GERMINATION AND SEEDLING DEVELOPMENT OF 2 MISTLETOES, AMYEMA-PREISSIIAND LYSIANA-EXOCARPI - HOST-SPECIFICITY AND MISTLETOE-HOST COMPATIBILITY

Potential hosts had no effect on seed germination of the mistletoes, A myema preissii and Lysiana exocarpi, but affected seedling holdfast fo rmation and leaf emergence. For A. preissii, formation of the holdfast and emergence of leaves occurred most rapidly in seedlings on its usu al host, Acacia nyssophylla. Among the six species inoculated with L. exocarpi seeds, formation of the holdfast was quickest on A. nyssophyl la and Myoporum platycarpum (usual hosts). Emergence of leaves was qui ckest in seedlings on A. nyssophylla, and on two non-hosts, Eucalyptus oleosa and Expcarpos aphyllus. For both mistletoe species, seedling m ortality was high during the first 3 months, with considerable variati on among different host species. After 6 months, little or no mortalit y was recorded on seedlings growing on their usual hosts. In contrast, seedlings on non-host species suffered continuing mortality and none survived the study period, except for 13% of the L. exocarpi seedlings , which persisted on Geijera linearifolia in a moribund state. The gro wth of seedlings on host and non-host species varied markedly. After 3 5 and 47 months, the average length of the longest shoot of two cohort s of A. preissii seedlings was 22 and 75 cm, respectively. After 47 mo nths, the average length of the longest shoot of L. exocarpi seedlings on A. nyssophylla, H. oleifolium and M. platycarpum was 57, 38 and 41 cm, respectively. For both mistletoe species, a proportion of individ uals on host species flowered and subsequently set fruits within 3 yea rs. In comparison, none of the plants sown on the non-host species gre w beyond seedling stage. The inability of A. preissii and L. exocarpi to establish on non-host species was attributed to mistletoe-host inco mpatibility.