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    New Zealand willows (Salix spp.), their metabolites and their plant-herbivore interactions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatu, New Zealand
    (Massey University, 2024-12-19) De Oliveira Mota, Claryssa
    New Zealand is a unique environment which affects how species behave, survive and interact with each other. Introduced species of willow (Salix spp) are used in New Zealand for various purposes, and several varieties (clones) have been developed (Gunawardana et al., 2014; McIvor, 2013). Various insect species attack willows in New Zealand. It is not yet known how the New Zealand environment would affect the secondary metabolites and species resistance to insect pests in willows, and host preferences of some pests have not yet been characterized. In my thesis I aimed to characterize chemistry (metabolites and volatile organic compounds) in several willow clones, as well as differences in clone preference in insect pests – giant willow aphid (GWA) Tuberolachnus salignus Gmelin, 1790 (Hemiptera: Aphididae) and red gall sawfly Pontania proxima Serville, 1823 (Hymenoptera: Tenthredinidae). The incidence and chemical aspects of galling by P. proxima on New Zealand willow clones has not yet been characterised. This information is vital for the selection of resistant cultivars and to understand potential indirect impacts on other insect species (e.g., natural enemies of competing herbivores). Chapter 1 is a literature review on plant secondary metabolites and their role in plant defence against insect herbivores, as well as review of willow insect pests with emphasis on P. proxima and giant willow aphid. This chapter questions how much we know about willows in New Zealand, what differences they present from the willows from other parts of the world, and how the New Zealand environment affects the insects that feed on willows. Do insect pests preferers the same species/clones in New Zealand as in other parts of the world? What makes P. proxima and GWA prefer certain clones? What makes some clones resistant and others susceptible? In Chapter 2, I explored the levels of damage caused by P. proxima to willow clones. Twelve willow clones (PN221, PN249, PN721, PN693, PN357, PN676, NZ1040, NZ1130, PN218, PN356, PN736 and PN742) used in New Zealand were selected and surveyed for P. proxima damage. Willows showed a range of resistance levels to P. proxima. These levels of resistance show as differences in P. proxima larval development (explored in Chapter 3), damage level and gall size. For example, clones PN221 and PN249 did not present galls, while clones PN736 and PN742 presented the highest level of damage in our field survey. Other clones had an intermediate level of damage, and some clones present with malformed galls. The survey also found that top sections of shoots had a significantly higher level of damage, while location and side of the plant had no effect, possibly because the experimental field was homogeneous in sun exposure and other abiotic factors such as soil fertility. Gall induction is still a mystery in the Salix spp - P. proxima system, mainly because the cecidogenic factor is not yet known. The clones used in Chapter 2 were further investigated in Chapter 3 to link plant resistance to P. proxima development and growth. Larval development was investigated and measured, and the phenolic and nutrient content of willow leaves was quantified. The resistance of willow clones to P. proxima appears to be guided by a combination of physical and chemical attributes of the plants. Overall, P. proxima appears to prefer clones with a lower phenolic content and lower leaf pilosity. This preference, however, is in contrast with previous European studies in which P. proxima showed preference for a higher level of phenolics. Plant phenology seems also to play a role in preference, with P. proxima preferring to oviposit in clones which develop earlier in the season, even if those clones do not offer optimal conditions for larval development. Among the studied clones, PN 221 and PN 249 (S. purpurea) showed the highest resistance levels to P. proxima with no galls. Among the clones that developed galls, PN676 (S. alba, female) was the clone that produced the smallest larva and is therefore considered more resistant. The fact that P. proxima has shifted its preference from willows with a high content of phenolic glycosides in its native range to willows with a low content of phenolic glycosides in New Zealand may be due to low predator pressure in New Zealand. Further studies are needed to investigate this shift and test this hypothesis. In Chapter 4, I investigated the metabolomics profiles of six willow clones (PN220, PN249, PN386, NZ04-106-073, PN218 and NZ1040) and whether the differences in metabolites influence the preference of insect pests to the six clones. With the metabolomic profile we are expecting to see differences in chemistry between the clones and their influence on the plants’ pest resistance. The most important compounds found were apigenin, isorhamnetin-3-O-glucoside, procyanidin B2, epicatechin, petunidin-3-O-β-glucopyranoside, kaempferide, kaempferol-3-glucuronide, quercetin-7-O-rhamnoside, unknown 1, isorhamnetin, peonidin-3-O-β-D-glucoside, luteolin-7-O-glucoside, procyanidin B1 and isorhamnetin-3-O-rutinoside. Due to the limited number of clones and limited number of replicates, I cannot draw definitive conclusions about the pattern of secondary metabolites in relation to resistance to the two insect herbivores – P. proxima and GWA. To our knowledge the direct effect of those metabolites on P. proxima and GWA was never tested. The resistance to P. proxima and GWA appears to be more correlated with phenological and morphological features of willow plants than with their chemistry. Chapter 5 is an investigation of the volatile profile of willow clones studied in Chapter 4. With the metabolomic and volatile profile we hoped to elucidate whether the chemistry of the clone influences clone resistance to P. proxima and GWA. These volatile organic compounds (VOCs) included two green leaf volatiles (GLVs), (Z)-3-Hexenyl acetate and (Z)-3-Hexenyl-α-methylbutyrate; one monoterpenes, (Z)-β-Ocimene; and eight sesquiterpenes, β-Elemene α-Cubebene, Copaene, Germacrene D, (Z)-β-Caryophyllene, (E)-α-Bergamotene, (α)-Farnesene, δ-Cadinene. The results show that willow clones have highly species-specific VOC blends, a conclusion backed up by other authors. Due to the limited number of clones and limited number of replicates, it was not possible to draw definitive conclusions about the pattern of volatile emissions in relation to resistance to the two insect herbivores – P. proxima and GWA. Resistance to P. proxima and GWA appears to be more correlated with phenological and morphological features of willow plants than with their VOC emissions. Chapter 6 is the recapitulation of the conclusions of the experimental chapters and relating it with the existing literature. The twelve willows tested in chapters 2-5 showed a range of metabolites, leaf volatiles (VOCs), and resistance levels to P. proxima which manifested as differences in P. proxima larval development, damage level and gall size. Overall, P. proxima appears to prefer clones with a lower phenolic content and lower leaf pilosity and those that develop earlier in the season. The VOCs in willow clones appear to be species-specific and are not clearly linked to insect resistance. We suggest that the levels of phenolic compounds and pilosity together better explain the preference of oviposition of P. proxima. The highest amount of secondary metabolites was found in clones NZ04-106-073 (S. lasiolepis × S. viminalis, Female), PN676 (S. alba L., Female) and PN221 (S. purpurea L., Male). NZ04-106-073 also showed the highest emission of VOCs. The most susceptible clones to P. proxima were PN736 (S. fragilis L., Male) and PN742 (S. fragilis L., Male). Tree willows are preferred by P. proxima to shrubs. Among the studied clones, PN221 and PN249 (both S. purpurea) showed the highest resistance levels to P. proxima with no galls. Among the clones that developed galls, PN676 (S. alba, female) was the clone that produced the smallest larvae and is therefore considered more resistant.
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    Evaluation of the 1986-1987 radiata pine clonal trials at Forest Research, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master in Applied Science at Massey University
    (Massey University, 1998) Concheyro, Silvia Claudia
    Clonal forestry, the establishment of plantations using tested clones, is highly sought after by the forestry industry in New Zealand and worldwide. Clonal testing is a vital element in the process leading to clonal forestry. Two clonal trials established in 1986 and 1987 by the Forest Research Institute with juvenile ortet material have been analysed in this study. The mating design in the 1986 clones-in-family trial was single-pair crossing with amplification of the clones by fascicle cuttings. It was replicated over two sites, and the trait analysed was diameter at 1.40 m height at ages 4,7, and 10 years. The estimation of additive, non-additive and genetic variances showed a high proportion of non-additive variance compared with the additive variance at one of the sites, whereas the proportion was less important at the other site. The high non-additive component of variance can be due to important dominance or epistasis, or to C-effects confounded with the non-additive variance. This trend was similar for all three ages. Realised genetic gains were obtained from selection of clones at age 10 years for clonal deployment and breeding. For clonal deployment, realised gains were high at both sites (13% and 16%). The gains were similar at both sites provided selection was based on performance values at the site, and not on indirect selection on performance of clones at the other site. Realised gains for selection at age 10 based on the performance of clones on combined sites (10% and 13%) were less than the maximum gain obtained at each individual site. Gains based on information from both sites (10% and 12% at respective sites) were more stable than those selections at any one site. For breeding, the level of gain was significantly inferior than for clonal deployment (4% and 8%), especially when the number of clones per family was restricted to one (2% and 4%). Realised gain on combined-site selection yielded less gain than direct selection at the optimum site for selection (1% and 2%). The presence of genotype x environment interaction emphasised the need to test clones in several sites if stability of performance is desired. It is possible to obtain gain from selections made at an early age, but selections made for breeding at the age of final assessment yielded greater expected total gain and gain per unit time. The mating design in the 1987 clones-in-family trial was a 3 x 3 disconnected factorial. The trial was established on a single site and the trait analysed was percentage of Dothistroma needle infection at ages 3,4 and 7years. The mating design allowed estimation of additive, dominance and epistasis variances, which were overestimated for the lack of replication over sites. In this trial measured for Dothistroma resistance, the additive variance was the major component of the genetic variance at both ages. The evolution of components of genetic variance was confounded with the level of Dothistroma infection. The analysis of these trials indicated the need to improve the mating and field designs to improve the accuracy in the estimation of genetic parameters, highlights the importance of annual or biennual measurements to determine trends of those parameters over time, and showed the difference in gains obtained from selection for breeding and clonal deployment for early selection and selection at the age of final assessment. Accuracy in the estimation of genetic parameters can be achieved using factorial mating designs together with serial propagation to reduce the incidence of C effects, and with replication over several sites. Further considerations have to be made to find the most appropriate field and statistical design, but alpha designs are a possibility to explore. Investment in a series of carefully planned clonal trials is fundamental to the future of clonal forestry in radiata pine.