Château-Musa - Bioversity International

Table 1. Experimental set up used to evaluate the effect of pot volume on the roots of ‘Grande naine’ and the nematode Radopholus similis.
Experiment I Experiment II Experiment III
Pot size 0.8, 3.3, 10 and 20 L 0.8, 3.3, 10 and 20 L 0.8, 3.3, 10 and 20 L
Soil composition Sandy loam (sand 61%, clay 3% and Sandy loam (sand 72%, clay 6% 5.1% of organic matter; pH=5.26;
loam 36%). 8.69% of organic matter; and loam 22%). Ca=5.88, Mg=1.14 et K=0.74 cmol/L ;
pH= 5.25 ; Ca=1.13, Mg=0.29 7.76% of organic matter; pH=4.7 ; P=7.5, Fe=88, Cu=2, Zn=0.4,
et K=0.17 cmol/L ; P=4, Fe=70, Cu=1, Ca=6.71, Mg=1.28 et K=0.78 cmol/L ; and Mn=20 mg/L.
Zn=1.1 and Mn=12 mg/L. P=12 ; Fe=81, Cu=4, Zn=0.7
and Mn=53 mg/L.
Inoculum 280 females of R. similis per liter of soil, None None
i.e. 230±56 in 0.8-L pots;
925±106 in 3.3-L pots;
2 800±153 in 10-L pots
and 5 600±160 in 20-L pots.
Evaluation times 70 days after transplanting 30, 60 et 90 days after transplanting 15 days after transplanting
Experimental design 15 replications per pot volume. Four pot sizes x three Completely randomized design
Pots arranged in a completely evaluation times with 10 replicates with 15 replications.
randomized design. per fractional in a completely
randomized design.
Root weight (g)
90
80
70
60
50
40
30
20
10
Thick roots
Thin roots
Fine roots
To extract nematodes, roots were chopped
up, homogenized and 25 g or less, depending
on the quantity available, were taken.
Extraction was carried out by the macerationsieving
method (Taylor and Loegering 1953)
adjusted as described by Araya et al. (1995).
The reproductive index (RI) of R. similis
was calculated by dividing the final number of
R. similis by the number in the inoculum (N f /N i ).
Three experiments were conducted. They are
described in Table 1.
Results
Experiment I
Root damage was transformed to √(x+0.5) and
R. similis data to log 10 (x+1). For the analysis
of the longitudinal distribution of R. similis
and its damage along the roots a repeated
measurements design was adopted, the
sections being the repeated measurements.
Figure 1. Effect of pot volume on total root weight and the weight of fine, thin and thick roots of ‘Grande naine’.
(Error bars are standard errors of mean total root weight, n=15).
0
0.82 3.3 10 20
Pot volume (L)
18
The non-transformed data are presented to
facilitate interpretation.
Total root weight differed (p=0.0001) between
pot volumes (Figure 1). Root weight increased
with pot volume up to 10 liters, regardless of
root thickness. No thick roots were found in the
0.82- and 3.3-L pots.
The highest percentage of damaged roots
was observed in fine roots. About 79% of
fine roots were damaged, compared to 24%
of thin roots and 9% of thick roots. For all
roots, damage differed (p=0.008) between
pot volumes (Figure 2). The percentage of
damage decreased as pot volume increased,
up to 10 liters, after which damage tended to
stabilize. The proximal section of the roots
was more damaged than the distal section
(p=0.0029) (Figure 2).
The density of R. similis and the total
number of R. similis numbers in thin roots was
significantly higher than in fine roots (Table 2).
A positive correlation was observed between
damage and density of R. similis in fine roots
(r=0.49, p=0.0001;) and thin roots (r=0.24,
p=0.06), whereas lack of data precluded doing
a similar analysis with thick roots.
The two smallest pot volumes had the
highest density of R. similis (483.7±74.7/g and
481.7±78.0/g). The mean density decreased
to 239.2±33.0/g in the 10-L pots and increased
to 400.5±46.0/g in the 20-L pots. No difference
was observed in the total number of R. similis
as a function of pot volume (p=0.20).
The proximal section of the roots had the
highest number of R. similis/g whereas the
distal section had the lowest (Table 3). The
two smallest pots always had a higher density
of R. similis than the bigger ones. The density
InfoMusa - Vol 12 - No.1