Variability and adaptability of Miscanthus species evaluated for energy crop domestication

A growing body of evidence indicates that second‐generation energy crops can play an important role in the development of renewable energy and the mitigation of climate change. However, dedicated energy crops have yet to be domesticated in order to fully realize their productive potential under unfavorable soil and climatic conditions. To explore the possibility of domesticating Miscanthus crops in northern China where marginal and degraded land is abundant, we conducted common garden experiments at multiple locations to evaluate variation and adaptation of three Miscanthus species that are likely to serve as the wild progenitors of the energy crops. A total of 93 populations of Miscanthus sinensis, Miscanthus sacchariflorus, and Miscanthus lutarioriparius were collected across their natural distributional ranges in China and grown in three locations that represent temperate grassland with cold winter, the semiarid Loess Plateau, and relatively warm and wet central China. Evaluated with growth traits such as plant height, tiller number, tiller diameter, and flowering time, the Miscanthus species showed high levels of genetic variation within and between species. There were significant site × population interactions for almost all traits of M. sacchariflorus and M. sinensis, but not M. lutarioriparius. The northern populations of M. sacchariflorus had the highest establishment rates at the most northern site owing to their strong cold tolerance. An endemic species in central China, M. lutarioriparius, produced not only the highest biomass of the three species but also higher biomass at the Loess Plateau than the southern site near its native habitats. These results demonstrated that the wild species harbored a high level of genetic variation underlying traits important for crop establishment and production at sites that are colder and drier than their native habitats. The natural variation and adaptive plasticity found in the Miscanthus species indicated that they could provide valuable resources for the development of second‐generation energy crops.     

Agronomic evaluation of prospective new crop species

Preliminary field evaluations for 162 species are reported. This work represents a portion of a team-oriented effort to develop new crops for American agriculture. These species are potential new oilseed sources of epoxy, crepenynic, erucic, and other fatty acids, and sources of seed gum, steroids, and pulp. Euphorbia lagascae andCephalaria setosa show the most promise for crop development as epoxy acid sources, but both require substantial improvement through breeding.Crepis alpina, a small-seeded species with excellent seed retention, is the best prospect for providing an oil rich in crepenynic acid. A selection and breeding program is under way. None of the species tested as erucic acid sources equalled the crop potential of crambe and selected Brassicas.Briza spicata, a small, moderately productive grass, is the richest known source of glycolipids.B. spicata has been grown successfully as a winter annual at several locations. Earlier maturity and better seedling vigor is needed inSatureja hortensis, a source of oil similar to linseed oil.Xeranthemum annuum, an attractive, winter annual and everlasting, is very good agronomically, but the use of the oil with its mixture of several fatty acids is not economically favorable.Solanum khasianum shows agronomic promise as a source of the steroid, solasodine.Cassia occidentalis, C. bonariensis, Crotalaria leioloba, andC. stipularia are productive potential seed gum sources. These species, especiallyCassia occidentalis, seem to be sufficiently good agronomically to justify intensive breeding. Of the various sources of pulp, emphasis is on kenaf because highyielding, well-adapted varieties are available.Crotalaria juncea merits breeding effort, and other species show sufficient promise for further evaluation.     

The crop milk: a potential new route for carotenoid-mediated parental effects

Allocation of carotenoid pigments, either through nutritional provisioning or from endogenous reserves, makes up a form of non-genetic parental investment to progeny that may contribute to fitness. To date, carotenoids derived from endogenous reserves have been acknowledged as important vectors in translating only avian female phenotype and environmental conditions experienced prior to laying. Here, we show that in columbidae, crop milk delivered by both parents may provide chicks with a large amount of endogenous carotenoids at the postzygotic stage. Major carotenoids were xanthophylls and beta-carotene, but their concentrations showed large variation among individuals. Interestingly, a large amount of this variation was explained by brood identity, suggesting either environmental influences and/or phenotypic influences on a parent's ability to transfer these biomolecules. Our study therefore illuminates a potential new route for endogenous carotenoid-mediated parental effects.     

Establishment and in vitro regeneration studies of the potential oil crop species Camelina sativa

Camelina sativa was successfully established in vitro and systems for the regeneration of shoots from leaf explants developed. Methods for the surface-sterilisation of seeds were used which gave 95% germination, though the in vitro grown seedlings failed to develop beyond 28 days culture. In a micropropagation system, the rooting response of nodal explants was increased from a control level of 26.4% to 46.7% by the addition of 5.4 μM NAA. Leaf explants were more efficient for the regeneration of root and shoots than hypocotyls. For regeneration from leaf tissue the use of auxin (NAA) alone in the medium above a level of 0.54 μM resulted in root or callus growth. Cytokinin, in the form of BA alone failed to induce regeneration, but a combination of 4.44 μM BA and 0.54 μM NAA induced shoot regeneration at rates over 10.0 shoots per explant. Regenerated shoots were successfully transplanted to soil and flowered and set seed normally. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genomics reveals new landscapes for crop improvement

The sequencing of large and complex genomes of crop species, facilitated by new sequencing technologies and bioinformatic approaches, has provided new opportunities for crop improvement. Current challenges include understanding how genetic variation translates into phenotypic performance in the field.     

Screening methods for the evaluation of crop allelopathic potential

There is increasing interest in the development of allelopathic crop varieties for weed suppression. Allelopathic varieties are likely to be able to suppress weeds by natural exudation of bioactive allelochemicals, thereby reducing dependence upon synthetic herbicides. Screening bioassays are essential tools in identifying crop accessions with allelopathic potential. A number of crops have been screened for this allelopathic trait, and key issues in selecting and designing screening bioassays are reviewed. It is recommended that a combination of different bioassays be used in the evaluation of crop allelopathic potential. Laboratory bioassays, field testing, and chemical screening are important steps, and none of them can be precluded if conclusive evidence of crop allelopathy is to be established. More concerted efforts are needed in screening crop germplasm before the development of allelopathic varieties occurs.     

Quantitative analysis of phenolics in selected crop species and biological activity of these compounds evaluated by sensitivity of Echinochloa crus-galli

The purpose of this study was to determine the content of selected phenolic compounds in white mustard, buckwheat, spring barley, oat and rye grown under field conditions. Moreover, the allelopathic efficiency of these compounds was evaluated by sensitivity of Echinochloa crus-galli. The aromatic acids: trans-cinnamic, salicylic, ferulic, chlorogenic, p-hydroxybenzoic, protocatechuic, p-coumaric and vanillic were separated from crop plants by TLC and determined spectrophotometrically. Differences in concentrations of analysed compounds were observed for most of the examined plant species. The highest concentration was noticed for cinnamic acid and ranged from 360 μg·g⁻¹ DW in rye to 2770 μg·g⁻¹ DW in spring barley. The relatively high concentration was noticed for ferulic acid (from 73.8 μg·g⁻¹ DW in buckwheat to 1046 μg·g⁻¹ DW in spring barley) and p-coumaric acid (from 50 μg·g⁻¹ DW in oat to 1499 μg·g⁻¹ DW in buckwheat). The observed differences in the phenolics content between two successive vegetation seasons can reflect the effect of abiotic and biotic environmental factors on the phenolics level in studied plants. In the greenhouse experiment the effect of particular compounds on the growth of Echinochloa crus-galli was also studied. It has been found that the examined phenolics, and especially trans-cinnamic acid and mixture of phenolic compounds, significantly inhibit the growth of Echinochloa crus-galli. The obtained results may contribute to the explanation of the biological activity of some phenolic compounds.     

Family-based association mapping in crop species

Identification of allelic variants associated with complex traits provides molecular genetic information associated with variability upon which both artificial and natural selections are based. Family-based association mapping (FBAM) takes advantage of linkage disequilibrium among segregating progeny within crosses and among parents to provide greater power than association mapping and greater resolution than linkage mapping. Herein, we discuss the potential adaption of human family-based association tests and quantitative transmission disequilibrium tests for use in crop species. The rapid technological advancement of next generation sequencing will enable sequencing of all parents in a planned crossing design, with subsequent imputation of genotypes for all segregating progeny. These technical advancements are easily adapted to mating designs routinely used by plant breeders. Thus, FBAM has the potential to be widely adopted for discovering alleles, common and rare, underlying complex traits in crop species.     

A new mechanism in plant engineering: The potential roles of microRNAs in molecular breeding for crop improvement

MicroRNAs (miRNAs) are small, endogenous, noncoding RNAs that negatively modulate the expression of genes by inhibiting translation or by promoting the degradation of target mRNAs. miRNAs are now known to have greatly expanded roles in a variety of plant developmental processes, in signal transduction, and in the response to environmental stress and pathogen invasion. Because of their ability to inactivate either specific genes or entire gene families, artificial miRNAs function as dominant suppressors of gene activity when brought into a plant. Consequently, miRNA-based manipulations have emerged as promising new approaches for the improvement of crops. This includes the development of breeding strategies and the genetic modification of agronomic traits. Herein, we highlight new findings regarding the roles of miRNAs in plant traits, and describe the current miRNA-based plant engineering approaches. Finally, we consider the feasibility of modulating current approaches to address future challenges such as breeding programs to increase crop yield.     

Plant hormone interactions: innovative targets for crop breeding and management

Here we highlight how both the root and shoot environment impact on whole plant hormone balance, particularly under stresses such as soil drying, and relate hormone ratios and relative abundances to processes influencing plant performance and yield under both mild and more severe stress. We discuss evidence (i) that abscisic acid (ABA) and ethylene act antagonistically on grain-filling rate amongst other yield-impacting processes; (ii) that ABA's effectiveness as an agent of stomatal closure can be modulated by coincident ethylene or cytokinin accumulation; and (iii) that enhanced cytokinin production can increase growth and yield by improving foliar stay-green indices under stress, and by improving processes that impact grain-filling and number, and that this can be the result of altered relative abundances of cytokinin and ABA (and other hormones). We describe evidence and novel processes whereby these phenomena are/could be amenable to manipulation through genetic and management routes, such that plant performance and yield can be improved. We explore the possibility that a range of ABA-ethylene and ABA-cytokinin relative abundances could represent targets for breeding/managing for yield resilience under a spectrum of stress levels between severe and mild, and could circumvent some of the pitfalls so far encountered in the massive research effort towards breeding for increases in the complex trait of yield.     

Sucrose accumulation in sugarcane: a potential target for crop improvement

Sugarcane is a highly productive crop plant with the capacity of storing large amounts of sucrose. Sucrose accumulation in the stem of sugarcane has been studied extensively. The initial recognition and characterization of the enzymes involved in sucrose synthesis and cleavage led to the widely accepted models of how sucrose accumulation occurs in the storage tissue. New insights were gained into the physiological role of individual enzyme activities in the process of sucrose accumulation in sugarcane. Studies on cell cultures and on isolated cell fragments initially supported and strengthened these models, but more recent research has revealed their weaknesses. A dynamic model of rapid cycling of sucrose and turnover of sucrose between vacuole, metabolic and apoplastic compartments explains much of the data, but the details of how the cycling is regulated needs to be explored. Genomic research into sucrose metabolism has been based on the premise that cataloging genes expressed in association with the stalk development would ultimately lead to the identification of genes controlling the accumulation of sucrose. Considerable progress has been made in understanding and manipulating the sugarcane genome using biotechnological and cell biology approaches. Thus, the greater understanding of physiology of sucrose accumulation and the sugarcane genome will play a significant role in the future sugarcane improvement programs and will offer new opportunities to develop it as a new-generation industrial crop.     

Okra,potential multiple-purpose crop for the temperate zones and tropics

Immature okra pods are commonly consumed as a vegetable. In addition, okra has attributes that could permit it to be used for other purposes. Leaves, buds, and flowers are edible; dried seeds could provide oil, protein, vegetable curd and a coffee additive or substitute. Foliage could be used for biomass, and the dried stems could serve as a source of paper pulp or fuel. The possible gossypol and cyclopropenoid contents of okraseed must be considered when food or feed use for monogastrates is contemplated. Although little development work has been done with okra, available germ plasm appears to be sufficiently diverse to permit genetic improvement.     

Plant potential for detoxification (review)

Data on the uptake, excretion, and biodegradation of organic xenobiotics by plants are reviewed. Detoxification pathways operating in plants and their role in remediation of biosphere are described. Structure-, concentration, and time-dependent effects of xenobiotics on the ultrastructural organization of cells are analyzed.     

Plant potential for detoxification (Review)

Data on the uptake, excretion, and biodegradation of organic xenobiotics by plants are reviewed. Detoxification pathways operating in plants and their role in remediation of the biosphere are described. Structure-, concentration-, and time-dependent effects of xenobiotics on the ultrastructural organization of cells are analyzed.     

Characterization of a new tyrosinase from Pycnoporus species with high potential for food technological applications

AIMS: Tyrosinase production by Pycnoporus cinnabarinus and Pycnoporus sanguineus was screened among 20 strains originating from various geographical areas, particularly from tropical environments. The tyrosinase from the most efficient strain was purified and characterized and tested for food additive applications. METHODS AND RESULTS: Monophenolase and diphenolase activities of tyrosinase were measured from cell lysate from the 20 Pycnoporus strains, for 8-10 days of cultivation. The strain P. sanguineus CBS 614.73 showed the highest productivity (45.4 and 163.6 U g(-1) protein per day for monophenolase and diphenolase respectively). P. sanguineus CBS 614.73 tyrosinase was purified from concentrated cell lysate, anion-exchange, size-exclusion and hydroxyapatite chromatography, with a final yield of 2% and a purification factor of 35-38. The pure enzyme was a monomere with a molecular mass of 45 kDa and it showed four isoforms or isoenzymes with pI between 4.5-5. No N-glycosylation was found. The N-terminal amino acid sequence was IVTGPVGGQTEGAPAPNR. The enzyme was shown to be almost fully active in a pH range of 6-7, in a large temperature range (30-70 degrees C), and was stable below 60 degrees C. The main kinetic constants were determined. The tyrosinase was able to convert p-tyrosol and p-coumaric acid into hydroxytyrosol and caffeic acid, respectively, and it could also catalyse the cross-linking formation of a model protein. CONCLUSIONS: Among the genus Pycnoporus, known for the production of laccase, the strain P. sanguineus CBS 614.73 was shown to produce one other phenoloxidase, a new monomeric tyrosinase with a specific activity of 30 and 84 U mg(-1) protein for monophenolase and diphenolase respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: This study identified P. sanguineus CBS 614.73 as a potential producer of a tyrosinase which demonstrated effectiveness in the synthesis of antioxidant molecules and in protein cross-linking.     

Plant genera and species new to China recently found in northwest Xinjiang

Two genera new to China, Fibigia and Pachyneurum and 10 species found in China for the first time, Puccinellia kalininae, Stellaria pulvinata, Nanophyton mongolicum, Capsella orienalis, Pachyneurum grandiflorum, Fibigia spathulata, Craniospermum tuvinicum, Euphrasia schischkinii, E. syreitschikovii, Veronica schmakovii along with 3 species previously unknown in Xinjiang, Rorippa indica, Acalypha australis, and Phalaris canariensis, found in northwest Xinjiang are reported. In addition, the distribution of two species in China is corrected: Lepidium densiflorum is firstly reported for Nei Mongol while the occurrence of Draba sibirica in Gansu is not confirmed. Results of floristic studies by the Chinese–Russian Altai expedition during 2004–2007 are also summarized including 34 species and 1 subspecies revealed as new for China; 7 species confirmed to occur in China; one genus and 5 species not confirmed for China, as well as a number of new records for various provinces, mostly Xinjiang.     

Different behaviour of crop species in phosphate absorption

Summary Isotopic-dilution technique was used to study the differential phosphate absorption abilities of several field crops. The response of crops was found to be inversely related to the ratio of phosphorus absorbed from the soil to that absorbed from the fertilizer. The ‘A’ values ranged from 2.03 ppm for mustard to 21.77 ppm for soybeans. A highly significant correlation (r=0.77**) was found between per cent yields and the ‘A’ values.