WALNUT PLANT SELECTION TO HYPOXIC SOIL RESISTANCE
Walnut (Juglans regia) tree is known to be very sensitive either to drought then to flooding. Of interest is the search of characters and parameters useful to select genotypes and/or phenotypes with the ability to survive in unfavorable conditions.
Walnut trees, J. regia of different provenience, and interspecific hybrids J. regia x J. nigra and J. regia x J. major were subjected to waterlogging when full expansion leaves were reached. Physicochemical measures gave indication of decrease of net CO2 assimilation after 1 day of waterlogging in all genotypes tested. After 3 days, some J. regia varieties trees showed rapid desiccation and lost of all leaves and some plants clearly died. On other hand trees of a selected progeny of J. regia and of hybrids did not shown any visible apparent damaging symptoms till 10–12 days of anoxia stress treatment.
Biochemical analyses of indole-acetic acid, abscisic acid, ethylene and ethanol content in leaves gave no significant difference between control and stress treated plants for the first two compounds, ethylene showed a rise of production that opposite the CO2 assimilation. Ethanol, present in control plants, increased approaching the time of appearance of chlorosis and wilting of leaves.
The data can confirm previous work that walnut trees have a low capacity to survive to soil anaerobiosis, but differences trough J. regia provenance and hybrid plants indicate the potentiality to select genotypes with more stress resistance capacity.