LAUSR

Variation in root system architecture (RSA) and morphology are important for improving phosphorus use efficiency (PUE) in wheat. This work aims to analyze the root system architecture and morphology of wheat genotypes to explain their variation in PUE. Two genotypes differing in PUE, RAC875 (P efficient) and Wyalkatchem (P inefficient) were grown in a sandy soil amended with adequate basal nutrients and two P rates (10 and 30 mg P kg−1). RSA traits were measured by freely available software, GiA roots and DIRT, and root hair features were measured using a microscope with an attached camera and LAS v3.6 software. Under low P supply, RAC875 produced greater shoot dry matter (DM) at 24, 27 and 48 days after sowing (DAS), and at maturity, RAC875 also had a higher grain yield at maturity. Enhanced P efficiency (biomass and seed yield at inadequate P supply relative to adequate P supply) was observed more so in RAC875 at all harvest times. P supply affected most RSA traits, with low P leading to reductions in convex hull area (CHA), root surface area, root volume, total root length and root tip number. RAC875 produced significantly greater CHA than Wyalkatchem at low P supply while Wyalkatchem had significantly larger CHA than RAC875 when P was non-limiting. RAC875 also had greater root hair density (RHD) than Wyalkatchem at low P level, but no difference was observed at adequate P. When grown under low P supply, a greater CHA and RHD in RAC875 were likely to contribute to improved P uptake, resulting in its higher shoot biomass and grain yield.