Haseeb, A.

Shukla, P.K.

Srivastava, N.K.

Horizon / Pleins textes

Fundam. appl. NemalOl., 1998, 21 (1), 103-105
Influence of pH on reproduction and damage
potential of Pratylenchus thornei on Mentha piperita (1)
Prabhat K. SHUKLA, Akhtar HASEEB and Neel K. SRIVASTAVA
Short note
Peppermint, Men[ha piperùa Huds. (Labiatae), is an
important essential oil-bearing plant cultivated in
tropical countries throughout the world. In India, the
root lesion nematode, Pratylenchus [hornei Sher &
Allen has been reported as the major problem of this
crop (Haseeb, 1994; Haseeb & Shukla, 1996). Gener-
ally, soil pH is not a major factor affecting the damage
caused by nematodes, except in extremely acid or
alkaline soils where the pH may inhibit the growth of
the plant or directly affect the nematode (Wallace,
1971). Moreover, several species of Pralylenchus can
reproduce weil in a wide range of pH (Grandison &
Wallace, 1974; Norton, 1978). The present study
concerns the influence of different pH levels on
growthloil yield of peppermint cv. MPS-l and repro-
duction/ damage potential of P [hornei.
Materials and methods
Dry sand (particles: 0.5-0.05 mm) was treated with
20 % HCI for 24 h and washed thoroughly in tap
water, then air dried and placed into steam sterilized
porcelain pots of 7.5 kg capacity. Full-strengrh Hoag-
land solution was prepared (Hoagland & Arnon,
1938). Three levels of pH of the Hoagland solution
(3.0, 6.0, and 9.0) were maintained by lM NaOH
solution or 20 % HCI.
Uniform healthy suckers (5 cm long) of M. piperùa
cv. MPS-1 were transplanted singly into porcelain
pots and irrigated with Hoagland solu tion at specified
pH on alterna te days. At fourth leaf stage, plants were
inoculated with 10 000 specimens of P [hornei (Pi)
obtained from pure culture maintained on ornamental
Chrysamhemum in glasshouse. For each pH level, five
pots were inoculated and five pots were left non-ino-
culated. Final data were collected 100 days after ino-
culation. Plant growth was determined by measuring
length, and fresh and dry weight of root and shoot.
Chlorophyll content was estimated according to the
Cenlral Inslilule of Medicinal and Aromalic Planls,
(CIMAP-CSfR), PO. CIMAP, Lucknow-226 015, India.
Accepted for publication 26 February 1997.
Key-words: Menlha piperùa, minr, pH, Prarylenchus rhornei.
(1) This paper is a porrion of a Docroral Thesis of the first
aurhor.
Fundam. appl. NemalOl. 1164-5571/98/01/ © Elsevier - ORSTOM
method of Arnon (1949). COz exchange rate of third
leaf (from apex) was measured in a closed system
using a portable photosynthesis model Li 6000
(LiCOR, USA). Estimation of total sugar in leaves
was made using the method described by Yemm and
Willis (1954). Total phenol content of third leaf was
estimated by the method of Swain and Hill (1959).
Essential oil content was determined by hydrodistilla-
tion of fresh shoot tissue using Clevenger (1928)
apparatus. Chlorophyll, COz exchange rate, total
sugar, total phenol and oil content in fresh shoot tis-
sue were measured on individu al replicates separately.
The final nematode population (Pf ) in 250 g soil from
each replicate for each pH level was determined using
sieving combined with Baermann funnel (Southey,
1986). Nematode population in 5 g of roots from each
replicate was determined by macerating rootlsucker
tissues in a waring blender (Southey, 1986). Repro-
duction factor (Rf) was calculated by the formula
Rf= Pf / Pi'
The experiment used a split plot design. The data
were statistically analyzed by analysis of variance
(Cochran & Cox, 1957). Signiticant differences were
determined using LSD test (P~ 0.01).
Results (Table 1)
Length and fresh and dry weight of plants, and oil
yield of peppermint were best at pH 6.0 followed by
3.0 then 9.0 in non-inoculated pots. In inoculated
pots, growth was inversely proportional to pH levels.
Percentage of oil yield was highest at pH 6.0 and low-
est at pH 9.0 irrespective of presence/absence of the
nematode.
The influence of pH on chlorophyll content, photo-
synthe tic rate, and total sugar content in leaves of
M. piperùa was similar to that on plant growth. Phe-
nol content in leaves was inversely proportional to pH
levels irrespective of the presence or absence of the
nematode. However, reduction in shoot fresh weight,
oil yield, COz exchange rate, leaf chlorophyll, total
sugar and phenol content were directly proportional
to pH levels. Reproduction of P [hornei was highest at
pH 6.0 followed by 9.0 then 3.0.
Analysis of dara indicates that the influence of
P [hornei on plant growth, oil yield, physiological and
biochemical changes in plants of M. piperila was
highly significant (P ~ 0.01), irrespective of pH levels.
103
P. K. Shukla el al.
TabLe 1. Influence of pH levels and inilial populalion demities (Pi) of Pralylenchus thornei on growlh and oil yieid, phoLOsymheLic
l'ale, LOLaI chlorophyLL, sugar, and phenoL conlenl in Leaves of Nl.entha piperila and on nemaLOde reproducLion.
pH Pi Significance
0 1000 pHxP j p.o pH+1
Root lengm (cm) 3.0 51.4 39.0
6.0 53.2 41.2 ** :;:* **
9.0 45.2 36.8
Shoot height (cm) 30 88.2 756
6.0 92.4 67.2 ** :;:* ';'*
90 68.6 59.2
Root fresh weight (g) 30 58.4 392
6.0 97.4 44.6 ** ::~ '* *:~
9.0 43.2 20.0
Shoot fresh weighl (g) 3.0 115.4 81.6
6.0 127.2 61.6 ** ~;:* *~
9.0 89.4 36.2
Root dry weight (g) 3.0 12.8 7.8
6.0 19.6 9.4 *:.!: ** **
9.0 8.6 4.2
Shoot dry weight (g) 3.0 22.4 15.4
6.0 23.6 12.4 *:;:; **
9.0 16.8 7.5
Oi 1yield (ml/l OOg fresh herb) 3.0 0.34 0.26
6.0 0.38 0.27 ** **
9.0 0.32 0.22
Total chlorophyll (mg/g fresh weight) 3.0 3.12 2.20
6.0 3.29 1.62 ** ** **
9.0 2.45 1.10
CO2 exchange rate (mg CO2/dm2/hour) 3.0 8.69 6.52
60 8.81 4.87 ** ** *:ic
9.0 7.29 3.74
Tolal sugar (mg/g fresh weight) 3.0 18.30 J .1.73
6.0 19.22 JO.57 ** ** **
9.0 16.92 7.31
Tolal phenoJ (mg/g fresh weight) 3.0 13.82 10.64
6.0 12.35 8.56 *:l: ** **
9.0 10.83 6.87
Final nematode population (tolal root) 3.0 0 3136
6.0 0 9780 *:.!:
9.0 0 7800
Final nematode population (7.5 kg soil) 3.0 0 37800
6.0 0 98400 *B
9.0 0 82700
Reproduction factor (Rf = Pf / Pi) 3.0 0 4.09
6.0 0 10.82 **
9.0 0 905
Each value is an average offive replicares - OPiat fix level ofpH, +pH at fix level of P;-** Significant (P~ 0.01), NS: not signi-
ficant.
104 Fundam. appl. NemaLOI.
At the contrary, the influence of pH on plant growth
varied in the presence or absence of the nematode.
Influence of pH on ail test parameters was highly sig-
nificant (P::; 0.01) in nematode-free plants but, in
plants inoculated with P lhornei non-significant
(P::; 0.01), differences in shoot dry weight and oil
yield were observed between pH 3.0 and 6.0. The
interaction between effect of P lhornei and pH levels
on various plant growth parameters and nematode
reproduction was highly significant.
Discussion
In the present investigation, growth and oil yield of
M. pipen·la, and reproduction of P lhornei were found
to be better at pH 6.0 than at pH 3.0 or 9.0. The
highest reduction in ail the test parameters was
observed at pH 9.0, which may be the result of a com-
pounded effect of pH stress and nematode damage
(Norton 1978).
Reproduction of P lhornei was significantly influ-
enced by pH. Nematode multiplication was lower at
pH 3.0 although nematode damages were present,
which indicates that this nematode species repro-
duced weil at a wide range of pH on M. pipen·la. The
present results may be useful in developing integrated
management strategies against P lhornei on M. pipe-
n·la since at lower pH the plant grows weil and
damage in crop yield is reduced.
Acknowledgements
The authors are grateful tO Dr. S. Kumar, Director, Cen-
trai Institute of Medicinal and Aromatic Plants, Lucknow
for providing the necessary facilities during the course of
investigations.
Vol. 21, n° 1 - 1998
Shorl note
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105


Influence of pH on reproduction and damage potential of Pratylenchus thornei on Mentha piperita

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