Identification of early and extra-early maturing tropical maize inbred lines resistant to Exserohilum turcicum in sub-Saharan Africa

Alejandro Ortega-Beltran,Abidemi Olutayo Talabi,Ranajit Bandyopadhyay,Richard Olutayo Akinwale,Baffour Badu-Apraku,Morakinyo Abiodun Bamidele Fakorede,Babatope Samuel Ajayo,Faith Ayobami Bankole

doi:10.1016/j.cropro.2020.105386

Alejandro Ortega-Beltran, Abidemi Olutayo Talabi + Show 6 more

Open Access

https://doi.org/10.1016/j.cropro.2020.105386

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Abstract

Northern corn leaf blight (NCLB) incited by the fungus Exserohilum turcicum is a foliar disease that significantly limits maize production and productivity in West and Central Africa (WCA), particularly in the mid-altitudes but during the last decade it has become a menace in lowland agro-ecologies. The most economical and environmentally friendly disease management strategy is the cultivation of maize varieties resistant or tolerant to NCLB. However, no early maturing (EM) and extra-early maturing (EEM) NCLB resistant varieties are commercially available in WCA. One hundred inbred lines each of EM and EEM derived from tropical maize germplasm were inoculated with a virulent isolate of E. turcicum at five locations in Nigeria during the 2017 and 2018 growing seasons. The objective of the study was to identify promising NCLB resistant lines and to investigate inter-relationships among the traits. Analysis of variance revealed highly significant genotype and genotype by environment (G × E) interactions for disease severity, grain yield (GYLD), and other agronomic traits. The average disease severity (TURC) values ranged from 1.9 to 5.8 and 2.9 to 5.7 for the EM and EEM inbred lines, respectively. The levels of reaction of the inbred lines to NCLB ranged from highly resistant to highly susceptible. Stepwise regression analysis showed that ears per plant, ear and plant aspects were significantly influenced by the disease scores. Ears per plant, ear and plant aspects, TURC and GYLD traits were employed to develop a base index (BI) for selecting NCLB resistant inbred lines for hybrid development. TZEI 135 and TZEEI 1 were outstanding in GYLD and also had the highest positive BI values in the EM and EEM inbred lines, respectively. The identification of NCLB resistant lines in this study has set the premise for development of NCLB resistant hybrids for WCA as well as the improvement of tropical maize breeding populations for NCLB resistance.

Highlights

A large proportion of the human population in sub-Saharan Africa (SSA), relies on maize as primary staple food crop
There was a protruded hilum at one end of all conidia, which is characteristic of E. turcicum (Sup plementary Figure 1)
We developed a base index (BI) for selecting early maturing (EM) and extra-early maturing (EEM) inbred lines for high yield potential, resistance to E. turcicum, and desirable agronomic traits

Summary

Introduction

A large proportion of the human population in sub-Saharan Africa (SSA), relies on maize as primary staple food crop. Maize harvested at the dough stage of grain-filling, referred to as green maize, may be roasted or boiled with or without the husk while the immature cooked grains are consumed as a snack or partial meal. A variety of traditional meals are produced with milled dry maize grains (Badu-Apraku and Fakorede, 2017). There is increased preference for maize grains over products of other crops as raw materials for emerging and growing livestock feed and brewery industries (Badu-Apraku et al, 2013; Badu-Apraku and Fakorede, 2017)

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