Pollination bag type has a significant impact on cone survival in mass production of controlled pollinated seeds in loblolly pine

Abstract

Since 2009, deployment of full-sib families of loblolly pine (Pinus taeda L.) has gained prominence in the southeastern United States. To produce full-sib seed, a pollination bag is used to isolate female strobili from outside pollen contamination, and a known pollen is applied at the time of maximum female strobilus receptivity. The goal of this study was to compare prototype pollination bags made by PBS International to the industry standard kraft paper pollination bag with and without a support wire for female strobili survival and to assess their efficiency for mass production of controlled cross loblolly pine seed. A multiyear study compared 13 pollination bag types at more than nine seed orchard sites across the southeastern United States. There were significant differences among bag types for conelet survival at the time of bag removal that persisted until cone harvest 18 months later. Female strobili bagged in prototype PBS-I2 were over three times more likely to survive to cone harvest than strobili inside the traditional kraft pollination bag. Two of the PBS bag types had the highest estimated filled seed per bag. One PBS bag was faster to install and remove than the kraft paper bag with a support wire. Study Implications: With the growing demand from forest landowners and forest managers in the southeastern United States to plant controlled cross loblolly pine seedlings of the best families, any improvements that can be made in the production of controlled cross seed is of great importance. Controlled cross seed is more difficult and more expensive to produce than open-pollinated seed because of several factors, and this study aimed to improve one portion of the production process, the environmental conditions during the time when female strobili are inside the pollination bags. Female strobili inside some pollination bag prototypes were over three times more likely to survive to cone harvest than those inside the industry standard kraft pollination bag. With almost 2 million pollination bags installed in the southeastern United States in 2019, this increase in cone survival could substantially increase controlled cross loblolly pine seed production. If loblolly pine seed orchard managers begin using these pollination bags to increase cone survival and seed yields, forest landowners in the southeastern United States could benefit from an increase in supply of controlled cross seedlings. If more controlled cross seedlings are deployed, this could lead to a substantial increase in timber volume and quality of loblolly pine plantations.