Identification of contrasting tropical popcorn inbreds for studying aluminum toxicity tolerance inheritance

Genetic improvement of crops is an essential approach to overcome the aluminum (Al) toxicity in acidic soils. The objectives of this study were to identify contrasting popcorn inbred lines with respect to Al tolerance and investigate its genetic control. Using a complete randomized block design, three sequential experiments were performed that assessed 18, 10, and 2 inbred lines growing in the presence and absence of Al. The inbreds were assessed for relative root growth (RRG), hematoxylin staining, Al content, and external root morphology. Then, the two most contrasting inbreds were crossed and jointly assessed with four derived generations in a fourth trial in a complete randomized block design. The plants were assessed for relative and net root length. The inbred 11–60 had the least RRG (0.02 and 0.06), the greatest accumulation of Al (1660.3 μg/g), and strong blue staining of the root tips with intense epidermal degradation. The inbred 11–133 had the most RRG (0.15–0.37) and the least hematoxylin staining, Al accumulation (926.4 μg/g), and root inhibition in the root tips, associated with no damages on root apices. Dominance effect contributed negatively with all Al-tolerance indexes, although in general, the average degree of dominance indicated partial dominance. The dominance × dominance effects contributed to increasing relative root length, whereas additive × additive effects increased net lateral root length. The individual narrow-sense heritabilities were high, ranging from 49.0 to 66.0%. Based in the results, recurrent selection based on progeny and hybrid breeding are recommended for developing Al-tolerant populations.