Abstract
Acidic soils hamper maize (Zea mays L.) production, causing yield losses of up to 69%. Low pH acidic soils can lead to aluminum (Al), manganese (Mn), or iron (Fe) toxicities. Genetic variability for tolerance to low soil pH exists among maize genotypes, which can be exploited in developing high-yielding acid-tolerant maize genotypes. In this paper, we review some of the most recent applications of conventional and molecular breeding approaches for improving maize yield under acidic soils. The gaps in breeding maize for tolerance to low soil pH are highlighted and an emphasis is placed on promoting the adoption of the numerous existing acid soil-tolerant genotypes. While progress has been made in breeding for tolerance to Al toxicity, little has been done on Mn and Fe toxicities. More research inputs are therefore required in: (1) developing screening methods for tolerance to manganese and iron toxicities; (2) elucidating the mechanisms of maize tolerance to Mn and Fe toxicities; and, (3) identifying the quantitative trait loci (QTL) responsible for Mn and Fe tolerance in maize cultivars. There is also a need to raise farmers’ and other stakeholders’ awareness of the problem of Al, Mn, and Fe soil toxicities to improve the adoption rate of the available acid-tolerant maize genotypes. Maize breeders should work more closely with farmers at the early stages of the release process of a new variety to facilitate its adoption level. Researchers are encouraged to strengthen their collaboration and exchange low soil pH-tolerant maize germplasm.
Highlights
Maize (Zea mays L.) is among the most widely grown crops in the world after rice (Oriza sativa L.)and wheat (Triticum aestivum L.)
The identification of quantitative trait loci (QTL) linked to secondary traits correlated with yield performance under conditions of either Fe or Mn toxicity could further enhance the efficiency of maize breeding for tolerance to low soil potential of hydrogen (pH)
QTL associated with secondary traits such as days to silking, anthesis-silking interval, and stay green characteristic under stressed environments [142,143] could have the potential to be utilized as indirect molecular predictors of performance of plants exposed to Fe and Mn toxicities
Summary
Maize (Zea mays L.) is among the most widely grown crops in the world after rice (Oriza sativa L.). Improving grain yield under acidic soil conditions is a major objective of maize breeding programs in many regions of the world. Combining ability analyses assess the potential value of inbred lines and identify the nature of gene action controlling various quantitative characters This information is essential for maize breeding focusing on developing hybrids, synthetics, and improved open pollinated cultivars [16] under low soil pH. This paper reviews maize improvement for tolerance to acidic soils using conventional and molecular technologies, with a special focus on the experimentations that have improved the acid tolerance of some maize genotypes It reviews the genetic, physiological, and biochemical mechanisms by which plants tolerate low soil pH stress. The intensification of research efforts to fill the identified gaps in information could improve on the efforts already made in the development of high-yielding and high-quality acid-tolerant maize cultivars
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