Effect of coptis (coptis chinensis, franch.) extract on c (zantedeschia sp.) soft rot, growth, yield and quality

Abstract

Calla lily (Zantedeschia sp.) is cultivated as a cut flower, pot plant or garden ornamental throughout the world and contributes to horticultural revenue for many countries including America, Holland, New Zealand and Kenya. However, bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum affects the commercial viability of this crop in Kenya. The disease infects calla lily at all stages of growth resulting in death of plants and decay of tubers. Bactericidal formulations and antibiotics currently used to reduce P. carotovorum proliferation are ineffective, phytotoxic and may promote bacterial resistance. Coptis chinensis Franch, a traditional Chinese medicinal herb contains alkaloids which include berberine and palmatine. The two have strong antibacterial activities. C. chinensis obtained by supercritical fluid extraction is marketed in Kenya as foliar feed (Dumiza 0.5 % SL) has label claims of boosting crop growth and development, improve crop immunity, vigour and recovery after bacterial disease attack. This study sought to determine the antibacterial activity of C. chinensis extract against Pectobacterium carotovorum subsp. carotovorum (in vitro) and the effect of the extract on calla lily growth, yield and quality (in vivo). In the in vitro study, sterilized petri dishes containing nutrient agar arranged in a in CRD design were inoculated with the bacterium and a drop of C. chinensis extract at different dilution levels added onto each plate individually. Inhibition zones were measured after 24 hours of incubation. Results showed that only the undiluted level (100%) of the extract inhibited the development of the bacterium. In vivo studies included pre-plant tuber spraying and crop media drenching with C. chinensis extract either immediately from planting or after full-foliage stage set up in RCBD. Data on plant growth, yield and quality of flowers and tubers, disease incidence and severity for each field study were collected over a period of two growing seasons and analysed using JMP 9 statistical software. Results indicated that application of C. chinensis extract increased plant height and leaf numbers and suppressed soft rot disease. The C. chinensis extract product can be used for management of calla lily soft rot.