Background Geophytes possess specialized storage organs - bulbs, tubers, corms or rhizomes, which allow their survival during unfovarable periods and provide energy support for sprouting and sexual and vegetative reproduction. Bulbing and flowering of the geophyte depend on the combined effects of the internal and external factors, especially temperature and photoperiod. Many geophytes are extensively used in agriculture, but mechanisms of regulation of their flowering and bulbing are still unclear. Results Comparative morpho-physiological and transcriptome analyses and quantitative validation of gene expression shed light on the molecular regulation of the responses to vernalization in garlic, a typical bulbous plant. Long dark cold exposure of bulbs is a major cue for flowering and bulbing, and its interactions with the genetic makeup of the individual plant dictate the phenotypic expression during growth stage. Photoperiod signal is not involved in the initial nuclear and metabolic processes, but might play role in the later stages of development, flower stem elongation and bulbing. Vernalization for 12 weeks at 4 degrees C and planting in November resulted in flower initiation under short photoperiod in December-January, and early blooming and bulbing. In contrast, non-vernalized plants did not undergo meristem transition. Comparisons between vernalized and non-vernalized bulbs revealed 14,000 differentially expressed genes. Conclusions Low temperatures stimulate a large cascades of molecular mechanisms in garlic, and a variety of flowering pathways operate together for the benefit of meristem transition, annual life cycle and viable reproduction results.The circadian clock appears to play a central role in the transition of the meristem from vegetative to reproductive stage in bulbous plant, serving as integrator of the low-temperature signals and the expression of the genes associated with vernalization, photoperiod and meristem transition. The reserved photoperiodic pathway is integrated at an upstream point, possibly by the same receptors. Therefore, in bulb, low temperatures stimulate cascades of developmental mechanisms, and several genetic flowering pathways intermix to achieve successful sexual and vegetative reproduction.

Juvenile and vegetative adult shoot apical meristems (SAM) are actively involved in acquisition of flowering competence, while the embryonic SAM is regarded as ``responsible'' only for germination. Comparative analyses of imbibed and stratified seeds of garlic Allium sativum show that only stratified seedlings produced bulbs and flower stems at the end of the season. Since the seed morphology of stratified and non-stratified seeds prior to sowing was similar, the differences are attributed to the molecular alterations in the embryonic SAM. Functional annotation analysis of 3000 differentially expressed genes suggests that seed imbibition reactivates the embryonic cell cycle, initiates the metabolism, and primes garlic seed germination. Stratification enhances DNA modifications, biosynthesis, cellular transport, and tissue development. Similar to vernalization of the vegetative buds, stratification of the embryonic SAM resulted in altered expression of meristem-identity and flowering homologs. Phase transitions from seed germination to flowering and bulbing in A. sativum are tightly connected, and possibly associated with downregulation of specific flowering repressor(s). The embryonic SAM plays an important role not only in seed germination, but in the entire plant life cycle, providing the foundation for the genetic regulation of major functional shifts in metabolism and development.

First Published in 2018. Routledge is an imprint of Taylor & Francis, an Informa company. © 1990 by CRC Press, LLC.

Flowering of onions is of great economical importance during the two growing seasons. When grown for bulbs, bolting plants - those which flower during the first season - are of very poor quality. The flower stalk of the onion, as in all Alliums, is an apical extension of the stem, but without histological differentiation into nodes and intern odes. Following induction and initiation, the differentiated central axis starts protruding and the scape is formed. The flower stalks of most commercially available cultivars reach a final length of 1 to 2 m, but flowering may also occur, though very rarely, within the fleshy scales of the bulb. The buds are grouped in small cymes of five to ten flowers each; the umbel is entirely enveloped by a spathe. This thin sheathing bract splits open when flowering begins. Temperature, day length and a level of nitrogen fertilizer seem to be the important environmental factors affecting flowering of the bulb onion. © 1990 by CRC Press, LLC.

Onion seed set and development are markedly affected by a number of factors, the most important ones being growth conditions, availability of pollinating insects, and the genetic make up of the individual plant. Cross-pollination is predominant in onions and leeks, in chives and most probably also in other alliums. However, onions are self-compatible, and regardless of earlier accounts, protandry does not prevent their self-pollination. In onions, pollen shed begins at anthesis and continues at irregular intervals for the next 24 to 36 h and may last up to 2 d. High temperatures and air humidities below 70% accelerate the process. Twelve to twenty four hours after pollination, the first pollen tubes with two sperm-nuclei, enter the micropyle. Onion seeds are produced in a wide range of environments, and weather conditions may change considerably during seed growth and ripening on the mother plant. These influence seed composition and subsequent performance. © 1990 by CRC Press, LLC.

Garlic flowering and bulbing are prone to photo-thermal regulation during its annual cycle. As in many other geophytes, these pathways are parallel but competitive, and can be manipulated by the environment. Both flowering and bulbing are of paramount physiological value, and of great horticultural interest. We argue that, in bolting garlic, differential regulation of only one of the two pathways by pre-planting vernalization is unfeasible, and that garlic's response to cold shows an optimal curve. Within limits, long vernalization treatments have resulted in rapid development of ‘Reproductive and Bulbing Phenotype’ with fast leaf elongation, early transition of the apical meristem to the reproductive state, development of axillary buds, flowering and bulbing. Low temperatures trigger primary signaling components, thus modulating organogenesis even under a relatively short photoperiod. We therefore propose that under a suboptimal photoperiod, favorable temperatures could substitute the plant's requirements for photoperiod and signal for the meristem transition, flowering and bulbing. The optimum response of the studied genotype was obtained after vernalization of four weeks at 4 °C. No transition of the apical meristem was evident in plants exposed to only short or no vernalization, namely the apex remained vegetative. These plants continuously produced foliage leaves, thus forming a “Leafy Phenotype” which did not branch, bulb or flower. Comprehension of the plant's response to environment is expected to facilitate physiological manipulations on the production of either bulbs or true seeds in garlic. © 2018

Background: Previously we demonstrated that an entire bacterial operon (the PRN operon) is expressible in plants when driven by the Tomato -yellow-leaf-curl-virus (TYLCV) -derived universal vector IL-60.Petroleum-derived plastics are not degradable, and are therefore harmful to the environment. Fermentation of bacteria carrying operons for polyhydroxyalkanoates (PHAs) produces degradable bioplastics which are environmentally friendly. However, bacterial production of bioplastics is not cost-effective, and attention is turning to their production in plants. Such "green" plastics would be less expensive and environmentally friendly. Hence, attempts are being made to substitute petroleum-derived plastics with "green" plastics. However, transformation of plants with genes of operons producing bioplastics has deleterious effects. Transformation of plastids does not cause deleterious effects, however it is a complicated procedures. Results: We have developed another TYLCV-based vector (SE100) and show that yet another bacterial operon (the phaCAB operon) when driven by SE100 is also expressed in plants. We employed the combination of SE100 and the phaCAB operon to drive the operon to the plastids and produce in plants a biodegradable plastic [polyhydroxybutyrate (PHB)].Here we indicate that the bacterial operon (phaCAB), when driven by the newly developed universal plant vector SE100 is directed to chloroplasts and produces in plants PHB, a leading PHA. The PHB-producing plants circumvent the need for complicated technical procedures. Conclusion: The viral vector system SE100 facilitated the production of the bio-plastic poly-3-hydroxybutyrate. This was achieved by using the full pha-CAB operon indicating that TYLCV based system can transcribe and translate genes from bacterial operons controlled by a single cis element. Our data hints to the participation of the chloroplasts in these processes.

A novel simple, fast qualitative method for detection and differentiation of PVY strains in potatoes by the LightCycler technology is described. Fluorescent-labeled probe designed to contain variable degree of homology with a ‘target sequence’ of several known reference PVY strains was annealed to PCR products of these viruses followed by a graded melting analysis. The specific characteristics of the melting curves enable the detection, distinction and differentiation of each of following four known PVY strains O-FL, O-RB, N and NTN, in a single reaction obviating the need for size or nucleotide sequence analyses. In addition, it was demonstrated that virus extracts from plants infected with more than one strain can be resolved using this procedure. The melting-curves of extracts from 55 market size tubers harvested randomly from commercial fields and compared with those of the reference virus strains, revealed the presence of O-FL, O-RB and NTN strains of PVY. © 2016, The Potato Association of America.

More than 50 species of the genus Allium have been cultivated worldwide for sustenance, flavor, and medicinal purposes, as well as for ornamentals, from the tropics to the temperate zone. In most alliums, intact tissues contain odorless, nonvolatile sulfur-containing molecules that upon cells' disruption break down enzymatically to form volatile flavor compounds that are responsible for the characteristic odor and taste of these species. The genetic makeup, photoperiod, and both storage and growth temperatures are the main factors controlling bulbing and florogenesis in these plant species. The most common Allium food crops are bulb onion garlic, leek, shallot, chives, and Welsh onion. Most fertile cultivated alliums are raised from seed, transplants, or sets. However, some sterile species, such as garlic, elephant garlic, rocambole tree onion, topsetting onions, and shallot are propagated vegetatively. During millennia of cultivation, no natural co-evolution with biotic and abiotic agents has taken place. Hence, most cultivated alliums lack many important traits, including resistance to pests and environmental stresses. Current efforts and employment of both classical and novel tools for genetic and plant physiology studies are expected to accelerate improvements in terms of distribution, yield, and quality of these important crops. © 2017 Elsevier Ltd. All rights reserved.

A concise description of the history, classification, cytology, and botany of potato is presented. The effects of the environment on the morphology, physiology, and development of the potato plant and the adverse effects of high temperatures, drought, and salinity on growth, tuber development, and tuber quality are described. Tuber dormancy and its control in association with storage and with 'seed' tubers' vigor are discussed. Principles of crop production, storage, and tuber quality are presented. © 2017 Elsevier Ltd. All rights reserved.