Commercial processing of Oriental lilies affects bud opening and metabolic dynamics

Lilies are a high value cut flower typically producing 4–5 flowers per stem, but the opening of young buds of Oriental hybrid lilies is often affected in cut flowers. Commercial treatment includes harvesting of the stem when the oldest bud is closed and at turning colour, approximately 2 ds before it would open on the plant. Stems are then rehydrated, stored chilled for up to 72 h and transported dry. To understand the effect of commercial treatment on the nutrient status metabolomes were compared throughout bud opening from different positions on the stem. At each developmental stage the metabolomic profile was affected by bud position and commercial treatment. Starch accumulated as long as buds remain closed; upon bud opening starch content declined. Reciprocally, sugar levels rose during flower opening and were affected by edge/ midrib location and commercial treatment. Glucose, fructose and sucrose levels remained higher in opened flowers still on the plant. AMY2 (amylase) transcript levels rose as did those of two sugar transporters (MST6 and SWEET7). Commercial processing therefore impacts on the metabolome and the ability to accumulate sugars in the opening flower bud. Commercial treatment delayed bud opening and the effect was dependent on the position of the bud on the stem. However, it had little impact on the rate of cell expansion during flower opening. Cell expansion in the different areas of the adaxial epidermis was unaffected by the commercial treatment. Furthermore, edge and adaxial tepal cells expanded faster during opening. Expression of cell expansion related genes (EXPA1 and LoPIP1) fell as flowers opened. This differential cell expansion in the tepal sectors could underpin the transition of a convex to a concave tepal shape during opening. In conclusion, commercial processing mainly affects the early stages of bud opening. Sugar and metabolite accumulation is compromised by commercial treatment, but this did not affect the capacity for cell expansion in the tepal. Furthermore, our data indicate that differential cell expansion in the different sectors of the tepals is important in lily flower opening, and that this is associated with starch breakdown and sugar accumulation

Commercial processing of Oriental lilies affects bud opening and metabolic dynamics

Lilies are a high value cut flower typically producing 4–5 flowers per stem, but the opening of young buds of Oriental hybrid lilies is often affected in cut flowers. Commercial treatment includes harvesting of the stem when the oldest bud is closed and at turning colour, approximately 2 ds before it would open on the plant. Stems are then rehydrated, stored chilled for up to 72 h and transported dry. To understand the effect of commercial treatment onu the nutrient status metabolomes were compared throughout bud opening from different positions on the stem. At each developmental stage the metabolomic profile was affected by bud position and commercial treatment. Starch accumulated as long as buds remain closed; upon bud opening starch content declined. Reciprocally, sugar levels rose during flower opening and were affected by edge/ midrib location and commercial treatment. Glucose, fructose and sucrose levels remained higher in opened flowers still on the plant. AMY2 (amylase) transcript levels rose as did those of two sugar transporters (MST6 and SWEET7). Commercial processing therefore impacts on the metabolome and the ability to accumulate sugars in the opening flower bud. Commercial treatment delayed bud opening and the effect was dependent on the position of the bud on the stem. However, it had little impact on the rate of cell expansion during flower opening. Cell expansion in the different areas of the adaxial epidermis was unaffected by the commercial treatment. Furthermore, edge and adaxial tepal cells expanded faster during opening. Expression of cell expansion related genes (EXPA1 and LoPIP1) fell as flowers opened. This differential cell expansion in the tepal sectors could underpin the transition of a convex to a concave tepal shape during opening. In conclusion, commercial processing mainly affects the early stages of bud opening. Sugar and metabolite accumulation is compromised by commercial treatment, but this did not affect the capacity for cell expansion in the tepal. Furthermore, our data indicate that differential cell expansion in the different sectors of the tepals is important in lily flower opening, and that this is associated with starch breakdown and sugar accumulation

A complex interaction between pre-harvest and post-harvest factors determines fresh-cut melon quality and aroma

Melons are prized for their characteristic aroma, however, pre-harvest growth, stage of ripening at harvest, post-harvest processing and storage conditions lead to quality changes in fresh-cut fruit. We considered changes in metabolites and gene expression over 14 days storage to assess underlying mechanisms and identify potential quality markers. Overall, 99 volatile organic compounds (VOCs) were detected and VOC profiles discriminated between two melon seasons, cut-size, storage temperatures and storage time, although season affected their discriminatory power. Abundance of two VOCs fell rapidly and was not associated with cut size, indicating their use as markers for early changes post-processing. Non-acetate to acetate ester ratio differed between the seasons and correlated with changes in alcohol acyl-transferase (CmAAT1) gene expression. Furthermore, CmAAT1 expression clustered with two ester VOCs that may be potential new products of this enzyme. Season also strongly affected post-harvest sugar content, most likely attributable to meteorological differences during growth. Storage temperature and cut size affected expression of transcription factors ERF71, ERF106, and TINY, whose expression generally rose during storage, probably related to increased stress. Thus, although time × temperature of storage are key factors, pre-harvest conditions and fruit processing impact significantly gene expression and aroma loss post-harvest

Storage of halved strawberry fruits affects aroma, phytochemical content and gene expression, and is affected by pre-harvest factors

Introduction: Strawberry fruit are highly valued for their aroma which develops during ripening. However, they have a short shelf-life. Low temperature storage is routinely used to extend shelf-life for transport and storage in the supply chain, however cold storage can also affect fruit aroma. Some fruit continue to ripen during chilled storage; however, strawberries are a non-climacteric fruit and hence ripening postharvest is limited. Although most strawberry fruit is sold whole, halved fruit is also used in ready to eat fresh fruit salads which are of increasing consumer demand and pose additional challenges to fresh fruit storage. Methods: To better understand the effects of cold storage, volatilomic and transcriptomic analyses were applied to halved Fragaria x ananassa cv. Elsanta fruit stored at 4 or 8°C for up to 12 days over two growing seasons. Results and discussion: The volatile organic compound (VOC) profile differed between 4 or 8°C on most days of storage. Major differences were detected between the two different years of harvest indicating that aroma change at harvest and during storage is highly dependent on environmental factors during growth. The major component of the aroma profile in both years was esters. Over 3000 genes changed in expression over 5 days of storage at 8°C in transcriptome analysis. Overall, phenylpropanoid metabolism, which may also affect VOCs, and starch metabolism were the most significantly affected pathways. Genes involved in autophagy were also differentially expressed. Expression of genes from 43 different transcription factor (TF) families changed in expression: mostly they were down-regulated but NAC and WRKY family genes were mainly up-regulated. Given the high ester representation amongst VOCs, the down-regulation of an alcohol acyl transferase (AAT) during storage is significant. A total of 113 differentially expressed genes were co-regulated with the AAT gene, including seven TFs. These may be potential AAT regulators

How do lilies open? The regulation of flower opening in lilies, and how to control it to improve post-harvest quality

Lilies are a commercial cut-flower crop highly popular in the UK for their large and colourful blooms. However, due to their perishable nature, cold/dark storage is necessary as part of commercial treatment to allow cut flowers to maintain their quality and developmental stage until purchase. Cold/dark storage has been shown to have an impact on the terminal bud’s ability to open in some varieties, particularly in stems with a greater number of buds per inflorescence. Understanding the opening process of lilies, and the endogenous and exogenous factors which may impact this process (particularly under commercial conditions) was an overarching aim of this project. Flower opening is driven by differential expansion or division of petal cells in other species, and firstly the mechanism of lily opening was characterised. Factors hypothesised to be affected by commercial treatment such as nutritional status (bud starch and soluble sugar content), time of opening, and secondary metabolism were confirmed to be significantly different between on plant and commercially treated lily buds. Position on stem was identified as a potentially important factor affecting the ability to open, nutritional status and bud metabolism over opening. RNA-sequencing was used to investigate expression patterns in buds which could open comparing to buds which failed to open as a result of commercial treatment-related stress. This differential expression analysis found several putative metabolic pathways associated with flower opening, alongside putative regulatory auxin and stress related elements. The phytohormone auxin was therefore explored as a potential treatment for commercial treatment-related stress due to its accelerating effect on lily opening and the correlated expression of auxin signal transduction components with lily opening. Overall, this work provides new insights into mechanisms of flower opening and indicates possible targets for improving commercially treated cut lily quality

Chapter 9 - Ethylene in floriculture

The cut flower industry is an increasingly globalized market, of economic importance worldwide. It relies on the transport of high value and high-quality flowers across long distances. Flowers follow a genetically controlled developmental program that starts with floral initiation and ends with petal senescence and often abscission. Ethylene is a key regulator in this senescence process in many species. Understanding which species or varieties are more or less ethylene sensitive and controlling ethylene through the flower supply chain is a major contributor to flower quality for the consumer. Our understanding of ethylene biosynthesis and signaling is largely based on model species such as Arabidopsis. However, a better understanding of ethylene in different floral organs, in different species and interactions with other growth regulators is emerging and is reviewed in this chapter. Several approaches have been tried for delaying floral senescence through manipulation of ethylene levels and ethylene perception both through chemical means and by generating transgenic lines. The success of these approaches to date is considered, and future technologies are reviewed for their application to floriculture