Fruit yield of common orange varieties in south-east Australia: Initial evaluation versus long term performance

• Four seasons cropping is insufficient to identify superior common orange varieties and reject inferior varieties.
• Only 25% of the common oranges varieties showed evidence of biennial bearing.
• Seasonality did not influence the tendency toward either irregular cropping or biennial bearing.

Fruit yield of 12 common orange varieties on either ‘sweet orange’ rootstock or ‘Carrizo citrange’ rootstock growing on light textured soil in south-east Australia were measured from 2000 to 2012. The varieties covered the range from early maturing (April) through to late hanging (March), and the trial was conducted to identify suitable varieties to ensure continuity of common orange supply to service the Australian fresh orange juice market. Based on the initial four seasons’ yield data, ‘Hamlin’ would have been selected for the June–August period, and ‘Salustiana’, which cropped relatively poorly in the initial four years, would have been rejected. Subsequent yields of fruit by ‘Salustiana’ trees meant that its overall cropping levels were similar to ‘Hamlin’, calling into question the adequacy of recommending a variety based on only an initial four years of observation. Although all varieties demonstrated some degree of irregular cropping, only three varieties could confidently be called biennial bearers. The tendency to irregular bearing (biennial or otherwise) was unrelated to a selection's seasonality, suggesting an inadequacy in our current understanding of the importance of the presence of fruit in determining the size of the return crop.