The effects of gamma-ray irradiation to strawberry (Fragaria X ananassa Duch.) calli on shoot regeneration, achene formation and morphological variations of regenerants

Abstract

Strawberry (Fragaria X ananassa 'Nyoho') calli, derived from anthers, were irradiated with gamma-ray at dosages from 100 to 1,600Gy (10Gy · hr-1) and their effects on callus growth, plant regeneration, and somaclonal variation were analyzed. The growth of callus and percentage of plant regeneration from the callus were reduced slightly at dosages less than 200 Gy, moderately at 400 Gy, and markedly above 800 Gy. Fruit growth associated with seed fertility (>50%) was morphologically normal at less than 100 Gy, whereas achene formation was significantly inhibited above 200 Gy. The percentages of morphological variation in regenerants formed from the irradiated callus were: 13.7 (no irradiation), 18.6 (100 Gy), 66.0 (200 Gy), 75.7 (400 Gy), and 97.0 (800 Gy). Furthermore, higher dosages yielded wider variations, e.g., thick and small leaf, light leaf color, white flesh, and long fruit. In some regenerants, more than one morphological aberrations developed, some of which were transmissible to daughter plants. These results revealed that the irradiating Strawberry callus with gamma-ray resulted in a higher degree and wider spectrum of somaclonal variation than did simple callus culture.