3.2. Significance of cultivation status, genetic group and
location on growth response traits
In the linear mixed model analysis, the effects of factors (i.e. ,
cultivation status, genetic group and location) varied across growth
response traits (Table 3). The cultivation status did not have
significant effects on RGRA, TNL and
TLDW (p >0.05), but did significantly
affect SLA and RL (Table 3). On average,
wild genotypes had the highest SLA (244
cm-2 g-1) but the difference was
only significant with the feral and not with the cultivated genotypes
(Appendix Table A. 3.). For RL, cultivated genotypes had
a significantly higher average value (0.0087 cm3cm-2) than wild and feral genotypes and there were no
significant differences between wild and feral RL values
(Appendix Table A.3.). There were no significant interaction effects
between cultivation status and treatment for any of the selected traits,
except for TL indicating that only for
TL, the treatment effect differed across cultivation
status. Under ample-water conditions, cultivation status had no
significant effects on TL while under restricted-water
conditions wild genotypes, had a significantly lower TLthan feral and cultivated genotypes whose TL’s were not
significantly affected by water availability. In the restricted-water
treatment, wild genotypes had the lowest average TLwhich was 24.4 % lower than the highest average TLobserved in feral genotypes (Appendix Table A.3.). These findings
suggest that in terms of TL, wild genotypes might be
more sensitive to low water availability than non-wild genotypes.
Genetic groups significantly differed in their TL,
TLDW and RL but not in the other three
traits (Table 3). Plants from the genetic group SC had the highest mean
TL which was 60.9 % higher than the lowest
TL observed in genetic group Kibale (Appendix Table
A.3.). The effect of the genetic group on TLDW was
similar to TL with genetic group SC having 67.6 %
higher mean TLDW than genetic group Kibale which had the
lowest TLDW (Appendix Table A.3.). For
RL, Zoka had the highest value which was 43.9 % higher
than the lowest RL observed in the genetic group Kibale
(Appendix Table A.3.). Interaction effects between genetic groups and
treatment were only observed in RGRA, implying that the
magnitude of the response in this trait to the water treatment differed
across genetic groups. The RGRA of genetic groups:
Budongo, SC and Zoka were significantly reduced due to restricted-water
supply but not that of genetic groups Itwara and Kibale (Fig. 1;
Appendix Table A.3.).
Overall, location as a factor had stronger effects on growth response
traits to ample and restricted-water supply than the two other factors,
cultivation status and genetic groups
(Table 3). Location had significant main effects and interaction effects
on all traits except on TNL, TLDW and
SLA (Table 3). This implies that the growth response
values significantly differed depending on the location from which the
genotypes were collected. For example, for TL, i.e. the
response trait with the strongest location effects (Table 3), location
Malabigambo had the highest average TL which was 73.7 %
higher than the lowest TL observed in Kibale. Drought
had no significant effects on the TL of genotypes
collected from Zoka, Itwara, Kibale, Kituza and Kawanda, while it
significantly reduced TL of genotypes collected from
Malabigambo, Kalangala and Mabira (Appendix Table A.4.). In absolute
terms, under ample-water conditions, Malabigambo had a significantly
higher TL (7263 (± 153) cm2) than all
other locations while Kibale’s TL (1413 (± 38)
cm2), was significantly lower than
TL’s at all locations except Zoka (Appendix Table A.4.).
Similarly, under restricted-water conditions; Malabigambo had the
highest TL (3711 (± 62) cm2) compared
to all other locations whereas Kibale had the lowest TL(1469 (± 42) cm2) which was significantly lower than
TL of all other locations except Zoka (Appendix Table A.
4.).