Maize straw mulching with uniconazole application increases the tillering capacity and grain yield of dryland winter wheat (Triticum aestivum L.)

Abstract

Improvements in wheat tillering in dry-land farming systems can be achieved by reducing soil water loss by straw mulching and enhancing the capability of wheat roots to capture soil water and N. However, the effects of the application of maize straw mulching in combination with uniconazole application on wheat tillering is not yet investigated. Field experiments were conducted during 2017–2018 (dry, 167 mm) and 2018–2019 (favorable, 222 mm) to investigate the combined effects of uniconazole (0 and 10 mg kg-1) and maize straw mulching (0 and 7500 kg ha-1) on soil water and root distribution, phytohormone signal transduction, total N uptake, plant N nutrition, tillering capability, and the expression of critical genes and metabolites in response to wheat tillering. Compared with no mulch control, straw mulching combined with uniconazole application increased soil moisture content and root length in the 0–20 cm soil layer and thereby increased total N uptake. Owing to allometric increases in aboveground N content and plant dry mass, uniconazole application combined with straw mulching increased the dry mass per kg N uptake and N nutrition index in the tillering and stem extension stages. Improved N nutrition index led to higher tiller emergence rate and tiller occurrence rate of first primary tillers and thus increased the number of fertile spikes and grain yield. Multi-omics integration analysis revealed that the increased tillering capability was associated with abscisic acid and gibberellic acid-mediated phenylpropanoid biosynthesis and glycerophospholipid metabolism because of their critical roles in lignin biosynthesis and the maintenance of cell membrane integrity in tiller node cells. The collective results indicate that maize straw mulching combined with uniconazole application improved the capability of wheat roots to capture soil moisture and N in addition to increasing lignin biosynthesis, ultimately enhancing tillering capability and grain yield of dryland winter wheat.