Effects of long-term selection for kernel oil concentration in KYHO, a high-oil maize population
A high-oil maize (Zea mays L.) (HOM) population, KYHO, was developed across 10 generations by selective breeding. The objectives of this investigation were to evaluate the effects of selection for kernel oil on correlated traits and measure the genetic variance of kernel oil content (KOC). Kernel oil content, kernel protein content (KPC), and kernel starch content (KSC) were estimated by near-infrared reflectance spectroscopy (NIRS); palmitic, stearic, oleic, linoleic, linolenic, and arachidic fatty acids were analyzed by gas chromatography. Also measured at the appropriate time during the growth cycle were plant anthesis (AT), plant height (PH), ear height (EH), 100 kernels weight (KW), and red ear cob ratio (RCR). Sampling and measurement of the various parameters occurred under the same conditions for each generation for three years. Kernel oil content greatly increased from 3.53% in cycle 0 to 12.66% in cycle 10; the predicted selection response per cycle was 1.01 ± 0.05%. The realized heritability (h2R) and broad-sense heritability (h2B) of KOC in KYHO were 0.38 and 0.99 respectively, suggesting significant genetic variability, especially additive variance, across 11 selection cycles. The correlated traits of stearic, oleic, unsaturated fatty acid, and KPC and RCR increased steadily from the original generation to the final cycle (C10), whereas the remaining parameters decreased. There were significant (P ≤ 0.01) genotypic and phenotypic correlations between KOC and all measured traits, with the exception of arachidic acid. Red ear cob ratio was significantly positively correlated with KOC, and increased 7.41% with each 1% KOC increase.