Triterpene methyl ethers of Chionochloa (Gramineae)

The leaf wax of twenty species of Chionochloa was examined for triterpene methyl ethers; twelve species gave positive yields. The known pentacyclic methyl ethers arundoin, miliacin, lupeol methyl ether and β-amyrin methyl ether were identified and the methyl ethers of the tetracyclic alcohols, cycloartenol and parkeol are reported as new natural products. Arundoin and miliacin occur in many species while the remaining compounds may be suitable chemotaxonomic markers.     

Biochemical genetic markers in sugarcane

Summary Isozyme variation was used to identify biochemical markers of potential utility in sugarcane genetics and breeding. Electrophoretic polymorphism was surveyed for nine enzymes among 39 wild and noble sugarcane clones, belonging to the species most closely related to modern varieties. Up to 114 distinct bands showing presence versus absence type of variation were revealed and used for qualitative characterization of the materials. Multivariate analysis of the data isolated the Erianthus clone sampled and separated the Saccharum spontaneum clones from the S. robustum and S. officinarum clones; the latter two were not differentiated from one another. The analysis of self-progenies of a 2n=112 S. spontaneum and of a commercial variety showed examples of mono- and polyfactorial segregations. Within the progeny of the variety, co-segregation of two isozymes frequent in S. spontaneum led to them being assigned to a single chromosome initially contributed by a S. spontaneum donor. This illustrates how combined survey of ancestral species and segregation analysis in modern breeding materials should permit using the lack of interspecific cross-over to establish linkage groups in a sugarcane genome.     

Hydrocarbons in leaf waxes of Saccharum and related genera

The composition of the n-alkanes in the leaf waxes of over 80 clones of Saccharum officinarum, S. edule, S. robustum, S. spontaneum and from a number of related species have been compared by GLC. The waxes contain predominantly odd alkanes, C₂₇–C₃₅, the major components being C₂₉ and C₃₁. In a number of clones, particularly of S. edule, a homologous series of alkenes was also present. No chemotaxonomic relationship could be derived from the compositions as the intraspecific variation was greater than the interspecific variations.     

Differential detection of transposable elements between Saccharum species

Cultivars of sugarcane (Saccharum) are hybrids between species S. officinarum (x = 10, 2n = 8x = 80) and S. spontaneum (x = 8, 2n = 5 – 16x = 40 – 128). These accessions have 100 to 130 chromosomes, 80–85% of which are derived from S. officinarum, 10–15% from S. spontaneum, and 5–10% are possible recombinants between the two genomes. The aim of this study was to analyze the repetition of DNA sequences in S. officinarum and S. spontaneum. For this purpose, genomic DNA from S. officinarum was digested with restriction enzymes and the fragments cloned. Sixty-eight fragments, approximately 500 bp, were cloned, sequenced and had their identity analyzed in NCBI, and in the rice, maize, and sorghum genome databases using BLAST. Twelve clones containing partial transposable elements, one single-copy control, one DNA repetitive clone control and two genome controls were analyzed by DNA hybridization on membrane, using genomic probes from S. officinarum and S. spontaneum. The hybridization experiment revealed that six TEs had a similar repetitive DNA pattern in the genomes of S. officinarum and S. spontaneum, while six TEs were more abundant in the genome of S. officinarum. We concluded that the species S. officinarum and S. spontaneum have differential accumulation LTR retrotransposon families, suggesting distinct insertion or modification patterns.     

Inheritance of triterpene methyl ethers in Cortaderia (Gramineae)

The distribution of triterpene methyl ethers in several generations of interspecific hybrids of Cortaderia indicates dominant gene control of their synthesis. The hybrid C. richardii × C. toetoe is an exception because synthesis of α- and β-amyrin methyl ethers is suppressed in F₁ and F₂, but is restored in the backcross F₁ × C. toetoe; this backcross generation was heterozygous for genes for the amyrin methyl ethers, and on selfing segregated in a simple Mendelian ratio.     

Characterisation of the double genome structure of modern sugarcane cultivars (Saccharum spp.) by molecular cytogenetics

Cultivated sugarcane clones (Saccharum spp., 2n=100 to 130) are derived from complex interspecific hybridizations between the speciesS. officinarum andS. spontaneum. Using comparative genomic DNA in situ hybridization, we demonstrated that it is possible to distinguish the chromosomes contributed by these two species in an interspecific F1 hybrid and a cultivated clone, R570. In the interspecific F1 studied, we observed n+n transmission of the parental chromosomes instead of the peculiar 2n+n transmission usually described in such crosses. Among the chromosomes of cultivar R570 (2n=107–115) about 10% were identified as originating fromS. spontaneum and about 10% were identified as recombinant chromosomes between the two speciesS. officinarum andS. spontaneum. This demonstrated for the first time the occurrence of recombination between the chromosomes of these two species. The rDNA sites were located by in situ hybridization in these two species and the cultivar R570. This supported different basic chromosome numbers and chromosome structural differences between the two species and provided a first bridge between physical and genetical mapping in sugarcane.     

Phylogenetic Analysis of Different Ploidy Saccharum spontaneum Based on rDNA-ITS Sequences

Saccharum spontaneum L. is a crucial wild parent of modern sugarcane cultivars whose ploidy clones have been utilized successfully in improving the stress resistance and yield related traits of sugarcane cultivars. To establish knowledge regarding the genetic variances and evolutional relationships of ploidy clones of Saccharum spontaneum collected in China, the rDNA-ITS sequences of 62 ploidy clones including octaploid clones (2n = 64), nonaploid clones (2n = 72), decaploid clones (2n = 80), and dodecaploid clones (2n = 96), were obtained and analyzed. The rDNA-ITS sequences of four species from Saccharum and Sorghum bicolor selected as controls. The results showed that decaploid clones (2n = 80) possess the most abundant variances with 58 variable sites and 20 parsim-informative sites in ITS sequences, which were then followed by octaploid clones with 43 variable sites and 17 parsim-informative sites. In haplotype diversity, all four population exhibited high diversity, especially nonaploid and decaploid populations. By comparing the genetic distances among four ploidy populations, the dodecaploid population exhibited the closest relationship with the nonaploid population, and then the relationship strength decreased successively for the decaploid population and then for the octaploid population. Population differentiation analysis showed that the phenomena of population differentiation were not found among different ploidy populations, and low coefficient of gene differentiation(Gst) and high gene flow(Nm) occur among these populations possessing close genetic relationship. These results mentioned above will contribute to the understanding of the evolution of different ploidy populations of Saccharum spontaneum and provide vital knowledge for their utilization in sugarcane breeding and innovation.     

Quantitative analysis of the effect of selection history on sugar yield adaptation of sugarcane clones

An objective of the CSR sugarcane breeding programme in Australia was to assess the scope for broadening the genetic base of the commercial sugarcane germ plasm through interspecific hybridization with Saccharum spontaneum clones. The contribution of both selection history and S. spontaneum to sugar yield and its components was investigated in the germ plasm pool assembled. The analysis was conducted on a data-set of 256 clones, consisting of parents and full-sib families generated from 32 biparental crosses, tested in six environments. The minimum number of generations back to S. spontaneum ancestor in the clone's pedigree was used as a germ plasm score. The geographical origin and selection history of each parent and their use in the biparental crosses were used to develop a selection history score for parents and offspring. The variation for seven attributes, cane yield, commercial cane sugar %, sugar yield, stalk number per stool, stalk weight, fibre % and ash % juice was partitioned according to the germ plasm and selection history scores. Significant (P<0.05) clone variation and clone x environment interaction for all attributes was present. The germ plasm scores accounted for a significant (P<0.05) component of the clone variation for all of the attributes except cane yield. There was an increase in sugar yield with an increase in the minimum number of generations back to a S. spontaneum clone. The selection history groups accounted for a high proportion of the variation among parental clones for all of the attributes except cane yield. This suggested that parents were the outcome of strong selection pressure for the commercial cane attributes. However, the selection history groups for the offspring produced by random mating of parents did not account for a high proportion of the variation for the attributes. Using the mixture method of classification we partitioned the 256 clones into five groups for patterns of performance for the seven attributes across the six environments. The five groups emphasized major differences in the patterns of performance for the seven attributes across environments. The distribution of germ plasm and selection history scores in each of the five groups indicated that their patterns of performance were associated with selection history and minimum generations to S. spontaneum. Therefore, both the analysis on selection history and germ plasm scores (extrinsic classification) and the analysis on the mixture method of classification (intrinsic classification) emphasized the influence of selection history on the sugar yield of sugarcane.     

中国十倍体割手密资源抗逆功能标记的遗传多样性分析

整倍体割手密是现代甘蔗品种重要的野生亲本和抗逆性状基因源,为了明确其抗逆相关基因的遗传背景,该研究选用来自脱水绑定因子DREB、水通道蛋白AQP、热激蛋白HSP70、WRKY1转录因子和随机引物组成的5对抗旱和耐高温相关功能标记,以63份甘蔗常用亲本材料和8份甘蔗原种作为对照,对中国保育的50份十倍体割手密(Saccharum spontaneum L.)进行遗传多样性分析。结果显示:(1)5对引物共获得119个扩增片段,其中110个为多态性条带,平均多态性条带比例为92.44%,平均多态信息量为92.53%,十倍体割手密抗旱功能标记多态性最高,甘蔗常用亲本材料耐高温功能标记多态性最高。(2)十倍体割手密在抗旱功能标记上具有较低的平均相似性系数值(0.541)和最大的分布范围(0.347~0.800),且主要集中在0.400~0.600之间,而在耐高温功能标记上甘蔗常用亲本材料虽拥有最大的分布范围(0.238~1.000),但甘蔗原种具有最低的平均相似性系数值(0.481),且相似性系数范围主要集中在0.400~0.600之间。(3)UPGMA聚类可将参试材料划分为较明显的两个大组,十倍体割手密与甘蔗常用亲本和甘蔗原种在聚类关系上表现出明显的不同。研究表明,十倍体割手密资源无论是在抗旱功能标记DBF、Aqua方面,还是在耐高温功能标记SCB174、SCB190方面都与甘蔗常用亲本和甘蔗原种具有较大的遗传差异,而且在抗旱功能标记方面表现出更为丰富的遗传变异,因此在后续甘蔗品种抗逆性状改良和亲本创新上应进一步加大十倍体割手密资源的利用。     

Identifying the Risks of Transgene Escape from Sugarcane Crops to Related Species, with Particular Reference to Saccharum spontaneum in Australia

Sugarcane is a major crop of tropical and sub-tropical climates. Modern cultivars are hybrids of several Saccharum species. Many attempts have been made to make intergeneric crosses to increase the diversity of germplasm available for breeding. Currently methods of incorporating new traits through genetic manipulation are also being researched. A review of the attempts by breeders to make hybridisations with sugarcane has been performed to determine the likelihood of spontaneous transfer of a transgene to a range of other species. When combined with the list of sexually compatible species growing outside of cultivation in Australia, Saccharum spontaneum L. was considered to be the most likely to spontaneously hybridise with commercial sugarcane. Using a combination of local knowledge and herbarium samples, S. spontaneum has been documented at five previously unpublished locations in Australia. Analysis of the DNA of plants growing at each of these locations, by molecular markers, showed vegetative propagation at three sites, predominantly vegetative propagation at a fourth and the presence of a more diverse set of plants at the fifth. At the latter location there may have been multiple introductions, interbreeding between clones or both. An analysis of both pollen and seed viability from these plants would discriminate between these options and determine whether S. spontaneum is interbreeding with commercial sugarcane.     

Evaluation of the cold tolerance of Saccharum spontaneum L. clones with different ploidy levels on the basis of morphological and physiological indices

• Saccharum spontaneum L. is one of the most important germplasm resources for modern sugarcane breeding. Exploring the cold tolerance of S. spontaneum clones with different ploidy levels and screening for cold‐tolerant material can be helpful in parent selection for breeding cold‐tolerant sugarcane.
• Morphological indices, leaf ultrastructure and physiological indices were used to evaluate the cold tolerance of 36 S. spontaneum clones with different ploidy levels (2n = 40, 48, 54, 60, 64, 78, 80, 88, 92 and 96).
• The morphological indices of S. spontaneum clones with different ploidy levels were positively correlated with ploidy. Under low‐temperature stress, the chloroplast and mitochondrial structures of the clones with high ploidy were more severely damaged than were those of clones with low ploidy. A comprehensive evaluation of the physiological indices showed that the 36 S. spontaneum clones could be divided into four categories: strongly cold tolerant, cold tolerant, moderately cold tolerant and cold sensitive. Correlation analysis of the morphological indices and cold tolerance revealed a significant negative correlation between cold tolerance and ploidy. On the basis of the morphological and physiological indices, optimal stepwise regression equations that can be used for the selection of cold‐tolerant S. spontaneum resources were established.
• The S. spontaneum clones with low ploidy are more cold tolerant than those with high ploidy. Clones 12‐37, 13‐10 and 12‐23 are strongly cold‐tolerant germplasm resources, which suggests these germplasm sources have high potential for use in breeding cold‐tolerant sugarcane.

     

Very close relationship of the chloroplast genomes among Saccharum species

We recently determined the complete sequence of the sugarcane chloroplast genome. Here, we have used the information for a comprehensive phylogenetic analysis of the genus Saccharum, using all six species (13 accessions). The polymorphisms between sugarcane and maize in 26 chloroplast genome regions were used for the analysis. In 18 of the 26 regions (a total of 5,381 bp), we found 41 mutations involving 17 substitutions, three inversions, six insertion/deletion mutations, and 15 simple sequence repeat length polymorphisms. Based on these results, we calculated a phylogenetic tree of the genus Saccharum, in which all six species are clearly separated. By the analysis, (1) S. sinense and S. barberi, which have identical sequences, belong to the same clade, whereas the other four species, S. officinarum, S. robustum, S. edule, and S. spontaneum, form an independent clade; (2) S. spontaneum has a paraphyletic relationship with the other five species; and (3) no or very low intraspecific variation was observed in S. officinarum, S. robustum, S. sinense, S. barberi, and S. edule, whereas higher intraspecific variation was observed in S. spontaneum. Based on the number of nucleotide substitutions, the divergence time between S. officinarum and S. spontaneum, and between S. officinarum and maize were calculated to be about 730–780 thousand years ago and about 5.9 million years ago, respectively. These results suggest that the cytoplasm of Saccharum species are very closely related.     

Molecular investigation of the genetic base of sugarcane cultivars

 Molecular diversity was analysed among 162 clones of sugarcane using DNA restriction fragment length polymorphism (RFLP). One hundred and nine of them were modern cultivars of interspecific origin; most of them were bred in Barbados or in Mauritius. Fifty three were from Saccharum officinarum species, which is the major source of genes in modern cultivars, prevailing over the part of the genome incorporated from the wild species Saccharum spontaneum. Twelve low-copy nuclear DNA probes scattered over the genome were used in combination with one or two restriction enzymes. A total of 399 fragments was identified, 386 of which were polymorphic. Each sugarcane clone displayed a high number of fragments per probe/enzyme combination, illustrating the polyploid constitution of the genome. Among the S. officinarum clones, those from New Guinea had the largest variability and encompassed that present among clones collected from the Indonesian Islands and those known to have been involved in the parentage of modern cultivars. This is in agreement with the hypothesis that New Guinea is the centre of origin of this species. The clones from New Caledonia formed a separate group and could correspond to S. officinarum clones modified through introgression with other members of the ‘Saccharum complex’. Despite the low number of S. officinarum clones used for breeding cultivars, more than 80% of the markers present in the whole S. officinarum sample were also found in modern cultivars due probably to a high heterozygosity related to polyploidy. Among the cultivars, the two main groups, originating from Barbados and Mauritius, were clearly separated. This appeared essentially due to S. spontaneum alleles present in Mauritian cultivars and absent in Barbadan ones, probably in relation to the regular use of early generation interspecific hybrids in the breeding program employed in Mauritius. Received: 9 November 1998 / Accepted: 19 November 1998     

Characterisation of the double genome structure of modern sugarcane cultivars (Saccharum spp.) by molecular cytogenetics

Cultivated sugarcane clones (Saccharum spp., 2n=100 to 130) are derived from complex interspecific hybridizations between the speciesS. officinarum andS. spontaneum. Using comparative genomic DNA in situ hybridization, we demonstrated that it is possible to distinguish the chromosomes contributed by these two species in an interspecific F1 hybrid and a cultivated clone, R570. In the interspecific F1 studied, we observed n+n transmission of the parental chromosomes instead of the peculiar 2n+n transmission usually described in such crosses. Among the chromosomes of cultivar R570 (2n=107–115) about 10% were identified as originating fromS. spontaneum and about 10% were identified as recombinant chromosomes between the two speciesS. officinarum andS. spontaneum. This demonstrated for the first time the occurrence of recombination between the chromosomes of these two species. The rDNA sites were located by in situ hybridization in these two species and the cultivar R570. This supported different basic chromosome numbers and chromosome structural differences between the two species and provided a first bridge between physical and genetical mapping in sugarcane.     

Cytogenetics of modern sugar canes

Modern sugar cane varieties are derived from interspecific crosses involving as many as four species. Because a chromosome increase accompanies certain crosses and backcrosses, modern varieties have very high aneuploid chromosome numbers and complicated genetics. Despite this complexity, the chromosome behavior of some modern varieties approaches that of allopolyploids. In achieving homozygosity, therefore, such varieties should respond to inbreeding almost like diploids. The meiotic chromosome behavior of F₁ hybrids and modern varieties indicates little or no genetic exchange between chromosomes ofSaccharum officinarum andS. spontaneum. Irradiation may break linkages between desirable and undesirableS. spontaneum genes not ordinarily broken by crossing-over between the chromosomes of the two species. The quick success of nobilizingS. spontaneum (recurrently back-crossing to “noble canes”) depends on a peculiar increase of the chromosomes ofS. officinarum. Experience with nobilizingS. spontaneum should not make breeders impatient when they turn to interspecific crosses unaccompanied by chromosome increases.     

Sugarcane Underground Organs: Going Deep for Sustainable Production

Sugarcane breeding has greatly advanced in recent decades, but many aspects of sugarcane physiology are still poorly understood, including the root-shoot relationships that ultimately affect yield. Traditional methods for studying root systems are imprecise due to methodological difficulties of in situ assessment and sampling; this seems especially true for the sugarcane root system. Studies on sugarcane roots lag well behind those on other crops, in part due to the large plant stature and long crop cycle. Commercial sugarcane cultivars are hybrids from crosses mostly between Saccharum officinarum and S. spontaneum made by breeders at the beginning of the last century. These hybrids have a genomic structure composed of 80% S. officinarum, 10% S. spontaneum and 10% recombinants of these two species. S. spontaneum is included in large part for the robustness of its underground organs (root and rhizome). The S. spontaneum genes controlling these characteristics may be lost during recurrent backcrosses with S. officinarum to increase sugar content and yield. Thus, ratooning ability is one of the most desired traits. Ratooning ability comes mainly from the rhizomatousness of S. spontaneum, but this trait has been diluted during the selection process so that the stubble of hybrids does not have rhizomes sensu stricto. In this review, we revisit some basic aspects of the sugarcane root system, mainly from an ecophysiological view, and point out considerations for breeders to consider in designing the architecture of a new sugarcane cultivar that can meet the need for sustainable agricultural production.     

Genotypic variability in vulnerability of leaf xylem to cavitation in water-stressed and well-irrigated sugarcane

Genotypic variability in vulnerability of leaf xylem to water-stress-induced cavitation was determined in four sugarcane (Saccharum sp.) clones using detached leaf segments in a hydraulic conductivity apparatus. Vulnerability curves were constructed by plotting the percentage of maximum conductivity versus leaf water potential (ψ_I) and fitting curves using a Weibull function. The ψ_I at which each clone lost 10, 50, and 80% of maximum conductivity was determined. Maximum conductivity per unit of leaf width was positively associated with metaxylem vessel diameter. The commercial clone H65-7052 exhibited the highest and the nondomesticated S. spontaneum exhibited the lowest conductivity. All four clones lost substantial conductivity at values of ψ_I less negative than −1.4 MPa, but H65-7052 was able to maintain 50% conductivity to lower ψ_I than the other clones. S. spontaneum sustained the most negative ψ_I (−1.99 MPa) before reaching the 80% conductivity loss point. Clone H69-8235 was consistently the most vulnerable to initial loss of conductivity. These vulnerability functions were used in conjunction with field measurements of ψ_I to estimate diurnal losses in leaf hydraulic conductivity under irrigated and droughted conditions. H69-8235 lost up to 50% of its conductivity during the day, even when well irrigated, and more than 80% when subjected to drought. The other clones exhibited lower conductivity losses. These losses are apparently reversed overnight by root pressure. Despite their close genetic relationships, these clones exhibited large differences in conductivity, in the vulnerability of their xylem to cavitation, and in gas exchange behavior. The potential for altering water relations by selecting for particular hydraulic characteristics is discussed.     

Phenolic constituents of Semecarpus anacardium

GLC-MS analysis of methylated bhilawanol from S. anacardium nuts and its oxidation product, the methyl ester of an aromatic carboxylic acid, conclusively proved that it contains more than seven closely related compounds. Two of them are major components which were isolated and shown to be 1-pentadec-Δ^5′-enyl-2,3-dimethoxybenzene (I) and 1-pent biflavanoids A, B and C have been also isolated from defatted nuts of S. anacardium. The first of these has been characterized as its methyl ethers. A₁ and A₂, for which biflavanone structures (VI) and (VII) are suggested on the basis of chemical and spectral evidence. The biflavanones B and C have been also characterized as their methyl ethers. Suggested structures are O-methyl derivatives of a IB-3′, IIA-8-binaringenin (XIV) for the former and IB-3′, IIA-8-biliquiritigenin (XV) for the latter.     

Three founding ancestral genomes involved in the origin of sugarcane

Background and AimsModern sugarcane cultivars (Saccharum spp.) are high polyploids, aneuploids (2n = ~12x = ~120) derived from interspecific hybridizations between the domesticated sweet species Saccharum officinarum and the wild species S. spontaneum.MethodsTo analyse the architecture and origin of such a complex genome, we analysed the sequences of all 12 hom(oe)ologous haplotypes (BAC clones) from two distinct genomic regions of a typical modern cultivar, as well as the corresponding sequence in Miscanthus sinense and Sorghum bicolor, and monitored their distribution among representatives of the Saccharum genus.Key ResultsThe diversity observed among haplotypes suggested the existence of three founding genomes (A, B, C) in modern cultivars, which diverged between 0.8 and 1.3 Mya. Two genomes (A, B) were contributed by S. officinarum; these were also found in its wild presumed ancestor S. robustum, and one genome (C) was contributed by S. spontaneum. These results suggest that S. officinarum and S. robustum are derived from interspecific hybridization between two unknown ancestors (A and B genomes). The A genome contributed most haplotypes (nine or ten) while the B and C genomes contributed one or two haplotypes in the regions analysed of this typical modern cultivar. Interspecific hybridizations likely involved accessions or gametes with distinct ploidy levels and/or were followed by a series of backcrosses with the A genome. The three founding genomes were found in all S. barberi, S. sinense and modern cultivars analysed. None of the analysed accessions contained only the A genome or the B genome, suggesting that representatives of these founding genomes remain to be discovered.ConclusionsThis evolutionary model, which combines interspecificity and high polyploidy, can explain the variable chromosome pairing affinity observed in Saccharum. It represents a major revision of the understanding of Saccharum diversity.     

Microbial community and treatment ability investigation in AOAO process for the optoelectronic wastewater treatment using PCR-DGGE biotechnology

This study aimed to explore the microbial community variation and treatment ability of a full-scale anoxic–aerobic–anoxic–aerobic (AOAO) process used for optoelectronic wastewater treatment. The sludge samples in the biological treatment units were collected and subsequently subjected to polymerase chain reaction (PCR) amplification and denaturing gradient gel electrophoresis identification and the wastewater components such as BOD₅ and NH₃–N were evaluated during the processes. The group specific primers selected were targeting at the kingdom Bacteria, the Acidobacterium, the α-proteobacteria, the β-proteobacteria ammonia oxidizers, Actinobacteria and methyllotrophs, and the 16S rDNA clone libraries were established. Ten different clones were obtained using the Bacteria primers and eight different clones were obtained using the β-proteobacteria ammonia oxidizer primers. Over 95 % of BOD₅ and 90 % of NH₃–N were removed from the system. The microbial community analysis showed that the Janthinobacterium sp. An8 and Nitrosospira sp. were the dominant species throughout the AOAO process. Across the whole clone library, six clones showed closely related to Janthinobacterium sp. and these species seemed to be the dominant species with more than 50 % occupancy of the total population. Nitrosospira sp. was the predominant species within the β-proteobacteria and occupied more than 30 % of the total population in the system. These two strains were the novel species specific to the AOAO process for optoelectronic treatment, and they were found strongly related to the system capability of removing aquatic contaminants by inspecting the wastewater concentration variation across the system.