Influence of Preculture Variables on Microspore Embryo Production in Brassica napus ssp. oleifera cv. Duplo

The effect of four preculture variables on microspore embryoinduction and growth were examined: (1) the source of the budselected for culture (apical or axillary inflorescence; (2)the method of harvest (single harvest of whole inflorescenceor sequential harvest of individual buds; (3) the length ofthe bud (2, 3 or 4 mm); and (4) the application of a 4 ^°Cpretreatment to the bud after harvest. Microscopic and macroscopicanalysis of every anther used for culture permitted an assessmentof the following parameters: (1) the percentage of induced buds;(2) the number of induced anthers per induced bud; (3) the numberof productive buds (with macroscopic embryos) as a percentageof the induced buds; (4) the degree of induction per inducedanther (an estimate of the number of microspores in which initialembryogenic divisions had commenced); and (5) embryoid survival(the number of embryos as a proportion of the degree of induction). The product of parameters 1 and 2 gave the number of inducedanthers and all five parameters were components of the finalyield - the number of embryos produced per bud cultured. It was found that the maximum number of induced buds (67·0per cent) occurred with 2 mm sequentially harvested non-pretreatedbuds. Overall, the values decreased with increasing bud lengthand were lower for pretreated and axillary buds. In contrast,the two other estimates of induction - number of induced anthersper induced bud and degree of induction per induced anther -both had maximum values from 3 mm sequentially harvested, pretreatedbuds from apical inflorescences. The highest final yield ofembryos per cultured bud (44·9) was found with 2 mm non-pretreatedbuds taken from a single harvest of the apical inflorescence.The study therefore confirmed that the different componentsof the final embryo yield are differentially affected by thefour preculture variables tested. These variables must be controlledif reproducible results are to be achieved. Brassica napus, tape, anther culture, pollen, microspore, haploid