No abstract

In this study, we investigated the potential of aflatoxin B 1 (AFB1) production by five Aspergillus flavus strains previously isolated from sorghum grains on cereals (barley, maize, rice, wheat and sorghum), oilseeds (peanuts and sesame) and pulses (greengram and horsegram). Five strains of A. flavus were inoculated on all food grains and incubated at 25°C for 7 days; AFB1 was extracted and estimated by enzyme-linked immunosorbent assay. All A. flavus strains produced AFB1 on all food grains ranging from 245.4 to 15 645.2 lg kg )1 . Of the five strains tested, strain Af 003 produced the highest amount of AFB1 on all commodities ranging from 2245.2 to 15 645.2 lg kg )1 . Comparatively, the AFB1 accumulation was high on rice grains ranging from 3125.2 to 15 645.2 lg kg )1 , followed by peanuts ranging from 2206.2 to 12 466.5 lg kg )1 . Less AFB1 accumulation was observed in greengram and sesame seeds ranging from 645.8 to 2245.2 and 245.4 to 2890.6 lg kg )1 , respectively. Our results showed that all food grains tested are susceptible to A. flavus growth and subsequent AFB1 production.

The antifungal activity of aqueous extracts of nine plants viz, Azadirachta indica, Parthenium hysterophorus, Momordica charantia, Allium sativum, Eucalyptus globules, Calotropis procera, Aloe vera, Beta vulgaris and Datura stramonium were assessed in vitro against Fusarium oxysporum f. sp. melongenae, Rhizoctonia solani and Macrophomina phaseolina, the soil borne phytopathogens. The assessment of fungitoxic effect was carried out by using three different concentrations i.e., 5, 10 and 20% against the test fungi, in terms of percentage of mycelial growth inhibition. The extract of A. sativum completely inhibited the mycelial growth of M. phaseolina at all the concentrations. The extracts of D. stramonium and E. globulus inhibited the mycelial growth of R. solani of 72%, and 70.7% respectively at 20% concentration, that of A. sativum, E. globulus and D. stramonium exhibited inhibition percentage of 63.3%, 61.8% and 61.1% respectively at 20% concentration on Fusarium oxysporum f. sp. melongenae. The application of plant extracts for disease management could be less expensive, easily available, non-polluting and eco-friendly.

Field experiments in vertisols of low, medium and high available soil phosphorus status were conducted to study the response of graded levels of P application to sunflower hybrid (KBSH-1). Effect of P to sunflower in increasing yield and yield attributes was more pronounced in low P status soil. Response equations for seed yield of sunflower at an applied P level have been worked out. Nutrient use efficiency and productive efficiency were also computed. Soil available P status was found to vary significantly only in low P status. Critical P level in soil was found to be 20 kg P ha-1 , below which sunflower may respond to phosphorus application.

Studies on one of the protein rich pulses, horsegram (Dolichos biflorus L.) were carried out to know how far these low risk pulses are free from aflatoxin contamination under severe insect infestation in storage. A total of 150 stored seed samples of horsegram were analyzed for the presence of aflatoxins by collecting 25 samples each of undamaged and insect damaged seeds of all the three varieties (PDM-1, PHG-1 and HG-96). More than 33% of insect damaged seed samples were contaminated with aflatoxin B1 and B2, whereas less than 8% of the undamaged seed samples contain only low levels of aflatoxin B2. Higher levels of aflatoxin B1 (up to 130 μg/kg) were reported in insect damaged seed samples of all the three varieties under study. The levels of aflatoxin B2 were always lower than aflatoxin B1 of the corresponding seed samples with insect damage. Aflatoxin B1 was reported in both the undamaged and insect damaged seed samples of all the three varieties of horsegram. It is evident from the varietal response studies that PDM-1 and HG-96 varieties of horsegram are highly vulnerable to aflatoxin contamination whereas, PHG-1 variety is relatively less susceptible to it. In general, insect infestation leads to increase in fungal invasion (including aflatoxigenic fungi) and this further enhances the levels of aflatoxin contamination in horsegram seeds.