| Sumario: | High yielding and stable early maturing provitamin A (PVA) maize hybrids with
combined stresses (drought and heat and Striga) tolerance are needed to combat
malnutrition, low yield and insecurity in sub-Sahara Africa (SSA). To address this
need, PVA, PVA-QPM (quality protein maize) inbred lines with Striga and drought
tolerant genetic make-up were developed through the massive effort of the
International Institute of Tropical Agriculture Maize Improvement Program (IITAMIP)
for its hybrid development and commercialization. This study was designed to
(i) to develop early maturing PVA single cross hybrids that are tolerant to multiple
stresses (combined drought and heat stress and Striga infestation), (ii) classify the set
of inbred lines into heterotic groups, (iii) assess the levels of resistance/tolerance of
inbred lines to Striga infestation and combined drought and heat stress tolerance in
selected early maturing PVA inbred lines, (iv) identify inbred and hybrid testers, and
(v) Determine the performance and yield stability of hybrids across contrasting
environments. A panel of two-hundred and ten single-cross hybrids were generated
from 50 selected early maturing PVA inbred lines using the Line x tester mating
design crossed to four commercial PVA early maturing inbred testers plus six single
crosses derived from intermating the four testers, plus four commercial checks. 250
PVA, PVA-QPM early maturing maize inbred lines plus six commercial inbred
checks were evaluated under Striga infestation, combined drought and heat stress
and optimal environments in Nigeria from 2019 to 2021 growing seasons. Days to
50 % anthesis and silking, plant and ear heights, plant and ear aspects
complemented grain yield of the inbred lines. These inbred lines are used in their
hybrid combination to produce outstanding PVA hybrids. General combining
ability (GCA) and specific combining ability (SCA) mean squares were significant
for grain yield and other traits indicating that additive and non-additive gene effects
were important in the control of the inheritance of grain yield and other traits across
the contrasting environments. Using the base indices as criteria for selection, 93
Striga resistant, 82 combined drought and heat tolerant and 36 inbred lines that
combined resistance/tolerance to both stresses were identified. TZEIOR 172 x
TZEIOR 108 and TZEIOR 202 x TZEI 25 has been identified as highest yielding
and most stable hybrids across the three contrasting environments. TZEIOR 21 x
TZEI 25 was identified as the preferred hybrid for Striga infested environments.
TZEIOR 202 x TZEIOR 164 was identified as the preferred hybrid under combined
drought and heat stress. The inbred line such as TZEIOR 201 and TZEIOR 202
recorded significantly positive GCA effects for grain yield across the contrasting
environments could be useful for developing Striga tolerant and/or combined
drought and heat tolerant hybrids and synthetic.
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