Common genetic basis for canopy temperature depression under heat and drought stress associated with optimized root distribution in bread wheat.

R Suzuky Pinto,Matthew P Reynolds

doi:10.1007/s00122-015-2453-9

Abstract

Key message QTL related to cooler canopy temperatures are associated with optimal root distribution whereby roots proliferate at depth under drought or near to surface under hot, irrigated conditions. Previous research using a bread wheat RIL population of the Seri/Babax cross showed that common QTL were associated with cooler canopies under both drought and heat-stressed conditions. A subset of RIL was grown under water-limited and hot-irrigated field environments to test how cooler canopies are related to root development. Eight sisters and the two parents were used in the study with genotypes grouped as COOL or HOT according to their respective QTL for canopy temperature and previous phenotypic data. Root mass production and residual available soil moisture were measured around anthesis at four depth profiles (from 0 to 120 cm depth). When considering different root profiles, there was a clear interaction of QTL with environment. Under water stress, the COOL genotypes showed a deeper root system allowing the extraction of 35 % more water from the 30–90 cm soil profile. The strategy under heat was to concentrate more roots at the surface, in the 0–60 cm soil layer where water was more available from surface irrigation. Since COOL genotypes showed better agronomic performance, it can be concluded that their QTL are associated with more optimal root distribution in accordance with water availability under the respective stresses. The study demonstrates the importance of root development under both water-limited and hot-irrigated environments, and shows a common genetic basis for adaptation to both stresses that appears to be associated with sensitivity of roots to proliferate where water is available in the soil profile.

Highlights

While the focus of most research in plants is on the above ground organs, the radicular system represents a high proportion of the total plant’s mass and energy requirement
In the heat experiments the differences between the two groups were 1.0 and 0.8 °C for CTv and canopy temperature during grainfilling (CTg) (Table 3)
The results showed that under drought, cooler canopy temperatures were associated with genetic gains of % in yield, % in biomass, and 40 % in deep roots, at 30–90 cm and 30–120 cm (Table 3; Fig. 1)

Summary

Introduction

While the focus of most research in plants is on the above ground organs, the radicular system represents a high proportion of the total plant’s mass and energy requirement. A comprehensive understanding of root mechanisms involved in, for example, drought and heat response, are imperative to the effort of increasing adaptation of crops to harsher environments under climate change. Roots have a range of functions including anchorage, mechanical support, nutrient and water uptake, and signaling. Roots are extremely sensitive to water deficit and high temperatures; for example, they show a narrow range of optimum growth temperature compared to other organs (Porter and Gawith 1999). Under high temperature field experiments, root growth was observed to be diminished due to a reduction in the carbon partitioned below ground, and the number, length and diameter of roots are especially affected if the heat occurs during the reproductive stage (Batts et al 1998).

Methods

Results

Discussion

Conclusion