STUDIES ON THE EFFECT OF PGPB ON CITRUS ROOTSTOCK UNDER TWO TYPES OF SOIL CONDITION

Abstract

Citrus one of the most economically important crops in Egypt, efforts are always put to increase the citrus cultivated lands, especially reclaimed lands. In the presented study, 19 isolates were isolated from the rhizosphere area of sandy soil cultivated with citrus and 15 isolates were isolated from the rhizosphere area of calcareous soil. These isolates possess the ability of producing ACC-deaminase, IAA, GA and sidrophore. They also possess the ability of dissolving phosphate and fixing atmospheric nitrogen. The most potent isolate from each soil were identified and their toxicity was evaluated using MTT assay. The sandy soil isolate was Stenotrophomonas maltophilia, which was the less toxic and safer isolate to use in agricultural applications. The calcareous soil isolate was Enterobacter cowanii, which, due to its higher toxicity level, is preferred to use in nonedible crops like decorative and wood forest plantations only. In vivo, the effects of Stenotrophomonas maltophilia were tested on two types of seed rootstock (Volcamariana and sour orange) in both the sandy soil and calcareous soil. The results revealed that this isolate was successful in improving the cultivate parameters in both types of treated soil. As for the treated soils, the shoot length of both types of soil was improved relatively equally, while the leaves number and the root length were better in the sandy soil compared to the calcareous soil.