Estudio de parámetros hídricos foliares en trigo (Triticum aestivum L.) y su uso en selección de genotipos resistentes a sequía

Abstract

The leaf water parameters ψs (solute potential), RWC (relative water content) and OA (osmotic adjustment) characterize the response of plants to water stress and presumably allow the identification of better adapted genotypes. These parameters, however, are highly influenced by the environment what makes their analysis difficult. In this work we hypothesize that it is possible to characterize and select drought resistant wheat genotypes based on the field value of the leaf water parameters using the appropriate analytical techniques. Thirty one wheat (Triticum aestivum L.) genotypes were grown in two field trials, one irrigated and one non-irrigated that received 218.3 mm of winter rain. The statistical design was a randomized complete block with two replicates. Between 77 and 121 days after emergence (DC 41 to DC 77), five samplings of relative water content (RWC) and solute potential of hydrated flag leaves (ψsh) were made in each replication of each trial (10 observations per trial). The replicates were sampled in alternate days with a 24-h interval between 12:00 and 14:00 h. During harvest, biomass, yield and yield components were measured. The observations both of RWC and ψsh were highly affected by environmental factors (ca. 80 % of the sum of squares) while they were not correlated between replications within each trial. For analysis purpose, each observation was considered as independent (10 observations for each leaf water parameter per genotype) and linear regressions were made of each leaf water parameter value of each genotype on the mean of all the genotypes at the time of sampling. Each genotype was characterized by its average value of leaf water parameter and the regression slope. The osmotic adjustment (OA) of each genotype was estimated by utilizing different methodologies proposed in the literature. Two genotype selections were made, one using the slope and average of ψsh, RWC and OA, and one that considered the slope and average of ψsh and RWC. The order of the genotypes of both selection criteria were then correlated with orders established by the three methods of calculation of OA, this established that the order that considers the slope and the average of ψsh, RWC and OA, correlated with the order established by the three methodologies to calculate OA. This points out that it is possible to use the slope criteria in the selection of genotypes that adjust osmotically. Leaf water parameters RWC, ψsh and OA were not correlated to yield. The slope of ψsh was negatively related to yield pointing to a survival role of OA. It is concluded that it is possible to select drought resistant genotypes using the mean and slope of ψsh, RWC and OA by removing part of the environmental noise.