Estimation of infectivity of different fractions of inocula of various acquired and indigenous VAM fungi at different stages of harvest.

CHARU TYAGI & ALOK ADHOLEYA.

Microbial Biotechnology, TATA Energy Res Inst, Habitat Place, Lodi Road, New Delhi 110003, INDIA,

Sudan grass (Sorghum sudanese L) seedlings were inoculated with a similar number of propagules from different indigenous and acquired VA-mycorrhizal fungi. Harvests were made at 10,20,40,60 and 90 days. Culture substrate were separated at each harvest into the three forms of the inoculum: root bits, crude substrates and root free substrates. Each fraction were checked for its ability to reinfect the same host. The root bit inocula gave the best performance at 40^th day harvest for five out of six inocula tested. The whole inocula and the root less inocula (comprised of spore and mycelia) did best at the end of the cycle. This information on the infectivity of the three inoculant at different stages in the production cycle will help in harvesting efficient and light inoculum.

Key words: VAM, Infectious propagules, Root bit inocula, Harvest stages, Spore inoculum