Rast, A.T.B.

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Systemic infection of tomato plants with tobacco mosaic virus following inoculation of seedling roots

NARCIS 

Wageningen Yield 

Neth. J. PI. Path. 79 (1973) 5-8 
Systemic infection of tomato plants with tobacco mosaic virus 
following inoculation of seedling roots 
A. TH. B. RAST* 
Institute of Phytopathological Research (IPO), Wageningen 
Accepted 21 June 1972 
Abstract 
In order to inoculate roots of tomato seedlings with tobacco mosaic virus, seeds were germinated 
singly in perforated plastic tubing obtained from ladies' hair curlers filled with sieved soil. The time 
which elapsed between inoculation of the roots and observation of first leaf symptoms varied with 
individual plants between one and ten weeks and was on average three to five weeks. As plant raising 
requires about six to eight weeks in winter, mosaic symptoms appearing in a tomato crop after 
planting out may well be the result of a root infection sustained during pricking off of the seedlings in 
the nursery. 
Introduction 
Fulton (1941), Roberts (1950) and Broadbent (1965a, b) showed that tomato plants 
can become infected with TMV through their roots. It was demonstrated that the 
upward movement of the virus in infected roots was much slower than its downward 
movement, probably because normally it is carried downward passively with the 
stream of assimilates. Like many soil-borne viruses (cf. Van Hoof, 1967) TMV was 
often found to be confined to the root system. Its entry into the stem and subsequent 
systemic infection of the aerial parts depended on season, age and susceptibility of the 
plant. Broadbent (1965a) found the time required for systemic infection varied between 
3 weeks and 6 months with an average of 2 to 3 months. This applied to plants of 
different ages, which were not exposed to root infection before at least 5 to 7 true leaves 
had developed. Tomato seedlings, however, became systemically infected within 
3 weeks following inoculation of the roots in summer and within 5 weeks in winter 
(Broadbent, 1965b). Van Winckel (1965) found the roots to be more often contami-
nated by the virus than the cotyledons, which suggests that the risks of root infection 
of seedlings are greater than infection of the cotyledons. For practical reasons it was 
important to know whether root infections occurring during pricking off seedlings in 
the nursery may be responsible for the appearance of mosaic symptoms soon after 
planting out. 
Methods 
Root inoculation of small batches of seedlings was carried out at monthly intervals in 
the winters of 1967/1968 and 1968/1969. To avoid contact with the cotyledons during 
* Stationed at the Glasshouse Crops Research and Experiment Station, Naaldwijk, The Netherlands. 
5 
I I I / I I / / I T"~!'~7~ 
perforated part of hair curler / 
piece of insulation tubing
 / 
sieved soil 
Fig. 1. Schematic representation of the 
method used for inoculation of seedling 
roots. 
Fig. 1. Schematische weergave van de 
gebruikte methode om wortels van zaai-
lingen te inoculeren. 
inoculation, tomato seeds were germinated singly in sieved soil pressed gently into 
pieces of perforated plastic tubing, obtained from ladies' hair curlers. These were slid 
into a piece of plastic insulation tubing and the whole buried in soil at a slight angle 
(Fig.1). A few days after germination the curlers containing the seedlings with clean 
rootlets fit for inoculation, were carefully lifted from the enclosing plastic tube. The 
rootlets were inoculated with a paint brush dipped in highly infective leaf sap prepared 
by grinding 1 g of infected tomato leaves in about 20 ml of tap water. The curlers with 
the seedlings were then transplanted into pots of 8 cm diameter. Subsequently the 
appearance of mosaic symptoms was recorded and at times both leaves and roots of 
plants not visibly infected, were separately assayed on Nicotiana glutinosa. As these 
Table 1. Systemic infection of tomato plants with TMV following inoculation of seedling roots. 
Sowing date 
1967/1968 
1968/1969 
11/9 
9/10 
9/11 
8/12 
10/1 
9/2 
10/3 
10/4 
10/9 
9/10 
11/11 
10/12 
10/1 
10/2 
11/3 
Inocu-
lation 
date 
21/9 
23/10 
22/11 
22/12 
22/1 
21/2 
21/3 
24/4 
24/9 
24/10 
25/11 
24/12 
24/1 
24/12 
24/3 
Num-Number of plants with first leaf 
ber of 
plants 
inoc-
ulated 
13 
14 
11 
13 
15 
17 
12 
9 
21 
25 
25 
25 
16 
16 
16 
symptoms 
1 2 
2 
2 
5 
2 
1 
1 
3 
5 
2 
5 
4 
5 
3 
2 
4 
6 
4 
1 
3 
3 
1 
3 
4 
2 
4 
8 
3 
1 
in weeks following 
noculation 
5 
1 
1 
6 
1 
6 
2 
5 
5 
5 
7 
3 
6 
6 
3 
4 
2 
5 
1 
7 
2 
6 
7 
2 
1 
2 
8 
3 
1 
1 
9 
3 
3 
10 
weeks 
1 
6 
Number of plants 
not 
infec-
ted 
4 
3 
5* 
9 
1* 
2 
4 
4* 
1 
6* 
4 
6 
1 
3 
3* 
infected in 
roots 
only 
0 
0 
-
0 
-
2 
0 
-
2 
-
0 
0 
4 
3 
-
roots + 
leaves 
9 
11 
6 
4 
14 
13 
8 
5 
18 
19 
21 
19 
11 
10 
13 
* = plants not assayed, actual state of infection being unknown. 
Tabel 1. Systemische infectie van tomateplanten met TMV na inoculatie van wortels van zaailing. 
Neth. J. PL Path. 79 (1973) 
plants had to remain alive, only pieces of the top leaves and of roots growing through 
the openings in: the bottom of the pots were used for the assay. 
Results and discussion 
The results presented in Table 1 are incomplete because no assays were made in part 
of the experiments, the remainder of plants without leaf symptoms possibly being in-
fected only in the roots. Nevertheless, the results show that only part of the plants 
became systemically infected by inoculation of seedling roots. The first leaf symptoms 
appeared towards the end of the 2nd week in five experiments (October 1967, February 
1968, April 1968, February 1969, March 1969) but only in the 4th or 5th week in five 
other experiments (November 1967, December 1967, October 1968, November 1968, 
January 1969). This suggests seasonal effects. In spite of the highly infective inoculum 
used, systemic infection developed very slowly as is indicated by the experiment in 
January 1969 in which six plants started to show symptoms during the 10th week. In 
some cases the infection was confined to the roots. Under commercial conditions simi-
larly infected plants remain undetected by the grower during the plant raising period, 
which may last from 6 to 8 weeks in winter. So it is possible that mosaic symptoms 
appearing shortly after planting out may still result from root infection during the 
seedling stage originating from infected seeds or contaminated seed coats. 
Samenvatting 
Systemische infectie van tomateplanten met tabaksmozaïekvirusnainoculatie van wortels 
van zaailingen 
Om bij kiemplanten van tomaat wortelinoculaties met TMV uit te voeren werden ge-
perforeerde plastiek hulzen, afkomstig van haarkrullers, met aarde gevuld en gebruikt 
voor het afzonderlijk laten kiemen van tomatezaden. Na inoculatie van de wortels, 
welke door de perforatie van de huls waren heengegroeid (Fig. 1), werden de desbe-
treffende kiemplanten tegelijk met de huls in potten overgeplant. Vervolgens werd het 
verschijnen van bladsymptomen afgewacht, terwijl van tijd tot tijd van uiterlijk niet-
geïnfecteerde planten zowel bladeren als wortels afzonderlijk werden getoetst op 
Nicotiana glutinosa. Uit de resultaten (Tabel 1) is gebleken, dat een aantal planten niet 
of slechts in de wortels werd geïnfecteerd. Bij de meeste planten had inoculatie van de 
wortels een systemische infectie tot gevolg. De periode tussen wortelinoculatie en 
waarneming van de eerste bladsymptomen varieerde voor de individuele planten van 
één tot tien weken met een, ruw geschat, gemiddelde van drie tot vijf weken. Aange-
zien met de opkweek van planten in de winter zes tot acht weken gemoeid zijn, is het 
niet uitgesloten, dat het verschijnen van mozaïeksymptomen kort na het uitplanten 
nog het gevolg is van een wortelinfectie in het kiemplantstadium. 
References 
Broadbent, L., 1965a. The epidemiology of tomato mosaic. Vul. Virus infection through tomato 
roots. Ann. appl. Biol. 55: 57-66. 
Broadbent, L., 1965b. The epidemiology of tomato mosaic. XI. Seed transmission of TMV. Ann. 
appl. Biol. 56: 177-205. 
Neth. J. PI. Path. 79 (1973) 7 
Fulton, R. W., 1941. The behaviour of certain viruses in plant roots. Phytopathology 31: 575-598. 
Hoof, H. A. van, 1967. Aaltjes als virusoverbrengers bij planten. Landbouwk. Tijdschr. 79: 38-42. 
Roberts, F. M., 1950. The infection of plants by viruses through roots. Ann. app. Biol. 7: 385-396. 
Winckel, A. van, 1965. Tabakmozaïekvirus op tomatenzaad. Agricultura, Leuven 4, 721-729. 
Addresses 
Proefstation voor de Groenten- en Fruitteelt onder Glas, Zuidweg 38, Naaldwijk, the Netherlands. 
Neth. J. PI. Path. 79 (1973) 


Systemic infection of tomato plants with tobacco mosaic virus following inoculation of seedling roots

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