Genetic diversity: Breeding to avoid future vulnerability

Crop industries require a foundation of broad genetic diversity as insurance against vulnerability to new biotic stresses. This study examined parental diversity and use of foreign germplasm in sugarcane cultivars and major crop improvement programs of the Queensland sugar industry. Parental diversity of cultivars was analysed at the parental and grandparental levels for the 1996 crop. Use of foreign clones in sequential groups of "Q" cultivars in the series Q79-Q175 was analysed. Trends in foreign clonal resources, and their use in crossing were analysed for 1988-1997. The proportions of foreign parental clones and parental diversity indices were determined for three selection stages in four programs. The Queensland crop is genetically vulnerable as two immediate parents account for 50% of production. Two grandparents are present in 67% of the crop. Reduced use of foreign parents in recent cultivar production was detected. The number of foreign clones maintained and their use in recombination has reduced substantially in the latter half of the past decade. The proportion of foreign parental clones in selection populations was acceptable in one program. Parental diversity indices were acceptable for early selection stages. A breeding strategy is proposed to address productivity and genetic diversity requirements jointly.