Quantifying variations in rhizosheath and root system phenotypes of landraces and improved varieties of juvenile maize

Rhizosheath and root system architecture (RSA) traits can provide insights into the capacity of a crop to exploit and acquire resources from the soil. This paper employed a rapid but simple screening and phenotyping approach to quantify the differences between selected maize landraces and improved varieties in terms of their rhizosheath and RSA characteristics at the seedling stage. Five maize landraces and thirteen improved varieties (eleven open-pollinated varieties and two hybrids, released in Ghana over the period 1984-2012) were used. Seeds were sown in nursery polybags, with two watering regimes (30% and 70% field capacity). Harvesting and screening for rhizosheath and RSA characteristics were done 7 days after sowing. The results showed that the improved varieties have superior RSA and rhizosheath characteristics compared to the landraces. The improved varieties were superior in shoot biomass, total root length, number of seminal roots, root hair length, and rhizosheath mass. The landraces were superior in terms of root hair density and root biomass. The improved varieties have similar RSA and rhizosheath characteristics independent of the era or period of release. Whilst rhizosheaths were partly explained by either root hair length or root hair density, denser root hairs seemed to compensate for shorter root hair in some genotypes. It is concluded that, at the juvenile stage, landraces and improved varieties of maize have significantly different rhizosheath and RSA characteristics. Yield advantages of improved varieties over that of locally cultivated maize landraces could be attributed to superior RSA and rhizosheath traits of the improved maize varieties. The approach adopted in this study can be useful for rapidly screening cereals at the juvenile stage for their RSA and rhizosheath characteristics.