QUANTITATIVE INHERITANCE OF FIJI DISEASE RESISTANCE IN SUGARCANE

The inheritance of Fiji disease resistance in sugarcane was studied, s o that strategies for breeding for resistance could be developed. Resi stance was highly heritable and most of the genetic variance was addit ive when infection pressure was low to moderate. Infection pressure wa s very heavy in one experiment and this reduced discrimination between parent clones and families. The data were skewed and this affected st atistical and genetical analyses which showed that non-additive geneti c variance was high. In general, however, it was concluded that select ion of resistant parents would produce families with resistant progeny . Some moderately susceptible families produced a small number of resi stant progeny and, if these families have agronomic merit, the breedin g strategy should enable such families to be planted. The computerised strategy adopted rejects crosses if the average susceptibility of the two parents is too high, and emphasises the use of more resistant par ent clones. As some susceptible clones will be selected, clones are su bjected to a field screening trial as soon as practicable. These strat egies have reduced the percentage of susceptible clones in the populat ion from 70-80% to 20-30%.