PLANT-PARASITIC NEMATODES ASSOCIATED WITH MAIZE, SORGHUM AND PEARL MILLET AND INTERACTIONS OF Pratylenchus brachyurus WITH MAIZE AND SORGHUM IN THE NIGERIAN SAVANNAS
PLANT-PARASITIC NEMATODES ASSOCIATED WITH MAIZE, SORGHUM AND PEARL MILLET AND INTERACTIONS OF Pratylenchus brachyurus WITH MAIZE AND SORGHUM IN THE NIGERIAN SAVANNAS
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Date
1997-11
Authors
CHINDO, PAUL SULE
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Abstract
This study was undertaken to determine the identity,
distribution and economic importance of plant-parasitic
nematodes associated with maize, sorghum and pearl millet.
Subsequently, the population dynamics of one of the most
important nematodes was studied in order to develop management
strategies for the nematode.
Twenty genera of plant-parasitic nematodes, occurring in
varying frequencies and populations in farmers' fields were
found associated with maize, sorghum, and pearl millet.
Cluster analysis classified the nematodes into three broad
groups. Group I, comprised nematodes that occurred frequently
and usually of high population. Group II, consisted of
nematodes that were not widely distributed and occurred
usually in low numbers while Group III, was made up of
nematodes of occasional occurrence and usually in very low
numbers. Out of the twenty nematode genera, six genera, viz.;
Helicotylenchus, Tylenchus, Pratylenchus, Scutellonema,
Aphelenchoid.es and Hoplolaimus appeared to be the most
important on account of the frequency of their occurrence, and
population densities.
Further analysis on the pattern of distribution/and or
association of the nematodes in the various fields resulted in
eight field groups, the nematode populations of each genera
varying from field to field. This suggests a close
relationship (interaction) between nematode species and field
conditions. The cropping systems in the field were found to
influence nematode occurrence and population densities.
Maize-based systems were particularly found to favour the
distribution and population densities of most nematode species
compared to systems dominated by sorghum, millet, and legumes.
Out of the six nematode genera rated as important in this
study, Pratylenchus brachyurus was selected and some detailed
studies conducted on maize and sorghum. P. brachyurus was
shown to be pathogenic on both maize and sorghum resulting in
significant reduction in plant growth. This reduction was
however more for maize than sorghum.
Results of the study on effect of different population
densities of P. brachyurus on maize showed that all growth
parameters were reduced at all populations tested when
compared to the check. Nematode invasion reached a maximum at
a density of 2000 nematodes and declined thereafter.
The reaction of thirteen maize cultivars to P. brachyurus
was studied in the screenhouse. None of the cultivars was
found to be resistant. Nematode multiplication was highest
in improved cultivars especially hybrids.
Studies on the population dynamics of the nematode in
June sown maize showed that P. brachyurus infected maize as
soon as roots emerged. Populations increased rapidly and
reached a maximum in roots and soil in early September and
late August, respectively.
Economic importance of P. brachyurus was determined by
treating infested field with furadan 3G at 2.0 kg a.i/ha.
Pre-plant (about 300 nematodes/500 ml soil) populations were
significantly reduced resulting in a yield increase of about
38%.
Description
A Dissertation submitted to the Postgraduate School,
Ahmadu Bello University, Zaria, in partial
fulfillment of the requirements for the
award of degree of Doctor of Philosophy
(CROP PROTECTION)
DEPARTMENT OF CROP PROTECTION
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY
ZARIA, NIGERIA
NOVEMBER, 1997
Keywords
PLANT-PARASITIC,, NEMATODES,, ASSOCIATED,, MAIZE,, SORGHUM,, PEARL,, MILLET,, INTERACTIONS, Pratylenchus brachyurus, MAIZE,, SORGHUM,, NIGERIAN,, SAVANNAS,