Interrelations among early vigor, flowering time, physiological maturity, and grain yield in tropical maize (Zea mays L.) under multiple abiotic stresses.
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We studied the interrelation among time to anthesis, physiological maturity, and grain yield in tropical maize (Zea mays L.) facing terminal drought and nitrogen deficiency. Sixty-one hybrids were grown under optimum, nitrogen deficient (LN), and drought-stressed (DS) conditions. Grain yield was negatively correlated with time to anthesis under DS (r = -0.4*) and positively correlated with the grain-filling period (optimum: r = 0.54**; LN: r = 0.61***; DS: r = 0.69***) across treatments. These results suggest that coselecting for grain yield, early anthesis, and a long grain-filling period within a maturity group could help increase grain yield. A second experiment involving eight hybrids contrasting for grain yield and time to anthesis was conducted under similar stresses to identify secondary traits associated with grain yield and time to physiological maturity: early vigor (measured as normalized differential vegetation index) correlated with grain yield under optimum (r = 0.77*) and LN conditions (r = 0.72*). Time to physiological maturity was associated with senescence across treatments (optimum: r = -0.97***; LN: r = -0.82*; DS: r = -0.81*), making senescence suitable to approximate physiological maturity. Repeatability for secondary traits (r(2) = 0.79 on average) was higher than for grain yield (r(2) = 0.68) across treatments. In light of the association of these traits with grain yield and their high repeatability, grain yield could be increased within a maturity group by simultaneously selecting for high normalized differential vegetation index during vegetative growth and early anthesis and low senescence during grain filling, in addition to grain yield.
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