Kort, J.

Sibma, L.

Wit, C.T., de

Wageningen Yield 

REPRINTED FROM: 
JAARB. J.B.S. 1964,119-124 
EXPERIMENTS ON COMPETITION AS A MEANS OF DETECTING 
POSSIBLE DAMAGE BY NEMATODES 
L. SIBMA, J. KORT and C. T. DE WIT 
I nstituut voor Biologisch en Scheikundig Onderzoek van Landbouwgewassen, Wageningen 
Mededeling 246 

Mededeling 246 van het !.B.S. 
EXPERIMENTS ON COMPETITION AS A MEANS OF DETECTING 
POSSIBLE DAMAGE BY NEMATODES 
L. SIBMA, J. KORT1) and C. T. DE WIT 
INTRODUCTION 
VAN DoBBEN (1955) cultivated barley and oats in monoculture and in mixed cul-
ture on plots with different pH-values. Below a pH of about 4 the yield of barley was 
pH-dependent whereas the yield of oats was not. The yield of barley sown in a mixture 
with oats, however, was pH-dependent below a pH of 5. The adverse effect of low 
pH-values of the soil on the pH-sensitive barley is apparently increased by cultivating 
these plants in a mixture with non pH-sensitive oats. 
DE WIT ( 1960) showed that a similar effect occurs in mixtures of healthy and dis-
eased plants, provided the disease occurs at an early stage. 
Hence, to enlarge the effect of a disease on growth it may be helpful to cultivate 
beside monocultures, mixtures of varieties that are resistant and not resistant to that 
disease. 
Experiments were carried out to determine whether the effect of nematodes on the 
growth of sensitive plants is increased by cultivating these plants in a mixture with 
nematode resistant plants. 
EXPERIMENTS WITH CEREAL ROOT EEL WORM ( Heterodera avenae Wolf.) IN 1961, 
1962 AND 1963 
To exclude difficulties which might arise from using eelworm populations of 
unknown composition, a population of biotype A of the eelworm (KaRT, DANTUMA 
and vAN EssEN, 1964) was used in the experiments with oats ( cultivar Marne) as a 
sensitive host and barley 191 of the International Barley Disease Nursery as non-
host. 
Plastic buckets of 5 liter capacity were filled with 7 kg of nematode-free soil ob-
tained from a depth of 50 em below a permanent pasture. In half the containers cysts 
were added to the soil which resulted in an infestation of 500-600 larvae per 200 ml 
of soil. 
The infested and non-infested containers were planted with 10 barley and oat 
plants in relative frequencies of 0, 0.2, 0.4, 0.6, 0.8 and 1 in three replicates. 
The containers were placed in an open shed with glass roofing to ensure natural 
synchronisation of the life cycles of plants and nematodes. Limited water was given by 
watering the plants from above (sub-optimal) or a contineous supply by providing a 
constant water table (optimal). 
After ripening, the plants were harvested and the total dry matter weight, seed and 
number of seeds were determined from each species per container. 
Since oats ripens about two weeks later than barley, the number of seeds is a better 
yield measure in competition studies than the dry-matter weight (DE WIT 1960). 
1) Plantenziektenkundige Dienst, Wageningen 
119 
The number of cysts and eggs at the end of the experiments were determined ac-
cording to KoRT (1960). 
TREATMENT OF THE RESULTS OF EXPERIMENTS ON COMPETITION BETWEEN SIMILAR 
SPECIES 
The method of treating competition experiments will be illustrated by means of the 
results of the 1962 experiment with barley and oats presented in fig. 2a. 
The number of barley and oat plants per container is given along the horizontal 
axis. The fraction of both varies between 0 and 1, but the total plant number is 10 
per container, throughout. The yields of barley and oats grown in monoculture are 
210 and 360 kernels/container, respectively. If the yield of each species in the mixtures 
should be proportional to the number of plants of that species, the observations should 
be formed on the straight, broken line through these points and the origins. It is seen 
that the yields for oats are higher and those for barley lower than by these lines. 
DE WIT (1960) showed that yields of both cereals in such a replacement series can 
be represented by 
0 _ kobZo M 0- 0 
kobZo + Zb 
[1] 
0 kboZb M b = b 
kboZb + Zo 
0 0 and Ob are the yields of oats and barley at plant-numbers Zo and Zb (Zo + Zb 
=constant) and M 0 and M b the yields of the monoculture. The constants kob and 
kbo are the relative crowding coefficients of oats in barley and barley in oats. When the 
two species are sufficiently similar, they may crowd for the same space and then 
k b 0 • k 0 b = 1 [2] 
This is always the case with barley and oats (DE WIT 1960). 
The curves that fit the observations in fig. 2a are drawn according to equation [1] 
with kob = 1/kbo = 6. 
RESULTS 
Experiment in 1961 
Sowing took place on March 30; after one week 1 g of ammonium nitrate (NH4N03) 
was given and an optimal water supply was maintained throughout the growing 
period. Both, oats and barley showed a rapid development and were harvested at the 
end of September. 
The yields in number of seeds per container are shown in fig. 1a for the non-infested 
soil and in fig. 1 b for the infested soil. The values of the constants in equation [1] as 
calculated from the data are given in table 1. 
TABLE 1. Mo, Mb and kob ( = 1/kbo) in 1961. 
non-infested 
680 
290 
1.0 
infested 
660 
260 
1.0 
kernels per container 
Fig. 4 gives the number of eelworms per unit contents of soil for both treatments. 
120 
FIG. 1. Results of the experiment in 
1961 with optimal supply, of water 
and nutrients and a succesful infes-
tation. 
• oats x barley 
Experiment in 1962 
102 kernels 
container 
7 
0 2 
10 Z0 8 
non- infested 
a 
4 8 zb 10 
6 4 2 0 
kernels /container 
infested 
b 
0 2 6 a zb 10 
10Z0 8 4 2 0 kernels/container 
Sowing was carried out on April 6; 1 g of ammonium nitrate was given 48 days 
later. A sub ... optimal water supply was maintained throughout the growing period. 
Especially the early growth of both plant species was poor. The harvest took place in 
the middle of August. Yields are given in fig. 2a and 2b and the values of the constants 
in equation [1] are given in table 2. 
TABLE 2. M 0 , Mb and kob ( = 1/kbo) in 1962. 
non-infested 
350 
infested 
385 
185 
1.3 
kernels per container 
210 
6.0 
The number of eelworms is also given in fig. 4. 
FIG. 2. Results of the experi-
102 kernels 
eontainer 
ment in 1962 with sub-optimal 
supply of water and a successful ~o z
0 infestation. • oats x barley 
Experiment in 1963 
non-infested 
kob :6 
4 
6 
a 
~ ~ zb 1g 
kernels/container 
102 kernels 
container 
6 
infested 
kob = 1.3 
~ ~ ~ zb W 
kernels/container 
Sowing was carried out on April 5; 1 g of ammonium nitrate was applied 14 days 
later and the plants were harvested at the end of August. 
121 
non -infested 
5 
a 
2 
kernels/container 
102 kernels 
container 
6 
5 
infested 
b 
4 6 sz6 10 6 4 2 0 
kernels/container 
FIG. 3. Results of the experiment in 
1963 with sub-optimal supply of wa-
ter and an unsuccessful infestation. 
e oats x barley 
Half the containers were supplied with optimal and the other half with sub-opti-
mal amounts of water. The yields of containers supplied with sub-optimal quantities of 
water are given in fig. 3a and 3b. 
The constants in equation [1], as calculated for the sub-optimal and optimal water 
treatments are given in table 3. 
TABLE 3. Mo, Mb, kob ( = 1/kbo) in 1963. 
sub-optimal water 
non-infested infested 
Mo 340 360 
Mb 155 125 
kob 18 18 
optimal water 
Mo 615 665 
Mb 110 125 
kob 18 18 
kernels/container 
kernels/container 
The number of nematodes at the time of harvest, averaged for both moisture 
regimes are given in fig. 4. 
DISCUSSION 
Fig. 4 shows that in 1962 nematodes were practically absent in the non~infested 
containers, but in the infested ones their number varied from 500 nematodes per 
200 ml of soil for the monoculture of barley to 6000 nematodes per 200 ml for the 
monoculture of oats. The number of nematodes per oat plant increased with increas-
ing relative frequency of oats in the containers. Hence the inoculation succeeded. In 
spite of a successful inoculation in 1962 the yields of oats as monoculture on infested 
and non-infested soil were the same (:fig. 2). Experiments in which only monocultures 
on infested and non-infested soil are compared, will not show any differences in yield 
resulting from the presence of nematodes. 
The absence of any influence of nematodes on yield in this kind of experiment may 
be due to the presence of sufficient roots to take up the limited amounts of water or 
nutrients or to the absence of damage by nematodes. These two possibilities can only 
be distinguished by comparing the yields of the mixed cultures. 
122 
FIG. 4. Density of the nematode population of 
infested and non-infested containers at the end 
of the experiment. 
nematodes 
200cc 
10.000 
5.000 
1000 
500 
1961 ~x1962} ~/ '''"''' 
• -·-·-. 1963 
------------------ 1961 
100 
50 
10 
non-infested 
------------------ 1963 
------------------1962 
oat plants 
10 container 
In the mixed culture on infested soil (fig. 2) the yield of oats is lower and that of 
barley higher in comparison to the non-infested soil. This effect of infestation is 
quantitatively accounted for by the value of the relative crowding coefficient kob 
which is 1.3 for the infested and 6 for the non-infested replacement series. 
The effect on yield must be due to damage of the roots of oats by nematodes in an 
early stage. This damage prevented oats from occupying its share of the available 
soil and enabled barley to occupy more than its share. 
Early activity of nematodes and a low supply of nutrients will enlarge the effect of 
infestation on the relative crowding coefficient. 
In 1961 inoculation with nematodes succeeded (fig. 4) but in that year neither the 
yields in monoculture nor in mixed culture were affected. Supply with nutrients and 
water had been so liberal that even in the mixed cultures the yield of oats was not 
limited by a supply by the roots. 
In 1963 there neither were differences between the replacement series with and 
without eelworms. This was true for both optimal and sub-optimal treatments. The 
data on the nematode numbers in fig. 4 show that the inoculation with nematodes for 
some reason was not successful. 
The yield of oats with optimal water supply was twice that with sub-optimal water 
supply, but the yield of barley was the same for both. In spite of this, the relative 
crowding coefficient of oats was about the same in both cases (table 3). This is be-
cause the relative crowding coefficient is determined in an early stage and the effects 
of water supply on growth occur later. 
The relative crowding coefficient of oats with .respect to barley was 18 in the last 
year of experimentation. Since it is convenient to work with relative crowding coeffi-
cients closer to one, it would have been better if 1 seed of oats had been replaced by 
2 seeds of barley, the mathematical treatment of a replacement series of this kind 
gives, of course, no difficulties (DE WIT, 1960). 
123 
SUMMARY 
An experiment was designed to show whether the damage by eelworm infestation in 
oats could be enlarged by competition with a resistant barley variety. 
Both cereals were grown in monoculture and as a mixed crop in containers filled 
with nematode-free soil and soil infested with cereal root eelworm. The infestation 
was successful in two out of three years, but the yield of oats in mixed culture was 
depressed by infestation. 
In no case was the yield of oats affected, when grown in monoculture. 
REFERENCES 
I. DoBBEN, W. H. VAN: Concurrentie tussen haver en zomergerst op een pH-trappenproefveld. 
Verslag C.I.L.O. ( 1955) 128-131. 
2. KoRT, J.: A technique for the extraction of Heterodera cysts from wet soil and for the estimation 
of their egg and larval content. Overdrukken Pl. Ziektenk. Dienst. Wageningen 233 ( 1960) 4 pp. 
3. KoRT, J., G. DANTUMA and A. VAN EssEN: On biotypes of the cereal root eelworm ( Heterodera 
avenae) and resistance in oats and barley. Neth. J. Plant Path. 70 ( 1964) 9-17. 
4. WIT, C. T. DE: On competition. Verst. Landbouwk. Onderz. 66.8 ( 1960) Wageningen 81 pp. 
Received: 17 April 1964. 
124 


1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
I 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
j 
I 
j 


Experiments on competition as a means of detecting possible damage by nematodes

Abstract

Similar works

Full text

Available Versions

Wageningen Yield

Name not available

NARCIS