A PRELIMINARY REPORT OF STUDY ON CITRUS MYCORRHIZAL FUNGI IN CHINA
Tang Zhenyao Zhang Yunxiu Wan Renxiu (Citrus Research Institute of Chinese Academy of Agricultural Science)
Two citrus mycorrhizal fungi, found in China, were named C C-l and C C-2 for the present. According to microscopical anatomy observation and pot inoculation experiments, both of them belong to Phytomycetus endophytic fungi and are of highly distinctive vesicular-arbuscular type mycorrhizal in associa-tion with citrus. C C-l possesses the characteristics of producing plenty of ve-sicles more than C C-2 and forming arbuscles in the parenchyma cells of root cortex. Hyphae of C C-l extend into rhizosphere soil to enlarge the absorptive area of roots and hyphae tip forms knotty microverru. In sterilized soil of pot culture, seedlings of seven citrus cultivars were inoculated with these two fungi respectively. Although most seedlings had been infected, yet the degree of mycorrhizal infection varied in different citrus cultivars. The best combinations were 'Glorious' orange (Citrus senensis) with C C-l and rough lemon (Citrus jambihiri) with C C-2. The percentage of their infection was about 70% and the lowest percentage was the trifoliate orange with these two fungi. Through the experimental period, mycorrhizae were consistently absent from control seedlings. Infection of these mycorrhizal fungi boosted the growth of citrus seedlings. Top growth of orange was increased as much as 2-fold than that of control seedlings. And the stem length of rough lemon infected with C C-2 was increased as much as 2.8-fold than that of control. There is a wide range of dependency on C C-l for growth of the seven citrus cultivars. Mycorrhizal dependency and root-scion ratio were discussed.