New fungicide is eco benign

TWO ISRAELI scientists say by pitting fungus against fungus, they have come up with an environmentally benign pesticide. A B Oppenheim and Ilan Chet of the Hebrew University in Jerusalem have found fungal enzymes called chitinases break down newly synthesised chitin, a major component of the cell wall of most fungi (Trends in Biotechnology, Vol 10, No 11).

Chitinases, which act as natural fungicides, are also produced in small quantities by bacteria and, in addition, chitinase-coding genes from rice, tobacco, cucumber and several microorganisms have been isolated. Chitinases can be introduced into irrigation water or incorporated as a coating around the seed to protect germinating seedlings. Scientists are trying to get genetically engineered rhizosphere bacteria found in the plant-root region of the soil to secrete chitinase. They are also trying to induce plants to manufacture the enzyme themselves by incorporating chitinase-coding genes obtained from another plant or microorganism.

Researchers have also constructed transgenic (genetically engineered) tobacco plants containing bean chitinase genes and found them more resistant than ordinary plants to a soil-borne fungus called Rhizoctonia solani.

Meanwhile, the New Scientist (Vol 136, No 1850) reports scientists have found the humble toadstool is a potent source for compounds effective against a whole range of fungal plant diseases, including some that are resistant to normal fungicides.

ICI in UK and BASF in Germany have derived synthetic fungicides similar to the compounds produced by toadstools. These compounds penetrate the spores of the fungi and disrupt the energy mechanism in fungal cells.

The BASF fungicide acts against many fungal diseases including scab in apples and pears and powdery mildew in apples, vines and sugar beet. The ICI product is effective against fungal diseases that affect barley and wheat. It also protects rice from blast and sheath blight, two major problems for rice farmers.