In two separate studies, seedlings from 20 loblolly pine (Pinus taeda L.) families and Virginian pine (Pinus virginiana Mill.) were used as root stocks for grafting loblolly pine seed orchard clones. The rootstocks were open-pollinated seedlings from orchard clones chosen to represent a wide range of flowering and survival capabilities, based on their performance in a first-generation seed orchard. Scions were derived from the same 20 loblolly clones. The effects of scion clone were significant and large for nearly all measured traits. Rootstock significantly affected survival, growth, flowering and foliar nutrients of the grafted ramets. Neither survival nor growth of the crafts was related to survival of growth of the orchard clones from which their rootstocks were derived, however. Survival of incompatible clones was enhanced by grafting on genetically related rootstocks.
The PDF includes an abstract in Finnish.
Indirect selection for resistance is superior to direct selection under certain conditions. The phenotypic correlation was studied between resistance to fusiform rust (Cronartium fusiforme) in loblolly pines (Pinus taeda L.), chosen by a newly-developed stability index, and the amount of resin acids, growth-inhibiting substances, and fatty acids extracted from pine tissue. No association was found between rust resistance and the amount of total or individual resin acids in clones or families. The amount of growth-inhibiting substances present in branches from full-sib families was greater in rust-resistant compared to rust-susceptible families. A strong association was found between resistance and the amount of long-chain fatty acids in four clones. A weak association was found between resistance and the amount of the fatty acid 18:2 in five other clones.
The PDF includes a summary in Finnish.