Genetic analysis of tolerance to aluminum toxicity in mazie (Zea mays)

Aluminum (Al) toxicity causes high yield losses and is directly linked to acidic soils.
Application of lime can ameliorate this problem, but it is costly and not feasible for
small scale farmers as they need to purchase both seed and lime. Developing maize
varieties that are tolerant to Al toxicity is cheaper and feasible for small scale farmers.
The purpose of this research was to i) identify maize genotypes with tolerance to
Aluminum toxicity, ii) evaluate the general and specific combining abilities for the
inbred lines and crosses respectively, iii) investigate the type of gene action
conditioning tolerance to aluminum toxicity in tropical maize, and iv) determine if
shoot length can be used as an indirect selection criterion for Al tolerance. Fourteen
maize inbred lines (CZL 083, L151, L552, CZL0814, CML312, L12, L3233,
CML511, L917, L2, CML538, L5522, CML 457, and CZL04007) were evaluated in
hydroponic conditions containing different concentrations of Al (0, 5, 10, 15 and
20mg/ L) in a 14 x 5 factorial completely randomized design with 3 replications at the
University of Zambia, plant physiology laboratory. Five parameters were measured:
root length, shoot length, number of root hairs, root and shoot biomass on eleventh day
after seed placement. Highly significant differences (P=0.001) were noted for both root
and shoot lengths. The results showed that inbred line CML 538 was highly tolerant
while inbred line L151 was the most susceptible with mean lengths of 15.44 cm and
6.11 cm respectively. To address objective ii, eleven inbred lines were selected and
mated in an 8 male (4 moderately tolerant and 4 susceptible) x 3 female (resistant)
North Carolina Design II. Results revealed that GCA effects due to both males and
females were highly significantly (P= 0.001) different from zero for root biomass. The
shoot length GCA effects (8.75 and 12.81) due to both male and female respectively
were significant (P=0.01). Similarly, the GCA effects due to females and males for
root length were significant P= 0.01 and P=0.05 respectively. The SCA effects for the
shoot length and root biomass were significant (P= 0.02). Both additive and nonadditive gene action were identified to be important for the root length as indicated by
a Baker’s ratio of 0.49. The association of root length to shoot length was significant
(correlation [r] = 0.72).