Biochemical and environmental factor responsible for chilli anthracnose and its management

Abstract

Among thirty chilli varieties/advance lines screened against Colletotrichum capsici, no cultivar exhibited immune reaction. Eighteen varieties expressed resistant response with disease rating of 2, while seven cultivars showed moderately resistant reaction with rating of 3. Two varieties displayed susceptible reaction with rating of 4 against anthracnose. Remaining three cultivars appeared to be highly susceptible with maximum disease rating of 5 towards anthracnose pathogen during the year 2011. Similarly in the second year of repetition, it was revealed again that only Tatapuri, Gola peshawari and Longi expressed high susceptibility with 82.50, 79.60 and 81.50% disease incidence, while two varieties i.e. C-68 and C-302 showed susceptible response with disease incidence of 60.10 and 61.67% respectively. Seven varieties namely Talhari, FSD-1, FSD-2, KA-2, NARC-4, Neelum and Maha gave rise moderately resistant reaction with disease incidence of 33.80, 32.53, 33.57, 31.40, 34.27, 32.03 and 25.63% and remaining eighteen varieties/lines i.e. Sanam, C-19, C-72, C-33, American dwarf, Arunalu, BSS-269, Burewala, Ghotki, Sabazpari, Skyline-2, Kurni, Anaheim, Wonder king, P-6, Harmal, Skyline-1 and Hot queen remained resistant with minimum disease incidence in the range of 13-25% against chilli anthracnose disease. There was remarkable variation (p ≤ 5) in the mineral status of reaction group (inoculated & un-inoculated), type (resistant & susceptible) and in varieties/lines of the host plant due to the infection by anthracnose disease. Nested random's effect analysis of variance revealed that 2.81 & 2.52 %, 2259, 1185.50, 64.95, 179.60, 431.63, 141.12 & 151.89 µg/g concentration was expressed by resistant plants as compared to susceptible one (1.88 & 1.66 %, 2562.67, 991.48, 35.40, 121.28, 140.87, 191.83 & 95.73 µg/g respectively) with regards to Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Zinc (Zn), Sodium (Na), Iron (Fe) and Copper (Cu) contents. Similarly, nested analysis of variance again exposed that 328.33 µg/ml, 132.49 µg/g, 258.32 µg/g & 1.19 mg/g concentration was articulated by resistant plants as compared to susceptible genotype (324.43 µg/ml, 77.06 µg/g, 208.70 µg/g & 1.13 mg/g respectively) regarding total soluble phenols (TSPh), total soluble sugars (TSS), total soluble protein (TSP) and total chlorophyll (TC) contents respectively. It is concluded that resistant cultivars accumulated more concentration of these minerals & biochemical compounds as compared to susceptible varieties and increase in their concentration in resistant plant can prevents the spread of pathogen by strengthening the biochemical and physiological processes of the host. There was overall significant correlation between temperature (maximum and minimum), wind speed and relative humidity with chilli anthracnose development. Weak correlation of rainfall was observed with disease progress. Maximum disease development was recorded at 80-90% relative humidity with 3.5 km/h wind speed, air temperature from 31-35°C and 18-22°C as maximum and minimum respectively. All the treatments inhibited the multiplication of C. capsici at all concentrations, however Carbendazim at 0.3% concentration, Azadirachta indica extract at standard dose (S) and their combination (0.3% + S) were found to be the most effective agent for the control of the pathogen. In the green house experiment, both Carbendazim and A. indica performed well in controlling anthracnose development again when applied as alone and in combination at (0.3%) and (S) concentration respectively. Among plant activators tested, Salicylic acid (SA) proved to be highly significant followed by Benzoic acid and KH2PO4 in the field experiments. In addition to this, SA greatly reduced disease incidence when it was applied in combination with Carbendazim and A. indica after 21 days of spraying. Consequently, Carbendazim and A. indica extract alone and in combination proved to be the most effective treatments both in-vitro and in-vivo conditions as well.