Heritability of response to inoculation by pine pitch canker of seedlings of radiata pine

Abstract

Summary Seedlings grown from more than 500 radiata pine (Pinus radiata D.Don) seedlots from Australia, New Zealand and Chile were inoculated with Fusarium circinatum, the cause of pitch canker, and subsequently assessed for response by measuring the length of the resulting lesion. Analysis of the data indicated, first, that there was considerable genetic variation for lesion length. On average, the New Zealand and Australian material appeared more resistant (shorter lesions) than the Chilean material, although it is not apparent why this should be so. Second, the heritability for lesion length is reasonably high, 0.34 to 0.78 depending on the population, suggesting that selection for resistance should result in useful genetic gains. Third, results from Australian control-pollinated families appear to indicate that resistance measured by lesion length is inherited primarily through the male parent. However, this does not appear to be consistent with results from Chilean and New Zealand control-pollinated material which are based on female parent identity. Further investigation is needed to reconcile these observations. A field trial of resistant, susceptible and native provenance materials has been proposed as the next phase of testing for resistance to pitch canker.