| dc.description.abstract | Common bean (Phaseolus vulgaris L.) is mostly cultivated in different areas where
seasonal rainfall is inconsistent and soil moisture stress limits grain yield production .
This study aimed at identifying biofortified common bean varieties with high seed weight
and high seed quality performance under different soil moisture levels. Two trials
comprising of five biofortified common bean varieties (PVA, HM21-7, RWR21-54,
RWR22- 45 and CDBIOB27) were subjected to 5 soil moisture levels (20; 40; 60; 80 and
100% of the pot capacity) in a split-plot arranged in a complete randomized design at
Kabete Field Station, University of Nairobi. At harvest time, data on pod number and
number of seeds per pod were taken. Pod weight, seed weight and the rate of seed weight
decrease due to water stress were also detemined. Seed lots from greenhouse experiments
were used in the laboratory conditions to evaluate seed quality parameters such as
germination rate, thousand seed weight, seed vigor index, seed moisture content, seed
health, Iron and Zinc content for different biofortified common bean under various soil
moisture levels. Variety CDBIOB27 performed poorly for all yield components while
variety RWR21-54 performed better than other varieties followed by variety RWR22-45
and HM21-7. No significant differences in seed weight were observed under 100%, 80%
and 60% pot capacity while 20% and 40% pot capacity gave the poorest lowest seed
weight. All other yield components had significantly low performance under 20% pot
capacity followed by performance under 40% pot capacity. The germination rate, seed
vigor index and thousand seed weight differed significantly depending on the different
biofortified varieties and soil moisture levels. There was no correlation between soil
moisture and the seed moisture content. The Iron and Zinc content differed significantly
depending on the common bean varieties and soil moisture levels. There was an
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interaction between soil moisture levels and variety on seed Zinc and Iron content.
Overall, variety RWR21-54 performed well and gave the highest seed weight per plot
(161.64g), 1000 seed weight (626.53g) and highest Iron content (66.64mg/kg) at 60% pot
capacity. The fungus incidence ranged from 14.5-52.5% (Aspergillus spp), 6-36%
(Rhizoctonia spp), and 0-9.5% (Penicillium spp) depending on the varieties and soil
moisture level. Incidence of Aspergillus spp decreased with decreased soil moisture
content. The study demonstrates that the soil moisture level can be maintained at 60%
without compromising the seed quality, Iron and Zinc content for the investigated
biofortified common beans. The general performance indicates that variety RWR21-54
performed better than other varieties at 80% and maintained this performance at 60% soil
moisture level. Field trials should be done in different climatic conditions to evaluate the
adaptation of variety RWR21-54 and RWR22-45 to different regions. | en_US |
