Morphological and physiological stability in two Populus deltoides commercial clones: identification of different acclimation strategies

BONNIN, SEBASTIÁN; FAUSTINO, LAURA INÉS; ALVAREZ, JAVIER; GRACIANO, CORINA

NoviSad

Simposio; IUFRO - VIII International Poplar Symposium; 2022

IUFRO

The stability in morpho-physiological traits influences the capability of Populus spp. genotypes for acclimating to contrasting environmental conditions. In Argentina, Populus deltoides ‘Australiano 129/60’ (A129) is the most widespread genotype in the low-diversed poplar plantations of the Delta del Río Paraná. This clone is a stable genotype that has good yields in different sites. Conversely, Populus deltoides ‘Guayracá INTA’ (GUA) is a genotype obtained few years ago from the Salicaceae breeding program developed by INTA. This new clone is potentially as productive as A129, but it is relatively unknown in its stability and capacity for acclimating to heterogeneous sites. The present study aimed to compare the morpho-physiological stability across 6 different environmental conditions representing a gradient of water and salt soil contents. One of the most common methods to evaluate stability is the regression coefficient bi (derived from a joint linear regression analysis). The comparison was made between GUA and A129 one-year-old plants, growing in 20 L pots under controlled conditions. The regression coefficient bi was calculated for 15 traits: total dry weight increment (TOTALDWI), stem dry weight increment (STEMSWI), leaves dry weight increment (LEAFDWI), roots dry weight increment (ROOTDWI), leaf area (FA), specific leaf area (SLA), stem-roots ratio (SRratio), slenderness index (SI), Dickson quality index (DQI), hydraulic conductivity (kh), specific hydraulic conductivity (ks), leaf hydraulic conductance (Kleaf), maximum stomatal conductance (gsmax), maximum electron transport rate (ETRmax) and chlorophyll content (SPAD). GUA was identified as a genotype similar to A129 with respect to the stability of the STEMDWI, with higher than average daily increment values and a bi index greater than 1. However, clear differences were observed in the bi values of the TOTALDWI and LEAFDWI. The clones were similar in the stability of water-use traits such as kh, ks, and Kleaf, but were completely different in ETRmax stability. While A129 was identified as a stable genotype in terms of ETRmax, GUA was observed as a clone that increases its photosynthetic capacity as growth conditions improve. These differences could be traduced in different above and belowground site occupations because of the variation in biomass partitioning, and in different nitrogen use derived from clonal photosynthetic variability. Both aspects are important to achieve a more diversified forest system in the region, sustaining or improving the level of productivity.