Studies on Puccinia recondita f. sp. tritici with special emphasis on adult plant resistance in wheat.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1986.Leaf rust (Puccinia recondita f.sp. tritici) of wheat (Triticum aestivum) was widespread in South Africa during 1983, 1984 and 1985 and often reached epidemic levels, especially on autumn-sown spring wheat in the Cape Province. Nine physiologic races were identified during the study period. The most common race was avirulent to the leaf rust differential genes Lr3a, 3bg, 3ka, 11, 16, 20 and 30 and virulent to Lr1, 2a, 2b, 10, 14a, 15, 17, 24. Resistance genes Lr9, Lr19, Lr21 and Lr26 were effective to all isolates tested. Evaluation of wheat genotypes for components of resistance, viz. infection type, latent period, number of uredinia and uredinium size, revealed three phenotypic reaction classes. The first group exhibited negligible resistance, the second was susceptible or moderately susceptible as seedlings but resistant as adult plants while the third group was resistant at all growth stages tested. Adult plant resistance was expressed by hypersensitive or non-hypersensitive reactions and the combination of components conditioning resistance varied. Adult plant resistance conferred by gene Lr22a was characterized by a long latent period, small uredinia, reduced sporulation and an absence of a differential interaction between components of resistance and different races of Puccinia recondita f.sp. tritici. Numbers of uredinia on flag leaves of RL6044 (Lr22a) were equal to those of a susceptible check, Line E. Lr22a was inherited as a partially recessive gene in crosses with Zaragoza and SST33. Assessment of latent period, number of uredinia and infection type in F4 and FS families homozygous for Lr22a and derived from crosses between RL6044 and Zaragoza or SST33, revealed significantly different levels of resistance between families. Differences were attributed to other genes modifying the expression of Lr22a. Adult plant resistance of Era, Glenlea, RL6044 and sinton was expressed prior to the fifth-leaf stage. Latent period increased and number of uredinia decreased as each wheat matured. While the latent period of the flag, flag-l and flag-2 leaf was similar within Era, Glenlea and RL6044, differences between these genotypes occurred. The latent period of flag leaves of Sinton was shorter than that of the two lower leaves. Significantly fewer uredinia developed on the flag-2 leaf of Glenlea. A reduction in temperature from 21 C to 15 C significantly increased latent period in Era, Glenlea and RL6044, and also restricted uredinium size on flag leaves of RL6044. The adult plant resistance of Glenlea crossed with Line E was conferred by two partially recessive genes. Additionally, F2 to FS progenies of this cross eXhibited high levels of hypersensitive seedling resistance at 29 - 31 C to certain isolates. The latter resistance was not conferred by Lr1 or by the LrT2 gene for mature plant resistance in Glenlea. The high-temperature expression of resistance could be due to a second gene for adult plant resistance or to a previously undetected seedling gene

The context of fetal ventriculomegaly in a developing country : a retrospective review

Thesis (MMed)--Stellenbosch University, 2019.AIM: The goal of this study is to describe fetal ventriculomegaly (VM) in a developing country population with regards to clinical presentation, associated findings, natural history and outcome. Materials and methods This retrospective observational study was conducted at Tygerberg Academic Hospital, a secondary and tertiary referral centre in the Western Cape Province. Data was collected from all pregnancies with a prenatal diagnosis of ventriculomegaly from 2013 to 2015. The initial presentation and associated findings with the natural history of VM was studied and a selection of perinatal outcomes was measured. Results A final cohort of 252 cases was analysed: 168 mild, 42 moderate and 42 severe cases of VM. The median gestational age at diagnosis was 23w4d, with 48,8% diagnosed after 24w0d. Mild VM was more likely to be unilateral (p<0,001) and isolated (p=0,006) when compared to moderate and severe VM. Mild VM was associated with multiple soft markers in up to a third of the cases and over half of the cases normalized during pregnancy; severe VM was associated with multiple major anomalies in 31,0% of the cases. The majority of major anomalies in all 3 groups were CNS defects in 25,8% and cardiac anomalies in 10,3%. Termination of pregnancy was opted for in 12,5% of mild, 35,7% of moderate and 59,5% of severe VM cases. Conclusion VM is a common prenatal finding but, in this setting, was often diagnosed late, which limits options for investigation and management. Associated findings included cardiac and other CNS abnormalities and increased with increasing severity of VM. Aneuploidies were encountered within all groups. In this cohort, unilateral VM was more associated with mild VM and may have been due to the inclusion of borderline VM, which was shown not to be a benign finding. Uptake of invasive testing and of TOP was low in this community and the late diagnosis may have contributed to that.Doelwit Die doelwit van die studie was om fetale ventrikulomegalie (VM) te beskryf in ‘n ontwikkelende land, spesifiek die kliniese beeld, geassosieerde bevindinge asook uitkomste. Metodes Die retrospektiewe observasie studie was gedoen te Tygerberg Akademiese Hospitaal, ‘n sekondêre en tersiêre verwysingshospitaal in die Wes Kaap. Data is gekollekteer van alle swangerskappe met ‘n prenatale diagnose van fetale ventrikulomegalie vanaf 2013 tot 2015. Die aanvanklike kliniese beeld en geassosieerde bevindinge was bestudeer, asook sekere perinatale uitkomste. Resultate ‘n Finale kohort van 252 gevalle was geanaliseer: 168 geringe, 42 matige en 42 erge gevalle van VM. Die mediane gestasie van diagnose was 23w4d, met 48,8% gediagnoseer na 24w0d. Geringe VM was meer waarskynlik unilateraal (p<0.001) asook geisoleerd (p=0,006) wanneer dit vergelyk word met matige en erge VM. Geringe VM was geassosieer met veelvuldige sagte merkers in ongeveer ‘n derde van die gevalle en meer as die helfte hiervan het genormaliseer tydens swangerskap. Erge VM was geassosieer met veelvuldige major abnormaliteite in 31,0% van die gevalle. Die meerderheid van die major abnormaliteite in al 3 groepe was sentrale senuweestelsel defekte in 25,8% en hart-anomaliteite in 10,3%. Terminasie van swangerskap is ondergaan in 12,5% van geringe, 35,7% van matige en 59,5% van erge VM gevalle. Gevolgtrekking VM is nie ‘n rare prenatale bevinding nie en in die studie was dit dikwels laat gediagnoseer, met gevolglik beperkte ondersoeke en behandelingsopsies. Geassosieerde bevindinge, veral hart en sentraal senuweestelse, was algemeen en meer gesien met die toenemend graad van VM. Aneuploidies was in al drie groepe waargeneem. In die kohort was unilaterale VM frekwent, maar was meer gesien in geringe VM. Dit was heel moontlik as gevolg van die insluiting van grensgeval VM, wat nie ‘n onskuldige bevinding was nie. Die opname van invasieve toetse, insluitend terminasie van swangerskap, was laag. Laat diagnose mag hiertoe bygedra het.Master

Additive Manufacturing of Devices Used for Collection and Application of Cereal Rust Urediniospores

Optimized inoculation procedures are an important consideration in achieving repeatable plant infection when working with biotrophic rust fungi. Several plant pathology laboratories specializing in rust research employ a system where the collection and application of fungal spores are accomplished using an exchangeable gelatin capsule. Urediniospores are collected from erumpent pustules on plant surfaces into a capsule fitted to a cyclone collector controlled by a vacuum pump. By adding light mineral oil to the same capsule, the spore suspension is then sprayed onto plants by means of a dedicated atomizer (inoculator) connected to an air pressure source. Although devices are not commercially available, modern day technologies provide an opportunity to efficiently design and manufacture collectors and inoculators. Using a process called Additive Manufacturing (AM), also known as “3D printing,” the bodies of a collector and inoculator were digitally designed and then laser-sintered in nylon. Depending on availability, copper or aluminum tubes were fitted to the bodies of both devices afterward to either facilitate directed collection of spores from rust pustules on plant surfaces or act as a siphon tube to deliver the spore suspension contained in the capsule. No statistical differences were found between AM and metal inoculators for spray delivery time or spore deposition per unit area. In replicated collection and inoculation tests of wheat seedlings with urediniospore bulks or single pustule collections of Puccinia triticina and P. graminis f. sp. tritici, the causal organisms of leaf rust and stem rust, consistent and satisfactory infection levels were achieved. Immersing used devices in acetone for 60 s followed by a 2 h heat treatment at 75°C produced no contaminant infection in follow-up tests

Additive Manufacturing of Devices Used for Collection and Application of Cereal Rust Urediniospores

Published ArticleOptimized inoculation procedures are an important consideration in achieving repeatable plant infection when working with biotrophic rust fungi. Several plant pathology laboratories specializing in rust research employ a system where the collection and application of fungal spores are accomplished using an exchangeable gelatin capsule. Urediniospores are collected from erumpent pustules on plant surfaces into a capsule fitted to a cyclone collector controlled by a vacuum pump. By adding light mineral oil to the same capsule, the spore suspension is then sprayed onto plants by means of a dedicated atomizer (inoculator) connected to an air pressure source. Although devices are not commercially available, modern day technologies provide an opportunity to efficiently design and manufacture collectors and inoculators. Using a process called Additive Manufacturing (AM), also known as “3D printing,” the bodies of a collector and inoculator were digitally designed and then laser-sintered in nylon. Depending on availability, copper or aluminum tubes were fitted to the bodies of both devices afterward to either facilitate directed collection of spores from rust pustules on plant surfaces or act as a siphon tube to deliver the spore suspension contained in the capsule. No statistical differences were found between AM and metal inoculators for spray delivery time or spore deposition per unit area. In replicated collection and inoculation tests of wheat seedlings with urediniospore bulks or single pustule collections of Puccinia triticina and P. graminis f. sp. tritici, the causal organisms of leaf rust and stem rust, consistent and satisfactory infection levels were achieved. Immersing used devices in acetone for 60 s followed by a 2 h heat treatment at 75 C produced no contaminant infection in follow-up tests

Fig rust caused by Phakopsora nishidana in South Africa

Fig rust, caused by Cerotelium fici, was first recorded in South Africa in 1927. Recent observations have revealed high incidence of rust and untimely defoliation of fig trees (Ficus carica) in residential gardens and commercial orchards. Using phylogenetic analysis, the causal organism of a fig rust isolate (PREM63073) collected in 2020 was confirmed as Phakopsora nishidana. Inoculation and microscope studies showed that mulberry plants were immune to P. nishidana isolate PREM63073. Infection of fig leaves occurred through stomata on the abaxial leaf surfaces. Very long germ tubes were observed for P. nishidana, often with no clear contact with the leaf surfaces and an apparent lack of directional growth towards stomata. Inoculated plants from 15 fig cultivars varied in their severity of leaf infection, whereas fruit of the cultivar Kadota developed reddish-brown blemishes without sporulation. Currently, C. fici and P. nishidana are recognised as occurring on F. carica in South Africa. This suggests a need to resolve the worldwide distribution and identity of the rust species involved

SMSS J130522.47-293113.0: A high-latitude stellar X-ray source with pc-scale outflow relics?

We report the discovery of an unusual stellar system SMSS J130522.47-293113.0. The optical spectrum is dominated by a blue continuum together with emission lines of hydrogen, neutral, and ionized helium, and the NIII, CIII blend at ~4640-4650 Å. The emission-line profiles vary in strength and position on time-scales as short as 1 d, while optical photometry reveals fluctuations of as much as ~0.2mag in g on time-scales as short as 10-15 min. The system is a weak X-ray source (f 0.3-10 = (1.2 ± 0.1) × 10 -13 ergs cm 2 s -1 in the 0.3-10 keV band) but is not detected at radio wavelengths (3s upper limit of 50 µJy at 5.5 GHz). The most intriguing property of the system, however, is the existence of two 'blobs', a few arcsec in size, that are symmetrically located 3'. 8 (2.2 pc for our preferred system distance of ~2 kpc) each side of the central object. The blobs are detected in optical and near-IR broad-band images but do not show any excess emission in Ha images. We discuss the interpretation of the system, suggesting that the central object is most likely a nova-like CV, and that the blobs are relics of a pc-scale accretion-powered collimated outflow

Potential for re-emergence of wheat stem rust in the United Kingdom

Wheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogen Puccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-late twentieth century. However, isolated outbreaks have occurred in recent years. Here we investigate whether a lack of resistance in modern European varieties, increased presence of its alternate host barberry and changes in climatic conditions could be facilitating its resurgence. We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years, with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25 years also suggest increasingly conducive conditions for infection. Furthermore, we document the first occurrence in decades of P. graminis on barberry in the UK. Our data illustrate that wheat stem rust does occur in the UK and, when climatic conditions are conducive, could severely harm wheat and barley production.</p

Die daarstelling van 'n effektiewe leerklimaat as onderwyskundige vaardigheid

M.Ed.Please refer to full text to view abstrac