Drought-driven Changes in Root Crown Architecture of Maize NILs

Plastic root traits that enhance the speed and effectiveness of soil colonization would be a winning strategy under drought. Such root architecture characteristics (i.e. root angle, root area, etc.) may favour soil resources exploration and acquisition. Therefore, understanding how roots respond to stress is important for improving crop productivity. The aim of this study was to identify possible rooting differences and their importance on the adaptive mechanisms to drought of two maize NIL`s (94-6-1-6 and 159-7-2-1) when compared to their parental line (B73). Sixteen rhizotrons one cubic meter capacity were installed under a prefabricated structure where soil moisture was precisely maintained at 12% and 23% (field capacity) in the drought and well-watered treatments, respectively. Maize NIL`s 94-6-1-6 was compared to B73 in 2014 while 159-7-2-1 was evaluated in 2015. In each case treatments were started at 40 days after sowing and morpho-physiological characteristics at canopy and root levels were evaluated. Even though the NIL`s studied here differentiate only for a small portion of their genomes it was evidenced contrasting morpho-physiological adaptations to drought. The 159-7-2-1 NIL closely followed the drought induced decrements showed by B73 in root crown characteristics (i.e. crown biomass, root angle opening, crown area) and increased WUE, suggesting a decreased uptake capacity and probably an optimized allocation of resources. On the other hand, the 94-6-1-6 NIL did not show any root crown morphological or WUE modifications due to drought while biomass productivity losses were somehow less affected than in B73. Such genotypic diversity in root architecture plasticity and water use could results in the introduction of efficient resource acquisition traits, however, the functional utility of developing an expanded lateral or a narrower deeper root system still need to be further evaluated since the morpho-physiological trait adaptations were not necessarily translated in largely mitigated productivity losses.

Acknowledgments: This study was funded by the Water4Crops – EU project, KBBE.2012.3.5-03.