Experimental induction of amorphous-like plugs in citrus and their possible association with soil factors

Abstract

Two year-old healthy citrus plants were transferred to pots containing soil collected from the vicinity of orange tree roots with decline symptoms and from those of healthy trees. Part of the soil was sterilized before using. After one year, the plants growing in soil from decline - affected trees showed leaf chlorosis even when growing on sterilized soil. After two years, those plants showed blockage of water uptake and translocation in the roots and trunk, while those growing on soil from non-affected trees were normal. Histochemical studies performed on samples obtained from roots and trunk of all plants growing in pots in trio presence of sterilized or non-sterilized soil, collected from the vicinity of plants showing symptoms of decline presented higher proportion of amorphous-like plugs in the xylem vessels in the roots than in the trunk. The higher amount of amorphous-like plugs in trio roots than in trio trunk seems to show that the vessel starts plugging in the roots. These results suggest a possible association of the soil with plug-induction in decaying citrus plants.