Studies on dwarfing mechanisms of dwarf rootstocks

对矮化砧木苗期矮化能力的准确评价，可以加快矮化砧木育种的进程。这项研究的目的是确定来自矮化砧木的愈伤组织是否像田间表现所预期的那样，在体外限制来自接穗品种的另一愈伤组织的生长。愈伤组织来源于桃树和日本李的茎段。这些愈伤组织生长在接穗位置，并在它们之间放置滤纸。桃愈伤组织在砧木位置，即与基质接触生长时，其重量比在桃愈伤组织下生长的轻。接穗部位的日本杨愈伤组织在桃愈伤组织上生长时重量较大。接穗部位的桃愈伤组织在桃愈伤组织和日本大桃愈伤组织上的生长情况相同。在另一项实验中，将桃愈伤组织转移到培养一周后移出的培养基中。桃愈伤组织在预先培养的桃愈伤组织中重量较轻。桃愈伤组织预培养不影响桃愈伤组织的生长。当桃愈伤组织和大白桃愈伤组织处于相邻位置而不接触时，有一种愈伤组织不影响邻近愈伤组织的生长，大白桃含有的酚类物质比桃子多，但桃愈伤组织的生长与大白桃及其自身的酚类物质含量无关。结果表明，可以用组织培养技术评价砧木的矮化能力，矮化是由日本杨体内释放的某些化合物引起的。

Accurate evaluation of the dwarfing ability of rootstocks at the seedling stage permits faster progress in breeding programs for the dwarf rootstocks. The objective of this study was to determine whether callus from a dwarfing rootstock restricted growth of another callus from a scion cultivar in vitro as would be expected from a field performance. Calli were derived from shoots of peach and Prunus japonica Thunb. These calli were grown in scion-stock position, placing filter paper between them. Peach callus in the stock position, i.e. grown in contact with the media, weighed less when grown under P.japonica callus than when grown under peach callus. P.japonica callus in the scion position weighed more when grown on peach callus. Peach callus in the scion position grew equally well on either peach or P.japonica callus. In another experiment, peach callus was transferred into the media where P.japonica callus was previously incubated for one week and then removed. Peach callus weighed less on the media previously incubated with P.japonica. Preincubation of peach callus did not affect growth of P.japanica callus. When peach and P.japonica calli were placed in the adjacent position without contact, one kind of callus did not affect growth of callus adjacent to it.P.japonica contained nore phenols than peach, but growth of peach callus was independent of phenol contents of P.japonica and itself. The results suggest that dwarfing ability of rootstocks couldbe evaluated by tissue culture techniques and that dwarfing is caused by some compounds released from P.japonica.