GENETIC VARIABILITY FOR SPROUTING ABILITY AND ESTABLISHMENT OF CASSAVA (Manihot esculenta Crantz) IN THE NIGERIAN SAVANNA.
GENETIC VARIABILITY FOR SPROUTING ABILITY AND ESTABLISHMENT OF CASSAVA (Manihot esculenta Crantz) IN THE NIGERIAN SAVANNA.
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Date
1998-03
Authors
OKONKWO, CHRISTIAN CHUKWUMA
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Abstract
The studies were carried out to estimate the extent of genetic variability and
character relations in cassava (Manihot esculenta Crantz) for sprouting and establishment
ability. Forty cassava clones comprising: 33 Nigerian cassava land races and 7 IITA
improved clones were selected for the study based on their popularity in the 36 states of
Nigeria.
The analysis of variance for sprouting ability, establishment ability, cutting
characteristics, growth parameters, cassava mosaic disease (CMD) and cassava bacterial
blight (CBB) showed highly significant differences (p=0.01) among the genotypes.
Combined analysis of variance for sprouting ability, establishment ability, growth
parameters,(no of shoots per plot, number of roots per plot, fresh weight of shoot, fresh
weight of root, dry weight of shoot, dry weight of root, plant height), CMD and CBB
revealed highly significant effects of clones, environments and their interactions (G x E).
Locations also differed significantly. Highly significant G x E interactions were observed for
all the traits measured. The estimates of genetic variances obtained in this study were
comparable among the locations. However kuru location had lower estimates than the other
locations.
The genotypic coefficients of variation (GCV) were lower than the phenotypic
coefficients of variation (PCV) in all the characters studied thus indicating considerable
influence of environment on the expression of these characters. The high GCV values for the
characters revealed that the range of variability in the population was large thus suggesting
that there is scope for further improvement of these traits through selection. The genetic
variances obtained were positive for all the traits studied. Significant genetic differences
existed for all the traits studied and varied widely among locations.
From the results, most cassava clones achieved their maximum sprouting potential
between 21 and 28 days after planting. Among all the locations, Samaru had the overall best
mean performance and Kuru location had the lowest mean performance. The TMS 30572
had the overall best mean performance across the four locations for sprouting and
establishment ability. Antiota, TMS 91934, 82/00661, 82/0058, Odungbo, Abachaji, and
Oyarugba had mean performance of above 90% sprouting ability and were among the best
clones selected for high sprouting ability and establishment potentials. The studies also
showed that evaluating for sprouting and supplying should be done between 21 and 28 days
after planting.
The forty cassava clones that were involved in the studies showed varying levels of
susceptibility to cassava mosaic disease and cassava bacterial blight. Amala, Atu Iwo, Bagi
Wawa, Oko Iywo, Olekanga, 2nd Agric were the most resistant clones in the population for
CMD, while TMS 81/00110, TMS 82/00058 and TMS 30572 were the resistant clones to
CBB.
Correlation coefficients in all the four locations between phenotypic and genotypic
correlation showed similar trend and magnitude. Genotypic coefficients of correlation were
higher than their corresponding phenotypic correlation coefficients. Highly significant
positive genotypic and phenotypic correlation coefficients were observed between sprouting
and establishment. Stake fresh weight, stake girth, stake volume, stake bulk density, had
significant positive genotypic and phenotypic correlation with sprouting and establishment.
Number of shoot, number of roots, fresh weight of shoot, fresh weight of root, dry weight of
shoot, dry weight of root and plant height were positively correlated with sprouting and
establishment. However, sprouting and establishment correlated significantly, but negatively
with number of nodes and pith wood ratio implying that increasing number of nodes of
cuttings and pith wood ratio would result in decrease of the sprouting ability of the different
genotypes. Similarly, the significant negative correlation between sprouting ability and
establishment and pith wood ratio indicated that increasing pith-wood ratio would also result
in decrease of the wood portion of the stakes thus reducing the food reserve in the wood and
consequently resulting to poor sprouting and establishment.
Significant but negative phenotypic correlations were observed between sprouting,
establishment and CMD and CBB recorded at 3 months after planting. The implication of
this observation for breeding could mean that selections aimed at increasing sprouting and
establishment abilities would probably lead to decreased pith-wood ratio, decreased CMD,
decreased CBB and decreased number of nodes, thus these characters could therefore be
improved simultaneously.
Description
A thesis Submitted to the Post Graduate School, Ahmadu Bello University, Zaria,
In partial fulfillment of the requirements for the award of the degree of Master of
Science in Crop Breeding
DEPARTMENT OF PLANT SCIENCE
Faculty of Agriculture
Ahmadu Bello University Zaria,
Nigeria
MARCH, 1998
Keywords
GENETIC,, VARIABILITY,, SPROUTING,, ABILITY,, ESTABLISHMENT,, CASSAVA,, (Manihot esculenta Crantz),, NIGERIAN,, SAVANNA.