Effect of shooting medium and source of material on grapevine (Vitis vinifera L.) shoot tip recovery after cryopreservation.

BACKGROUND: Selecting experimental material at the optimal physiological stage is of paramount importance for successful cryopreservation. OBJECTIVE: The study was to investigate the effect of the physiological state of grapevine buds on their regrowth after liquid nitrogen exposure. METHODS: In a first set of experiments, we tested the regrowth of cryopreserved buds sampled from microcuttings cultured on shooting medium containing benzylaminopurine or zeatin riboside for various durations. In a second set of experiments, we studied the regrowth after liquid nitrogen exposure of buds sampled from different positions on the stem of in vitro plantlets. RESULTS: Regrowth of cryopreserved buds sampled from microcuttings was higher (30%), compared to buds sampled directly from in vitro plantlets (23%), for all culture durations of microcuttings on shooting medium tested (2-6 weeks). Addition of cytokinin in the shooting medium improved regrowth of cryopreserved buds compared to buds sampled from microcuttings cultured on medium devoid of growth regulators; however similar results were obtained with the two cytokinins tested. Buds sampled on nodes 3-4 and 6-7 (from the top of the stem) displayed higher regrowth compared to shoot tips. No significant differences were noted in regrowth after cryopreservation between buds sampled from microcuttings produced from the terminal node, or nodes 3-4 and 6-7. CONCLUSION: The physiological state of the plant material is important for cryopreservation success. Actively growing buds sampled from microcuttings displayed higher regrowth compared to buds sampled directly on in vitro plantlets.

The DROOPING LEAF and OsETTIN2 genes promote awn development in rice.

The awn is a long needle-like appendage that, in some grass species, is formed on the lemma that encloses floral organs together with the palea. In rice, most wild species and most strains of Oryza sativa ssp. indica generate an awn, whereas most strains of O. sativa ssp. japonica do not. In japonica, the long-awn characteristic appears to have been lost during domestication and breeding programs. Here, we found that the genes DROOPING LEAF (DL) and OsETTIN2 (OsETT2) are involved in awn development in the awned indica strain Kasalath. Genetic analyses and RNA-silencing experiments indicate that DL and OsETT2 act independently in awn formation, and that either gene alone is not sufficient for awn development. Scanning electron microscopy revealed that the top region of the lemma (a putative awn primordium) is larger in an awned floret than in an awnless floret. OsETT2 is expressed in the awn primordium in the awned indica floret, but not in the awnless japonica floret except in the provascular bundle. DL is expressed underneath the primordium at similar levels in both indica and japonica florets, suggesting non-cell-autonomous action. We hypothesize that loss of expression of OsETT2 in the awn primordium is probably associated with the failure of awn formation in japonica strains.

Comparative study of inflorescence development in Oleaceae.

PREMISE OF THE STUDY: Investigations of inflorescence architecture offer insight into the evolution of an astounding array of reproductive shoot systems in the angiosperms, as well as the potential to genetically manipulate these branching patterns to improve crop yield and enhance the aesthetics of horticultural species. The diversity of inflorescences in the economically important family Oleaceae was studied from a comparative developmental point of view for the first time, based on species of seven genera (Chionanthus, Fontanesia, Fraxinus, Jasminum, Ligustrum, Olea, Syringa). METHODS: Series of developmental stages of chemically fixed inflorescences were studied with epi-illumination light microscopy. KEY RESULTS: All taxa studied have inflorescences with terminal flowers. The inflorescences are mostly panicles, but in some cases thyrsoids or compound botryoids. Phyllotaxis of the flower-subtending bracts is mostly decussate, rarely tricussate (Fraxinus) or spiral (Jasminum). Accessory flowers or accessory inflorescences, almost unknown in Oleaceae as yet, were found in two genera. In Syringa, common bract-flower primordia are formed by a delay in early bract development compared to flower development. Such a delay is also expressed by the loss of bracts in the distal part of inflorescence branches in Syringa and Chionanthus. CONCLUSIONS: Significant variation in branching pattern and phyllotaxy was observed among the studied species of Oleaceae. The suppression of bracts and formation of accessory flowers were found as special features of inflorescence ontogeny. The occurrence of accessory flowers and accessory partial inflorescences is interesting from the point of view of dense and flower-rich inflorescences in ornamental species.

Fine mapping of a major quantitative trait loci, qSSP7, controlling the number of spikelets per panicle as a single Mendelian factor in rice.

In our previous studies, one putative QTL affecting number of spikelets per panicle (SPP) was identified in the pericentromeric region of rice chromosome 7 using a recombinant inbred population. In order to define the QTL (qSPP7), RI50, a recombinant inbred line with 70% of genetic background same as the female parent of Zhenshan 97, was selected to produce near-isogenic lines for the target region in the present study. In a BC(2)F(2) population consisting of 190 plants, the frequency distribution of SPP was shown to be discontinuous and followed the expected Mendelian ratios (1:2:1 by progeny test) for single locus segregation. qSPP7 was mapped to a 0.4 cM region between SSR marker RM3859 and RFLP marker C39 based on tests of the BC(2)F(2) population and its progeny. Its additive and dominant effects on SPP were 51.1 and 24.9 spikelets, respectively. Of great interest, the QTL region also had effects on grain yield per plant (YD), 1,000 grain weight (GW), tillers per plant (TPP) and seed setting ratio (SR). Significant correlations were observed between SPP and YD (r = 0.66) and between SPP and SR (r = -0.29) in the progeny test. 1082 extremely small panicle plants of a BC(3)F(2) population containing 8,400 individuals were further used to fine map the QTL. It turns out that qSPP7 co-segregated with two markers, RM5436 and RM5499 spanning a physical distance of 912.4 kb. Overall results suggested that recombination suppression occurred in the region and positional cloning strategy is infeasible for qSPP7 isolation. The higher grain yield of Minghui 63 homozygote as compared to the heterozygote suggested that Minghui 63 homozygote at qSPP7 in hybrid rice could further improve its yield.

The importance of barley genetics and domestication in a global perspective.

BACKGROUND: Archaeological evidence has revealed that barley (Hordeum vulgare) is one of the oldest crops used by ancient farmers. Studies of the time and place of barley domestication may help in understanding ancient human civilization. SCOPE: The studies of domesticated genes in crops have uncovered the mechanisms which converted wild and unpromising wild species to the most important food for humans. In addition to archaeological studies, molecular studies are finding new insights into the process of domestication. Throughout the process of barley domestication human selection on wild species resulted in plants with more harvestable seeds. One of the remarkable changes during barley domestications was the appearance of six-rowed barley. The gene associated with this trait results in three times more seed per spike compared with ancestral wild barley. This increase in number of seed resulted in a major dichotomy in the evolution of barley. The identification of the six-rowed spike gene provided a framework for understanding how this character was evolved. Some important barley domestication genes have been discovered and many are currently being investigated. CONCLUSIONS: Identification of domestication genes in crops revealed that most of the drastic changes during domestication are the result of functional impairments in transcription factor genes, and creation of new functions is rare. Isolation of the six-rowed spike gene revealed that this trait was domesticated more than once in the domestication history of barley. Six-rowed barley is derived from two-rowed ancestral forms. Isolation of photoperiod-response genes in barley and rice revealed that different genes belonging to similar genetic networks partially control this trait.

Identification and characterization of a major QTL responsible for erect panicle trait in japonica rice (Oryza sativa L.).

Panicle erectness (PE) is one of the most important traits for high-yielding japonica cultivars. Although several cultivars with PE trait have been developed and released for commercial production in China, there is little information on the inheritance of PE traits in rice. In the present study, 69 widely cultivated japonica cultivars and a double haploid (DH) population derived from a cross between a PE cultivar (Wuyunjing 8) and a drooping panicle cultivar (Nongken 57) were utilized to elucidate the mechanisms of PE formation and to map PE associated genes. Our data suggested that panicle length (PL) and plant height (PH) significantly affected panicle curvature (PC), with shorter PL and PH resulting in smaller PC and consequently more erect. A putative major gene was identified on chromosome 9 by molecular markers and bulk segregant analysis in DH population. In order to finely map the major gene, all simple sequence repeats (SSR) markers on chromosome 9 as well as 100 newly developed sequence-tagged site (STS) markers were used to construct a linkage group for quantitative trait locus (QTL) mapping. A major QTL, qPE9-1, between STS marker H90 and SSR marker RM5652, was detected, and accounted for 41.72% of PC variation with pleiotropic effect on PH and PL. another QTL, qPE9-2, was also found to be adjacent to qPE9-1. In addition, we found that H90, the nearest marker to qPE9-1, used for genotyping 38 cultivars with extremely erect and drooping panicles, segregated in agreement with PC, suggesting the H90 product was possibly part of the qPE9-1 gene or closely related to it. These data demonstrated that H90 could be used for marker-aided selection for the PE trait in breeding and in the cloning of qPE9-1.

Architectural evolution and its implications for domestication in grasses.

BACKGROUND: The cereal crops domesticated from grasses provide a large percentage of the calories consumed by humans. Domestication and breeding in individual cereals has historically occurred in isolation, although this is rapidly changing with comparative genomics of the sequenced or soon-to-be sequenced genomes of rice, sorghum, maize and Brachypodium. Genetic information transferred through genomic comparisons is helping our understanding of genetically less tractable crops such as the hexaploid wheats and polyploid sugarcane, as well as the approx. 10 000 species of wild grasses. In turn, phylogenetic analysis helps put our knowledge of the morphology of cereal crops into an evolutionary context. GRASS ARCHITECTURE: Domestication often involves a change in the pattern and timing of branching, which affects both vegetative and inflorescence architecture, and ultimately yield. Cereal grasses exhibit two main forms of vegetative architecture: the pooid and erhartoid cereals such as wheat and rice have multiple basal tillers, while panicoid cereals such as maize, sorghum and the millets have few tillers or even only a single main stem. These differences are reflected in the differences between the wild species of pooid and some erhartoid grasses, which emphasize basal branching over axillary branching, and the panicoid grasses, where axillary branching is more frequently found. A combination of phylogenetic and genomic analysis is beginning to reveal the similarities and differences between different cereal crops, and relate these to the diversity of wild grasses to which they are related. Recent work on genes controlling branching emphasizes that developmental genetics needs to be viewed in both an evolutionary and ecological framework, if it is to be useful in understanding how morphology evolves. Increasingly, exploring the phylogenetic context of the crop grasses will suggest new ways to identify and create combinations of morphological traits that will best suit our future needs.

Pollinator response to female and male floral display in a monoecious species and its implications for the evolution of floral dimorphism.

Pollinator-mediated selection has been hypothesized as one cause of size dimorphism between female and male flowers. Flower number, ignored in studies of floral dimorphism, may interact with flower size to affect pollinator selectivity. In the present study, we explored pollinator response, and estimated pollen receipt and removal, in experimental populations of monoecious Sagittaria trifolia, in which plants were manipulated to display three, six, nine or 12 female or male flowers per plant. In this species, female flowers are smaller but have a more compressed flowering period than males, creating larger female floral displays. Overall, pollinators preferred to visit male rather than female displays of the same size. Both first visit per foraging bout and visitation rates to female displays increased with display size. However, large male displays did not show increased attractiveness to pollinators. A predicted relationship that pollen removal, rather than pollen receipt, is limited by pollinator visitation was confirmed in the experimental populations. The results suggest that the lack of selection on large male displays may affect the evolution of floral dimorphism in this species.

Fine mapping of a quantitative trait locus for grain number per panicle from wild rice (Oryza rufipogon Griff.).

SIL040, an introgression line (IL) developed by introgressing chromosomal segments from an accession of Oryza rufipogon into an indica cultivar Guichao 2, showed significantly less grains per panicle than the recurrent parent Guichao 2. Quantitative trait locus (QTL) analysis in F2 and F3 generations derived from the cross between SIL040 and Guichao 2 revealed that gpa7, a QTL located on the short arm of chromosome 7, was responsible of this variation. Alleles from O. rufipogon decreased grains per panicle. To fine mapping of gpa7, a high-resolution map with 1,966 F2 plants derived from the cross between SIL040 and Guichao 2 using markers flanking gpa7 was constructed, and detailed quantitative evaluation of the structure of main panicle of each of F3 families derived from recombinants screened was performed. By two-step substitution mapping, gpa7 was finally narrowed down to a 35-kb region that contains five predicted genes in cultivated rice. The fact that QTLs for five panicle traits (length of panicle, primary branches per panicle, secondary branches per panicle, grains on primary branches and grains on secondary branches) were all mapped in the same interval as that for gpa7 suggested that this locus was associated with panicle structure, showing pleiotropic effects. The characterizing of panicle structure of IL SIL040 further revealed that, during the domestication from common wild allele to cultivated rice one at gpa7, not only the number of branches and grains per panicle increased significantly, more importantly, but also the ratio of secondary branches per panicle to total branches per panicle and the ratio of grains on secondary branches per panicle to total grains per panicle increased significantly. All these results reinforced the idea that gpa7 might play an important role in the regulation of grain number per panicle and the ratio of secondary branches per panicle during the domestication of rice panicle.

Advances in maize genomics: the emergence of positional cloning.

Positional cloning has been and remains a powerful method for gene identification in Arabidopsis. With the completion of the rice genome sequence, positional cloning in rice also took off, including the cloning of several quantitative trait loci. Positional cloning in cereals such as maize whose genomes are much larger than that of rice was considered near impossible because of the vast amounts of repetitive DNA. However, conservation of synteny across the cereal genomes, in combination with new maize resources, has now made positional cloning in maize feasible. In fact, a chromosomal walk is usually much faster than the more traditional method of gene isolation in maize by transposon tagging.

Developmental anatomy and morphology of the ovule and seed of heliconia (heliconiaceae, zingiberales).

The developmental anatomy and morphology of the ovule and seed in several species of Heliconia were investigated as part of an embryological study of the Heliconiaceae and to provide a better understanding of their relationships with the other families of the Zingiberales. Heliconia species have an ovule primordium with an outer integument of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte and a single parietal cell, which in turn are divided only anticlinally to form a single parietal layer, disintegrating later during gametogenesis. The embryo sac was fully developed prior to anthesis. In the developing seed, the endosperm was nuclear, with wall formation in the globular stage; a nucellar pad was observed during embryo development, but later became compressed. The ripe fruit contained seeds enveloped by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum at the basal end; the embryo was considered to be differentiated. Most of these characteristics are shared with other Zingiberales, although the derivation of the operculum from the funicle and the formation of the main mechanical layer by the endocarp are unique to the Heliconiaceae.

[Mapping QTLs controlling vascular bundle and panicle-related traits from Yuanjiang common wild rice (Oryza rufipogon Griff.)].

An advanced backcross population (BC3F2), derived from the cross between Yuanjiang common wild rice as the donor parent and Teqing as recurrent parent, was used to map QTLs controlling the number of vascular bundle and panicle-related traits from Yuanjiang common wild rice. Seven QTLs controlling the number of large vascular bundles in peduncle were detected on chromosome 1, 2, 3, 4, 7 and 10. Five QTLs for the number of small vascular bundles in peduncle were mapped on chromosome 1, 2, 3, 4 and 8. A total of 15 QTLs for the number of primary and secondary rachis branches and spikelets per panicle were identified on all chromosomes except chromosome 11 and 12. Most of alleles derived from O. rufipogon Griff. showed negative effect that reduced significantly vascular bundle, rachis branches and spikelets per panicle, suggesting that during the evolution from common wild rice to cultivated rice, favorable alleles were retained while removed undesirable ones. Most of QTLs controlling vascular bundle, rachis branches and spikelets per panicle showed cluster form or close linkage on chromosomes. The directions of their additive effects were consistent, which explained the genetic basis of significant correlation of their phenotypic characters. All the information suggested parallel evolution relationship among these traits.

Competence to respond to floral inductive signals requires the homeobox genes PENNYWISE and POUND-FOOLISH.

The transition from vegetative to reproductive development establishes new growth patterns required for flowering. This switch is controlled by environmental and/or intrinsic developmental cues that converge at the shoot apical meristem (SAM). During this developmental transition, floral inductive signals cause the vegetative meristem to undergo morphological changes that are essential for flowering. Arabidopsis plants containing null mutations in two paralogous BEL1-like (BELL) homeobox genes, PENNYWISE (PNY) and POUND-FOOLISH (PNF), disrupt the transition from vegetative to reproductive development. These double mutants are completely unable to flower even though the SAM displays morphological and molecular changes that are consistent with having received floral inductive signals. These studies establish a link between the competence to receive floral inductive signals and restructuring of the SAM during floral evocation.

Interactions among moths, crossbills, squirrels, and lodgepole pine in a geographic selection mosaic.

Repeated patterns among biological communities suggest similar evolutionary and ecological forces are acting on the communities. Conversely, the lack of such patterns suggests that similar forces are absent or additional ones are present. Coevolution between a seed predator, the red crossbill (Loxia curvirostra complex), and lodgepole pine (Pinus contorta var. latifolia) exemplifies the ecological and evolutionary predictions for coevolving systems. In the absence of another seed predator and preemptive competitor (pine squirrels Tamiasciurus hudsonicus), natural selection by crossbills results in the evolution of larger cones with thicker distal scales, while relaxation of selection by squirrels results in the evolution of cones with more seeds and a greater ratio of seed mass to cone mass. However, in one range, the Little Rocky Mountains, distal scale thickness has diverged as expected but cone size has not. In these mountains seed predation by lodgepole pine cone borer moths (Eucosma recissoriana) was about 10 times greater than in other ranges lacking squirrels. We quantified moth predation and cone traits and found that moths select for smaller cones with fewer seeds. Thus, selection by moths in the Little Rocky Mountains counters both selection by crossbills for large cone size and relaxation of selection by squirrels favoring more seeds per cone and accounts for the relatively small and few-seeded cones in these mountains. It is also apparent that selection by crossbills changes seed defenses in a manner that favors seed predation by moths, whereas selection by squirrels likely reduces such predation. These results demonstrate the importance of considering the evolutionary consequences of community context in locally evolved (coevolved) traits and interactions.

Comparison methods for branching and axillary flowering sequences.

Comparing branching and axillary flowering patterns accurately is a major issue both in botany and in various agronomic contexts. Data take the form of sequences which naturally represent the underlying structural information of branching and axillary flowering patterns. Various comparison methods are proposed based either on sequence alignment or on the computation of dissimilarity measures between (hidden) Markovian models built from sets of sequences. Sequence alignment is a natural complement to the exploratory tools and statistical models proposed in Guédon et al. (J. Theor. Biol. 212 (2001) 481) with the distinctive feature of applying to individual sequences. Comparison methods may also be used to reveal some grouping within a set of sequences or to evaluate the strength of a predefined grouping of sequences. The proposed approach is illustrated by examples corresponding to different plant species and different biological or agronomic objectives.

Genetic and morphological characterization of the barley uniculm2 (cul2) mutant.

Axillary meristem growth and development help define plant architecture in barley (Hordeum vulgare L). Plants carrying the recessive uniculm2 (cul2) mutation initiate vegetative axillary meristem development but fail to develop tillers. In addition, inflorescence axillary meristems develop into spikelets, but the spikelets at the distal end of the inflorescence have an altered phyllotaxy and are sometimes absent. Double mutant combinations of cul2 and nine other recessive mutations that exhibit low to high tiller number phenotypes resulted in a uniculm vegetative phenotype. One exception was the occasional multiple shoots produced in combination with granum-a; a high tillering mutant that occasionally produces two shoot apical meristems. These results show that the CUL2 gene product plays a role in the development of axillary meristems into tillers but does not regulate the development of vegetative apical meristems. Moreover, novel double-mutant inflorescence phenotypes were observed with cul2 in combination with the other mutants. These data show that the wild-type CUL2 gene product is involved in controlling proper inflorescence development and that it functions in combination with some of the other genes that affect branching. Our genetic analysis indicates that there are genetically separate but not distinct regulatory controls on vegetative and inflorescence axillary development. Finally, to facilitate future positionally cloning of cul2, we positioned cul2 on chromosome 6(6H) of the barley RFLP map.

STY1 and STY2 promote the formation of apical tissues during Arabidopsis gynoecium development.

Gynoecium ontogenesis in Arabidopsis is accomplished by the co-ordinated activity of genes that control patterning and the regional differentiation of tissues, and ultimately results in the formation of a basal ovary, a short style and an apical stigma. A transposon insertion in the STYLISH1 (STY1) gene results in gynoecia with aberrant style morphology, while an insertion mutation in the closely related STYLISH2 (STY2) gene has no visible effect on gynoecium development. However, sty1-1 sty2-1 double mutant plants exhibit an enhanced sty1-1 mutant phenotype and are characterized by a further reduction in the amount of stylar and stigmatic tissues and decreased proliferation of stylar xylem. These data imply that STY1 and STY2 are partially redundant and that both genes promote style and stigma formation and influence vascular development during Arabidopsis gynoecium development. Consistently, STY1 and STY2 are expressed in the apical parts of the developing gynoecium and ectopic expression of either STY1 or STY2 driven by the CaMV 35S promoter is sufficient to transform valve cells into style cells. STY1::GUS and STY2::GUS activity is detected in many other organs as well as the gynoecium, suggesting that STY1 and STY2 may have additional functions. This is supported by the sty1-1 sty2-1 double mutants producing rosette and cauline leaves with a higher degree of serration than wild-type leaves. STY1 and STY2 are members of a small gene family, and encode proteins with a RING finger-like motif. Double mutant analyses indicate that STY1 genetically interacts with SPATULA and possibly also with CRABS CLAW.

Two new Fagopyrum (Polygonaceae) species, F. gracilipedoides and F. jinshaense from Yunnan, China.

Two new Fagopyrum (Polygonaceae) species, F. gracilipedoides and F. jinshaense, are described. Fagopyrum gracilipedoides was only found at Baoshan village, Lijiang district, Yunnan province, China. This species resembles the weedy species, F. gracilipes in morphology but they differ in both mating system and ploidy level; F. gracilipedoides is a heterostylous self-incompatible diploid species (2n = 16), whereas F. gracilipes is a self-compatible tetraploid species (2n = 32). Fagopyrum jinshaense was found along the Jinsha River valley near the border of Sichuan, Yunnan, and Tibet in China. Fagopyrum jinshaense is morphologically similar to F. gilesii, but they differ in the morphology of their inflorescences. Fagopyrum jinshaense has long spike-like inflorescences, whereas F. gilesii has a compact head-like one. Both F. jinshaense and F. gilesii are self-incompatible with heterostylous flowers and are diploid. Interspecific crosses between the two new species and already known species in the urophyllum group of Fagopyrum resulted in the production of self- and cross-sterile hybrids in the species combinations attempted. These results indicated that both new species are reproductively isolated from other Fagopyrum species. Molecular phylogenetic analysis based on the nucleotide sequence of the trnK gene intron in chloroplast DNA revealed the following points: 1) F. gracilipedoides, F. rubifolium and F. gracilipes / F. capillatum showed a trifurcating relationship and 2) F. jinshaense formed a clade with F. pleioramosum, F. callanthum, and F. macrocarpum, and was only distantly related to F. gilesii. In the clade of F. capillatum, F. gracilipes, F. gracilipedoides and F. rubifolium, the breakdown of self-incompatibility accompanying genome duplication seems to have occurred twice independently.