Evaluation of Phytoextracts Against Pathogens of Black Point Disease of Wheat Grains

INTRODUCTION

In India, wheat occupies the prime position among food crops. It is the second important food crop being next to rice in the world. The whet grains are exposed for a fairly long period during the growth of crops and are easily vulnerable to the attack of fungi as compared to the seeds born in pods or other kinds of fruits. Amongst the various fungi which invade wheat grain in the field, infection by Alternaria alternata and Helminthosporium sativum has been found associated with blackening of the germinal end of wheat grain and causes a disease commonly referred to as ―Black Point‖. In India, this disease is prevalent in almost all the states, where wheat crop is grown (gaur 1986). It causes a significant loss in grain germinability, seedling growth, and nutrient quality of wheat. The different strategies for plant disease control include the use of fungicides, biological control, and cultural practices. In the recent past, plant-based products have been found to possess antifungal, antibacterial, and antiviral properties. The use of phytoextracts has been added advantage of little interference to biological equilibrium and no residual toxicity, hence hold a great promise to manage various diseases (Cook & Baker 1983; Sarvamangla et al 1993). It was, therefore, considered worthwhile to study the efficacy of phytoextracts of 10 wild plants found near wheat fields.

The pathogens of black point disease viz., Alternaria alternata, and Helminthosporium sativum were obtained by plating 100 discolored grams on PDA medium following agar plate technique (ISTA, 1966). The pathogens were purified and maintained in PDA slants. Aqueous extracts of leaves of 10 wild plants viz., Adhatoda vasaca, Azadirachta indica, Arzemone Mexicana, Cassia tora, C. occidentalis, Eucalyptus globus, Sonchus as para, Senebiera Didyma, Solanum nigrum and Tridex sp with 50 ml sterile water by grinding 50-gram leaves and then filtered through the double layer of muslin cloth were obtained these extracts were added to PDA to obtain the desired conclusion and was autoclaved 5mm mycelial disc taken from the periphery of the fresh culture of pathogens was placed in the center of Petri dish and incubated at 28 +- 1 degree C for 8 days B.O.D incubator. The untreated set served as control. After the incubation period, the diameter of the colony was recorded and present inhibition in fungal growth was calculated. Suitable replications were maintained for each treatment as adopted by Sarvamangla et al, (1993).

A perusal of Table 1 indicates that phytoextracts of leaves of 10 plants caused variable inhibition of mycelial growth of 2 test pathogens. However, significant inhibition of mycelial growth was noted in phytoextracts of Azadirachta indica, Eucalyptus globus, Cassia occidentalis, and Adhatoda Masaka. The maximum inhibition was observed with phytoextracts of Azadirachta indica and the minimum inhibition was recorded in the case of Tridex sp. Antifungal activities of phytoextracts have been reported by several workers (Dayaram, 1997, Kumar & Shabana 2002, Singh, 2008 and Ghasolia & Shivpuri, 2008). The plant species having more antifungal activities viz., Azadirachta indica, Eucalyptus globus, Adhatoda Masaka, and Cassia occidentalis are widely available near wheat fields in March when flowering occurs. So, the leaf extracts can be sprayed twice at a 15-day interval to avoid infection of developing grains, which will serve as the cheap and safe management of black point disease of wheat.

The author is highly thankful to the Principal and Head of the Botany Dept. Agra College, Agra for providing facilities and constant encouragement. Also, the author would like to thank Dr. Surender Singh (Retd), it would have not been possible without his guidance and support.

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Assistant Professor, Department of Botany, Agra College, Agra