Model Short Communication
Suppression effect of Capsicum chinense Jacq. on Southern rootknot nematode
[Meloidogyne incognita (Kofoid and White)] in peppers and tomato
J.K. Peterson and H.F. Harrison
USDA-ARS Vegetable Laboratory, 2875 Savannah Highway, Charleston, SC 29414, USA
Phone (Office): +390881741632, FAX (Office): +390881741632, Phone (Home): +390881686273,
Mobile Number, E. Mail: ...........
(Received in revised form: ------------)
ABSTRACT
We evaluated the available sources of C. chinense for resistance to M. incognita
and found that all commercial sources of the two types (Habanero and Scotch Bonnet)
were moderately susceptible or susceptible. However, four heirloom cultigens, all
of the Scotch Bonnet type, showed levels of resistance similar to resistant C. annuum.
Three of the cultigens were studied released as PA-353, PA-398 and PA-426
Key words: Capsicum annuum, Capsicum chinense, companion planting, Lycopersicon
esculentum, Meloidogyne incognita, pepper, rootknot nematode, tomato
Please arrange in Alphabetical Order.
'Correspondence author. Foot Note, Author please add at end of Page 1 of Ms?
INTRODUCTION
In a greenhouse study it was observed that roots of the nematode (
Meloidogyne incognita)
susceptible tomato (
Lycopersicon esculentum Mill.) cv. 'Rutgers' showed reduced
galling when intertwined with roots of a nematode resistant pepper (Capsicum chinense
Jacq.) 'Scotch Bonnet', growing adjacently in the bench. Thies
et al. (6) reported
that a highly nematode resistant Cayenne pepper (
Capsicum annuum L.) used as a rotational
crop inrootknot infested fields allowed subsequent successful growth of a highly
susceptible pepper. These observations indicate that companion planting with nematode
resistant peppers may provide adequate protection to susceptible vegetable plants.
This study was designed to confirm these observations and provide a quantitative
measure of the efficacy of the proposed companion planting.
MATERIALS AND METHODS
The
Capsicum annuum breeding line PA-136 (I) and the tomato cultivar 'Rutgers' were
used as susceptible plants. The highly nematode resistant G. chinense breeding line
PA-426 (2, 3) served as companion plant. A one week old tomato or susceptible pepper
seedling was planted in the center of a 12 L pot, containing a mixture of 50% pure
coarse sand and 50% of a commercial peat, vermiculite mixture. The susceptible,
center plants were inoculated with 10 ml of a nematode egg suspension (3000 eggs)
in water, dripped around the stem of the susceptible plant. The egg suspension was
prepared from infected peppers as described by Hussey and Barker (5). After inoculation
the pots were thoroughly watered. An experiment, with either a susceptible pepper
or tomato, consisted of two treatments viz., number of companion plants per pot
(0,1,2,4) and inoculation with nematode (not inoculated, inoculated). The treatments
were replicated 6 times and the pots were arranged in a completely randomized design
and the experiments were repeated over time. One full set of experiments was conducted
in winter, when greenhouse temperatures ranged between 20-29 C and one set in summer
when temperatures -ranged between 24-32 C. Gall indices were independently estimated
by two persons and the numbers were averaged for each plant. The following scale
was used: I -no galls; 2 -few galls, root system fully intact; 3 -many galls, root
system in good condition; 4 -large number of galls, throughout root system, root
system discoloured, barely functioning; 5 -massive number of galls, degradation
of root system. Data from two complete experiments were combined for analysis of
variance and means were separated using Duncan's Multiple Range test at P = 0.05.
RESULTS AND DISCUSSION
The nematode resistant pepper companion plants had no visible infection and significantly
reduced galling in the susceptible tomato or pepper plants (Table 1). The susceptible
tomatoes and peppers showed the same trend; reduced galling with increasing numbers
of companion plants. Dry weights of the root systems of the susceptible tomato or
pepper plants increased with more galling, even though the number of thin feeder
roots decreased sharply when no companion plants were present. When four companion
plants were present, root dry weights of the susceptible plants showed no significant
differences between infected and non-infected plants (Table 2 and 3). Root dry weights
of susceptible versus resistant plants are presented separately, because the infected
tomato plants attained more dry weight in winter (Table 2, Experiment 1) than in
summer (Table 2, Experiment 2). Root dry weights of the infected nematode susceptible
pepper plants did not show significant differences between infected and non-infected
plants (Table 2 and 3). Root dry weights of susceptible versus resistant plants
are presented separately, because the infected tomato plants attained more dry weight
in winter (Table 2, Experiment 1) than in summer (Table 2, Experiment 2). Root dry
weights of the infected nematode susceptible pepper plants did not show significant
differences between the two seasons (Table 3). When four companion plants were present,
their total root dry weight was approximately 1.3 g/L. At this root density the
average gall index for the susceptible tomato plants declined from 4.8 (degrading
root system) to 3.3 where the root system was in good condition. Similarly, the
average gall index for the susceptible pepper went from 3.6 (large number of egg-masses,
root system poorly functioning) to 2.2 (root system intact).
CONCLUSIONS
Fery and Thies (2) evaluated the available sources of
C. chinense for resistance
to
M. incognita and found that all commercial sources of the two types (Habanero
and Scotch Bonnet) were moderately susceptible or susceptible. However, four heirloom
cultigens, all of the Scotch Bonnet type, showed levels of resistance similar to
resistant
C. annuum. Three of the cultigens were studied in detail (3) and released
as PA-353, PA-398 and PA-426 (4). The resistance in
C. chinense was conditioned
by a single dominant gene, which is allelic to the dominant gene that conditions
much of the resistance in
C. annuum. It might be expected that sources of
C. annuum
or
C. chinense which have this dominant gene could afford protection against
M. incognita
when used as companions with susceptible vegetable plants.
ACKNOWLEDGEMENTS
The authors are thankful to Andrea Gilliard for her valuable contribution to this
paper.
REFERENCES
(Please add Recent References of last 10-years [Arranged in Alphabetical Order] are preferred)
Please critically follow the Style/Pattern of References as under:
- Dukes, P.D., Fery, R.L. and Thies, J.A. (1997). PA-136 Cayenne pepper, an exceptional
host for production of southern root-knot inoculum. HortScience 32:
335.
- Fery, R.L. and Thies, J.A. (1997). Evaluation of Capsicum chinense Jacq. cultigens
for resistance to the southern rootknot nematode.HortScience32: 923-926.
- Fery, R.L. and Thies, J.A. (1998). Genetic analysis of resistance to the southern
root-knot nematode in Capsicum chinense Jacq.Journal of American Society of Horticultural
Sciences123: 1008-1011.
- Fery, R.L. and Thies, J.A. (1998). PA-353, PA-398 and PA-426: southern root-knot
nematode-resistant Capsicum chinense Jacq. germplasm lines.HortScience 33:
760- 761.
- Hussey, R.S. and Barker, K.R. (1973). A comparison of methods of collecting inocula
of Meloidogyne spp., including a new technique. Plant Diseases Reporter 57:
1025-1028.
Add Tables and Figures after the References?