Abstract:
Aluminum (Al) toxicity on acid soils adversely afects maize yields, which can be overcome by
combining soil amendments with genetic tolerance. In maize, ZmMATE1 confers Al tolerance via Al activated citrate release, whereby citrate forms non-toxic complexes with Al3+ in the rhizosphere.
Here, we investigated Al tolerance mechanisms in maize germplasm originated from Kenya based on
quantitative trait loci (QTL) mapping. Five QTLs and four epistatic interactions explained ~51% of the
phenotypic variation for Al tolerance. The lack of Al tolerance QTL on chromosome 6 and the much
lower expression of ZmMATE1 in both Kenyan lines than in Cateto Al237, which donates the superior
allele of ZmMATE1, strongly indicate that this gene does not play a signifcant role in Al tolerance in
neither parent. In turn, maize homologs to genes previously implicated in Al tolerance in other species,
ZmNrat1, ZmMATE3, ZmWRKY and ZmART1, co-localized with Al tolerance QTL and were more
highly expressed in the parent that donate favorable QTL alleles. However, these candidate genes will
require further studies for functional validation on maize Al tolerance. The existence of Al tolerance
mechanisms independent from ZmMATE1 suggests it is possible to develop highly Al tolerant cultivars
by pyramiding complementary Al tolerance genes in maize.
