Abstract
Increasing resistance against foliar diseases is an important goal in the Pinus radiata D.Don breeding program in New Zealand, and screening for resistance has been in place for some time, since the late 1960s. The current study presents results of four progeny trials within the breeding program to investigate whether multiple disease resistance could be detected against three different needle diseases in P. radiata: Dothistroma needle blight (DNB) caused by Dothistroma septosporum, Cyclaneusma needle cast (CNC) caused by Cyclaneusma minus, and red needle cast (RNC) caused by Phytophthora pluvialis. Four progeny trials in the North Island of New Zealand were available to estimate heritabilities and between-trait genetic correlations. Two of the trials were assessed for DNB, involving 63 full-sib families. A third trial was assessed for CNC, involving 172 half-sib families, and a fourth trial was assessed for RNC, involving 170 half-sib families. Disease resistances had moderate estimates of heritability (0.28–0.48) in all trials. We investigated the potential for multiple disease resistance to the three foliar diseases by estimating genetic correlations between disease resistances using a spatial linear mixed model. The correlation between DNB and CNC resistance was favorable and strong (0.81), indicating that genotypes that are highly resistant to DNB also have a high resistance to CNC. These results suggest that selection based on resistance to DNB could allow for simultaneous indirect selection for resistance to CNC, usually only expressed at a later age. This would allow selections to be made earlier due to the earlier expression of DNB than CNC and reduce the number of expensive disease assessments being undertaken. Conversely, genetic correlation estimates for RNC with DNB and CNC were close to zero, and very imprecise. As such, later-age assessments for this disease would still be required.
Highlights
Our objectives were (1) to estimate variance components and heritability estimates for resistance against Dothistroma needle blight (DNB), Cyclaneusma needle cast (CNC), and red needle cast (RNC); (2) to investigate whether multiple disease resistance could be detected against the three different pathogens that cause needle damage; (3) to estimate the correlated response to selection based on genetic correlations between traits; and (4) to investigate whether there was any genotype by environment interaction level (G×E) for resistance against DNB in two progeny trial sites
The severities of infection were highest for RNC with a mean disease score of 41.83%, and the lowest for DNB1 with mean disease score of 21.14%
Severity for CNC in our study was lower than that reported by Suontama et al (2019), who reported serious severity of CNC in a 9-year-old P. radiata trial located in Mangatu, on the east coast of New Zealand's North Island, and assessed in 2015
Summary
Pinus radiata plantations in New Zealand do, face serious threats due to foliar diseases (Burdon, 2008). These include Dothistroma needle blight (DNB), Cyclaneusma needle cast (CNC), red needle cast (RNC), and physiological needle blight (PNB). A similar loss in volume of 7–13 m3 ha−1 was estimated per 10% increase in the proportion of DNB affected trees (Van Der Pas, 1981) To put these values into context, the economic cost of DNB to the New Zealand forest industry has been estimated at $19.8 million (NZD) per annum from lost productivity and the cost of chemical control measures such as aerial spraying of copper oxides (Watt et al, 2011a). The economic cost of CNC is likely even higher, with some estimates of $38 million (NZD) per annum for trees aged between 6 and 20 years (Bulman and Gadgil, 2001; Watt et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
