Abstract

Despite advances in winter wheat breeding, root traits and root biological activity remain poorly understood and scarcely considered in breeding programs because the extraction of root systems is often considered complex, time-consuming, and labor-intensive. Knowing and improving root traits and soil chemical conditions could increase the efficiency of agrochemical applications and nutrient uptake by wheat. The objective of this research was to study and compare the rhizosphere biological activity as well as the root and aerial development with respect to phosphorus availability of different winter wheat varieties released in Chile between 1965 and 2020, grown under field conditions in an Andisol. Fourteen different winter wheat varieties were planted. A randomized complete block design was established, with four replications per variety. Soil samples were taken up to 60-cm depth from complete root systems at three different phenological stages: tillering, anthesis, and maturity. Rhizosphere biological activity, root morphology and physiology, and colonization by arbuscular mycorrhizae were measured. Mycorrhizal colonization reached 7% up to 20-cm root depth and 63% at a depth of 20-40 cm. Tillering presented the highest microbial activity, with Laurel (1987) being significantly higher. The highest enzyme activity was observed at anthesis, with Pionero (2013) being significantly higher. Root exuded mainly succinate, being 76% higher than the other carboxylates. Tukan (1993) presented the highest total exudation (57%), while Chevignon (2020) had longest root length (460 cm). Mycorrhizal colonization was inversely proportional to phosphorus levels. The varieties showed higher microbial and enzymatic activity until anthesis. No trend toward reduced root morphology and physiology or rhizosphere biological activity was observed in relation to the release year.