Combining Ability and Inheritance Nature of Agronomic Traits and Resistance to Pink Stem (Sesamia cretica) and Purple-Lined (Chilo agamemnon) Borers in Maize

Abstract

The pink stem borer (PSB), Sesamia cretica (Lepidoptera: Noctuidae) purple-lined borer (PLB), Chilo agamemnon (Lepidoptera: Crambidae) and European corn borer Ostrinia nubilalis, (Lepidoptera: Crambidae) are considered the most devastating insect pests of maize production in the Mediterranean region. The frequent use of chemical insecticides has resulted in the evolution of resistance to various insect pests as well as the pernicious impact on natural enemies and environmental hazardousness. Therefore, developing resistant and high-yielding hybrids is the best economic and environmental approach to cope with these destructive insects. Accordingly, the objective of the study was to estimate the combining ability of maize inbred lines (ILs), identify promising hybrids, determine gene action controlling agronomic traits and resistance to PSB and PLB, and investigate inter-relationships among evaluated traits. A half-diallel mating design was employed to cross seven diverse maize inbreds to generate 21 F₁ hybrids. The developed F₁ hybrids, alongside high-yielding commercial check hybrid (SC-132), were assessed in field trials for two years under natural infestation. Substantial variations were obtained among the evaluated hybrids for all recorded characteristics. The non-additive gene action was major for grain yield and its contributing traits, while the additive gene action was more important in controlling the inheritance of PSB and PLB resistance. The inbred line IL1 was identified to be a good combiner for earliness and developing short-stature genotypes. Additionally, IL6 and IL7 were recognized as excellent combiners to enhance resistance to PSB, PLB and grain yield. The hybrid combinations IL1×IL6, IL3×IL6, and IL3×IL7 were determined to be excellent specific combiners for resistance to PSB, PLB and grain yield. Strong positive associations were identified among grain yield, its related traits, and resistance to PSB and PLB. This implies their importance as useful traits for indirect selection for improving grain yield. Otherwise, the resistance against PSB and PLB was negatively associated with the silking date, indicating that earliness would be favorable for escaping from the borer's attack. It could be concluded that the inheritance of PSB and PLB resistance can be governed by the additive gene effects, and the IL1×IL6, IL3×IL6, and IL3×IL7 hybrid combinations can be recommended as excellent combiners for resistance to PSB and PLB and good yield.

Keywords: Zea mays; borers resistance; combining ability; high-yielding; insect infestation.

Figure 1

Resistance of the developed 21 F₁ hybrids and the commercial check (SC-132) for purple-lined borer (PLB) and pink stem borer (PSB) resistance.

Figure 2

Dendrogram of the phenotypic distances among 21 F₁ maize hybrids based on the evaluated agronomic traits (a) and corn borers resistance measurements (b).

Figure 3

Biplot of the first two principal components for the evaluated agronomic traits and resistance to corn borers of the evaluated hybrids. DTS: days to 50% silking; PH: plant height; EH: ear height; EL: ear length; ED: ear diameter; NRPE: number of rows per ear; NKPR: number of kernels per row; HKW: hundred kernel weight; GY: grain yield (ton ha ⁻¹); PLB: purple-lined borer; and PSB: pink stem borer resistance.

Figure 4

Daily minimum temperature, maximum temperature, and solar radiation for the two growing seasons.