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.
