Effect of seasonal conditions on fleece weight and its components in merino sheep grazing Mitchell grass pasture in North West Queensland

SUMMARY Seasonal conditions in the pre to post natal period and selected periods before and during wool growth were described using climatic measures and estimates of the quality and quantity of pasture on offer derived from a validated pasture production model (GRASP). The variation in greasy and clean fleece weight, yield, staple length, fibre diameter, neck and side wrinkle score of Merinos grazing Mitchell grass in north west Queensland was explained in terms of these pasture and climatic measures and animal characteristics such as reproductive status, age and skin area. Multiple regression equations predicting clean and greasy fleece weight from the proportion of days in the wool growth period that the green pool in the pasture was less than one kg/ha, the percentage utilisation of the pasture, age, reproductive status and skin area of the ewes explained 87% and 79% of the variation respectively. Equations with similar predictors explained 58-85% of the variation of the other components. The inclusion of pasture conditions in the pre to post natal period did not significantly improve the predictions of the animal’s later performance. 22nd Biennial Conference.

Influence of nitrogen based supplements on live weight, fertility and mortality of heifers grazing dry season native pasture

Supplements containing urea or biuret were fed in the dry season to yearling and two year old pregnant heifers grazing native spear grass pastures in north Queensland. Liveweight change and survival during the dry season and fertility in the following year were measured. In the first experiment during a relatively favourable dry season, supplementation significantly (P<0.01) reduced liveweight loss in yearling heifers (5 vs. 32 kg). In the following year during a drought, supplement significantly (P<.01) reduced liveweight loss in yearling heifers (32 vs. 41 kg) and significantly (P <0.01) reduced mortalities (23.5% vs. 5.2%) in pregnant and lactating heifers. The supplement had no significant effect on subsequent fertility in either experiment. 14th Biennial Conference.

Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum

Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

Optimising between and within family selection for harvest weight in prawns with restricted harvest size.

Manual grading of prawns restricts the number that can be harvested. A restricted harvest size places a limit on the opposing within family and between family sources of selection pressure. A simulation study with inbreeding constrained at 0.5% per generation, a harvest size of 2000, heritability of 0.3, common family environmental effect of 0.1, indicates that maximum response to selection could be achieved with as few as 40 families. Increasing the number of families above 80 may reduce total selection response. It is important to be aware that increasing the number of families may not always yield a greater genetic response.

Bycatch weight, composition and preliminary estimates of the impact of bycatch reduction devices in Queensland's trawl fishery

This report provides quantitative information on the effects of turtle excluder devices (TEDs) and bycatch reduction devices (BRDs) on the catch rates of bycatch, prawns, scallops and byproduct species, such as Moreton Bay bugs and Balmain bugs, in Queensland’s major trawl fishing sectors. It also provides biological information on, and management advice for several species referred to in the Fishery Management Plan as the permitted species. Several recommendations are included for reducing bycatch in the trawl fishery and for sustaining stocks of the permitted species.

Pollination methods, stigma receptivity and pollen tube growth in Eucalyptus argophloia

Eucalyptus argophloia Blakely (Western white gum) has shown potential as a commercial forestry timber species in marginal environments of north-eastern Australia. We measured early pollination success in Eucalyptus argophloia to compare pollination methods, determine the timing of stigma receptivity and compare fresh and stored pollen. Early pollination success was measured by counting pollen tubes in the style of E. argophloia 12 days after pollination. We compared the early pollination success of 1) Artificially Induced Protogyny (AIP), one-stop and three-stop methods of pollination; 2) flowers pollinated at 2 day intervals between 2 days before and 6 days after anthesis and 3) fresh pollen and pollen that had been stored for 9 months. Our results show significantly more pollen tubes from unpollinated AIP and AIP treatments than either the one-stop pollination or three-stop pollination treatments. This indicates that self-pollination occurs in the unpollinated AIP treatment. There was very little pollen tube growth in the one-stop method indicating that the three-stop method is the most suitable for this species. Stigma receptivity in E. argophloia commenced six days after anthesis and no pollen tube growth was observed prior to this. Fresh pollen resulted in pollen tube growth in the style whereas the stored pollen resulted in a total absence of pollen tube growth. We recommend that breeding programs incorporating E. argophloia as a female parent use the three-stop pollination method, and controlled pollination be carried out at least six days after anthesis using fresh pollen.

Prediction of breeding values for average fruit weight in mango using a multivariate individual mixed model

Mango is an important horticultural fruit crop and breeding is a key strategy to improve ongoing sustainability. Knowledge of breeding values of potential parents is important for maximising progress from breeding. This study successfully employed a mixed linear model methods incorporating a pedigree to predict breeding values for average fruit weight from highly unbalanced data for genotypes planted over three field trials and assessed over several harvest seasons. Average fruit weight was found to be under strong additive genetic control. There was high correlation between hybrids propagated as seedlings and hybrids propagated as scions grafted onto rootstocks. Estimates of additive genetic correlation among trials ranged from 0.69 to 0.88 with correlations among harvest seasons within trials greater than 0.96. These results suggest that progress from selection for broad adaptation can be achieved, particularly as no repeatable environmental factor that could be used to predict G x E could be identified. Predicted breeding values for 35 known cultivars are presented for use in ongoing breeding programs.

Postharvest physiology and volatile production by flowers of Ptilotus nobilis

Ptilotus nobilis (Lindl.) F. Muell. has potential in the floriculture industries as a cut flower crop. Ethylene production and respiration rates, fresh weight changes and volatile scent production from cut inflorescences of P. nobilis cultivars Passion (dark pink flowers) and Purity (white-green flowers) were measured during vase life. Inflorescence weight loss was significant (P<0.001) during vase life with wilting and colour loss being the primary reasons for loss of vase life. Inflorescences ready for the cut market stored and at 22 degrees C had vase lives of >12 d. Ethylene production by inflorescences was low to negligible. Treatment with silverthiosulphate (STS) and ethylene had no effects on vase life. Evidently, ethylene did not play a role in determining the postharvest longevity of cut P. nobilis flowers. Respiration rates of inflorescences were high at harvest (>700 mg CO2 kg(-1) FW h(-1)) and declined gradually there-after during vase life. Total volatile emissions followed a similar pattern. For Passion, respiration rates of immature florets were significantly greater (P=0.02) than florets from other developmental stages while the calyx produced the most CO2. For Purity, respiration rates of florets of different maturities did not differ and the reproductive tissue produced the most CO2. Only fully opened mature florets with their stigma and anthers revealed, emitted significant quantities of volatiles (P<0.001) and primarily from the calyx tissue for both cultivars. The individual volatiles differed somewhat for the two cultivars. However, both produced significant quantities of benzaldehyde, 3,5-dimethoxytoluene and benzyl alcohol. These. compounds have previously been associated with desirable floral scent. (C) 2013 Elsevier B.V. All rights reserved.

Fine mapping of qGW1, a major QTL for grain weight in sorghum

Key message We detected seven QTLs for 100-grain weight in sorghum using an F 2 population, and delimited qGW1 to a 101-kb region on the short arm of chromosome 1, which contained 13 putative genes. Abstract Sorghum is one of the most important cereal crops. Breeding high-yielding sorghum varieties will have a profound impact on global food security. Grain weight is an important component of grain yield. It is a quantitative trait controlled by multiple quantitative trait loci (QTLs); however, the genetic basis of grain weight in sorghum is not well understood. In the present study, using an F2 population derived from a cross between the grain sorghum variety SA2313 (Sorghum bicolor) and the Sudan-grass variety Hiro-1 (S. bicolor), we detected seven QTLs for 100-grain weight. One of them, qGW1, was detected consistently over 2 years and contributed between 20 and 40 % of the phenotypic variation across multiple genetic backgrounds. Using extreme recombinants from a fine-mapping F3 population, we delimited qGW1 to a 101-kb region on the short arm of chromosome 1, containing 13 predicted gene models, one of which was found to be under purifying selection during domestication. However, none of the grain size candidate genes shared sequence similarity with previously cloned grain weight-related genes from rice. This study will facilitate isolation of the gene underlying qGW1 and advance our understanding of the regulatory mechanisms of grain weight. SSR markers linked to the qGW1 locus can be used for improving sorghum grain yield through marker-assisted selection.

Postharvest physiology and volatile production by flowers of Ptilotus nobilis

Ptilotus nobilis (Lindl.) F. Muell. has potential in the floriculture industries as a cut flower crop. Ethylene production and respiration rates, fresh weight changes and volatile scent production from cut inflorescences of P. nobilis cultivars Passion (dark pink flowers) and Purity (white-green flowers) were measured during vase life. Inflorescence weight loss was significant (P < 0.001) during vase life with wilting and colour loss being the primary reasons for loss of vase life. Inflorescences ready for the cut market stored and at 22 °C had vase lives of >12 d. Ethylene production by inflorescences was low to negligible. Treatment with silverthiosulphate (STS) and ethylene had no effects on vase life. Evidently, ethylene did not play a role in determining the postharvest longevity of cut P. nobilis flowers. Respiration rates of inflorescences were high at harvest (>700 mg CO2 kg−1 FW h−1) and declined gradually thereafter during vase life. Total volatile emissions followed a similar pattern. For Passion, respiration rates of immature florets were significantly greater (P = 0.02) than florets from other developmental stages while the calyx produced the most CO2. For Purity, respiration rates of florets of different maturities did not differ and the reproductive tissue produced the most CO2. Only fully opened mature florets with their stigma and anthers revealed, emitted significant quantities of volatiles (P < 0.001) and primarily from the calyx tissue for both cultivars. The individual volatiles differed somewhat for the two cultivars. However, both produced significant quantities of benzaldehyde, 3,5-dimethoxytoluene and benzyl alcohol. These compounds have previously been associated with desirable floral scent.

Postharvest physiology and volatile production by flowers of Ptilotus nobilis

Ptilotus nobilis (Lindl.) F. Muell. has potential in the floriculture industries as a cut flower crop. Ethylene production and respiration rates, fresh weight changes and volatile scent production from cut inflorescences of P. nobilis cultivars Passion (dark pink flowers) and Purity (white-green flowers) were measured during vase life. Inflorescence weight loss was significant (P < 0.001) during vase life with wilting and colour loss being the primary reasons for loss of vase life. Inflorescences ready for the cut market stored and at 22 °C had vase lives of >12 d. Ethylene production by inflorescences was low to negligible. Treatment with silverthiosulphate (STS) and ethylene had no effects on vase life. Evidently, ethylene did not play a role in determining the postharvest longevity of cut P. nobilis flowers. Respiration rates of inflorescences were high at harvest (>700 mg CO2 kg−1 FW h−1) and declined gradually thereafter during vase life. Total volatile emissions followed a similar pattern. For Passion, respiration rates of immature florets were significantly greater (P = 0.02) than florets from other developmental stages while the calyx produced the most CO2. For Purity, respiration rates of florets of different maturities did not differ and the reproductive tissue produced the most CO2. Only fully opened mature florets with their stigma and anthers revealed, emitted significant quantities of volatiles (P < 0.001) and primarily from the calyx tissue for both cultivars. The individual volatiles differed somewhat for the two cultivars. However, both produced significant quantities of benzaldehyde, 3,5-dimethoxytoluene and benzyl alcohol. These compounds have previously been associated with desirable floral scent.