Effect of seed quality on subsequent seed germination and growth of radiata pine in the nursery : [thesis, National Diploma of Horticulture]

Abstract

Seed orchards now produce sufficient seed for all of New Zealand's Pinus radiata seed requirements. These orchards have been established with grafts and cuttings of the best clones following extensive tree breeding. It is important that seed from these orchards has high viability, germinative energy and growth in the nursery to maximise the number of seedlings raised from each kilogram of seed. There have been complaints about seed orchard seed quality from nurserymen, particularly about small seed size and poor, uneven germination. There are many potential causes for seed quality problems in seed orchards, and special seed collections were organised to examine some of these. Results from laboratory germination and nursery bed sewings gave the following results: There were no significant differences in germination and subsequent growth between seedlings produced from seed collected off trees grown from seedlings, cuttings or grafts. This is an encouraging result, since seed orchards are established with cuttings and grafts from selected clones. Similarly, there were no significant differences between seedlings produced from seed collected from healthy and unhealthy cuttings. This indicates that the resin bleeding noticed in unhealthy cuttings has not affected the seed quality. However. while there was no difference between seedlings produced from seed collected from healthy and unhealthy grafts, seed collected .from very unhealthy grafts was smaller, and had poorer germination. Seed from very unhealthy grafts also produced a poorer percentage of plantable seedlings. Therefore, seed should not be collected from very unhealthy grafts. The effect of time of seed collection was not consistent. Seed collected in June and July from an open-pollinated seed orchard at Kaingaroa gave good germination and produced high quality seedlings. The earlier seed collection in May from Kaingaroa resulted in poorer germination and later seedling growth. However, with seed collected from a control pollinated seed orchard at Amberley, the best germination and better seedling growth came from the early May collection. while the later June and July seed collections gave poorer results. The effects of time of seed collection and open-pollinated compared with control pollinated will need further study, using seed collected from only one site to avoid possible environmental effects. Seed from mature crop cones germinated very well and produced high quality seedlings. However, seed from first cone crops were smaller. germinated poorly and produced fewer and poorer quality seedlings. 'Ihis experiment indicates that cones should not be collected for commercial use from small trees just coming into cone production.