Markers for seedling and adult plant crown rot resistance in four partially resistant bread wheat sources

QTL identified for seedling and adult plant crown rot resistance in four partially resistant hexaploid wheat sources. PCR-based markers identified for use in marker-assisted selection. Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in many wheat-growing regions globally. Complete resistance to infection by F. pseudograminearum has not been observed in a wheat host, but germplasm with partial resistance to this pathogen has been identified. The partially resistant wheat hexaploid germplasm sources 2-49, Sunco, IRN497 and CPI133817 were investigated in both seedling and adult plant field trials to identify markers associated with the resistance which could be used in marker-assisted selection programs. Thirteen different quantitative trait loci (QTL) conditioning crown rot resistance were identified in the four different sources. Some QTL were only observed in seedling trials whereas others appeared to be adult plant specific. For example while the QTL on chromosomes 1AS, 1BS, and 4BS contributed by 2-49 and on 2BS contributed by Sunco were detected in both seedling and field trials, the QTL on 1DL present in 2-49 and the QTL on 3BL in IRN497 were only detected in seedling trials. Genetic correlations between field trials of the same population were strong, as were correlations between seedling trials of the same population. Low to moderate correlations were observed between seedling and field trials. Flanking markers, most of which are less than 10 cM apart, have now been identified for each of the regions associated with crown rot resistance.

Estimates of genetic parameters for growth and wood properties in Eucalyptus pellita F. Muell. to support tree breeding in Vietnam

Eucalyptus pellita demonstrated good growth and wood quality traits in this study, with young plantation grown timber being suitable for both solid and pulp wood products. All traits examined were under moderate levels of genetic control with little genotype by environment interaction when grown on two contrasting sites in Vietnam. Eucalyptus pellita currently has a significant role in reforestation in the tropics. Research to support expanded of use of this species is needed: particularly, research to better understand the genetic control of key traits will facilitate the development of genetically improved planting stock. This study aimed to provide estimates of the heritability of diameter at breast height over bark, wood basic density, Kraft pulp yield, modulus of elasticity and microfibril angle, and the genetic correlations among these traits, and understand the importance of genotype by environment interactions in Vietnam. Data for diameter and wood properties were collected from two 10-year-old, open-pollinated progeny trials of E. pellita in Vietnam that evaluated 104 families from six native range and three orchard sources. Wood properties were estimated from wood samples using near-infrared (NIR) spectroscopy. Data were analysed using mixed linear models to estimate genetic parameters (heritability, proportion of variance between seed sources and genetic correlations). Variation among the nine sources was small compared to additive variance. Narrow-sense heritability and genetic correlation estimates indicated that simultaneous improvements in most traits could be achieved from selection among and within families as the genetic correlations among traits were either favourable or close to zero. Type B genetic correlations approached one for all traits suggesting that genotype by environment interactions were of little importance. These results support a breeding strategy utilizing a single breeding population advanced by selecting the best individuals across all seed sources. Both growth and wood properties have been evaluated. Multi-trait selection for growth and wood property traits will lead to more productive populations of E. pellita both with improved productivity and improved timber and pulp properties.

An investigation of environmental conditions experienced during the life of high-value wood components and products

Australian forest industries have a long history of export trade of a wide range of products from woodchips (for paper manufacturing), sandalwood (essential oils, carving and incense) to high value musical instruments, flooring and outdoor furniture. For the high value group, fluctuating environmental conditions brought on by changes in temperature and relative humidity, can lead to performance problems due to consequential swelling, shrinkage and/or distortion of the wood elements. A survey determined the types of value-added products exported, including species and dimensions packaging used and export markets. Data loggers were installed with shipments to monitor temperature and relative humidity conditions. These data were converted to timber equilibrium moisture content values to provide an indication of the environment that the wood elements would be acclimatising to. The results of the initial survey indicated that primary high value wood export products included guitars, flooring, decking and outdoor furniture. The destination markets were mainly located in the northern hemisphere, particularly the United States of America, China, Hong Kong, Europe (including the United Kingdom), Japan, Korea and the Middle East. Other regions importing Australian-made wooden articles were south-east Asia, New Zealand and South Africa. Different timber species have differing rates of swelling and shrinkage, so the types of timber were also recorded during the survey. Results from this work determined that the major species were ash-type eucalypts from south-eastern Australia (commonly referred to in the market as Tasmanian oak), jarrah from Western Australia, spotted gum, hoop pine, white cypress, black butt, brush box and Sydney blue gum from Queensland and New South Wales. The environmental conditions data indicated that microclimates in shipping containers can fluctuate extensively during shipping. Conditions at the time of manufacturing were usually between 10 and 12% equilibrium moisture content, however conditions during shipping could range from 5 (very dry) to 20% (very humid). The packaging systems incorporated were reported to be efficient at protecting the wooden articles from damage during transit. The research highlighted the potential risk for wood components to ‘move’ in response to periods of drier or more humid conditions than those at the time of manufacturing, and the importance of engineering a packaging system that can account for the environmental conditions experienced in shipping containers. Examples of potential dimensional changes in wooden components were calculated based on published unit shrinkage data for key species and the climatic data returned from the logging equipment. The information highlighted the importance of good design to account for possible timber movement during shipping. A timber movement calculator was developed to allow designers to input component species, dimensions, site of manufacture and destination, to see validate their product design.

An assessment of Pythium spp. associated with soft rot disease of ginger (Zingiber officinale) in Queensland, Australia

In Australia, Pythium soft rot (PSR) outbreaks caused by P. myriotylum were reported in 2009 and since then this disease has remained as a major concern for the ginger industry. From 2012 to 2015, a number of Pythium spp. were isolated from ginger rhizomes and soil from farms affected by PSR disease and assessed for their pathogenicity on ginger. In this study, 11 distinct Pythium spp. were recovered from ginger farms in Queensland, Australia and species identification and confirmation were based on morphology, growth rate and ITS sequences. These Pythium spp. when tested showed different levels of aggressiveness on excised ginger rhizome. P. aphanidemartum, P. deliense, P. myriotylum, P. splendens, P. spinosum and P. ultimum were the most pathogenic when assessed in vitro on an array of plant species. However, P. myriotylum was the only pathogen, which was capable of inducing PSR symptoms on ginger at a temperature range from 20 to 35 °C. Whereas, P. aphanidermatum only attacked and induced PSR on ginger at 30 to 35 °C in pot trials. This is the first report of P. aphanidermatum inducing PSR of ginger in Australia at high temperatures. Only P. oligandrum and P. perplexum, which had been recovered only from soils and not plant tissue, appeared non-pathogenic in all assays.

Research into crown rot and wilt diseases of strawberries in Queensland

Plant losses due to fungal diseases in strawberry (Fragaria × ananassa Duch.) can potentially cause total loss of production. Three fungal pathogens, Fusarium oxysporum f. sp. fragariae, Colletotrichum gloeosporioides and Macrophomina phaseolina, cause similar crown rot and wilt symptoms in strawberries in Queensland. Since the withdrawal of methyl bromide in 2005, no effective chemical control of any of the three pathogens has been available. This study aims at identifying sources of plant genetic resistance that can be used in the breeding program to develop resistant cultivars for use as part of an integrated disease management plan in commercial strawberry production. Results from glasshouse pathogenicity and screening trials on the three pathogens showed that when breeding for resistance against a pathogen, resistance to other pathogens also needs to be considered, e.g., cultivar 'Festival' is resistant to F. oxysporum f. sp. fragariae, but is highly susceptible to C. gloeosporioides. The cultivars 'Earlisweet', 'Kabarla' and 'Phenomenal', two seedling clones and four DAFF breeding lines were resistant to C. gloeosporioides. Cultivar 'Suncoast Delight' showed the most promising level of resistance to M. phaseolina. These cultivars, breeding lines and seedling selections have been made available for incorporation into the crossing program to support the Queensland strawberry breeding program.

Genetic variation in growth and wood-quality traits of Corymbia citriodora subsp. variegata across three sites in south-east Queensland, Australia

Ten growth or wood-quality traits were assessed in three nearby Corymbia citriodora subsp. variegata (CCV) open-pollinated family-within-provenance trials (18 provenances represented by a total of 374 families) to provide information for the development of a breeding program targeting both pulp and solid-wood products. Growth traits (diameter at breast high over bark [DBH], height and conical volume) were assessed at 3 and 7 years of age. Wood-quality traits (density [DEN], Kraft pulp yield [KPY], modulus of elasticity [MoE] and microfibril angle [MfA]) were predicted using near-infrared spectroscopy on wood samples collected from these trials when aged between 10 and 12 years. The high average KPY, DEN and MoE, and low average MfA observed indicates CCV is very suitable for both pulp and timber products. All traits were under moderate to strong genetic control. In across- trials analyses, high (>0.4) heritability estimates were observed for height, DEN, MoE and MfA, while moderate heritability estimates (0.24 to 0.34) were observed for DBH, volume and KPY. Most traits showed very low levels of genotype × site interaction. Estimated age–age genetic correlations for growth traits were strong at both the family (0.97) and provenance (0.99) levels. Relationships among traits (additive genetic correlation estimates) were favourable, with strong and positive estimates between growth traits (0.84 to 0.98), moderate and positive values between growth and wood-quality traits (0.32 to 0.68), moderate and positive between KPY and MoE (0.64), and high and positive between DEN and MoE (0.82). However, negative (but favourable) correlations were detected between MfA and all other evaluated traits (−0.31 to −0.96). The genetic correlation between the same trait expressed on two different sites, at family level, ranged from 0.24 to 0.42 for growth traits, and from 0.29 to 0.53 for wood traits. Therefore simultaneous genetic improvement of growth and wood property traits in CCV for the target environment in south-east Queensland should be possible, given the moderate to high estimates of heritability and favourable correlations amongst all traits studied, unless genotype × site interactions are greater than was evident. © 2016 NISC (Pty) Ltd

Control of grey mould and stem-end rot in strawberry plants growing in a subtropical environment

The effect of different fungicide programs on grey mould (caused by Botrytis cinerea) and stem-end rot (caused by Gnomoniopsis fructicola) affecting strawberry plants (Fragaria ×ananassa cv. Festival) was studied in subtropical Australia over three years. The treatments involved a range of different synthetic multi- and single-site fungicides with different modes of action, a plant-defence promoter, plant extracts (lupin and rhubarb), organic acids, fatty acids, a salt, two strains of Bacillus subtilis, and single strains of B. amyloliquefaciens, Streptomyces lydicus and Trichoderma harzianum. Standard programs based on captan and thiram alternated, and applied with iprodione, fenhexamid, cyprodinil + fludioxonil, and penthiopyrad resulted in 3–4 % of unmarketable fruit compared with 25–38 % in the water-treated controls. There was no difference in the level of disease suppression when five or thirteen applications of single-site fungicides were rotated with the two multi-site fungicides. The incidence of unmarketable fruit was similar to the standard programs using isopyrazam (in 1 year out of 2), or penthiopyrad, fluazinam, chlorothalonil or thiram alone (in 1 year out of 1). The other fungicide programs were generally less effective. There were strong relationships between marketable yield and the incidence of unmarketable fruit over the three years (R2s = 0.82–0.93). A strategy based on thiram and captan applied alternately, with reduced applications of single-site fungicides is recommended and should reduce the chance of resistance to single-site fungicides becoming widespread in populations of the grey mould fungus. Although the program based on thiram alone had a similar incidence of unmarketable fruit as the standard program, repeated weekly applications of thiram are not recommended as they may cause unacceptable residues in the fruit. There were issues with some of the other fungicides due to phytotoxicity, residues, or difficulties with registering new fungicides that are in the same chemical group as currently registered products.