Rooting Ability of Eucalyptus dunnii Maiden Mini-Cuttings Is Conditioned by Stock Plant Nighttime Temperature

TL;DR

Lower nighttime temperatures in stock plants reduce rooting success in Eucalyptus dunnii cuttings, affecting commercial propagation.

Contribution

The study reveals how stock plant nighttime temperature affects rooting through physiological and transcriptomic changes in Eucalyptus dunnii.

Findings

Rooting significantly decreased with lower nighttime temperatures, especially in clone B.

Cold nights reduced soluble carbohydrates and foliar nutrients in cuttings.

Cold temperatures altered auxin-related gene expression, affecting rooting processes.

Abstract

Clonal propagation often must incorporate heaters to warm stock plants and stabilize growth. This study investigates the impact that different temperature regimes for stock plants have on the rooting capacity of mini-cuttings derived therefrom. Experiments were conducted in growth chambers using two clones of Eucalyptus dunnii Maiden, with clone A’s rooting being moderately better that that of clone B in commercial production. Root primordia differentiation and elongation were faster in clone A than clone B. Stock plants were maintained for one month under two temperature conditions: Δ0 (26/26 °C day/night) and Δ10 (26/16 °C). The main results indicate that rooting significantly decreased with the reduction in nocturnal temperature. Clone A exhibited a 38% reduction in rooting, whereas clone B showed a more pronounced decrease of 65%. In cold nights, soluble carbohydrates at the cutting bases dropped by approximately 25% considering both clones, and overall foliar nutrients also decreased. Cutting base transcript profiles revealed that cold nights decreased the expression of efflux auxin transporter PIN1, increased expression of auxin catabolism-related enzyme DAO, and that expression of auxin nuclear receptor TIR1 remained stable. Fine management of clonal gardens by adjusting thermal conditions can optimize the physiological status of donor plants and enhance the rooting potential and establishment of the derived cuttings.

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