育 种 甜菜属种间杂交方法的研究—…··—……·—……·、……·—·—·,……··—、—·——·—…··一.^.··—·——。——·—一1(11) 甜菜O-型系与甜菜优势育种—………、……·——·—………………—………—·—·、·—·—………—·—·—·———·一 1(2 Study on Breeding Methods of Hybridization between Beet Genus - ... ·· - ...... ································································································································································ · - · -. - · - A 1 (11) Sugar beet O-type and sugar beet Advantage Breeding - ........., ...... · - · - .................. - ......... - · - ·, · - · - ... ... - · - · · · --- · a 1 (2