Variation among provenances and families of blackbutt (Eucalyptus pilularis) in early growth and susceptibility to damage from leaf spot fungi

Growth to 38 months and severity of Mycosphaerella leaf disease and target spot (caused by Aulographina eucalypti (Cooke & Mass.) von Arx & Muller) were assessed in a Eucalyptus pilularis Smith (blackbutt) family trial in New South Wales (NSW), Australia. Significant variation in growth, disease, and defoliation was found among the 40 provenances and 321 families tested; however, relatively few provenances had concentrations of superior or poor families. Most families in three higher altitude NSW provenances were superior for volume increment, while three southeast Queensland provenances had low mean volume increment. Mycosphaerella damage and defoliation tended to be low in several higher altitude northern NSW provenances, but the southeast Queensland provenances had significantly higher mean defoliation. Individual narrow sense heritability estimates were low to moderate for Mycosphaerella damage (0.38) and defoliation (0.22) and low for Aulographina damage (0.13) and volume increment (0.13). Significant genetic and phenotypic correlations between Mycosphaerella damage and defoliation were low and positive. Low to moderate negative correlations occurred between Mycosphaerella damage and volume increment and between defoliation and volume increment, suggesting that Mycosphaerella leaf disease, in particular, and defoliation had deleterious effects on tree growth. However, the impact of these foliar pathogens on the volume of E. pilularis is often low, so selecting for growth and form alone in the early stages of domestication could provide acceptable gains in yield.