A new method of propagation of arbuscular mycorrhizal fungi in field cropped sesame (Sesamum indicum L.)

Abstract

Though arbuscular mycorrhizal (AM) fungi are indigenous to agricultural soils, their beneficial effects to host plants could be further improved by inoculation with efficient species. The method of AM propagation described in the present study uses oil cake as a supporting medium for the simultaneous delivery of sesame seeds and AM inoculum to the field. Experiment was conducted in a farmer’s field located at Avoor, Kerala, India where sesame was cultivated as a winter crop in rice fallows. Oil cake entrapped with sesame seeds (var. Tilatara) and AM fungus (Funneliformis dimorphicus) inoculum was prepared by thoroughly mixing sterilized coconut cake and neem cake (5:1 v/v), surface sterilized sesame seeds and sterilized spore sieving of F. dimorphicus from a pot culture in a 10% solution of a polysaccharide gum obtained from the seeds of Strychnos potatorum L. Entire mix was moulded into 2.5 cm cubes (ca. 5g) containing approximately 25–30 seeds and 200–300 spores cube−1 and shade dried before application. The cubes were broadcast @ 600 kg ha−1 in inoculated treatments. In uninoculated treatments, the oil cake cubes devoid of the fungal component was used. Harvested root samples from the inoculated treatments showed a high frequency (%F) and intensity (%M) of colonization by AM fungi as well as frequency of vesicles (%V) and arbuscules (%A) compared to uninoculated control. The growth (root length, shoot length and leaf area) and yield characters (pod number, seed number, seed weight and oil content) of sesame plants were significantly (p=0.05) improved under the present method of AM propagation indicating its viability under field condition.