Parental contribution to progeny during experimental spawning of jungle perch, Kuhlia rupestris

When releasing captive-bred animals into wild populations, it is essential to maintain the capacity for adaptation and resilience by minimising the effect on population genetic diversity. Populations of the jungle perch (Kuhlia rupestris) have become reduced or locally extinct along the Queensland coast; thus, captive breeding of K. rupestris for restocking is presently underway. Currently, multiple individuals are placed in a tank to produce larvae, yet the number of adults contributing to larval production is unknown. We performed a power analysis on pre-existing microsatellite loci to determine the minimum number of loci and larvae required to achieve accurate assignment of parentage. These loci were then used to determine the number of contributing participants during a series of four spawning events through the summer breeding season in 2012-2013. Not all fish contributed to larval production and no relationship was found between male body size and parentage success. In most cases, there was a high skew of offspring to one mating pair (62% was the average contribution of the most successful pair per tank). This has significant implications for the aquaculture, restocking and conservation of K. rupestris.

Evidence for different QTL underlying the immune and hypersensitive responses of Eucalyptus globulus to the rust pathogen Puccinia psidii

The rust Puccinia psidii infects many species in the family Myrtaceae. Native to South America, the pathogen has recently entered Australia which has a rich Myrtaceous flora, including trees of the ecologically and economically important genus Eucalyptus. We studied the genetic basis of variation in rust resistance in Eucalyptus globulus, the main plantation eucalypt in Australia. Quantitative trait loci (QTL) analysis was undertaken using 218 genotypes of an outcross F2 mapping family, phenotyped by controlled inoculation of their open pollinated progeny with the strain of P. psidii found in Australia. QTL analyses were conducted using a binary classification of individuals with no symptoms (immune) versus those with disease symptoms, and in a separate analysis dividing plants with disease symptoms into those exhibiting the hypersensitive response versus those with more severe symptoms. Four QTL were identified, two influencing whether a plant exhibited symptoms (Ppr2 and Ppr3), and two influencing the presence or absence of a hypersensitive reaction (Ppr4 and Ppr5). These QTL mapped to four different linkage groups, none of which overlap with Ppr1, the major QTL previously identified for rust resistance in Eucalyptus grandis. Candidate genes within the QTL regions are presented and possible mechanisms discussed. Together with past findings, our results suggest that P. psidii resistance in eucalypts is quantitative in nature and influenced by the complex interaction of multiple loci of variable effect.

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.

Single gene resistance to Fusarium oxysporum f. sp. cubense Race 4 in the wild banana Musa acuminata subsp. malaccensis

Fusarium wilt of banana, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of banana. A particularly virulent strain of the pathogen, tropical race 4 (TR4), presents an emerging threat to banana producing regions throughout the world. No commercially acceptable banana cultivar is resistant to TR4 and, as with all strains of the Fusarium wilt pathogen, there is no effective chemical control. Genetic resistance to TR4 has been observed in the diploid wild banana Musa acuminata subsp. malaccensis, which has consequently received attention as a potential source of Fusarium resistance genes. The aim of this research was to determine the pattern of inheritance of the resistance trait by screening plants for resistance to Foc subtropical race 4 (SR4) and TR4. Our results showed that the F1 progeny of self-fertilized malaccensis plants challenged in pot trials against SR4 (VCGs 0120, 0129, 01211) and TR4 (VCG 01213/16) segregated for resistance according to a Mendelian ratio of 3:1 which is consistent with a single dominant gene hypothesis.

Genetic diversity of stay-green sorghums and their derivatives revealed by microsatellites

The genetic variability of 28 sorghum genotypes of known senescence phenotype was investigated using 66 SSR markers well-distributed across the sorghum genome. The genotypes of a number of lines from breeding programmes for stay-green were also determined. This included lines selected phenotypically for stay-green and also RSG 03123, a marker-assisted backcross progeny of R16 (recurrent parent) and B35 (stay-green donor). A total of 419 alleles were detected with a mean of 6.2 per locus. The number of alleles ranged from one for Xtxp94 to 14 for Xtxp88. Chromosome SBI-10 had the highest mean number of alleles (8.33), while SBI-05 had the lowest (4.17). The PIC values obtained ranged from zero to 0.89 in Xtxp94 and Xtxp88, respectively, with a mean of 0.68. On a chromosome basis, mean PIC values were highest in SBI-10 (0.81) and lowest in SBI-05 (0.53). Most of the alleles from B35 in RSG 03123 were found on chromosomes SBI-01, SBI-02 and SBI-03, confirming the successful introgression of quantitative trait loci associated with stay-green from B35 into the senescent background R16. However, the alternative stay-green genetic sources were found to be distinct based on either all the SSRs employed or using only those associated with the stay-green trait in B35. Therefore, the physiological and biochemical basis of each stay-green source should be evaluated in order to enhance the understanding of the functioning of the trait in the various backgrounds. These genetic sources of stay-green could provide a valuable resource for improving this trait in sorghum breeding programmes.