Abstract:
Maize landrace accessions constitute an invaluable gene pool of unexplored alleles that
can be harnessed to mitigate the challenges of the narrowing genetic base, declined genetic gains,
and reduced resilience to abiotic stress in modern varieties developed from repeated recycling of
few superior breeding lines. The objective of this study was to identify extra-early maize landraces
that express tolerance to drought and/or heat stress and maintain high grain yield (GY) with other
desirable agronomic/morpho-physiological traits. Field experiments were carried out over two years
on 66 extra-early maturing maize landraces and six drought and/or heat-tolerant populations under
drought stress (DS), heat stress (HS), combined both stresses (DSHS), and non-stress (NS) conditions
as a control. Wide variations were observed across the accessions for measured traits under each stress,
demonstrating the existence of substantial natural variation for tolerance to the abiotic stresses in the
maize accessions. Performance under DS was predictive of yield potential under DSHS, but tolerance
to HS was independent of tolerance to DS and DSHS. The accessions displayed greater tolerance
to HS (23% yield loss) relative to DS (49% yield loss) and DSHS (yield loss = 58%). Accessions
TZm-1162, TZm-1167, TZm-1472, and TZm-1508 showed particularly good adaptation to the three
stresses. These landrace accessions should be further explored to identify the genes underlying their
high tolerance and they could be exploited in maize breeding as a resource for broadening the genetic
base and increasing the abiotic stress resilience of elite maize varieties.
