BA-Induced Shoot Formation in Indian Hawthorn

A study was conducted to determine effects of multiple weekly applications of different concentrations of a synthetic cytokinin, benzyladenine (BA), on two Indian hawthorn [Rhaphiolepis Lindl. Cor. Poir. indica (L.) Lindl. (Crataegus indica L.)] cultivars, ‘Olivia’ and ‘Eleanor Taber’. In a greenhouse in winter 2000-2001, ‘Olivia’ Indian hawthorn received four weekly applications of 2500 ppm or 5000 ppm BA. At 45 days after last treatment (DALT) untreated plants had formed no new shoots, while plants treated with 2500 and 5000 ppm BA produced 6.8 and 5.4 new shoots, respectively. New leaves of plants treated with 5000 ppm BA were abnormally mottled, twisted, and cupped. In an outdoor nursery in summer 2001, ‘Olivia’ in 3.8 liter (#1) and 26.5 liter (#7) containers received three and two applications, respectively, at concentrations from 0 to 5000 ppm. Untreated plants in 26.5 liter (#7) containers formed 4.7 new shoots at 30 days after initial treatment (DAIT), and new shoots increased from 83 with 1250 ppm BA to 126 with 5000 ppm BA. Plants in 26.5 liter (#7) containers were retreated in September, at which time shoots were inactive. At 30 DAIT controls averaged less than one new shoot per plant, while plants averaged 18 new shoots when treated with 1250 ppm BA and 105 new shoots when treated with 5000 ppm BA. In spring 2002, plants in 3.8 liter (#1) containers were retreated following the same protocol as in 2001, in conjunction with a new set of ‘Olivia’ and the Indian hawthorn cultivar, ‘Eleanor Taber’. At 30 DALT new shoot formation increased three fold in ‘Olivia’ and five fold in ‘Eleanor Taber’ after three applications of up to 5000 ppm BA. Injury increased with increasing BA rates in ‘Olivia’ at 30 DALT, with leaf cupping and discoloration apparent on plants treated with concentrations above 1250 ppm. No injury was observed in ‘Eleanor Taber’. By 90 DALT new shoots had matured normally and exhibited minimal phytotoxic symptoms.