| dc.description.abstract | Sorghum is a major staple food source in many African countries. In Kenya, it is
cultivated by small-scale farmers. Gadam sorghum is the common variety mainly
grown for brewing, manufacture of animal feeds and sorghum cakes. However, its
yield is about 0.8 t ha-
which is low compared to international standards. This is
exacerbated by birds' that tend to have a preference for it. The use of birds' resistant
sorghum varieties containing higher amounts of tannin than Gadam is a strategy to
minimize the damage. However, tannin is an anti-nutritional factor that binds proteins
together and inhibits many enzymes in in vitro assays reducing their digestibility and
efficiency of utilization. Production of hybrids is one way of improving yield through
heterosis. The objective of this study was to evaluate the performance of sorghum
through hybridization of Gadam sorghum and hard coat tannin sorghum varieties. The
study was conducted at the University of Embu research farm. The experiment was
laid out in a Randomized Complete Block Design (RCBD) with three replicates. Four
(4) sorghum varieties namely, Serena, Gadam, Seredo and Kari/Mtama-1 (used as a
control due to its low tannin content) were sourced from the KALRO seed unit at
Katumani. Sowing of sorghum varieties was staggered over three weeks to
synchronize heading time to enable crossing. Development of F1 hybrid lines was done
by reciprocal crossing of Gadam and other varieties, using manual emasculation
method. Crosses and their reciprocals were used as plant materials while parents were
the controls. Data taken was; compatibility between the parents, changes in levels of
expression of the tannin gene, grain nutritional levels, heterosis and yield traits
compared to their parents. Collected data was subjected to a one-way analysis of
variance (ANOVA) using R statistical software. Mean separation was done using
Tukey’s Studentized Range (HSD) at 95% confidence level. The cross Gadam x
Serena, Serena x Gadam and the parent Gadam exhibited moderate mean plant height
values of 99.5 cm, 120.5 cm and 103.3 cm respectively. The cross Gadam x Serena
recorded a desirable negative mid-parent heterosis of -19.89 and -16.16 for plant height
and days to maturity respectively. All F1 hybrids recorded positive mid parent heterosis
for the weight of full panicle, weight of a thousand seeds, number of tillers per plant,
number of reproductive tillers and panicle length indicating possible yield
improvement of Gadam sorghum through hybridization. The crosses Gadam x Seredo,
Seredo x Gadam, Gadam x Serena and Kari/Mtama-1 x Gadam recorded significantly
lower grain filling percentages compared to their parents. Both RNA levels and tannin
content were observed to be at the maximum at soft dough stage and declined in
subsequent stages indicating synchrony between RNA levels and tannin levels.
Parents, crosses and reciprocals also differed significantly (p<0.001) for crude protein,
fat, crude fibre, ash, carbohydrates, moisture and tannin content with values ranging
from 5.323% to 10.390%, 1.691% to 2.299%, 2.230% to 3.520%, 1.215% to 1.360%,
76.790% to 85.677% , 5.433% to 9.667% and 0.034 mg/g to 1.763 mg/g respectively.
In conclusion, all the F1 hybrids have positive mid parent heterosis for number of
reproductive tillers, number of tillers per plant, panicle length, weight of full panicle,
and a thousand seed weight. There is maternal influence on days to heading, flowering
and maturity, and a thousand grain weight. The lower grain filling percentage recorded
in the F1 hybrids indicates that the parental lines used have a narrow wide compatibility
gene. The decline in Tan1 gene after the soft dough stage shows that Tan1 gene
expression in sorghum is determined by the level of seed maturity. The F1s showed
marginal improvement in crude protein, crude fibre and carbohydrates but need to be
evaluated further to determine the influence of hybridization on total nutrition. Also,
heterosis can be utilized to improve the growth and yield of sorghum. | en_US |
