MYCORRHIZAL DEPENDENCY OF SOUR ORANGE IN RELATION TO PHOSPHORUS AND ZINC NUTRITION

ABSTRACT

Citrus-growing areas in the Çukurova Region (Eastern Mediterranean) show a rapid increase since major field crops in the region are being shifted to the Southeast Anatolia of Turkey. The area is very productive, however, most of the soils have very low plant available nutrients, such as phosphorus (P), zinc (Zn), iron (Fe), and manganese (Mn). This research was undertaken to find out whether citrus plants are dependent on mycorrhiza in relation to P and Zn nutrition. Seedlings of sour orange (Citrus aurantium L.) were grown in a silty soil (Çanakç soil series (Typic Xerofluvents)) low in P and inoculated with Glomus clarum and fertilized with 3 levels of P (0, 100, and 200 ppm) and 3 levels of Zn (0, 2.5, and 5 ppm) in 3 kg soil. Irrespective of P and Zn treatments, mycorrhizal inoculation increased shoot and root dry weight more than tenfold compared to the non-inoculated plants. Since native indigenous mycorrhizal spores were eliminated due to soil sterilization, strongly mycorrhizal dependent sour orange (Citrus aurantium L.) seedlings were stunned and not responded to the P and Zn supply in non-mycorrhizal inoculated soils. The results revealed that G. clarum inoculation significantly increased plant P, Zn, and Cu uptake. The G. clarum inoculated plants had less N, Fe, and Mn concentration than non-inoculated plants. The results obtained showed that sour orange is strongly mycorrhizal dependent (MD). Nevertheless, with increasing P and Zn supply, mycorrhizal dependency was gradually decreased. The decrease in mycorrhizal dependency was more pronounced for P requirement rather than Zn requirement.

ACKNOWLEDGMENTS

We thank Prof. Dr. I. Çakmak for critically reading the manuscript and making suggestions for improvement.