Relationship between phenology and frost damage to female strobili of pine wood nematode-resistant clones of Japanese black pine (Pinus thunbergii): a case study in an experimental crossing garden during the spring of 2020

ABSTRACT

To clarify the factors affecting the level of spring frost damage in seed orchards of pine wood nematode (PWN)-resistant Pinus thunbergii, we investigated the frost damage to the female strobili of 13 PWN-resistant P. thunbergii clones in an experimental crossing garden during the spring of 2020. Monthly air temperatures from January to March 2020 were higher than the corresponding temperatures in the previous six years, whereas the temperatures in April 2020 were lower compared to the previous years. The number of female strobili on the upper and lower branches of the trees averaged 4.7 and 2.7, respectively. The spring frost damaged 6% and 22% of the strobili on the upper and lower branches, respectively. A generalized linear mixed model analysis confirmed that this difference was significant; moreover, it showed significant clonal variation in the female strobili mortality. The mortality risk to the female strobili of each clone was negatively correlated to the time required for the female strobili to bloom. Thus, the P. thunbergii clones with an early flowering phenology are more likely to suffer from spring frost damage.

KEYWORDS:

• Female flower
• blooming
• reproductive phenology
• clonal variation
• frost injury

Acknowledgments

We are appreciative technical staffs of KRBO for their support of our research.

Disclosure statement

No potential conflict of interest was reported by the authors.