Sugarcane Clones Research Articles

O3 Sensitivity in a Potential C4 Bioenergy Crop: Sugarcane in California

The C4 perennial grasses have many potential virtues as bioenergy crops—high productivity and water use efficiency, multiyear crop cycle that minimizes replanting costs, and wide environmental adaptation. In the productive San Joaquin Valley (SJV) of California, these species also confront high levels of ozone (O3) air pollution. It is often assumed that C4 species will exhibit tolerance to O3, relative to C3 species, based on limited crop yield‐loss data and on responses to a contrasting gaseous air pollutant, sulfur dioxide (SO2). Tolerance to O3 of high‐biomass C4 crops such as sugarcane (Saccharum spp.) has not been demonstrated. Here we tested the hypothesis that a clone of sugarcane currently grown on a small commercial scale in the O3–impacted SJV will exhibit tolerance to O3 The hypothesis was disproven. Biomass production declined by over one‐third and allocation to roots declined by over two‐thirds, over a range of O3 exposures (4, 58, and 114 ppb, 12‐h means). These responses are comparable to responses previously reported for O3–sensitive C3 crop species. Greater O3 tolerance may be required to maximize the potential viability of bioethanol production using tall tropical grasses such as sugarcane (for sucrose) or energy canes (for cellulose) in O3–impacted western valleys. In the case of the locally successful sugarcane clone examined here, the C4 photosynthetic pathway did not confer resistance to O3 exposure.

Genotypic variation of resistance to the spotted stalk borer Chilo sacchariphagus (Bojer) in sugarcane: evidence of two distinct resistance mechanisms

AbstractWe carried out an assessment of the resistance status to the spotted stalk borer Chilo sacchariphagus in a sample of 32 international sugarcane clones in Reunion. Our objectives were to characterize the genotypic variability of resistance and to characterize the role of leaf and stalk resistance in the global resistance. A significant genotypic variability in the % exited tunnels and in the leaf feeding injuries confirmed the existence of two resistance mechanisms located respectively in the leaves and in the stalk. Leaf resistance and stalk resistance exhibited genotypic and phenotypic correlation with stalk tunnelling injuries. No phenotypic or genotypic correlations were observed between leaf resistance and stalk resistance. Both resistances contributed independently to the global resistance quantified by the stalk tunnelling. The resistance status of the two main cultivars cultivated in Reunion was assessed within our germplasm sample: ‘R 570’ was one of the most resistant clones and ‘R 579’ proved to be moderately susceptible.

Source - sink differences in genotypes and water regimes influencing sucrose accumulation in sugarcane stalks

Relatively little is known about the physiological basis for variation in sucrose content among sugarcane clones despite substantial research at the molecular and biochemical levels. We used irrigation and continuous monitoring of photosynthesis and plant extension rate to modify dry matter partitioning in four clones differing widely in sucrose content. Three pot experiments were conducted on two low sucrose content clones, KQ97-2599 and KQ97-2835, and two high sucrose content clones, Q117 and KQ97-5080, in a temperature-controlled glasshouse. As expected, sucrose content on a dry mass basis of whole stalks was greater in high (55% maximum) than in low sucrose clones (40% maximum), but sucrose content in the two clones selected for low sucrose reached 55% in some internodes. Differences between clones in whole-plant net photosynthesis and aerial biomass accumulation were small. However, biomass was distributed over fewer stalks in the high sucrose clones (4–7 stalks per pot) than in the low sucrose clones (9–11 stalks per pot). The high sucrose clones also allocated a considerably greater proportion of dry matter to the stalk (70% maximum) than the low sucrose clones (60% maximum). It is suggested that the relatively large amount of new leaf tissue produced by the high tillering, low sucrose clones placed an additional demand for structural photo-assimilate in these clones and delayed the accumulation of sucrose in the stalk. The results indicated that there is little direct genetic control on the maximum amount of sucrose that can accumulate in stalk tissue and that genetic contrasts in sucrose content reside more in the morphology of the plant and responses to ripening stimuli such as mild water stress, and how these traits influence supply and demand for photo-assimilate.

Levantamento da incidência de Leifsonia xyli subsp. xyli em plantios de cana-de-açúcar do noroeste do Paraná

O raquitismo-da-soqueira, causado por Leifsonia xyli subsp. xyli é considerado uma das mais importantes doenças bacterianas da cana-de-açúcar (Saccharum spp.). Para verificar a possível ocorrência de Leifsonia xyli subsp. xyli na região noroeste do Paraná, foi realizado um levantamento em 32 áreas de plantio de duas usinas, utilizando-se o método sorológico "Dot blot" e um protocolo baseado na reação em cadeia da polimerase. As amostras foram coletadas em áreas cultivadas com 8 variedades e 2 clones, a partir de plantas em diferentes épocas de corte, perfazendo um total de 1395 amostras. Constatou-se a presença da bactéria no fluído fibrovascular de plantas da variedade SP77-5181 coletado em uma das propriedades, com índice de incidência de 23%. Esses resultados indicam a incidência de Leifsonia xyli subsp. xyli no noroeste do Paraná.

Effects of periodic flood stress on sugarcane yield and yield contributing characters

An investigation was conducted at two farmers’ field viz Lalpur (Natore) and Sirajgonj during two consecutive cropping seasons (2003–2005) to screen flood stress tolerant sugarcane clones. At Lalpur location clones such as I 110-98, I 139-98, I 142-98 and I 137-96 showed highly tolerant reaction having tolerance rating scale 1 against periodic natural flood stress, and obtained 118.8, 99.2, 108.3 and 121.4 t ha−1 estimated cane yield respectively. At Sirajgonj location clones such as I 82-98, I 98-98, I 110-98, I 139-98, I 142-98, I 202-97 and I 137-96 showed tolerant reaction having tolerance rating 2, and produced 114.3, 112.7, 112.3, 80.6, 102.8, 103.2 and 113.9 t ha−1 estimated cane yield respectively. Results indicate that BSRI bred above mentioned clones have built in potential to grow up to 90 cm depth periodic flood stress period for 90days.

SELEÇÃO PARA PRODUTIVIDADE, ESTABILIDADE E ADAPTABILIDADE DE CLONES DE CANA-DE-AÇÚCAR EM TRÊS AMBIENTES NO ESTADO DO PARANÁ VIA MODELOS MISTOS

O objetivo deste trabalho foi estimar parâmetros genéticos e selecionar clones de cana-de-açúcar na fase T3 no estado do Paraná, utilizando a metodologia REML/BLUP. O trabalho foi realizado em três ambientes de produção no Estado do Paraná (Colorado, Paranavaí e Mandaguaçú), em fase T3 com 236, 243 e 202 clones, respectivamente, e duas variedades padrões (RB72454 e RB835486). O experimento foi em blocos aumentados com duas repetições, sendo a variável analisada toneladas de brix por hectare (TBH). Os clones foram selecionados via modelos mistos, utilizando o critério MHPRVG (média harmônica da performance relativa dos valores genéticos preditos). Os clones mais adaptados, estáveis e produtivos pela metodologia MHPRVG foram: RB9371, RB975245 e RB975316. O uso do critério MHVG (média harmônica dos valores genéticos) deve ser empregado com cautela quando se faz seleção para estabilidade e produtividade em experimentos desbalanceados, isto é, quando todos os clones não estão presentes em todos os ambientes testados.

Genetic divergence and parent selection of sugarcane clones

The objective of this study was to estimate the genetic divergence of 140 sugarcane clones of the series RB97, in phase T3 of the Sugarcane Genetic Improvement Program of the Universidade Federal do Parana, at three locations by multivariate analysis, using the linear mixed model and grouping analysis by the Tocher procedure, based on Mahalanobis´ generalized distance. The evaluated traits were number of stalks per plot, mass of ten stalks, Brix and Brix per plot in kg. The number of groups varied according to the evaluated environment. Based on the results, combinations of one of the most divergent clones RB975008, RB975112, RB975019 RB975153 and RB975067 with any one of the most productive clones RB975269, RB977533, RB975102, RB975317 and RB975038 are recommended.

ADAPTABILIDADE E ESTABILIDADE FENOTÍPICA DE CLONES PRECOCES DE CANA-DE-AÇÚCAR NO ESTADO DO PARANÁ

O objetivo deste trabalho foi avaliar a adaptabilidade e a estabilidade fenotípica de clones precoces de cana-de-açúcar em 11 locais no estado do Paraná durante 3 safras (33 ambientes). Os locais de instalação dos experimentos foram: Jandaia do Sul, São Pedro do Ivaí, São Tomé, Nova Londrina, Rondon, Jussara, Ibaití, Cidade Gaúcha, Bandeirantes, Paranavaí e lguatemi. Foram utilizados 18 clones precoces RB e duas variedades padrões (RB855156 e RB855453). As unidades experimentais foram compostas por parcelas úteis de quatro sulcos de 8 m, espaçados entre si por 1,40 m; sendo o delineamento utilizado o de blocos ao acaso com 3 repetições. A variável utilizada foi tonelada de pol por hectare (TPH) e o método de avaliação da adaptabilidade e estabilidade foi por análise não-paramétrica. O coeficiente de determinação genotípica para o caráter avaliado foi de alta magnitude (70%). Na série estudada os clones mais estáveis e produtivos foram RB925211, RB946903 e RB956911 tanto para ambientes favoráveis como desfavoráveis. Alguns clones apresentaram adaptação específica para ambientes favoráveis ou para ambientes desfavoráveis.

Increasing sucrose accumulation in sugarcane by manipulating leaf extension and photosynthesis with irrigation

High sucrose content (SC) in sugarcane stalks is a priority for all sugarcane industries world wide. Partitioning to sucrose in the cane stalk is related to the supply of photo-assimilate and the demand for assimilate by other organs. If photosynthesis could be maintained, but leaf and stalk growth constrained, by genetics or management during the stalk elongation phase, it may be possible to reduce stalk height and to increase both SC and sucrose yield. This paper reports an experiment designed to test this hypothesis and to develop a methodology to assess variation in response to source–sink manipulation in sugarcane clones. The research was conducted on a ‘low’ (Q138) and a ‘high’ (Q183) SC cultivar in two temperature controlled and airtight glasshouses (chambers) at CSIRO’s Davies Laboratory in Townsville, Australia. Potted plants of each cultivar were placed in two chambers of the Tall Plant Facility (TPF). In one chamber, plants were irrigated to minimise water stress while plants in the other chamber were irrigated to reduce plant extension rate (PER) considerably more than photosynthesis. Water stress reduced gain in total biomass by 19% and gain in top mass by 37%, and increased sucrose mass gain by 27%. During the experiment, SC of dry matter increased 37% in the dry treatment and only 8% in the wet treatment and this effect was greater in Q183 than in Q138. Water stress reduced whole plant photosynthesis by 18%, thus largely accounting for the 19% reduction in biomass accumulation and it reduced PER by 41%, corresponding to the 37% reduction in mass of tops. Reduced PER resulted in reduced demand for photo-assimilate by fibre and tops thus allowing excess assimilate to accumulate in the form of sucrose. The techniques developed here to control PER and measure the resulting changes in carbon partitioning now allow further examination of both the control of the balance between growth and sucrose storage and the extent of genotypic variation to the response of reduced PER.

Shoot Apex Development at Various Stages of Flowering in Sugarcane (Saccharum spp. hybrid)

A study was carried out to understand the flowering behaviour of some commercial sugarcane clones of sub-tropical India and the changes taking place in the target tissues in relation to flowering. The clones studied showed a wide range of flowering behaviour. The shoot apex tissues showed initiation of changes much before the short blade stage. The changes were characterized by an increase in the length and width of the shoot tip tissues and primordial initiation. These changes could be observed 4–5 weeks before the initiation of short blade, which is considered to be an early stage at which flowering could be detected. This gives an idea about specific stages of the crop at which, changes in gene expression patterns during the transition from vegetative to reproductive stage may be observed.

Genetic diversity associated with in vitro and conventional bud propagation of Saccharum varieties using RAPD analysis

AbstractPolymorphisms in the genomic DNA of eight varieties maintained by conventional bud propagation (via rhizomes) and by in vitro shoot tip cultures were detected by RAPD analysis of sugarcane varieties. The study estimated the genetic diversity induced after in vitro multiplication of these varieties. Higher (28.9%) and lower (12%) numbers of polymorphic bands were detected in plants propagated via rhizomes; the genetic similarity estimate varying from 0.63 to 0.80. Plants of SP90‐3723 and SP91‐1049, or RB85‐5113 and SP90‐3723, varieties involving greater genetic distances may be indicated as progenitors in breeding programmes. In vitro multiplication of RB86‐7515, RB85‐5113, RB83‐5054 and SP86‐42 varieties increases genetic variability, while in vitro multiplication of SP91‐1049, SP90‐1638, RB92‐8064 and SP90‐3723 leads to genetic similarity. Results show that the RAPD technique is an effective tool for detecting polymorphism in sugarcane clones and it allows quick collection of the necessary information (more genetically divergent plant varieties) to guide new crossing in sugarcane breeding programmes.

Isolation of nucleotide binding site‐leucine rich repeat and kinase resistance gene analogues from sugarcane (Saccharum spp.)

Resistance gene analogues (RGAs) have been isolated from many crops and offer potential in breeding for disease resistance through marker-assisted selection, either as closely linked or as perfect markers. Many R-gene sequences contain kinase domains, and indeed kinase genes have been reported as being proximal to R-genes, making kinase analogues an additionally promising target. The first step towards utilizing RGAs as markers for disease resistance is isolation and characterization of the sequences. Sugarcane clone US01-1158 was identified as resistant to yellow leaf caused by the sugarcane yellow leaf virus (SCYLV) and moderately resistant to rust caused by Puccinia melanocephala Sydow & Sydow. Degenerate primers that had previously proved useful for isolating RGAs and kinase analogues in wheat and soybean were used to amplify DNA from sugarcane (Saccharum spp.) clone US-01-1158. Sequences generated from 1512 positive clones were assembled into 134 contigs of between two and 105 sequences. Comparison of the contig consensuses with the NCBI sequence database using BLASTx showed that 20 had sequence homology to nuclear binding site and leucine rich repeat (NBS-LRR) RGAs, and eight to kinase genes. Alignment of the deduced amino acid sequences with similar sequences from the NCBI database allowed the identification of several conserved domains. The alignment and resulting phenetic tree showed that many of the sequences had greater similarity to sequences from other species than to one another. The use of degenerate primers is a useful method for isolating novel sugarcane RGA and kinase gene analogues. Further studies are needed to evaluate the role of these genes in disease resistance.

Detecção do Sugarcane mosaic virus no Paraná e limpeza somaclonal por cultura de tecidos

Um isolado do Sugarcane mosaic virus (SCMV) causando sintomas de mosaico em plantas de cana-de-açúcar do clone RB925268 foi identificado no estado do Paraná. Gemas axilares extraídas de colmos infectados, medindo de 4 a 8 mm, foram utilizadas como explantes e regeneradas em plântulas em meio de cultura MS, suplementado ou não com o antiviral ribavirina, nas concentrações variando de 10-60 mg/L. O efeito fitotóxico da ribavirina foi constatado, resultando na morte dos explantes em concentrações iguais ou superiores a 30 mg/L. Após seis meses de aclimatação das plantas em estufa plástica, o vírus não foi detectado nas plantas provenientes do meio MS contendo ribavirina na concentração de 25 mg/L, confirmado através dos ensaios de inoculação mecânica em sorgo 'Rio' e de RT-PCR.

PROPORSI MIKROSPORA UNINUKLEAT PADA EMPAT KLON TEBU (Saccharum spp.)

An experiment to study the two different morphological characters of four clones of sugarcane (Saccharum spp.) panicles containing more than 50 percent of uninucleate microspore development was conducted in Tissue Culture Laboratory at Biology Faculty, Gadjah Mada University, Yogyakarta, since March until May 2006. Morphological characters of both kinds of panicles i.e. unsheated- and sheated flowers from sheat flag leaf were observed. Mean, percentage, and standard deviation from the mean value of the six different stages of microspore development e.g. tetrad, early- and late-uninucleate, early- and late-binucleate, and multinucleate or pollen grains were statistically used in this calculation. All data percentages were analyzed by variance analysis through General Linier Model Procedure, and comparisons between means of the uninucleate microspore development based on the two different morphological characters of four clones was calculated by Least Significance Difference method. Comparisons between the two different panicles characteristics in accordance with the proportion of the uninucleate microspore development, however, were analyzed by T-student procedure. All calculations were done by using SAS program of computer statistics package. Result of the research showed that: (1) the unsheated panicles were contained less than 50 percent of uninucleate (early- and late-uninucleate) microspore development; (2) the sheated panicles tend to be in high proportion of early- and late-uninucleate microspore development, and multinucleate or pollen grains, and (3) the more away of spikelets or anthers positioned in the panicle or sub-panicle, the more number or percentage of uninucleate microspores development were tend to be gradually decreased.

Uptake of nitrogen, phosphorus and potassium by some promising mid late maturing sugarcane clones

A field experiment was conducted at the ECC farm of Sugarcane Breeding Institute, Coimbatore during 1999–2000 to evaluate promising mid late maturing sugarcane clones for nutrient use efficiency. Twelve clones including three standards were planted in a clay soil (Typic Haplustert). Nitrogen, phosphorus and potassium contents were estimated in dry leaves, green tops and stem on dry weight basis and their uptake in different parts was calculated. Total nutrient uptake and uptake per tonne of cane were also computed. Significant clonal variations in N, P and K uptake by various plant parts viz., dry leaves, green tops and stem, total uptake in above ground parts and uptake per tonne of cane (physiological use efficiency). Total N uptake ranged from 88.55 kg/ha in CoTl 93116 to 148.52 kg/ha in Co 7219. The lowest uptake of 0.88 kg N per tonne of cane was recorded in Co 86032 and the highest uptake of 1.47 kg/tonne of cane was registered in Co 93018. Clones identified for better N use efficiency were Co 94011, Co 94015 and CoTl 93116. Total P uptake by above ground parts ranged from 34.95 kg/ha in CoTl 93116 to 57.97 kg/ha in Co 7219. The uptake of phosphorus per tonne of cane ranged from 0.34 kg in Co 94012 to 0.56 in Co 93018 with a mean of 0.48 kg. Clones Co 94012, Co 94016, Co 94015, Co 94009 and CoTl 93116 were identified for better P use efficiency. The total K uptake in above ground parts varied from 108.55 kg/ha (CoTl 93116) to 305.98 kg/ha (Co 7219) with a mean of 210.25 kg/ha. The K uptake per tonne of cane ranged from 1.44 kg in CoTl 93116 to 2.91 kg in Co 7219 with a mean of 2.09 kg. Clones identified for better potassium use efficiency were CoTl 93116, Co 93018 and Co 94012. Co 86032 was found superior among the standards in nutrient use efficiency.

Levels of phenolic compounds and enzyme activity can be used to screen for resistance of sugarcane to smut (Ustilago scitaminea)

Smut is a major disease of sugarcane plants and is caused by the fungus Ustilago scitaminea. Resistance to smut seems to be a multifactorial process. The current criteria for the selection of resistant varieties are applied by discarding sensitive specimens rather than improving resistance mechanisms through analysis of the molecular bases for resistance. This paper correlates the sensitivity or resistance to smut with changes in sugarcane leaf levels of free phenolic compounds, and phenylalanine ammonia-lyase and peroxidase activities, in response to elicitors from U. scitaminea mycelium. The interaction was studied in sugarcane leaf discs obtained from cultivars Barbados 42231, which is susceptible to smut, and Mayari 55–14, which is highly resistant to smut. The elicitors enhanced the levels of hydroxycinnamic and hydroxybenzoic acids mainly in the resistant cultivar. p-Coumaric (from hydroxycinnamic acids) and syringic acid (from hydroxybenzoic acids) were the phenolic acids that showed a major accumulation pattern. Cultivar Mayari 55–14 had high phenylalanine ammonia-lyase activity without accumulation of free hydroxycinnamic acids. The increase in peroxidase activity was important in the defence mechanism but was not a determinant for the defence. Cultivar Barbados 42231 showed low phenylalanine ammonia-lyase activity as accumulation of caffeic acid produced feedback inhibition of the enzyme. A simple model for studying the level of resistance of new sugarcane clones for helping breeding programs is proposed.

Role of chemometrics for at-field application of NIR spectroscopy to predict sugarcane clonal performance

This paper demonstrates the crucial role of chemometrics in facilitating the knowledge transfer of a laboratory derived rating for sugarcane clonal performance (based on GC measurements) towards a rapid near infrared (NIR) spectroscopic methodology for at-field screening applications. NIR sugarcane stalk spectra were collected from 65 sugarcane clones, which were obtained from two widely different geographical regions. An exploratory principal component analysis (PCA) of an NIR spectral data matrix of the sugarcane clones showed a clear trend along PC1 similar to that found from the GC measurements, with the resistant clone (Q90) being well discriminated from the susceptible one (NCo310). Biplots related the NIR spectral frequencies with the spectral objects. Cellulose and lignin bands (4248 and 4406 cm − 1 respectively) were associated with the well performing clones and epicuticular wax bands (4346 and 5781 cm − 1 ) with the poorly performing ones. Several partial least squares (PLS) regression models were constructed from the spectral objects, and satisfactorily predicted the traditional sugarcane performance ratings (SEP range +/− 0.7–0.9 traditional units for the verification data, and the Measured versus Predicted R 2 range 0.880–0.910). In addition, the stalk spectra were investigated with the use of multicriteria decision-making methods, PROMETHEE and GAIA. This demonstrated that the spectral objects could be ranked on the basis of the NIR information alone, and that this rank order was in agreement with traditionally determined ratings. Thus, the performance of sugarcane clones could be assessed from molecular information as from the earlier laboratory GC measurements, and therefore, can be obtained completely independently of any conventional nominal ratings scales.

Highly polymorphic microsatellite dna markers for sugarcane germplasm evaluation and variety identity testing

The objective of this study was to evaluate the entire set of 221 sugarcane microsatellite (SSR) markers from the International Sugarcane Microsatellite Consortium for their utility on molecular characterization of elite U.S. germplasm. Five elite U.S. sugarcane clones were tested, including two cultivars LCP 85-384 and HoCP 96-540 from Louisiana, two cultivars CP 72-1210 and CP 85-1308 from Florida, and Green German, an active parental clone used in both states. The 5’ ends of all forward primers were labeled with the fluorescent phosphoramidite dye, FAM and PCR-amplified DNA fragments detected using a semi-automatic capillary electrophoresis system. The sizes of DNA fragments were computed accurately by running genotyping software calibrated against 16 fluorescence-labeled DNA size standard fragments. Evaluation criteria included PCR robustness, extent of the presence of irregular peaks, and the polymorphism information content (PIC). Sixty-seven SSR markers (30% of the total) were found to be highly robust, with PIC values ranging from 56% to 80%. Of these, 40 (60%) markers contained dinucleotide repeats, 11 (16%) markers contained trinucleotide repeats, and 16 (24%) markers contained composite repeats. A total of 467 alleles were scored, of which 350 were polymorphic, averaging five polymorphic alleles per marker, with their sizes ranging from 80 to 460 bp. Several of these highly polymorphic SSR markers have proven useful in sugarcane germplasm evaluation, variety identity tests, cross fidelity assessment, and polycross paternity analysis.

Associations between DNA markers and resistance to diseases in sugarcane and effects of population substructure

Association between markers and sugarcane diseases were investigated in a collection of 154 sugarcane clones, consisting of important ancestors or parents, and cultivars. 1,068 polymorphic AFLP and 141 SRR markers were scored across all clones. Data on the four most important diseases in the Australian sugarcane industry were obtained; these diseases being pachymetra root rot (Pachymetra chaunorhiza B.J. Croft & M.W. Dick), leaf scald (Xanthomonas albilineans Dowson), Fiji leaf gall (Fiji disease virus), and smut (Ustilago scitaminea H. & P. Sydow). By a simple regression analysis, association between markers and diseases could be readily detected. However, many of these associations were due to the effects of embedded population structure and random effects. After taking population structure into account, we found that 59% of the phenotypic variation in smut resistance ratings could be accounted for by 11 markers, 32% of variation for leaf scald and pachymetra root rot rating by 4 markers, and 26% of Fiji leaf gall by 5 markers. The results suggest that marker-trait associations can be readily detected in populations generated from modern sugarcane breeding programs. This may be due to special features of past sugarcane breeding programs leading to persistent linkage disequilibrium in modern parental populations.

Responses in ion leakage of wild sugarcane (Saccharum spontaneum L.) clones to enhanced ultraviolet-B radiation under field conditions

Field studies were conducted to determine the potential for alterations in ion leakage and the intraspecific variation in ion leakage sensitivity of 20 wild sugarcane clones (Saccharum spontaneum L.) to enhanced ultraviolet-B (UV-B, 280–315nm) radiation in two consecutive years. The clones were collected from original sites with different altitude (from 0 to 1650 m) and latitude (from 18–37 °N). The supplemental UV-B radiation was 5.00 kJ m−2, simulating a depletion of 20 % stratospheric ozone. Across all clones tested in the present study, a significant change (P<0.01 or 0.05) in ion leakage for 11 in tillering, 14 in elongation and 15 in flowering in 2003, and for 9 in tillering, 5 in elongation and 5 in floweing in 2004 were observed. In general, intraspecific responses of ion leakage of wild sugarcane clones to enhanced UV-B radiation existed under field conditions for two consecutive years, although intraspecific difference in 2003 was more obvious than that in 2004. Wild sugarcane clones originating from lower latitude or high elevation were not necessarily the more tolerant to enhanced UV-B radiation.