Sugarcane is among the most efficient producers of biomass per unit area. Populations derived from crosses between sugarcane and related wild species provide a wide source of variation from which various types of canes with high biomass can be identified. To this end, the objective of this study was to characterise and identify high biomass genotypes for multiple uses from the local inter-specific derived germplasm collection. Sixty genotypes of different generations (wild, F1, BC1, BC2) were screened visually and on sucrose and fibre content from the population. They were evaluated in replicated trials with four commercial varieties used as controls. Traits of economic importance, particularly, sugar, fibre and different aboveground biomass yields were measured. Data on cane quality characters were taken at two sampling dates and characters were measured on both fresh and dry weights. The trials were followed up to the first ratoon crop. The source data were validated and few genuine outliers observed were appropriately corrected. A total of 29 parametric traits were analysed individually in each crop cycle. Results showed good reliability of the trials with coefficient of variations within the acceptable limits and good repeatability (H2) values for the majority of the traits. There was a good variation among genotypes allowing selection to operate effectively. Although precisions achievable were higher with dry weight measurements than their corresponding fresh weights, negligible differences were observed with selection simulations. It appeared that in the population of inter-specific derived clones, selection based on cane quality data collected at the pre-harvest season (April) was less efficient than those taken at early-harvest (July). Multivariate data analyses efficiently summarised the data and identified groups of similar genotypes. Principal component analysis was very helpful in visualising the existing variations in the population. Six main clusters were obtained, of which three were of economic interest. Based on inherent variations in cane quality and biomass traits, four types of canes were defined for multiple uses. From Type 1 to Type 4 canes there was a continuous progress in fibre percent. The trait was negatively correlated to sucrose content and the high fibre canes were generally thinner and taller than the commercial controls. A selection algorithm was developed that identified 11 high potential genotypes simultaneously. Biomass yields of three genotypes exceeded those of the commercial controls by >40%. Fibre percent of one Type 4 cane reached 23% while that of the commercial varieties fluctuated at 13%. The results confirmed that high biomass varieties, with variable sucrose and fibre contents, could be obtained from the inter-specific populations. The different types of canes identified provided additional opportunities to exploit the total aboveground biomass of the crop for different end-uses, particularly for bioenergy production. The selection algorithm developed will be extended to the whole selection programme for classifying new sugarcane varieties.

A recent accumulating body of evidence points to the importance of nitric oxide (NO) as a signal molecule involved in the regulation of many physiological and biochemical processes in plants. This study was aimed at investigating the involvement of reactive nitrogen species (RNS), in particular NO and peroxynitrite (ONOO-), in the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), resistance response of wheat (Triticum aestivum L.). Resistant (cv. Tugela DN) and near isogenic susceptible (cv. Tugela) wheat plants were grown under the greenhouse conditions in trays at 24 oC (± 2 oC) and were infested at an early three leaf stage with approximately 20 RWAs (biotype RWASA1) per plant. RWA infestation induced an early accumulation (3-9 hours post infestation) of NO to a higher level in the resistant than susceptible plants. A corresponding increase in the activity of nitrate reductase (NR, EC 1.6.6.1) and inhibition studies using sodium tungstate (NR inhibitor) confirmed its involvement in NO production during the RWA resistance response. In addition, results indicated that the reduction of nitrate (NO3-) to nitrite (NO2-) involves NR and subsequently, nitrite reductase (NiR, EC 1.7.7.1) is responsible for the direct production of NO from NO2-. Inhibition studies using a nitric oxide synthase (NOS, EC 1.14.13.39) inhibitor, N-nitrilo-L-arginine-methyl ester (L-NAME), further proved that NOS has no significant effect on NO production during the RWA resistance response. In an experimental approach using sodium nitroprusside (SNP, NO donor) and / or sodium tungstate (NR inhibitor), it was discovered that NO acts as a signal for the induction of activities of secondary defense related enzymes such as the intercellular β-1,3-glucanase and peroxidase. Higher β-1,3-glucanase transcript accumulation after SNP treatment in resistant plants further supported the involvement of NO as signal molecule during the RWA defense response. In addition, results revealed that NO acts upstream of salicylic acid (SA) during the signaling events. High production of ONOO- [a product of an interaction between superoxide anion (O2-) and NO] in resistant plants after RWA infestation, suggests its involvement in the RWA resistance response. Inhibition of β-1,3-glucanase and peroxidase activities by urate (a specific inhibitor of ONOO- production), further suggests the involvement of ONOO- in the induction of the secondary RWA defense response. Furthermore, it was found that SNP root application of wheat plants resulted in transient resistance only. However, in contrast to root treatments, application of SNP as a seed dressing was more effective and has indeed a great potential of alleviating RWA damage in the susceptible plants by reducing aphid attraction as well as the intrinsic rate of aphid increase.

Cassava brown streak disease (CBSD) is an important biotic constraint to cassava production in cassava growing areas of east, central and southern Africa. A study was initiated to study the genetics of CBSD resistance and search for molecular markers associated with disease resistance. Two resistant and two susceptible cassava parents were selected based on their flowering ability, genetic distance and phenotypic reaction to CBSD. They were crossed in a half diallel to produce six families and F1 progeny plus parents were screened for their reaction to CBSD and evaluated for yield traits at two locations. Results indicated that general combining ability (GCA) was higher than specific combining ability (SCA) for CBSD root necrosis, CBSD severity in the shoot at three, six and nine months after planting (MAP), cassava mosaic disease (CMD) severity at three, six and nine MAP and harvest index indicating the importance of additive gene action in controlling CBSD resistance. Results indicated that CBSD resistance was quantitatively controlled by polygenic genes. Higher SCA than GCA was detected for number of roots per plant, fresh root weight per plant and fresh shoot weight per plant indicating the importance of non-additive gene effects in controlling yield traits. The Namikonga x Albert cross was used to generate a segregating mapping population comprising of 190 F1âs which was planted and screened for CBSD reaction at two locations and genotyped using 605 SSR markers. A total of 220 polymorphic SSR markers, tested on 60 F1 and 51 S1, were finally used for linkage analysis and four genetic linkage maps were produced. The maps produced included integrated (male and female), Namikonga (female), Albert (male) and Namikonga-S1maps which spanned a distance of 995.46cM, 779.48 cM, 854.26 cM and 524.58 cM consisting of 174, 131,123 and 124 mapped SSR markers respectively. Mean map distance between markers ranged from 4.23 cM in Namikonga-S1 to 6.94 cM in Albert map while average map length per linkage group was 43.23 cM, 45.85 cM, 47.46 cM and 30.86 cM for integrated, Namikonga, Albert and Namikonga-S1 maps respectively. The linkage maps were used for QTL analysis and three putative QTL were detected on the integrated map on linkage groups C4, C16 and C18 linked to NS945, ESSRY105 and two flanking markers SSRY4 and ESSRY96 respectively. One QTL linked to NS667 was detected on Namikonga map on linkage group N4 while four putative QTL were detected on the Namikonga-S1 map on linkage groups S1 (at Chambezi and Naliendele in 2008), S8 and S12a at Chambezi 2008 and on S17 at Naliendele 2008. These QTL were respectively found to be linked to SSRY295, NS347 and SSRY4. These findings will have an implication in breeding for CBSD resistance. The observed relative importance of additive gene effects will mean that a mass recurrent selection will be the most efficient approach for CBSD resistance breeding in cassava. Markers associated with CBSD resistance will greatly improve selection efficiency for CBSD resistance in which selection for resistant genotypes can efficiently be done at seedling stage.

The main objective of this research was to determine relationships between selected mixogram parameters and grain, milling, rheological, baking qualityrelated and baking quality characteristics to assist wheat breeders in selecting earlier for desirable primary rheological and baking criteria as required by the Wheat Technical Committee in South Africa when only small grain/flour samples are available. Highly significant differences were observed from combined ANOVAâs among genotypes, environments and GXE interactions for most of the measured characteristics. Genotypes contributed significantly to the variance in hectolitre mass, thousand kernel mass, kernel diameter, break flour yield, flour yield, farinogram water-absorption, alveogram dough stability (P-value), alveogram dough distensibility (L-value), alveogram P/L-value, alveogram dough strength, SDS-sedimentation volume, wet gluten content, loaf volume and loaf volume expressed on a 12% protein basis. Environments had a larger effect on hardness index, vitreous kernels, grain protein content, falling number, flour protein content, flour colour, flour colour expressed on a 76% flour yield basis and mixogram water-absorption. Highly significant positive and negative correlations were observed between the selected mixogram parameters (as determined by Mixsmart software) and grain, milling, rheological, baking quality-related and baking characteristics. Multiple stepwise regressions indicated mixogram parameters to be poorly predictable by grain and milling characteristics. Mixogram parameters (total area and tailheight) were identified as selection criteria to assist wheat breeders in selecting earlier for acceptable primary rheological and baking criteria of importance during cultivar release in South Africa.

ï§ This study was undertaken to transfer resistance against Acanthoscelides obtectus into South African dry bean cultivars; to select breeding lines with increased resistance against A. obtectus through bioassay with adult insects of the species; to develop a recombinant inbred line population, which could be used in future research for near infrared spectroscopy or any other technique; to test the yield ability, resistance against A. obtectus, seed size and colour of the developed breeding lines (progeny) and comparing it to that of the susceptible commercial parents and arcelin donor parent in the breeding scheme and to identify backcross progeny lines equal or better in all characteristics than the commercial parents. ï§ Crosses were made between six commercial and semi-commercial South African dry bean cultivars (recurrent parents) and the SMARC4-PN1 breeding line (arcelin donor parent). Parental characteristics were recovered in a backcross breeding programme. Bioassays were conducted with adult A. obtectus insects to identify resistant backcross progeny lines. The most resistant backcross progeny lines were selected for evaluation in a yield trial, and bioassay, against the commercial parents. A population of 95 F6 RI lines was developed from which the 10 most resistant and 10 most susceptible (as determined through a bioassay with adult insects of the species A. obtectus) were selected. ï§ A replicated yield trial was conducted and one RI line (BRUX1100-2) was shown to have significantly higher yield ability than the commercial parents. A replicated bruchid emergence test was conducted where one RI line (BRUX1100-2) was shown to have significantly higher bruchid resistance than the arcelin donor parent. The seed size evaluation showed that ten backcross progeny lines had significantly smaller seed size than the commercial parents and seven backcross progeny lines had seed colour that could be compared to that of the commercial parents. ï§ The combination of all the important parental traits along with good bruchid resistance was not attained in any single backcross progeny line with only two backcrosses. Another one or possibly two cycles of backcrossing would be necessary for the further recovery all of these characteristics.

Cassava provides more dietary energy per unit area than any staple crop but native cassava starch has limited food and industrial applications. Different transgenic biotechnology approaches and ex situ physical and chemical starch modifications have been used to obtain desirable traits suitable for various food applications. But consumers are skeptical about the safety of the genetically modified foods and chemical residues. To meet the demand, gamma irradiation (this is energetic electromagnetic wave) which does not leave any residue, was used as a tool to induce in planta variation in amylose production. The four highest amylose producing plants N441P54 (32.7%), N223P12 (31.1%), N373P2 (27.2%), N329P11 (26.8%) and four lowest amylose producing plants N96P16 (14.0%), N353P6 (13.9%), N166P2 (13.2%), N476 P22 (11.7%) observed in the M1V2 generation were found to be significantly different from any one of the four controls HO008 (19.7%), HO001 (22.0%), UCC090 (22.6 %) and UCC026 (20.9%). Mutation is uncontrollable and could also lead to unexpected useful mutants. From this study four unexpected putative free-sugar mutants were identified, which could be used for bioethanol and glucose syrups production; two exceptional deep fissured and flaky mutants for the food industry; seven mutants with transition from A- to C-types of X-ray diffraction patterns with very high levels of crystallinity indexes suitable for replacing acid modified starches in pressing tablets in the pharmaceutical industries were discovered. Based on DSC classification, three gelatinization categories were observed. These were plants without gelatinization transition, plants with gelatinization transition and plants with merged gelatinization and melting transitions, occurring within gelatinization zone during calorimetric scanning from 25 â 110°C. The first and third categories included most of the putative mutants described in the research chapters and they were suitable for shortening the starch processing time required in most commercial starch applications in industry.

This study was conducted with the objectives of assessing the genetic diversity of sorghum accessions that were obtained from different geographical locations in Ethiopia, as well as South Africa, using phenotypic traits, AFLP markers, minerals, starch and protein. Twenty phenotypic traits were subjected to ANOVA and highly significant differences were observed for all traits among accessions. Some important characteristics were found to be significantly correlated, which could allow for selection of related secondary characteristics to improve primary characteristics. Cluster analysis grouped accessions into five clusters based on similarity. These results would be useful in a breeding programme for selecting sorghum accessions to improve production. Nine qualitative morphological traits were also analysed using the Shannon Weaver diversity index (Hâ). The results showed that the average Hâ was 0.59. The highest polymorphism was recorded for the glume colour (0.84), while the lowest was recorded in panicle compactness and shape (0.31). This indicated that there was wide variability among accessions studied. The cluster analysis for the qualitative traits also identified accessions based on their similarity and differences based on their genetic distances. Hence, visual selection and measurements of the sorghum attributes in field trials could be used to select the desirable traits and improving yield and stability of the accessions in breeding programmes. AFLP analysis showed high genetic similarity of Ethiopian landraces, as well as breeding material from the Ethiopian and South African sorghum breeding programmes, even though the phenotypical characterisation showed high variability. This indicated the possibility that South African and Ethiopian breeding material may have a common ancestry. The morphological, AFLP and combined morphological and AFLP cluster analysis clearly distinguished between all accessions, even though they were genetically similar. Sorghum kernels were used to determine the mineral, starch and protein composition of the sorghum accessions. The ANOVA of the traits revealed highly significant variation among the accessions studied. Furthermore, PCA grouped accessions according to their similarity/differences in the four quadrants which confirmed that there was variation among them for these nutritional traits. Therefore, there would be potential for selecting accessions for specific mineral and protein content for human consumption, and specific starch and amylose content for industrial use. The sugar content of the stalks also indicated the potential to develop dual sorghum cultivars where both the seed and sugar can be produced from the same plants.

This study was undertaken to evaluate 11 wheat genotypes for aluminium tolerance using three laboratory based evaluation methods. Four parameters namely the root length before aluminium treatment, the root re-growth after aluminium treatment, the portion of the root affected by aluminium treatment, stained with hematoxylin and root tolerance index were measured on the two longest (primary and secondary) roots of each seedling to determine the effect of aluminium toxicity on the physiological development of the seedling roots. With the root re-growth method it was possible to distinguish between three categories of tolerance (moderate, intermediate and tolerant) that will be very helpful in future resistance breeding for aluminium tolerance. With this method it is possible to discriminate between individuals in a population for aluminium tolerance. Similar data was obtained for the primary and secondary roots, which indicated that the age of the roots are not a limiting factor for aluminium tolerance screening with the nutrient bioassay. Although the root re-growth method discriminated between the different aluminium tolerance categories, a better indication of aluminium tolerance categories was achieved with the root tolerance index method. With the above methodology in place it was possible to observe an increase in aluminium tolerance in some progeny after gene recombination and it was possible to discriminate between good aluminium tolerant progeny and progeny showing no genetic gain from the hybridisation. It was also shown that there were no reciprocal effects for aluminium tolerance in wheat. There were genetic differences for aluminium tolerance between the genotypes used in this study and this methodology can be successfully implemented in an aluminium tolerance-breeding programme for wheat. This study indicated that there is useful methodology to effectively follow the genetic gains during gene-recombination for aluminium tolerance and, secondly that there are different genetic resources available in wheat that can be utilised to increase aluminium tolerance.

The aim of this study was to assess, classify and describe the natural vegetation along the Vet River. The study was restricted to the vegetation of the islands, banks as well as the floodplains. The Vet River is situated in the Free State Province, South Africa. The study area covers approximately 8 928 hectares including the surface area of the Erfenis Dam, which is situated downstream of the confluence of the Groot Vet and Klein Vet Rivers. There are several towns in the catchment of the Vet River which include: Exelcior, Winburg, Theunissen and Hoopstad. The area around the river also has a provincial nature reserves namely: Willem Pretorius Game Reserve along the Sand River, a tributary of the Vet River, the Erfenis Dam Nature Reserve near Theunissen and the Sandveld Nature Reserve downstream of Hoopstad. The area is mostly situated in the Highveld climatic region with cold and dry conditions due to the high elevation and the inland continental aspects of the area. Furthermore the area is characterised by warm summers with strong summer rainfall patterns and mild winters with drought. The rainfall received is mostly in the form of regular showers and thunderstorms during the months of October to March. The geology of the area is dominated by the Karoo Supergroup which was deposited during the period of 310 to 182 million years ago. Only the Ecca, Beaufort and Stormberg Groups occur in the study area. In the area, two biomes are present. These biomes are the Grassland biome (which occur between sea level to 2 850m above sea level) which mainly represent the high central plateau of South Africa and the Savanna biome (occur at altitudes below 1 500m above sea level) which mostly occur in areas with a strongly seasonal rainfall and a distinct dry season which usually occur in winter. The Vet River cuts through seven vegetation types. Various kinds of wetlands occur along the Vet River. All of them falls within the RAMSAR definition of a wetland namely: âwetlands are areas of marsh, fen (peat-accumulating wetland that receives some drainage from surrounding mineral soil and usually supports marshlike vegetation), peatland (generic term of any wetland that accumulates partially decayed plant matter) or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metresâ. The presence of wetlands in the study area lead to the search for a proper definition for these unique systems as they also perform certain functions and can be seen as valuable ecological laboratories because of their habitat and species diversity. Riparian areas is seen as the interface between aquatic and terrestrial ecosystems, however these areas can also be defined as frequenting, growing on, or living on the banks of streams or rivers. These areas are usually narrow and linear and can be regarded as corridors for migrating species. During the study 240 sample plots were placed within various homogenous vegetation types along the Vet River. The Braun Blanquet cover-abundance scale was applied in this study. The vegetation analysis led to the classification and identification of 14 plant communities, 21 sub-communities and 11 variants which were discussed phytosociologically: The communities can be divided into those communities that occur in the mountains, those communities that occur in the riverine areas on plains and the communities that occur in the floodplains or pans along the Vet River.

Manihot esculenta ssp flabellifolia possesses valuable genetic variability for protein and disease resistance genes that were introgressed into cultivated cassava. FLA 444- 5 with a protein content of 10.5% (dry weight basis) was hybridised with cassava through controlled crosses and backcrossed to cassava to obtain the B1P2 family used in this study. The interspecific hybrids had protein values ranging from 0.77% - 11.25%, which indicated introgression of the trait. Application of in vitro seed germination, overcame the bottleneck of seed dormancy and insufficient planting materials for replicational trials at an early stage of evaluation. High positive and negative correlations were estimated in the B1P2 backcross family for yield traits, quality traits, and pests. Moderate to high heritability values were estimated for commercial roots, roots per plant, harvest index, root weight, fresh root yield, dry root yield, dry matter content, post harvest physiological deterioration, and protein content. Protein content and dry matter content were negatively correlated, but not significantly. Location and year did not show any significant difference in protein yield by genotype. Evaluation of whitefly in this study showed a high number of genotypes (86.70%) being resistant to infestation and infection in this Colombian high pressure pest region. SSR markers (817) were screened in the parental lines and four B1P2 progenies, 402 polymorphic markers were identified; of which 105 were used for map construction. The genetic map consisted of 29 linkage groups spanning 1249.55 cM with average marker interval of 16.16 cM. A total of three QTL (protg.7, protg.13 and protg.23) controlling protein were identified in the three different environments, with one QTL present across all three environments. The individual effects of alleles at these QTL ranged from 15% to 25% of the phenotypic variance explained.