CHARACTERIZATION OF EMBRYOGENIC MANGO CULTURES SELECTED FOR RESISTANCE TO COLLETOTRICHUM-GLOEOSPORIOIDES CULTURE FILTRATE AND PHYTOTOXIN

Embryogenic nucellar cultures of two poly-embryonic mango cultivars, ' Hindi' and 'Carabao', were selected for resistance to the culture filt rate and phytotoxin of a virulent strain of Colletotrichum gloeosporio ides Pent. that was isolated from mango leaves. The cultures were recu rrently selected either with progressively increasing concentrations o f culture filtrate or by continuous challenge with the same concentrat ion of either culture filtrate phytotoxin. Mycelium growth was inhibit ed when the pathogen was cocultured with the selected, resistant embry ogenic cultures. Conditioned plant growth medium containing macerated resistant embryogenic cultures did not inhibit mycelium growth, confir ming that extracellular anti-fungal compounds were involved in the def ense response. Enhanced secretion of chitinase and glucanase was obser ved in the plant growth medium in which resistant embryogenic cultures and regenerated somatic embryos were grown in comparison with the con trols.