Typescript. / Bibliography: leaves 115-123. / Photocopy. / xiv, 123 leaves, bound ill. 29 cm

Dissertation (PhD) -- University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Sugarcane (Saccharum spp. hybrids) is a commercial crop plant capable of storing up to 20% sucrose on a fresh mass basis in the culm. Knowledge about gene expression during sugarcane growth and maturation is limited. The aim of this study was to assess whether an Expressed Sequence Tag (EST)-based approach towards analysis of sugarcane would reveal new information about gene expression and metabolic processes associated with sugarcane growth and development. The specific objectives were two-fold: firstly, to develop an EST database for sugarcane and secondly, to identify and analyse genes that are expressed in different sugarcane tissue types and developmental stages, with a specific focus on leaf and culm. An EST database for sugarcane was initiated to obtain information on sugarcane gene sequences. A total cDNA library was constructed from sugarcane immature leaf (leaf roll: meristematic region) tissue and 250 clones randomly selected and subjected to single-pass DNA sequence analysis. Sugarcane ESTs were identified by sequence similarity searches against gene sequences in international databases. Of the 250 leaf roll clones, 26% exhibited similarity to known plant genes, 50% to non-plant genes while 24% represented new gene sequences. Analysis of the identified clones indicated sequence similarity to a broad diversity of genes. A significant proportion of genes identified in the leaf roll were involved in processes related to protein synthesis and protein modification, as would be expected in meristematic tissues. Submission of 495 sugarcane gene sequences to the dbEST database represented the first sugarcane ESTs released into the public domain. Two subtracted cDNA libraries were constructed by reciprocal subtractive hybridisation between sugarcane immature and maturing internodal tissue. To explore gene expression during sugarcane culm maturation, partial sequence analysis of random clones from maturing culm total and subtracted cDNA libraries was performed. Database comparisons revealed that of the 337 cDNA sequences analysed, 167 showed sequence homology to gene products in the protein databases while 111 matched uncharacterised plant ESTs only. The remaining cDNAs showed no database match and could represent novel genes. The majority of ESTs corresponded to a variety of genes associated with general cellular metabolism. ESTs homologous to various stress response genes were also well represented. Analysis of ESTs from the subtracted library identified genes that may be preferentially expressed during culm maturation. The expression patterns of sugarcane genes were examined in different tissue sources and developmental stages to identify differentially expressed genes. cDNA arrays containing 1000 random clones from immature leaf and maturing culm cDNA libraries were hybridised with poly (At RNA from immature leaf, mature leaf, immature culm and maturing culm. All cDNAs examined hybridised to all four probes, but differences in signal intensity were observed for individual cDNAs between hybridisation events. No cDNAs displaying tissue- or developmental-stage specific expression were detected. Comparisons between hybridisation patterns identified 61 cDNAs that were more abundantly expressed in immature and mature leaf than the culm. Likewise, 25 cDNAs preferentially expressed in immature and maturing culm were detected. ESTs established for the differentially expressed cDNAs revealed sequence homology to a diverse collection of genes in both the leaf and the culm. These included genes associated with general cellular metabolism, transport, regulation and a variety of stress responses. None of the differentially expressed genes identified in the culm were homologous to genes known to be associated with sucrose accumulation. To examme differences at the level of gene transcription between low sucroseaccumulating and high sucrose-accumulating tissues, subtracted cDNA libraries were utilised. To isolate cDNAs differentially expressed during culm maturation, cDNA arrays containing 400 random clones (200 from each library) were screened with total cDNA probes prepared from immature and maturing culm poly (At RNA. Results indicated that 36% and 30% of the total number of cDNAs analysed were preferentially expressed in the immature and maturing culm, respectively. Northern analysis of selected clones confirmed culm developmental stage-preferential expression for most of the clones tested. ESTs generated for the 132 differentially expressed clones isolated exhibited homology to genes associated with cell wall metabolism, carbohydrate metabolism, stress responses and regulation, where the specific ESTs identified in the immature and maturing culm were distinct from each other. No developmentally regulated ESTs directly associated with sucrose metabolism were detected. These results suggest that growth and maturation of the sugarcane culm is associated with the expression of genes for a wide variety of metabolic processes. In addition, genes encoding enzymes directly involved with sucrose accumulation do not appear to be abundantly expressed in the culm. / AFRIKAANSE OPSOMMING: Kommersiële suikerriet variëteite (Saccharum spp. hibriede) is in staat om tot 20% sukrose op 'n vars massa basis in die stingel op te berg. Kennis oor geenuitdrukking tydens groei en rypwording is beperk. Die doel van die huidige studie was om vas te stelof 'n grootskaalse karatersisering van die geenvolgordes wat uitgedruk word "Expressed Sequence Tag (EST)-based approach" tot nuwe inligting aangaande die aard en omvang van metabolisme tydens groei en ontwikkeling van suikerriet sal lei. 'n Tweeledige benadering is in hierdie studie gevolg. Eerstens is 'n data basis oor die gene wat uitgedruk word "EST" databasis opgestel. Tweedens is gene geïdentifiseer en gekarakteriseer wat spesifiek op verskillende stadiums van ontwikkeling en in spesifiek weefsel uitgedruk word. Vir die opstel van die EST-databasis is 250 klone uit 'n totale cDNA biblioteek vanaf RNA uit suikerrietblaarweefsel (blaarrol:meristematiese streek) op 'n lukraak basis gekies en aan 'n enkel eenrigting DNA volgorde analise onderwerp. Suikerrriet EST's is geïdentifiseer deur middel van homologie soektogte teen geenvolgordes in internasionale databasisse. Uit die 250 blaarrol klone het 26% ooreenkomste met bekende plant gene en, 50% met nie-plant gene getoon. Ongeveer 24% het nuwe geenvolgordes verteenwoordig. Analise van die geïdentifeseerde klone het ooreenkomste met 'n breë diversiteit van gene getoon. 'n Betekenisvolle gedeelte van gene wat in die blaarrol geïdentifiseer is, is by proteïensintese en proteïenmodifikasies betrokke. Dit is in ooreenstemming met wat van meristematiese weefsel verwag kan word. Die 495 suikerriet geenvolgordes wat in die internasionale dbEST databasis gestort is, is die eerste sodanige inligting in die publieke domein. Twee spesifieke cDNA biblioteke (subtraction libraries) wat volgordes spesifiek aan onvolwasse suikerriet en rypwordende internodale weefsel bevat is voorberei. Geenuitdrukking gedurende die rypwordingsproses van die suikerrietstingel is bestudeer deur geenvolgorde analises van onwillekeurige geselekteerde klone van die twee eDNA biblioteke te doen. Van die 337 geenvolgordes wat geanaliseer is het 167 homologie met bekende gene en net 111ooreenkomste met ongekarakteriseerde plant gene getoon. Die oorblywende geenvolgordes het geen ooreenkomste met bekende gene getoon nie en daar kan dus aanvaar word dat hulle nuwe gene verteenwoordig. Die meerderheid ESTs het ooreenkomste met verskeie gene wat met sellulêre metabolisme geassosieer word getoon. ESTs wat homoloog was aan verskeie spannings geassosieerde gene was ook goed verteenwoordig. Die analise het gene wat by voorkeur tydens stringelrypwording uitgedruk word geidentifiseer. Die geenuitdrukkingspatrone van suikerriet in weefsels van verskillende oorsprong en ontwikkelingstadia is ondersoek om differensieel uitgedrukte gene te identifiseer. Reekse wat 1000 lukrake eDNA klone van onvolwasse en rypwordende stingel eDNA biblioteke is met poli-(A)-RNA van onvolwasse blaar, volwasse blaar, onvolwasse stingel en volwasse stingel gehibridiseer. Al die eDNA klone wat ondersoek is het met al vier die peilers gehibridiseer. Die intensiteit van die seine het egter grootliks gevarieer. Die analise het gelei tot die identifisering van 61 eDNA klone wat teen hoër vlakke in onvolwasse en volwasse blaar as in die stingel uitgedruk word. Daar is ook 25 eDNA klone wat by voorkeur in onvolwasse en rypwordende stingel uitgedruk word gevind. Gene wat geassosieer word met gewone sel metabolisme, vervoer prosesse, regulering en verskeie spannings-geassosieerde reaksies, is in die twee groepe teenwoordig. Geeneen van die volgordes wat selektief uitgedruk word kan met gene wat direk met sukrose akkumulering verband hou geassosieer word nie. Ten einde eDNA klone wat differensieel tydens rypwording van die stingel uitgedruk word te isoleer, is 400 eDNA klone (200 van elke biblioteek) lukraak geselekteer en met totale eDNA peilers, wat uit onvolwasse en rypwordende stingel poli-(A)-RNA voorberei is, gesif. Resultate het aangetoon dat 36% en 30% van die totale getal eDNA klonewat geanaliseer is, by voorkeur in die onvolwasse en rypwordende stingel uitgedruk word. RNA kladanalises van geselekteerde klone het getoon dat die meeste ontwikkelingstadium spesifieke uirtdrukkingspatrone het. Daar is gevind dat 132 van die EST klone homologie met gene geassosieerd met selwand- en koolhidraatmetabolisme, spannings geassosieerde- en reguleringsreaksies, toon. Die spesifieke ESTs wat in die onvolwasse en rypwordende stingel geïdentifiseer is het van mekaar verskil. Nie een van die ESTs wat geïdentifiseer is kan direk met sukrose metabolisme geassosieer word nie. Hierdie werk toon baie duidelik aan dat groei en rypwording van die suikerrietstingel met die uitdrukking van gene geassosieerd is wat by 'n hele aantal metaboliese prosesse betrokke is. Die resultate toon ook dat die gene wat vir ensieme kodeer wat direk by sukrose akkumulering betrokke is, nie teen hoë vlakke in die stingel uitgedruk word nie.

Crop rotation is not commonly practised in the sugarcane industry in South Africa. It has, however, proven to be beneficial to other crops in South Africa. The objective of this study was to determine the impact of soybean-sugarcane crop rotation on selected physiological and phenological indicators of sugarcane performance and its subsequent effect on cane and estimated recoverable crystal (ERC) yields. A field trial was conducted at Mount Edgecombe, where soybean cultivar A5409RG and sugarcane cultivar NCo376 were planted under drip irrigation with different management practices. After the soybean crop, the following sugarcane crop was planted and fertilized with different levels of nitrogen (N) fertilizer (50% and 100% of the recommended N rate). The effects on sugarcane growth were recorded by taking into consideration date of emergence, plant height, tiller population, leaf N, plant performance index and chlorophyll content. Sugarcane yield and quality at harvest were also evaluated. Tiller population in all crop rotation treatments at Mount Edgecombe weresignificantly (P<0.05) higher than the monocrop treatment. There was a trend of increased leaf N in all of the cane-after-soya (crop rotation) crops compared to the cane-after-cane (monocrop) treatment, although this was not significant. A similar pattern was obtained with respect to the chlorophyll content and plant performance index. Sugarcane yields at Mount Edgecombe did not differ significantly between monocrop and crop rotation treatments. Crop rotation with soybean is beneficial for cane production, but its long term impact on soil quality and farm economy requires further investigation. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.

An experiment was conducted at Pongola (27°24´S, 31°25´E; 308m altitude) in South Africa to study the effects of season on growth and potential biomass and sucrose yields on nine commercial sugarcane cultivars. The treatments that were the focus in this study consisted of the cultivars NCo376, N25 and N26 ratooned in March, April, May, August and December. The crops were well fertilized and kept free of weeds and diseases. Irrigation applications were scheduled with a computer programme to keep the crops free of stress at all times. Shoot populations were counted regularly to study shoot density dynamics. Leaf appearance rates, sizes, numbers and senescence were measured to study the development of green leaf area. Green foliage, dead trash and stalk mass were measured at 4, 8, 10, 11 and 12 months in each of the starting times and also at 13 months in the March, April and May ratoon crops. The fibre, sucrose and non-sucrose content of stalks were determined on these harvesting occasions. Yields were calculated in terms of individual shoots and area (m‾²). The fraction of PAR intercepted by the developing canopies was measured until full canopy and daily intercepted solar radiation was interpolated for the entire crop. An automated meteorological station adjacent to the experiment site provided daily weather data. Shoot densities were described by thermal time, however, average peak shoot densities were lowest in the May ratoon (31.8 m‾²) and highest in the December ratoon (48.7 m‾²). Shoot senescence was most rapid in August and December ratoons. At the final harvest shoot densities were highest in the March, April and May ratoon (14.8 to 14.2 m‾²) crops. NCo376 (16.4 m‾²) and N25 (13.6 m‾²) had higher final shoot densities than N26 (10.5 m‾²). Leaf appearance rate was also well described by thermal time, however the first twelve leaves took longer to appear in crops started in December i.e. the first phyllochron was longer (109.5°C d) than in crops started at other times (80.4 to 94.5°C d). Leaves produced during the early stages of December and August ratoon crops were larger (e.g leaf number 13 of N26 was 443 to 378 cm²) than in other crops. April and May ratoon crops produced much smaller leaves (e.g leaf number 9 of N26 was 170 to 105 cm²). Leaf senescence was slower in April and May ratoon crops (0.36 to 0.46 leaves per 100°C d) than in March (0.51 to 0.59 leaves per 100°C d) or August and December ratoon crops (0.60 to 0.68 leaves per 100°C d). December ratoon crops produced very high green leaf area indexes (LAI) (>7.0) at the age of four months; all other crops had lower LAI (3.3 to 6.0) and most peaked later (8 to 11 months of age). The LAI of N25 peaked at the age of 8 months while NCo376 and N26 peaked when 10 to 11 months old. Seasonal fraction of solar radiation intercepted was high in the March ratoon crops (0.84) and declined to 0.63 in the May ratoon crops and was highest in the December ratoon crop (0.88). N26 intercepted lower fractions of PAR than NCo376 and N25, particularly in the May and August ratoon crops. Biomass accumulation, although initially slow, tended to be linear in the March, April and May ratoon crops in relation to intercepted radiation. In August and particularly in the December ratoons biomass accumulation was initially rapid, and RUEs were high (2.65 g MJ‾¹ at 114 days in the December ratoon crops). However, biomass accumulation slowed when these December ratoon crops experienced winter. Low growth rates after winter, as well as low shoot densities resulted in December ratoon crops having produced significantly lower above-ground biomass yields (4 886 g m‾² at the age of 12 months) than March, April and May ratoon crops (6 760 to 5 715 gm‾² at the age of 12 months). The December ratoon crops responded poorly to the better growing conditions in spring and second summer and accumulated little biomass after winter. N26 shoots grew rapidly during the first 6-8 months of the December ratoon crop and it yielded better than NCo376 and N25 at harvesting (biomass yields were 5.8 and 13.3% higher at the age of 12 months, respectively). April ratoons produced significantly higher biomass yields (6 760 g m‾²) than March, August and December ratoons. May ratoon crops produced the highest cane fresh mass yields (18 151 g m‾²) and April, May and August ratoons produced significantly higher sucrose yields than March and December ratoons. The highest sucrose yield was produced by the April ratoon crop of N26 (2 385 g m‾²). On average, across the five ratoon dates, NCo376, N25 and N26 produced similar sucrose yields (1 902 to 1 959 g m‾²). Foliage production was severely limited during winter while sucrose accumulation was less affected by the low temperatures, resulting in accumulation of sucrose in the top sections of the culm. Low temperatures slowed the development of canopies in March, April and May ratoon crops, but these crops were able to recover their growth rates and produced high biomass and sucrose yields at the age of 12 months. The December ratoons experienced low winter temperatures (<12°C) when they had already accumulated relatively high yields and became moribund during winter. They were unable to accumulate any significant amounts of biomass during final four months before the final harvest at the age of 12 months. NCo376, N25 and N26 all yielded poorly in the December ratoon crop. However, there are cultivars that appear to be less sensitive to the low winters and are able to yield relatively well when they are ratooned in December. Sucrose yields of March, April and May ratoons were increased substantially (10.6 to 22.7%) by harvesting at the age of 13 months rather than at the age of 12 months. The poor growth of December ratoon crops after winter is possibly due to the recently revealed feedback signaling by high sugar levels induced by low temperatures on photosynthesis. The incorporation of the effects of low temperature and the feedback signaling with the objective of better simulating yields of December ratoons is a proposed study at the South African Sugarcane Research Institute. Annual mean sucrose yields of NCo376, N25 and N26 crops were estimated to be 17% higher in March than in December ratoons. The suggested short term remedy therefore of the poor December yields is to shift milling seasons to include March and exclude December harvested crops in the northern irrigated regions. March crops grow vigorously during the months close to harvesting and therefore have lower levels of sucrose content which can be corrected with chemical ripeners. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

First, the field survey campaigns have been carried out from March 22, 2007 to December 27, 2007 around 5-15 days in the interval in the study area of Nansha Island. The field work includes the survey of spatial distribution of various land use and crop types and the ground measurements of the crop biophysical parameters (such as the plant height, leave area index, fresh biomass, and plant water content) and the soil parameters (such as the soil water content and surface roughness parameters) of rice field and sugarcane field. And at the same time, the ENVISAT ASAR data were acquired from March 22, 2007 to December 27, 2007 in the interval of 35 days. During the acquisition dates of the ENVISAT ASAR data, the field surveys were also conducted. / Fourth, the sufficient ground measurements and simultaneous C-band HH- and VV-polarized SAR data of sugarcane crop have enriched the knowledge of understanding the temporal radar scatter mechanisms in sugarcane canopies. The C-band VV-polarized radar backscatters are larger than those of HH-polarization during the sugarcane growth cycle, and the difference is around 0.5 dB to 2 dB. The theoretical model MIMICS was adapted in modeling the scattering terms in sugarcane fields to interpret the temporal behavior of radar backscatters. For more robotic operation, the empirical regression models were used in estimation of the sugarcane LAI and fresh biomass, and mapping the sugarcane growth situation. The accuracies of the sugarcane LAI map and Biomass map are 0.74 and 0.70, respectively. / In conclusion, the C-band ENVISAT ASAR data can be efficiently used in the Pearl River Delta to monitor the crop growth, including the crop spatial distribution, crop acreages, and crop growth situation evaluation. The efficient crop growth monitoring program can not only help instruct the flexible farming actions, but also estimate the crop yield production for the decision-making government. (Abstract shortened by UMI.) / Second, field surveys were combined with the ENVISAT ASAR data to map the agricultural area. The analysis of the temporal radar backscatter characteristics of various land cover categories demonstrated that the time series of C-band SAR data is efficient in separating the eight land cover categories (rice paddy, sugarcane, banana, lotus ponds, mangrove wetlands, fish ponds, seawater, and buildings) in the PRD. The decision tree classifier is also approved to work efficiently on satellite SAR images with an overall accuracy of 77% and the Kappa coefficient of 0.74. The acreages of the land cover categories were also derived from the classification result with accuracies from 70% to 90%. / The Pearl River Delta is a typical developing region. It lies in the cloud-prone and rainy area of south China with multi-species of crops cultured in the agriculture areas. With a goal of developing an efficient, timely and accurate crop growth monitoring program in this area, field measurement, satellite SAR remote sensing technique, quantitative analysis of the crop biophysical parameters, and radar backscatter modeling methods have been integrated to study the multi-temporal and multi-polarized SAR data in estimating plant parameters (LAI, fresh biomass) of rice and sugarcane crop, and mapping the agricultural land cover categories of the study area in the PRD. / Third, in the study of rice growth monitoring, the trends of the relationships between C-band radar backscattering coefficients and rice parameters (plant height, LAI, fresh biomass, et al.) are proved to be constant with the reports in previous literatures. It was demonstrated that the differences between HH- and VV-polarized backscatter are not so evident (around 0.5 dB) in rice paddy canopies during the crop growth cycle. Moreover, by inducting a semi-empirical soil surface scattering component, a modified Water Cloud Model was developed to simulate the radar backscatter in rice crop canopies in different ground background situations (water surface, and soil surface) and to estimate the rice LAI and above ground fresh Biomass with reasonable accuracy. The rice growth conditions were displayed by LAI map and Biomass map generated from the model estimation, and the accuracies of the LAI and Biomass level classification are 0.77 and 0.71. / Wang, Dan. / Advisers: Hui Lin; Jin-Song Chen. / Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 132-138). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.