Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata

Genetically controlled asynchrony in anthesis is an effective barrier to gene flow between planted and native forests. We investigated the degree of genetically controlled variation in the timing of key floral developmental stages in a major plantation species in subtropical Australia, Corymbia citriodora subsp. variegata K.D. Hill and L.A.S Johnson, and its relative C. maculata K.D. Hill and L.A.S. Johnson. Flowering observations were made in a common garden planting at Bonalbo in northern New South Wales in spring on 1855 trees from eight regions over three consecutive years, and monthly on a subset of 208 trees for 12 months. Peak anthesis time was stable over years and observations from translocated trees tended to be congruent with the observations in native stands, suggesting strong genetic control of anthesis time. A cluster of early flowering provenances was identified from the north-east of the Great Dividing Range. The recognition of a distinct flowering race from this region accorded well with earlier evidence of adaptive differentiation of populations from this region and geographically-structured genetic groupings in C. citriodora subsp. variegata. The early flowering northern race was more fecund, probably associated with its disease tolerance and greater vigour. Bud abundance fluctuated extensively at the regional level across 3 years suggesting bud abundance was more environmentally labile than timing of anthesis. Overall the level of flowering in the planted stand (age 12 years) was low (8–12% of assessed trees with open flowers), and was far lower than in nearby native stands. Low levels of flowering and asynchrony in peak anthesis between flowering races of C. citriodora subsp. variegata may partially mitigate a high likelihood of gene flow where the northern race is planted in the south of the species range neighbouring native stands

The role of BoFLC2 in cauliflower (Brassica oleracea var. botrytis L.) reproductive development

In agricultural species that are sexually propagated or whose marketable organ is a reproductive structure, management of the flowering process is critical. Inflorescence development in cauliflower is particularly complex, presenting unique challenges for those seeking to predict and manage flowering time. In this study, an integrated physiological and molecular approach was used to clarify the environmental control of cauliflower reproductive development at the molecular level. A functional allele of BoFLC2 was identified for the first time in an annual brassica, along with an allele disrupted by a frameshift mutation (boflc2). In a segregating F2 population derived from a cross between late-flowering (BoFLC2) and early-flowering (boflc2) lines, this gene behaved in a dosage-dependent manner and accounted for up to 65% of flowering time variation. Transcription of BoFLC genes was reduced by vernalization, with the floral integrator BoFT responding inversely. Overall expression of BoFT was significantly higher in early-flowering boflc2 lines, supporting the idea that BoFLC2 plays a key role in maintaining the vegetative state. A homologue of Arabidopsis VIN3 was isolated for the first time in a brassica crop species and was up-regulated by two days of vernalization, in contrast to findings in Arabidopsis where prolonged exposure to cold was required to elicit up-regulation. The correlations observed between gene expression and flowering time in controlled-environment experiments were validated with gene expression analyses of cauliflowers grown outdoors under 'natural' vernalizing conditions, indicating potential for transcript levels of flowering genes to form the basis of predictive assays for curd initiation and flowering time.

Postharvest manual answers many questions

Many authors have noted that consumer confidence in buying fresh flowers is strongly related to their perceived value in that quality and vase life must be high and consistent over time for consumers to repeat buy. Growers, wholesalers, exporters and retailers seek practical information about recommended handling and treatments at the harvest and postharvest stages, including that relating to flowers native to Australia and South Africa ("wildflowers"). This information is essential for products to be of high quality with an acceptable vase life for the end consumer, especially if exported. Published postharvest manuals generally focus on traditional flower crops and so rarely include many, or any, wildflowers. A manual entitled Postharvest Handling of Australian flowers from Native Plants and Related Species was published in 2002 and addressed this gap, but required updating. This situation presented an opportunity to provide in-depth information to compliment the Australian wildflower quality specifications (see accompanying paper in the same volume), and to assemble the latest knowledge on wildflower quality and postharvest issues. The resultant manual contains extensive information about harvesting, quality issues and recommended postharvest care focussed on wildflowers. Much of the information is documented for the first time, being based on the most up to date research and development (R&D) as well as practical experience of the floral supply chain, researchers and other technical experts. The manual provides practical and detailed information on postharvest treatment of fresh wildflowers for growers, florists, wholesalers and exporters to use on a daily basis. It discusses the many unique features of wildflowers that must be understood and managed in order to maximise their quality and vase life after marketing and export. The manual also includes postharvest advice for 16 flower- and foliage lines for which quality specifications were not produced. This advice is presented according to the same template as the specifications.

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.