SELECTION IN STRAWBERRY WITH RESISTANCE TO PHYTOPHTHORA ROOT ROT FOR HYDROPONICS

Young plantlets for in vitro selection were implanted into a two-layer agar medium to which P.n.p.No.FAR892 was inoculated to induce the fungous infection to the roots simultaneously during the rooting. 86 regenerated plantlets derived from the culture of stamens of strawberry (Fragaria X ananassa cv. ‘Nyoho’) and 118 seedlings (Fragaria X ananassa cv. ‘Aiberry’) were tested by using this in vitro method.

As a result, 4 regenerated plantlets (4.7%) and 4 seedlings (3.4%) showed remaining healthily and it has been made possible to make a distinction between the plantlets resistant to the attack of mycelia germinated from P.n.p. cystospores and those susceptible to the pathogen during 3 weeks.

Again the regeneration culture system from the flower organs (an anther, a filament, a style, and an ovary) of ‘Aiberry’ was examined to select resistant plants to pathogen from among the somatic cell mutants.

Each organ was picked separately from the bud, and implanted on Linsmaier & Skoog (LS) agar medium (George et al.,1987) to which growth regulators (BA, NAA, and 2,4-D) were added in various concentrations, and cultured. Then, shoot formations from callus tissues were observed most frequently from the ovary -derived callus when 2 mg/1 BA and 0.1 mg/1 2,4-D were added to LS medium. The induced shoots finally developed into intact plants on LS growth regulator-free agar medium.

These results have shown that it is effective to combine this in vitro selection method with the ovary culture as a means of producing ‘Aiberry’ with resistance to Phytophthora root rot.