RECOVERY AND OSMOTIC ADJUSTMENT OF ADVANCED CYCLES OF MASS SELECTION IN WHEAT

Abstract

In order to evaluate the morphological and physiological changes occurred in wheat Triticum aestivum L. materials in response to mass selection, as well as their recovery ability after drought five genotypes were studied; these included a balanced composite F₂, (CB F₂), two cycles of mass selection with recombination carried out under drought conditions (cycles 2 and 5, SMVS CR2 and SMVS
CR5), and two cycles of mass selection without recombination, also carried out under drought conditions (cycles 3 and 6, SMVS SR3 and SMVS SR6). The genotypes were treated with two levels of moisture: well-watered and drought-stressed; drought stress consisted of two consecutive cycles of drought each one imposed by withholding the water until the permanent wilting point was observed, then water to field capacity was supplied. The variables measured were transpiration rate, water potential and its
components (osmotic and turgor potentials) and also osmotic adjustment. Dry weight of shoot, root and grain were measured, as well as the root/shoot ratio. Results showed that advariced selection cycles under drought, recovered their transpiration rate after
watering them to field capacity, in a higher extent than the original materials. The most advanced seletion cycles (CR5 and SR6) showed a higer ability to adjust themselves osmótically than the CB F₂, and the less advanced selection cycles. With respect to the dry weight of the different organs, no clear tendency among the genotypes was observed.