .52 0 .60
Clon t st d Yi ld (g/plant) TN 64 245 .1 C70-141 235 .3 C72-130 233 .4 C72-738 218 .6 C68-106 203 .1 C72-769 196.0 C72-554 195 .3 C72-324 193 .5 C68-220 190.1 TN 68 181 .9 TN 66 181 .3 C72-38 172.6 TN 67 168 .5 C72-277 142.1 C71-66 136 .0 C70-244 129 .4 TN 57 115 .6 C70-220 113 .7 C70-203 93 .4 C67-222 72.4
3.0
z
0.5
07
2.0
Y = 0.3044 + 0 .0062x
r = 0 .30
n= 20
19
20
18
16
15
0
-//
i ' 1
70
85
100
115
was found to b poor in both sourc pot ntial and sink capacity . As in 1986 trial, no corr lation was obs rv d b tw n th sourc pot ntials and r -spons s of sourc s to sinks (Fig . 3) . How v r, sink capaciti s w r highly corr lat d with r spons s of sinks to sourc s (Fig . 4) . In ord r to d t rmin th r lativ contribution of sourc pot ntial and sink capacity to th tub rous root yi ld, a yi ld trial of th 20 xp rim ntal clon s without grafting was conduct d simultan ously . Th r sults w r pr -s nt d in Tabl 5 .
12
13
Discussion
Grafting proc dur s, though t dious and labo-rious, p rmit us to scr n th sourc pot ntials and sink capaciti s of sw t potato s . Our pr s nt study cl arly confirm d th arly r ports by Hahn (1977, 1982) that sourc pot ntials and sink capac-iti s vari d among clon s or cultivars .
Th dry tub rous root yi ld of sw t potato is d p nd nt on sourc pot ntial and sink capacity . R c ntly, Bouwkamp & Hassam (1988) d
mon-0
8
9
7
6
SOURCE
POTENTIAL (g/plant
Fig. 3.
R lation b tw n sourc pot ntial (x) and r spons of sourc to sink (y) for 20 xp rim ntal sw t potato clon s (1987 trial) . Thnumb rs by points r f r to clon s ranking in Tabl 3 .
4
3
2
1
I i 1
130
145
160
0
1 .0
0.8
0.6
0.2
20 18 16 1280 90
100
110
120
130
140
150
SINK
CAPACITY
(9/plant )
Fig. 4. R lation b tw n sink capacity (x) and r spons of sink to sourc (y) for 20 xp rim ntal sw t potato clon s (1987 trial) . Th numb rs by points r f r to clon s ranking in Tabl 4.
strat d that th r lativ importanc s of sourc po-t npo-tial and sink capacipo-ty chang d during th grow-ing s ason and diff r d among cultivars . Und r th ir conditions, sourc pot ntials pr dominat d ov r sink capaciti s in t rms of ff cts on dry tub r-ous root yi ld . In our pr vir-ous work, w also r -port d that th r lativ contribution of sourc po-t npo-tial and sink capacipo-ty po-to dry po-tub rous roopo-t yi ld was d p nd nt upon growth p riod (Li & Kao, 1985b) . Sourc pot ntial was mor limiting than sink capacity wh n growth p riod was '4 months, but th y ar qually important wh n growth p riod was 6 months . In th pr s nt study, th growth
p riod was 5 months . TN 64 and C72-130 had th high st yi lds among th 20 xp rim ntal clon s (Tabl 5) . Th s two clon s had good sourc po-t npo-tials bupo-t poor sink capacipo-ti s . Oth r high-yi ld-ing clon s such as C70-141, C72-738, C68-106 and C72-769 show d both high sourc pot ntials and sink capaciti s . Low-yi lding clon s such as C67-222 and C70-220 w r obs rv d to b poor in both sourc and sink . Anoth r low-yi lding clon was C70-203, show d high sink capacity but low sourc pot ntial . Thus, sourc pot ntial app ars to b mor important than sink capacity wh n growth p riod was 5 months .
Assimilat
translocation is d t rmin d by th
photosynth tic capacity of sourc , and sink
activ-ity . Sink activactiv-ity alt rs th photosynth tic capacactiv-ity
through aff cting assimilat
translocation which is
r gard d as r spons of sourc to sink . By contrast
r spons of sink to sourc
r f rs to th
chang s in
sink capacity wh n photosynth tic capacity
chang-s . Hahn (1982) d monchang-strat d that chang-sourc pot
n-tial show d significant r lationship with r spons
of sourc to sink, which contradicts what w
pr
-s nt d h r . Our r -sult-s -s
m to sugg st that th
clon s with high sourc , pot ntials do not n c
ssar-ily hav
high r spons of sourc
to sink . It m ans
that photosynth tic capacity of a clon
with high
sourc
pot ntial is unlik ly to b
alt r d by th
chang of sink capacity . Th discr pancy b tw
n
Hahn's r sults and ours is possibly du to diff r nt
growth p riod us d . Th growth p riod of Hahn's
xp rim nt was 3 months, wh r as that of ours was
5 months .
Although TN 64 had th high st yi ld and sourc
pot ntial of th
xp rim ntal clon s, this clon had
th low st r spons of sourc to sink (Tabl 3 and
5) . It is lik ly that th
assimilat
translocation of
TN 64 is l ss s nsitiv to th chang s of sink
activ-ity .
It has b
n shown that high-yi lding g notyp s
g n rally partition d mor photosynthat to tub
r-ous roots than low-yi lding g notyp s (Bhagsari &
Harmon, 1982 ; Hu tt, 1976 ; Li & Kao, 1985b) . In
th pr s nt inv stigation, a significant r lationship
was found b tw
n sink capacity and r spons
of
sink to sourc . Accordingly, s l ction of clon s
with high sink capaciti s and id al d gr
s of r
-spons of sink to sourc is possibl . In oth r words,
s l ction for larg sink will, to a c rtain xt nt, l ad
to improv m nt of translocation capacity .
Acknowl dg m nt
This r s arch was support d by th
Council of
Agricultur , R public of China .
R f r nc s
Bhagsari, A.S . & S .A . Harmon,1982. Photosynth sis and pho-tosynthat partitioning in sw t potato g notyp s . J . Am r . Soc. Hort . Sci . 107 : 506-510 .
Bouwkamp, J .C . & M .N.N. Hassam, 1988 . Sourc -sink r la-tionships in sw t potato . J. Am r. Soc. Hort . Sci . 113 : 627-629 .
Hahn, S .K ., 1977. A quantitativ approach to sourc pot ntials and sink capaciti s among r ciprocal grafts of sw t potato vari ti s . Crop Sci . 17: 559-562 .
Hahn, S . K . ,1982 . Scr ning sw t potato for sourc pot ntials . Euphytica 31 : 13-18 .
Hozyo, Y., 1970 . Growth and d v lopm nt of tub rous root in sw t potato . Proc . Intl . Symp . Trop . Root Crops 2 : 22-23 . Hu tt, D .O ., 1976 . Evaluation of yi ld variability quality of
sw t potato cultivars in subtropical Australia . Expl . Agric. 12: 9-16.
Li, L . & C .H . Kao, 1985a. Inv stigation of sourc -sink r lation-ship in sw t potato by r ciprocal grafts . Bot . Bull . Acad mia Sinica 26 : 31-38 .
Li, L . & C . H . Kao,1985b . Dry matt r production and partition of six sw t potato (Ipomo a batatas L .) cultivars . J . Agric. Assoc. China (N w s ri s) 131 : 10-23 .
Wilson, L. A . ,1967 . Th us of root d l av s and graft plants for th study of carbohydrat m tabolism in sw t potato . Proc. Intl . Symp . Trop . Root Crops 1 : 46-57 .