Defensive mechanisms of the selected drought tolerant apple commercial cultivars ‎crossed by morphologies, growth and biochemical traits

Post-drought stress phenotyping and cropping assessments of 93 apple cultivars and genotypes led to individuation of 14 commercials and two drought tolerant genotypes, capable to keep the crop til ripening. Further studies were achieved at post-stress stage. Scion tree vigor components as tree height, shading area, trunk diameter, internode length and thickness, leaf length and width, stock length and diameter, leaf page hair fitness, leaf area index, leaf axis angle, cortex color, stomata number of annual shoots, hair fitness on annual shoot apex to distinct the defense mechanisms of the evolved stable traits were invetigated. The proline and total carbohydrates contents of the leaf samples were measured as well as fruit biochemical traits of pH, TSS and TA of the tolerant and susceptible 'Golden Delicious' and 'Assali'. Positive correlation was found between reduced total photosynthetic area and drought tolerance so that tree vigor was ranked as weak in 12 Cvs, middle in 2 Cvs and only high in 2 Cvs. The tolerant CVs tree height, shading area, trunk diameter, leaf area index, leaf length and width, internode length demonstrated lower values but the annual shoots presented higher rates of leaf stalck length and diameter shoot diameter, and higher hair density of leaf and shoot apex. The mean if internode length, 9/91 mm, was lower in tolerant Cvs than controls as 19.31 mm. The leaf samples of tolerant Cvs had higher proline 1.55 mg/l, total chlorophyll contents of 27.48 than 1.35 and 22.56 related to the controls. The control Cvs showed increased leaf carbohydrates 162.57 mg/l than tolerant Cvs 125.7 mg/l.