Eastern White Pine Flowering in Response to Spray Application of Gibberellin A4/7 or Procone™

Abstract

Eastern white pine (Pinus strobus L.) is an important forestry species in the northeastern and midwestern United States and in eastern Canada. Induction of early and reliable flowering and cone production will shorten the breeding cycle and aid in the development of genetically improved white pine. The objective of this study was to determine if a foliar spray application of gibberellin A4/7 (GA4/7) or ProCone™ would induce both male and female strobili on young grafted eastern white pine selected for white pine blister rust resistance. Trees were sprayed (500 mg L-1) weekly in 1998 during the period of rapid shoot elongation (mid-May through July), for a total of 11 applications. Flowering data were collected June 15, 1999. Twenty-five out of 53 genotypes produced male strobili. For all genotypes studied, the total number of male strobili clusters per tree (and the mean number ± SE of pollen-cones per cluster) produced with GA4/7, ProCone™, or untreated controls were: 643 (7.1 ± 0.3); 574 (7.9 ± 0.3); and 79 (8.3 ± 0.8), respectively. Twenty out of 53 genotypes produced female strobili. For all genotypes studied, the total number of female strobili per tree (and the mean number ± SE of female strobili per shoot) produced with GA4/7, ProCone™, or untreated controls were: 87 (1.1 ± 0.1); 130 (1.3 ± 0.1); and 33 (0.6 ± 0.1), respectively. Eleven genotypes produced both male and female strobili. Control trees that flowered may have been the result of spray drift. The results indicate that a foliar spray application of GA4/7 or ProCone™ at 500 mg L-1 will induce both male and female strobili, but not on all selected genotypes of eastern white pine.

Aplicación experimental y operacional de giberelinas para inducir floración en Pino oregón (Pseudotsuga menziesii (Mirb.) Franco)

“…Para efectos de estimular floración, el AG4/7 puede aplicarse como aspersión foliar o Inyectarse directamente en el tallo de la planta o injerto. En el primer caso, segeen Pijut (2002) las concentraciones más efectivas flucteean entre 100 y 600 mg/L de solución. En el caso de las inyecciones, la absorción por la planta es más directa de modo que las concentraciones son menores; Ross (1977) utiliza 25 mg/L, inyectados en el tallo, justo bajo el comienzo de la copa viva y Greenwood (1977) 50 mg/L, inyectados algunos millmetros bajo la yema terminal.…”

“…En cualquier caso, ya sea que la solución se aspe~e foliarmente o se inyecte, es recomendable repetirla varias veces durante la temporada, ya sea semanal o bisemanalmente. El nremero de repeticiones que ha sido efectivo varia entre 1 y 11 (Pijut, 2002). Hare (1984) concluye que tres aspersiones bisemanales (200 mg/l) resultan efectivas en Pinus taeda, P elfiottii y P. palustres.…”

Survival of side grafts with scions from pure species Pinus engelmannii Carr. and the P. engelmannii × P. arizonica Engelm. var. arizonica hybrid

“…Flowering can occur on the grafts 2 years after grafting has taken place. However, the seed production time of grafts in Pinus species can vary from 5 to 7 years, depending on the species (Luukkanen & Johansson, 1980;Pijut, 2002). One method that is used to accelerate seed production in grafts is the application of hormones, such as gibberellins (Hare, 1984;Pijut, 2002).…”

Peer Review #2 of "Survival of side grafts with scions from pure species Pinus engelmannii Carr. and the P. engelmannii × P. arizonica Engelm. var. arizonica hybrid (v0.1)"

“…Flowering can occur on the grafts two years after grafting has taken place. However, the seed production time of grafts in Pinus species can vary from five to seven years, depending on the species (Luukkanen & Johansson, 1980;Pijut, 2002). One method that is used to accelerate seed production in grafts is the application of hormones, such as gibberellins (Hare, 1984;Pijut, 2002).…”

“…However, the seed production time of grafts in Pinus species can vary from five to seven years, depending on the species (Luukkanen & Johansson, 1980;Pijut, 2002). One method that is used to accelerate seed production in grafts is the application of hormones, such as gibberellins (Hare, 1984;Pijut, 2002). Although grafts may sometimes show adequate initial growth and flowering (Pérez-Luna et al, 2019), mortality can occur due to possible incompatibility between the scion and the rootstock after germplasm production, even five years or more after grafting (Jayawickrama, Jett & McKeand, 1991;Valera et al, 1999;Valdés, Centeno & Fernández, 2003).…”