, ~ @ "002 Kluwer Academic Publishers. Printed in the Netherlands. 119 Mutation induction by y and X-ray irradiation in tissue cultured lotus

Mutations of tissue cultured lotus were induced by treating plantlets with either acute y-rays at doses of 0, 2, 3,4, 5 or 6 krad or X-rays at doses of 0, 1,2,3,4 or 5 krad. The 2-krad dose of either y- or X-ray treatments resulted in a 50 % survival rate. The use of y- and X-rays to induce mutation in lotus resulted in 21 altered characteristics. Mutants from 1- and 2-krad of either y or X-rays had long secondary roots and numerous adventitious roots. These mutants also exhibited good shoot growth and healthy rhizome development. Most plants treated with 3-5 krad of either y- or X-rays exhibited abnormal characteristics including vitrification, chlorosis, deformed petioles and in addition had inhibited growth of lateral buds, secondary roots and rhizomes. All plants treated with 6 krad of y-rays died within 4 weeks. Control plants had stoma lengths of 2.56 jLm and cytological analysis of the root tips confirmed the diploid chromosome number of 16. Two groups of aneuploid cells were achieved using irradiation at doses of 3 and 4 krad of either y- or X-ray. Chromosome numbers were 2n=18 and 20 with associated stoma lengths of 3.43 and 4.34 jLm, respectively. Abnormal stomata (cyclocytic and deformity) were observed in plants treated with 4 krad of y-ray. Abbreviations: 2iP-N-isopentenyl adenine; IAA-indole-3-acetic acid Introduction Buds from rhizomes (Figure lA) of lotus werester