Thesis (MScAgric)--Stellenbosch University, 2021. | ENGLISH ABSTRACT: It is the objective of every farmer to obtain high yields and therefore the use of good quality seeds is of importance. Most soils that support wheat cultivation are zinc (Zn) deficient. Biofortification was shown to be a solution to improve mineral content (particularly Zn) of cereals. Improved Zn content has secondary benefits during seedling development under Zn deficient conditions. On the other hand, yields are limited by other factors such as weeds, soil borne diseases and environmental stresses such as extreme drought conditions. All these factors reduce productivity of wheat, which have implications for global food demand to meet a growing population. The use of seeds with high vigour ensure investment returns because these seeds are believed to have better germination and tolerance against biotic and abiotic stresses. This study aims to investigate the influence of seed Zn levels on vigour of wheat accessions with varying quality attributes. Seed Zn has been associated with improving agronomic traits such as germination and optimum field emergence. The influence of seed Zn was investigated through laboratory and field experiments. Vigour was determined using the EC test, standard germination test, according to ISTA and accelerating ageing test (AA). Field experiments were conducted at two different localities, namely Langgewens and Roodebloem, respectively. Proper mineral content is vital for germination and zinc has been reported to improve vigour of seeds. The electrical conductivity (EC) test provided the best estimate of seed vigour, R1H (51.3 mg kg-1) had the least electrolyte leakage as well as, the best germination (>80%). Results indicated that seed vigour is affected by age, seed Zn concentration and locality of the seeds and their weight. Adequate Zn in wheat is an essential micronutrient required during physiological processes like germination. Accessions were one year apart with optimal germination from one-year old accessions. Due to natural ageing or artificial ageing, seeds lose vigour over time. The potential of using Zn-biofortified seeds still need to be investigated further because some of the accessions which had low zinc content managed to perform similarly to high Zn content accessions. Increasing sowing depth had a significant effect (p>0.05) on germination and emergence of wheat. This study revealed that seed Zn is beneficial to a seedling during early development. In field experiments and despite variation in seed Zn concentrations, both experiments at Langgewens and Roodebloem had uniform canopies at harvest. The benefits of high seed Zn content were inconclusive. Zinc biofortified seeds had an advantage of better germination and good establishment under different environmental conditions. However, the benefits of high seed Zn concentrations seemed to be sensitive to the availability of Zn in the soil. Zinc plays a crucial role in early stages from germination to emergence and early growth stages (tillering) but does not seem to influence the growth of wheat at later growth stages. | AFRIKAANSE OPSOMMING: Die doelwit van enige produsent is om hoë opbengste te behaal en daarom is die gebruik van goeie kwaliteit saad belangrik. Die meeste grond waarop koring verbou word het tekorte aan sink (Zn). Biofortifikasie is reeds bewys as ‘n oplossing om die mineraalinhoud (veral Zn) van grane te verbeter. Sekondêre byvoodele van verhoogde Zn inhoud is die beter ontwikkeling van saailinge onder toestande waar Zn beperkend is. Aan die ander kant word opbrengs beperk deur faktore soos onkruid, grondgedraagde siektes en omgewingsstremmings soos uiterste droogtetoestande. Al hierdie faktore verlaag die produktitwiteit van koring, wat gevolge het vir die globale voedselaanvraag om ‘n groeiende populasie te voed. Die gebruik van saad met goeie lewenskragtigheid verseker goeie opbrengs op insetkostes deurdat hierdie saad na bewering beter ontkiem en beter weerstand het teen biotiese an abiotiese stremmings. Die doel van hierdie studie was om die invloed van Zn vlakke op die lewenskragtigheid van koringmonsters met wisselende kwaliteitseienskappe te ondersoek. Sinkinhoud van saad word verbind met verbeterde agronomiese eienskappe soos ontkieming en vestiging in die land. Die invloed van Zn inhoud van saad is ondersoek deur laboratorium- en veldproewe. Lewenskragtigheid is bepaal deur middel van elektriese konduktiwiteitstoetse (EK), standaard ontkiemingstoets (volgens ISTA voorskrifte) en die versnelde verouderingstoets (VV). Veldproewe is uitgevoer op twee lokaliteite, naamlik Langgewens en Roodebloem respektiewelik. Voldoende mineraalinhoud is onontbeerlik vir ontkieming en Zn is bekend daarvoor dat dit lewenskragtigheid van saad verbeter. Die EK toets het die beste beraming van lewenskragtigheid verskaf: R1H (51.3 mg Zn kg-1) het die minste elektroliete gelek en ook die beste ontkiemingspersentasie getoon (>80%). Die resultate het getoon dat lewenskragtigheid van die koringsaad beïnvloed is deur ouderdom, Zn inhoud van die saad, oorsprong van die saad en hulle massa. Voldoende Zn in saad is essensieel vir fisiologiese prosesse soos ontkieming. Saadmonsters het met een jaar verskil in ouderdom en optimale ontkieming is verky van een jaar oue saad. As gevolg van natuurlike en versnelde veroudering het saad met tyd hulle lewenskragtigheid verloor. Die moontlikheid om saad wat met Zn gebiofortifiseer is te gebruik om te plant moet verder ondersoek word omdat sommige saadmonsters met lae Zn inhoud net so goed presteer het as saadmonsters met hoë saad Zn inhoud. Dieper saaidieptes het ‘n betekenisvolle (p<0.05) invloed gehad op die ontkieming en vestiging van koringsaad. Hierdie studie het getoon dat genoegsame Zn inhoud van saad voordelig is vir vroeë ontwikkeling van saailinge. In die veldproewe het beide proewe op Langgewens en Roodebloem uniforme plantstande gehad tydens oes, ongeag variasie in Zn inhoude van die saad. Die voordele van hoë Zn inhoud van die saad was nie opmerklik nie. Saad wat met Zn gebiofortifiseer is het die voordeel van beter ontkieming en vestiging onder verskillend omgewingstoestande. Die voordele van hoë Zn inhoud van saad blyk egter beïnvloed te word deur die beskikbaarheid van Zn in die grond. Sink speel ‘n belangrike rol in vroeë groeistadia van ontkieming tot vestiging en tot stoelvorming, maar blyk nie die groei van koring op latere groeistadia te beïnvloed nie. | Masters

In this study, we investigated the effects of wheat root exudates on soil bacterial communities in the watermelon rhizosphere using quantitative PCR and Illumina MiSeq sequencing. The qPCR results showed that wheat root exudates significantly increased the abundance of total bacteria, Pseudomonas, Bacillus and Streptomyces spp. Illumina MiSeq sequencing results showed that wheat root exudates significantly changed the bacterial community structure and composition. These results indicated that plant root exudates play a role in plant-to-plant signalling, strongly affect the microbial community composition.

Abstract. The aim of this study was to investigate the influence of long-term nitrogen-phosphorus fertilization and meteorological conditions during the period 1990-2019 on test weight of durum wheat grain in Central South Bulgaria. The influence of nitrogen and phosphorus rates – 0, 40, 80, 120 and 160 kg.ha-1, as well as combined NP fertilization in the same rates on durum wheat grain under conditions of stationary long-term fertilizing experiment in cotton-durum wheat crop rotation was studied. The analysis of the results showed that the test weight was below the standard requirements in eight of the studied years, and in 22 years the average test weight exceeded the requirements. The values in 17 years were over 80.0 kg. The test weight decreased by increasing the N rates above 80 kg and the lowest average value was seen at N160 – 79.4 kg. The Р application in rates from 40 tо 160 kg.ha-1 indicated a tendency to increase the test weight. Good values were realized by combining a moderate to high phosphorus rates Р80-160 with low N levels N40-80. Weather conditions during the 30-year period have a strong significant impact on the test weight of the grain.

The impacts of intercropping of canola (Ca) with faba beans (Fb), field peas (Fp), garlic (G), or wheat (Wh) were evaluated on the cabbage aphid, Brevicoryne brassicae (Linnaeus, 1758), natural enemies and canola yields in row ratios of 3Ca : 3Fb, 3Ca : Fp, 3Ca : 3G, and 3Ca : 3Wh in 2018 and 2019. In both years, the lowest aphid population was recorded in 3Ca : 3G. In 2018, the aphid population was significantly (P &lt; 0.05) lower in 3Ca : 3Fp than in the monoculture, while, in 2019, it was lower in the intercrops compared to the monoculture. Furthermore, none of the intercrops, except 3Ca : 3Fb, showed a significant increase in the predator diversity and parasitism rate. The dry seed weight loss was higher in the monoculture and 3Ca : 3Wh than in the other intercrops. Based upon the obtained results, decreasing the density of the cabbage aphid and increasing the canola yield by intercropping canola with the faba bean, the field pea or garlic is possible with this system. The inferences of these outcomes, which are associated with the integrated pest management (IPM) in canola cropping systems, are discussed.

The waxy wheat shows special starch quality due to low amylose content. However, less information is available concerning the physicochemical properties of starch in different waxy wheat under different irrigation. In this study, two wheat near-isogenic lines (NILs) and a normal wheat cultivar were used to investigate the contents, size distribution and crystallinity of starch by biochemical methods, laser-diffraction and X-ray diffraction analysis. The amylose content in wheat grains was the lowest in waxy wheat lines, SJZ8-N, followed by the partly waxy wheat lines, SJZ8-P, and the highest in the normal wheat, SJZ8, with significant differences among wheat lines. Waxy wheat starch had more B-type granules and a higher degree of crystallinity than normal wheat starch, with the order as SJZ8-N &gt; SJZ8-P &gt; SJZ8. When compared with the conventional and water-saving irrigation, the rainfed treatment showed the lowest starch content, amylose content (except SJZ8-N), amylopectin content and relative crystallinity in the three wheat lines indicating that water deficiency was not benefited starch accumulation and crystal formation in wheat grains. It was concluded that (1) wheat lines not only differed in amylose content but also in size distribution and crystallinity of starch; (2) irrigation markedly influenced the physicochemical characteristics of wheat starch; therefore, the irrigation schemes could be adjusted to achieve high-quality wheat production.

In the industrial production process of traditionally fermented flour products, the influence of a certain storage period of fresh flour on the production process and product features of Chinese steamed bread(CSB) as fermented food is very prominent, and often causing quality fluctuations. In this paper, the lab-milled 3 flours were taken as 3 repeat samples set under the condition of room temperature, with the tools of dough rheo-fermentation instrument and other equipment. Regular analysis on rheo-fermentation and other properties of the dough, as well as the quality sensory evaluation of Chinese steamed bread (CSB) was conducted to determine a reasonable storage period for fresh wheat flour. The results showed that during the storage processes, the dough stability time increased and the weakening degree decreased, with the dough rheological property improved. The fermentation volume of rheo-fermentometer decreased significantly, so as the volume of the CSB. But the trend of change of the sensory evaluation characteristics of the CSB was not obvious. The test results by instrument Rheo F4 can reflect the rheo-fermentation properties of the dough,wherein rheo-fermentometer, such as the time required for maximum development (T1), maximum development reached by the dough (Hm), and dough development height at final fermentation time (h), have obvious guiding for production of the CSB. We therefore suggest that the flour to be used for the industrial production of CSB should stay in storage for more than 7 days after milling.

Thesis (MScAgric)--Stellenbosch University, 2021. | ENGLISH ABSTRACT: Mycotoxigenic fungi play an important role in wheat production. They produce toxic secondary metabolites that are detrimental to human and animal health and some of these fungi are also phytopathogens. Fusarium spp. are also responsible for Fusarium head blight which is one of the most destructive diseases of wheat, globally while Fusarium mycotoxins deoxynivalenol (DON), nivalenol and zearalenone (ZEA) are most frequently detected in wheat grain. Alternaria spp. are ubiquitously associated with wheat in most regions and can cause black point, leaf blight and leaf spot on wheat. Mycotoxins produced by this genus, such as alternariol, alternariol monomethyl ether and tenuazonic acid, frequently contaminate wheat grain. Other mycotoxigenic fungi present in wheat grain include Penicillium spp. that can produce ochratoxins, Aspergillus spp. that can produce ochratoxin and aflatoxin and Claviceps spp. that produces ergot alkaloids. Disease and mycotoxin contamination caused by mycotoxigenic fungi can be managed with the integrated use of tillage practices, crop rotation, fungicides, host resistance and disease forecasting systems. To determine the fungal composition and mycotoxin contamination in commercial wheat grain in South Africa, wheat was sampled over two seasons at 49 locations across all major wheat production regions. A total of 4 223 fungal isolates were obtained with Alternaria as the predominant genus (87%) followed by Fusarium and Epicoccum (4%), respectively. Fusarium graminearum (25%) and F. poae (15%) were the Fusarium spp. with the highest abundance and incidence in samples. The biggest difference in fungal composition was found between the production regions of the Western Cape and those isolated from the rest of South Africa. Samples from the Western Cape had a higher abundance of Alternaria spp., but the fungal diversity in these samples were lower than samples from other provinces. DON was detected in 12 samples and 3-acetyldeoxynivalenol in three samples, while 15-acetyldeoxinivalenol, ZEA and sterigmatocystin were only detected in one sample each. To determine the influence of agronomic practices and climate on fungal composition and mycotoxin contamination, information on agronomic practices was obtained from growers and weather data (humidity and temperature) was measured with data loggers at each location. Associations were found between the incidence of DON and rotations with F. graminearum host crops (maize, wheat, barley and soybeans) and also between irrigation and the incidence of Cladosporium, Epicoccum, Penicillium, Nigrospora, F. brachygibbosum, the Fusarium incarnatum-equiseti species complex, F. poae and F. oxysporum. A positive correlation was found between F. graminearum and DON contamination. Correlations were also found between weather conditions before anthesis and the abundance of Alternaria, Epicoccum, Nigrospora and F. brachygibbosum. This study reports on the fungal composition and natural mycotoxin contamination of commercial wheat in South Africa in association with weather and agronomic practices. It revealed the distribution of fungal genera in the different wheat production areas and showed that mycotoxin contamination is relatively low in South African wheat grain. It further highlights certain relationships between climate, agronomic practices, fungal composition and mycotoxin contamination in commercial wheat. Future studies should use polymerase chain reaction- based methods to determine fungal biomass in wheat grain to allow for the accurate determination of correlations between weather variables and fungi in grain. | AFRIKAANSE OPSOMMING: Mikotoksigeniese swamme speel ’n belangrike rol in koring produksie. Hulle produseer giftige sekondêre metaboliete wat skadelik is vir mense en diere en sommige van hierdie swamme is ook patogenies. Fusarium spp. is ook verantwoordelik vir Fusarium aarskroei wat wêreldwyd een van die skadelikste siektes op koring is terwyl Fusarium mikotoksiene deoksinivalenol (DON), nivalenol and zearalenone (ZEA) word die meeste in koringgraan gevind. Alternaria spp. is oorheersend op koring in meeste streke en kan ook Swart punt, Blaarskroei en Blaarvlek op koring veroorsaak. Mikotoksiene wat deur hierdie genus geproduseer word, soos alternariol, alternariol-monometiel-eter en tenuasoniesesuur, kontamineer gereeld koringgraan. Ander mikotoksigeniese swamme wat op koringgraan voorkom sluit in Penicillium spp. wat okratoksiene produseer, Aspergillus spp. wat okratoksiene en aflatoksiene produseer en Claviceps spp. wat ergotalkaloïede produseer. Siekte en mikotoksien-kontaminasie wat deur mikotoksigeniese swamme veroorsaak word kan beheer word deur die geïntegreerde gebruik van grondbewerking, wisselbou, swamdoders, gasheerweerstand en siekte-voorspellingsisteme Om die swam-samestelling en mikotoksien kontaminasie op kommersiële koringgraan in Suid-Afrika te bepaal, is graanmonsters oor twee seisoene op 49 lokaliteite oor alle hoof koring produksie streke versamel. ’n Totaal van 4 223 swam isolate is verkry uit die graanmonsters. Alternaria was die oorheersende genus (87%) gevolg deur Fusarium en Epicoccum (4% elk). Fusarium graminearum (25%) en F. poae (15%) was die Fusarium spp. met die hoogste voorkoms en getalle. Die grootste verskil in swam-samestelling tussen monsters was verkry tussen die streke in die Wes-Kaap en dié in die res van Suid-Afrika. Monsters uit die Wes- Kaap het hoër Alternaria getalle gehad, maar die swam diversiteit in hierdie mosters was laer as dié van ander provinsies. DON was in 12 monsters gevind en 3-asetieldeoksinivalenol in drie monsters. Mikotoksiene, 15-asetieldeoksinivalenol, ZEA en sterigmatosistien was net in een monster elk gevind. Om die invloed van verbouingspraktyke en klimaat op swam-samestelling en mikotoksien-kontaminasie te bepaal, is inligting oor die verbouingspraktyke by produsente verkry en weer data (humiditeit en temperatuur) is met dataloggers gemeet by elke lokaliteit. Assosiasies is gevind tussen die voorkoms van DON en wisselbou met F. graminearum gasheer gewasse (mielies, koring, gars en sojabone) en ook tussen besproeiing en die voorkoms van Cladosporium, Epicoccum, Penicillium, Nigrospora, F. Brachygibbosum, die Fusarium incarnatum-equiseti spesies kompleks, F. poae en F. oxysporum. ’n Positiewe korrelasie is gevind tussen F. graminearum and DON-kontaminasie. Korrelasies is ook gevind tussen die weerstoestande voor blomtyd en die en die hoeveelheid Alternaria, Epicoccum, Nigrospora and F. brachygibbosum isolasies in monsters. Hierdie studie doen verslag oor swam-samestelling en natuurlike mikotoksien kontaminasie in kommersiële koring in Suid-Afrika. Dit onthul die verspreiding van swam genera in die verskeie produksie streke en wys ook dat mikotoksien kontaminasie in Suid- Afrikaanse koringgraan relatief laag is. Verder lig dit seker verhoudings tussen klimaat, verbouingspraktyke, swam-samestelling en mikotoksien-kontaminasie in koringgraan uit. Toekomstige studies moet gebruik maak van polimerasekettingreaksie gebaseerde tegnieke om swam biomassa in koringgraan te bepaal sodat korrelasies tussen weer-veranderlikes en swamme akkuraat bepaal kan word. | Masters

Fusarium head blight (FHB) represents a damaging disease of cereal spikes caused by mycotoxin-producing Fusarium fungi revealing adverse effects on grain quality and yield. Chinese spring wheat (Triticum aestivum L.) cv. Sumai 3 represents a major source of FHB resistance thanks to Fhb1 QTL on 3BS chromosome conferring resistance to FHB and encoding a lectin-like protein. The aim of our study lied in a comparison of proteome response to Fusarium culmorum inoculation and mycotoxin deoxynivalenol (DON) application at 10 d after inoculation (dai) in spikes of resistant wheat cultivar Sumai 3 and susceptible wheat cultivar SW Kadrilj. Proteome analysis revealed profound impact of Fusarium inoculation and mycotoxin application on plant energy metabolism. Fusarium inoculation decreased photosynthesis and ATP biosynthesis and increased the level of stress-protective proteins (chaperones such as Hsc70, lectins). Genotype related differences observed at 10 dai indicated an active acclimation in Sumai 3 as indicated by increased content of some enzymes involved in phenolics biosynthesis (phenylalanine ammonia lyase PAL, BAHD acyltransferase), jasmonate biosynthesis (lipoxygenase LOX), and oligosaccharide biosynthesis (sucrose synthase SuSy, UDP-glucose uridylyltransferase) which are an important part of glycoproteins such as lectins and other pathogen-responsive biomolecules. The study thus provides data on plant acclimation to Fusarium infection which may underlie superior resistance of Sumai 3 cultivar.

Two proof of concept experiments were summarize this year. One finalized, one first year data analysed