Analysis of influence factors on browning of blackberry explants and selection of suitable culture condition

Effects of five factors including types of basic medium and explant,branch dark treatment time,anti-browning agent and illumination intensity on explant browning and axillary bud inducing were investigated using blackberry(Rubus spp.) cultivar 'Kiowa' as experimental object.The results show that on six basic media(MS,1/2 MS,B5,1/2 B5,N6 and 1/2 N6),the explants inoculated on MS medium show a lower browning rate(37.78%),the highest inducing rate of axillary bud(67.89%) and good growth status.The browning degree of explant has a certain relationship with lignification degree and sampling part.The lowest browning rate(19.67%),higher inducing rate of axillary bud(91.89%) and good growth status are obtained using the upper stem segment of semi-lignification branch of one year old as explants.Dark treating for a certain time before inoculating can inhibit the browning of explants and the anti-browning effect of dark treating for 3 d is the best.Different types and concentrations of anti-browning agents added in media have some effects on explant browning and axillary bud inducing,and the anti-browning effects of adding 3 000 mg·L-1active carbon or 200 mg·L-1 VC are better.Certainly,the browning degree of explant associates with the illumination intensity in culture process,and under 1 500 lx illumination condition,the browning rate is lower(15.66%) and the inducing rate and growth status of axillary bud are better.According to the results,the culture conditions suitable for anti-browning of blackberry explants are as follows: using the upper stem segment of semi-lignification branch of one year old as explants,treating them in dark condition for 3 d with 15 ℃,then inoculating on MS medium added 3 000 mg·L-1 active carbon or 200 mg·L-1 VC(containing 20 g·L-1 sucrose,5.6 g·L-1 agar and 0.2 mg·L-1 6-BA,pH 5.8),under 1 500 lx illumination condition for culture.