EFFECT OF AUXIN TREATMENT AND SUBSTRATE NATURE ON IN VITRO ROOTING AND ESTABLISHMENT IN SOIL OF CITRUS PLANTLETS

Abstract

In order to stimulate in vitro rooting and acclimatization of micrografted citrus plants, studies were performed to test the effect of substrate and auxin treatment on in vitro rooting and define techniques for good establishment in soil. In MS medium, liquid or solidified with agar, 2.5% and 5% of the plantlets respectively developed lateral roots. In a peat-perlite (1:1) mixture, soaked with MS solution, 37.5% of the plants formed lateral roots. Dipping the plantlets into a concentrated solution of IBA (10 g l -1 ) for some seconds, just before putting them into culture tubes, stimulated the development of lateral roots in 68% of the plants and favoured the formation of a good secondary root system in 25% of the plants. During acclimatization several potting mixes evaluated: sand, peat, sand-perlite (1:1), peat-perlite (1:1) and a soil mixture (soil-manure-peat, 1:1:1) as a control. On the soil mixture 12.5% of the plants died and those that survived formed a poor root system. The plants grown on sand, peat, sand-perlite and especially those on peat-perlite, developed a good root system. Much better results were obtained when the plants were dipped, just before their planting, in a concentrated solution of IBA (10 g l -1 ). One hundred percent of these plants were well established in the soil and developed a rich secondary root system.