Efficacy of VAM ( Vesicular – Arbuscular Mycorrhizal ) on Red rot Disease in Sugarcane.

Red Rot Disease 

Sugarcane plants

Glomus Mosseae

Glomus fasciculatum

Colletotrichum falcatum

Efficacy of  VAM  ( Vesicular – Arbuscular  Mycorrhizal ) on Red rot Disease in Sugarcane.

( My dissertation work for the award of the degree M.Sc in Microbiology.)

In this work , efficacy of VAM  ( Vesicular – Arbuscular  Mycorrhizal ) on the red rot disease in sugarcane  ( Saccharum officinarum L ) was studied. In the present study , the sugarcane plants were taken as host plants. Glomus mosseae and Glomus fasciculatum were taken as mycorrhizal members .  Colletotrichum falcatum , causative agent of red rot disease , was taken as a pathogen.  The mycorrhizal members were inoculated individually and also in combination with the pathogen. Some of the plant products like phenol ,  ortho dihydric  phenol , peroxidase , catalase , phenol oxidase and ascorbic acid oxidase  which are involved in the defense mechanism were analyzed .

Red rot of sugarcane , a seed – piece transmissible fungal disorder , caused by colletotrichum falcatum , is the most serious disease in India (Agnihotri , 1990 ).  The disease has been responsible for phasing out of numerous commercial sugarcane genotype like CO 213 , CO 299 , CO 312 , CO 313 etc. ( S.pandey and V.P. Agnihotri , 1996 ) .

In the present analysis , it was observed Glomus fasciculatum  induced more phenol production when the sugarcane was infected by Collectotrichum falcatum. The same Glomus fasciculatum was responsible for increased production of ortho – dihydric phenol in sugarcane following the infection of collectotrichum falcatum. It has been observed that certain common phenolic compounds ( toxic to pathogens ) are produced and accumulate at faster rate after infection. Accumulation of phenols and phytoalexins in VAM plants has been reported ( Krishna and Bagyaraj , 1984; Morandi et al 1984 ) which have been found in tissues of variety of plants during pathogenesis  (Vidhya sekaran 1988).

In the present analysis , increased level of ascorbic acid oxidase activity was observed in Glomus mosseae treatment than the other treatments. Both catalase and peroxidase activities were observed in higher level in the Glomus fasciculatuom treated sugarcane platns. Similarly the phenol oxidase activity was also very high in the treatment of Glomus fasciculatum inoculated after the inoculation of colletotrichum falcatum.

The VAM fungi are well known to bring about physiological changes in plants via increasing various enzymatic activities ( Gianinazz et al 1991 ).

The increased peroxidase activity by VAM fungi may be due to VAM inoculation also resulted in increased activity of phenol oxidase enzyme. This increased phenol oxidase activity might be responsible for increased phenolic contents in the plants.   Peroxidase and phenol oxidase are important enzyme of the defence mechanism of plants against pathogens. Both these enzymes are involves in the oxidation of phenolic components into quinines , which are toxic to the pathogen ( Nishimathur , 1995 ).

The present investigation once again proved that in a way VAM is involved in the resistance mechanism of plants. Both Glomus mosseae and  Glomus fasciculatum  are involved in the enhancement of defence mechanism against red rot disease. But Glomus fasciculatum induces somewhat better response over Glomus mosseae. 

Note: Pictures are taken from internet.