Abdel-Rahman E.M.,University of KwaZulu - Natal |
Ahmed F.B.,University of KwaZulu - Natal |
van den Berg M.,South African Sugarcane Research Institute
International Journal of Applied Earth Observation and Geoinformation | Year: 2010
The aim of this study was to explore the use of in situ spectroscopy for estimating sugarcane leaf nitrogen (N) concentration. Leaf spectral reflectance was measured using a field spectroradiometer in the 350-2500 nm range from sugarcane variety N19 crops of 6-7 months old under on-farm conditions. Lab-determined leaf N concentrations of the samples taken ranged from 1.00% to 1.55%. Vegetation indices based on simple ratio (SR); viz. SR (743, 1316), SR (743, 1317) and SR (741, 1323) generated from first-order derivatives of leaf reflectance showed the best correlation with leaf N concentration, with r2 values of 0.76 (P < 0.01), 0.75 (P < 0.01) and 0.74 (P < 0.01), respectively. The root mean square errors of prediction (RMSEP) using a leave-one-out cross validation method were 0.089% (P < 0.01) for SR (743, 1316), 0.092% (P < 0.01) for SR (743, 317) and 0.084% (P < 0.01) for SR (741, 1323). These results suggest that the in situ spectroscopy has potential use in predicting sugarcane leaf N. © 2009 Elsevier B.V. All rights reserved.
Ramburan S.,South African Sugarcane Research Institute
South African Journal of Plant and Soil | Year: 2011
The adaptability of new sugarcane (Saccharum spp.) cultivars to time of harvest (TOH), and reasons for yield variability between harvest times are currently unclear in South Africa. The objectives of this study were to evaluate the adaptability of commercial cultivars to TOH and to identify environmental factors responsible for differential cultivar responses. Two field trials consisting of the same set of seven commercial cultivars were established on adjacent fields and harvested either early (April/May) or late (October/November) in the season for six ratoons. Climatic data were summarized within individual growth stages (establishment, elongation, and ripening) and used to create environmental covariates for thermal time (TT), rainfall (RAIN), radiation (RAD), and a water stress index (WSI). Additive main effects and multiplicative interaction (AMMI) analysis, principal components analysis (PCA), factorial regression, and covariate-effect biplot analysis were used to analyse and interpret the genotype x environment (G x E) interaction for three commercial variables. The G x E interactions were significant (P<0.001) for all three variables. The AMMI biplots showed distinct separations between environments, and characterized cultivars according to their adaptability to early (NCo376, N36, N35, N29) and late (N27, N19, N17) harvesting. PCA and factorial regression identified RAD and TT as significant environmental covariates affecting TOH, while WSI and RAIN had insignificant effects. The covariate-effect biplot identified correlations between plant population and early harvests, while stalk mass was correlated to late harvests. These findings will inform selection strategies and future interpretive studies involving sugarcane G x E interactions.
Ramburan S.,South African Sugarcane Research Institute
Field Crops Research | Year: 2014
Non-repeatable genotype. ×. ratoon (G. ×. R) and genotype. ×. site. ×. ratoon (G. ×. S. ×. R) interactions in sugarcane ( Saccharum sp.) restricts the evaluation of repeatable genotype. ×. site (G. ×. S) interactions, which is important for test site evaluation in breeding programs. Non-repeatable genotype. ×. environment (G. ×. E) interactions are rarely analysed and interpreted further in sugarcane. The aim of this study was to use environmental characterisation and multivariate methods when non-repeatable interactions dominate to (i) illustrate and interpret the confounding crop-year effects in sugarcane and its contribution to non-repeatable G. ×. E, (ii) investigate the nature and magnitude of G. ×. E interactions, and (iii) gain insights into test site similarities in the coastal region of South Africa to improve the efficiencies of the testing network. Variation in estimated recoverable crystal yield was larger for non-repeatable components compared to repeatable components in eight out of ten planting series. Additive main effects and multiplicative interaction (AMMI) biplots illustrated the differential genotype interactions with crop-years of the same trial. Principal components analysis (PCA) illustrated how crop-years clustered together on biplots in response to key environmental covariates derived from climatic data and crop growth models. Based on interpretations using integrated multivariate methods, it is hypothesised that non-repeatable G. ×. E interactions may be larger in autumn compared to spring harvests. AMMI biplots for individual crop-years showed that site T2 is redundant, and should be removed from the trial network without loss of information. Integrated environmental characterisation and multivariate visual appraisals are proposed as alternatives to understanding non-repeatable G. ×. E when crop and year effects cannot be separated experimentally. Hypotheses generated through visual appraisals should be subsequently tested quantitatively. © 2013 Elsevier B.V.
Ramburan S.,South African Sugarcane Research Institute |
Zhou M.,South African Sugarcane Research Institute |
Labuschagne M.,University of the Free State
Field Crops Research | Year: 2011
An understanding of the causes of genotype × environment (G × E) interactions is essential for the implementation of efficient selection and evaluation networks. Currently, studies involving the interpretation of sugarcane (Saccharum spp.) G × E interactions are limited. The objective of this study was to investigate the relative influence of environmental factors on the G × E interactions of sugarcane under rainfed conditions in South Africa through a comprehensive analysis of a multi-environment trial (MET) dataset. Fifteen commercial cultivars were evaluated over 147 environments (trial × ratoon combinations) across the coastal (C), hinterland (H) and midlands (M) regions of the sugar industry. Environments were characterized according to five site covariates (soil depth, clay percentage, organic matter percentage, nitrogen mineralization category, and total available moisture) and nine seasonal covariates (time of harvest, age at harvest, average daily heat units, solar radiation, rainfall, evaporation, and three derived water stress indices).Additive main effects and multiplicative interaction (AMMI) biplots for cane yield (TCANE), estimated recoverable crystal percent (ERC) and tons ERC (TERC) revealed overlapping of C and H environments, while M environments formed unique clusters characterized by specific cultivar adaptabilities. Principal components analysis (PCA) allowed visualization of the covariates determining the regional separation patterns. AMMI interaction principal components axes (IPCA) 1 and 2 scores were correlated to the covariates and showed that harvest age, temperature, and water stress were mainly responsible for separation of M environments from C and H environments on the TCANE and TERC biplots. Time of harvest was identified as an important covariate influencing ERC G × E patterns in the C and H regions. The third water stress index (based on a ratio of observed yields to simulated irrigated yields) was a dominant factor influencing G × E patterns within the C and H regions and was identified as a superior indicator of water deficient environments for future studies. The M trials were characterized by shallower soils with lower total available moisture and greater variability in this regard compared with the C and H trials. Nitrogen mineralization category, organic matter percent, and clay percent were not significantly correlated to IPCA scores, while soil depth was identified as a major site selection criterion in the M region. The M region should be treated as a single mega-environment, while the C and H regions could be combined for future interpretive studies, where covariates should be summarized within growth phases. The results of this study will assist in restructuring the MET network through exploitation and targeting of the relevant environmental factors within the different regions. © 2011 Elsevier B.V.
Ramburan S.,South African Sugarcane Research Institute
Field Crops Research | Year: 2015
Recent changes in cultivar composition, the renewed drive to increase harvest age (HA), and the impacts of the Eldana borer (Eldana Saccharina Walker: Lepidoptera Pyralidae) in the rainfed regions of South Africa have created uncertainty about the optimal HA of sugarcane. This study aimed to (i) review the optimal HA of sugarcane in the coast and inland regions, (ii) determine the variability in optimal HA with cultivar, and (iii) investigate the interactions between cultivar eldana resistance levels and HA on productivity. A secondary objective was to summarise the results of dedicated cultivar. ×. HA experiments to evaluate the importance of this interaction. Cultivar evaluation trial data from 1980 to 2014 were categorized by region, HA, cultivar, and cultivar eldana resistance category. Mean estimated recoverable crystal yields (TERC) and percentage internodes bored (%IB) by eldana were plotted against HA using polynomial regression to investigate effects of region, cultivar, eldana resistance, and their interactions. Additionally, three separate cultivar. ×. HA factorial trials were analysed using linear mixed models. The HA and its associated interaction terms were highly significant (P<. 0.001) and generally accounted for more variation than the cultivar and crop main and interaction terms in the trial-based analyses. The combined data mining analysis showed that on average, the optimal HA in the coast and inland regions were 15 and 22 months, respectively. A cultivar. ×. HA. ×. region. ×. eldana infestation level interaction was demonstrated, suggesting that a generic optimal HA for specific cultivars cannot be recommended. There was a reduction in optimal HA for newer released cultivars, suggesting possible indirect selection for early maturity in the breeding programs for these regions. Eldana susceptible cultivars were more sensitive to damage as HA increased (4.1 compared with 3.1%IB per additional growth month for susceptible vs. resistant cultivars, respectively). Eldana resistance was essential for achieving the benefits of increased HA in the coastal region. The study highlights the importance of HA to sugarcane productivity and illustrates how an experimental database can be used to inform breeding strategies and gain insights into a key management factor of industrial importance. © 2015 Elsevier B.V.
van Heerden P.D.R.,South African Sugarcane Research Institute
Sugar Tech | Year: 2014
Although information from Brazil and Australia indicate that trinexapac-ethyl (Moddus®) is an excellent new sugarcane ripener, there is no information on the response of South African varieties to this chemical. The objective of this investigation was to establish the ripening potential of this chemical in a local variety and to compare responses with current industry standards, 2-chloroethyl phosphonic acid (Ethephon®) and fluazifop-p-butyl (Fusilade Forte®). Evaluation was conducted in an irrigated plant and first ratoon crop of variety N32 at Pongola, South Africa. The field trial was laid out as a complete randomised design with five replicates per treatment. The nine treatments comprised: (a) untreated control, (b) Ethephon® (1.5 L/ha) applied 84 days before harvest (DBH), (c) Fusilade Forte® (0.2 L/ha) applied 43 DBH, (d) Moddus® at three rates (0.8, 1 and 2 L/ha) applied 70 DBH, (e) Ethephon® (1.5 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 84 and 43 DBH, and (f) Moddus® (0.8 and 1 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 70 and 43 DBH. The various ripener treatments improved estimated recoverable crystal (ERC) yields in the 12-month old crops by between 1.6 and 4.9 t/ha when compared with the control. Moddus® applied at 0.8 and 1 L/ha achieved similar improvements as Fusilade Forte® and Ethephon®, but at 2 L/ha outperformed the latter two ripeners by up to 1.9 t ERC/ha. Best ERC yield responses were achieved in the three combination treatments. However, the Moddus®-Fusilade Forte® combination treatments outperformed the standard Ethephon®-Fusilade Forte® combination treatment by up to 1 t ERC/ha. These results indicate that Moddus® is an effective sugarcane ripener under South African high-potential irrigated conditions and that improved in ERC yields exceeding those obtained with current industry standards might be possible. © 2013 Society for Sugar Research & Promotion.
Lopes M.S.,International Maize and Wheat Improvement CIMMYT |
Araus J.L.,International Maize and Wheat Improvement CIMMYT |
Araus J.L.,University of Barcelona |
Van Heerden P.D.R.,South African Sugarcane Research Institute |
Foyer C.H.,University of Leeds
Journal of Experimental Botany | Year: 2011
Adaptation to abiotic stresses is a quantitative trait controlled by many different genes. Enhancing the tolerance of crop plants to abiotic stresses such as drought has therefore proved to be somewhat elusive in terms of plant breeding. While many C 4 species have significant agronomic importance, most of the research effort on improving drought tolerance has focused on maize. Ideally, drought tolerance has to be achieved without penalties in yield potential. Possibilities for success in this regard are highlighted by studies on maize hybrids performed over the last 70 years that have demonstrated that yield potential and enhanced stress tolerance are associated traits. However, while our understanding of the molecular mechanisms that enable plants to tolerate drought has increased considerably in recent years, there have been relatively few applications of DNA marker technologies in practical C 4 breeding programmes for improved stress tolerance. Moreover, until recently, targeted approaches to drought tolerance have concentrated largely on shoot parameters, particularly those associated with photosynthesis and stay green phenotypes, rather than on root traits such as soil moisture capture for transpiration, root architecture, and improvement of effective use of water. These root traits are now increasingly considered as important targets for yield improvement in C 4 plants under drought stress. Similarly, the molecular mechanisms underpinning heterosis have considerable potential for exploitation in enhancing drought stress tolerance. While current evidence points to the crucial importance of root traits in drought tolerance in C 4 plants, shoot traits may also be important in maintaining high yields during drought. © 2011 The Author.
Paraskevopoulos A.L.,South African Sugarcane Research Institute |
Singels A.,South African Sugarcane Research Institute
Computers and Electronics in Agriculture | Year: 2014
Various technologies exist to support scientific irrigation scheduling, each with its own strengths and weaknesses. Weather-based crop models are good at estimating evapotranspiration and future irrigation needs over large areas, while electronic soil water sensors are able to provide good estimates of soil water status at a given point. Synergy may be obtained by combining these technologies to enhance their usefulness for irrigation management. The objective of this study was to incorporate real-time field records of soil water status into a weather based sugarcane simulation system and to evaluate its use for supporting irrigation scheduling in 15 sugarcane fields in South Africa. Layered soil water status data from capacitance probes were converted to root zone available soil water content (ASWC) using linear scaling. Field specific calibration coefficients were derived from drainage and extraction patterns. An analysis of simulation outputs and observed cane yields suggested that yields were substantially below potential for seven out of the 15 fields. Two fields had prolonged periods of water stress due to under-irrigation, as reflected by the fact that yields from simulations based on measured soil water data were substantially below the potential yield. Yields in six fields were probably limited by poor husbandry as suggested by the fact that observed yields were well below simulated yields using measured soil water data. The system was demonstrated to commercial and small-scale farmers and extension officers during a series of workshops. The integrated system provides enhanced support for irrigation water management for sugarcane production. Farmers and extension specialists can understand the impact of irrigation practices on the soil water regime and its impact on crop growth and yield. This is a good basis for making adjustments to irrigation practices and for benchmarking crop performance and water use efficiency. It also has value for supporting irrigation scheduling decisions. © 2014 Elsevier B.V.
Zhou M.,South African Sugarcane Research Institute |
Joshi S.,South African Sugarcane Research Institute
Sugar Tech | Year: 2012
Relocation of South African Sugarcane Research Institute (SASRI) rain-fed research stations was due to urban encroachment and to increase representativeness of research farms. The relocation also coincided with the Recoverable Value (RV) payment system in 1998, which penalized growers for low sucrose content. After 12 years of trials, the large data set collected provided an opportunity to evaluate trends and progress. The objective of this study was to determine trends in broad sense heritability (H) over time and evaluate their implications on SASRI breeding strategies. Data were analysed using the mixed procedure of the Statistical Analysis System to estimate variance components used to calculate H. The coastal short cycle and midlands programs produced significant decrease in H for yield and marginal increase for sucrose content. The irrigated and coastal long cycle produced increase in H for yield. The breeding strategies resulting from the shift to RV payment system increased H for yield in irrigated and coastal long cycle probably due to stable populations for irrigated and increased efficiency for coastal long cycle. The coastal short cycle and midlands showed decreasing trends in H for yield probably due to intensive selection for sucrose content on populations with narrow genetic diversity. The H proved to be an effective parameter for evaluating breeding and selection strategies. © 2012 Society for Sugar Research & Promotion.
South African Sugarcane Research Institute | Date: 2010-09-17
A method of modifying at least one carbohydrate in a tissue of a plant is described. The method is typically applied to a sugarcane plant of the genus Saccharum method and includes the steps of inserting into a plant cell a gene silencing cassette which includes nucleic acid operably linked to transcription elements such as a monocotyledonous promoter for transcribing the nucleic acid in a plant cell, wherein transcription of the nucleic acid decreases activity of UMP synthase. The method further includes the steps of regenerating a transgenic plant from the plant cell and producing the tissue with increased carbohydrate content. Vectors for use therefor, as well as a transformed plant cell and a transgenic plant or plant part containing or derived from a transformed plant cell are also described.