STUDIES ON GENETIC VARIATIONS IN A SORGHUM VARIETY (Sorghum bicolor (L.). Moench) IRRADIATED WITH COBALT 60 (CO60)
STUDIES ON GENETIC VARIATIONS IN A SORGHUM VARIETY (Sorghum bicolor (L.). Moench) IRRADIATED WITH COBALT 60 (CO60)
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Date
1998-02
Authors
ABA, DANIEL AFANG
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Abstract
Genetic variability was created in a common sorghum variety SK5912 (SAMSORG
17) using gamma-ray irradiation from Cobolt 60 (Co60) source. The M0 seeds
were grown in the off-season of 1985/86. This was bulk harvested and planted as M,
bulk in 1986. In 1986, 90 M2 single seed selections were made from single plants
selected based on height, yield and disease resistance. These were advanced to M3
in 1987, out of which 34 M4 family selections were obtained for evaluation. The 34
M4 family selections were harvested and threshed. The seeds from each family were
divided into three equal portions for evaluation. The 34 M4 plant types were
evaluated in a randomized complete block design (RCBD) for three years (1989, 1990
and 1991) in the Institute for Agricultural Research (I.A.R) farms. Data were
collected on 22 characters, (i) eight (8) panicle characters, (ii) eight (8) leaf
characters, and (iii) six (6) stem (culm) characters.
Coefficients of variability (C.V%) were high for panicle characters, than for
leaf and stem characters. They ranged from 1.65% for days to 50% flowering to
4.15% for grain weight per spikelet. Heritability estimates were high for most panicle
characters (>45%) while they were moderate for both the leaf and stem characters
(<40%).
There were highly significant mean squares for all characters except for grain
weight per spikelet in the combined analysis. There were high and significant
correlations (r= >0.5) between the lengths of first and second leaf sheaths (r=0.689)
and also the lengths of internodes (r=0.652, 0.628 and 0.634). Highly significant
but negative correlation was found between length of first leaf shealth and width of
spikelet (r = -0.840) in 1991.
Variance components from the combine analyses showed that genotypic
variancve was high for all characters except for percentage protein and weight of
spikelet. All other characters had lower genotypic variances than their respective
phenotypic and error variances.
Principal components extracted from the combine correlation matrix showed
high variability in leaf and stem characters than in the panicle characters. Internode
lenth and leaf sheaths length load significantly on the first factor in the individual
years as well as in the combined. Ploting the first two factors of all the years (Fl and
F2) in a common scale showed that internode length and leaf sheath length were
clustered together in one quadrant; grain weight per panicle, grain weight per
spikelet, days to 50% flowering and width of spikelet where also clustered together
which is indicating the close relationship between these characters.
The negative correlation between the leaf and stem characters with days to
50% flowering and some panicle characters might be suggesting that selection for
shorter plants which have erect leaf could result in increase in yield and early
maturing plant. However, there were low correlations between internodes length,
length of leaf blade and length of leaf sheath which were highly variable with most
panicle characters (yield components). It might be more effective to select directly
for grain weight per panicle, length of panicle, spikelet number per panicle and grain
weight per spikelet together with these photosynthetic structures for better
improvement in yield in our 'plant types
Description
A Dissertation Submitted to the Postgraduate School, Ahmadu Bello University in partial fulfilment of the
requirements for the degree of Doctor of Philosophy in Plant Breeding.
DEPARTMENT OF PLANT SCIENCE
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY
ZARIA - NIGERIA.
FEBRUARY, 1998
Keywords
GENETIC,, VARIATIONS,, SORGHUM,, VARIETY,, (Sorghum bicolor (L.). Moench),, IRRADIATED,, COBALT