Presented as Hungerford's Thesis (Ph. D.)--University of Wisconsin--Madison, 1924. / Cover titles. Reprinted from Journal of agricultural research: Part 1: vol. XIX, no. 6 (15 June 1920), p. 257-278, plates 38-48 -- Part 2: vol. XXIV, no. 7 (19 May 1923), p. 607-620, plates 1-4 -- Part 3: vol. XXV, no. 9 (1 Sep. 1923), p. 363-402, plates 1-6. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1933. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

1. The difficulties in separating the individual members of the Uromyces pisi group are outlined. 2. A review of the literature on rust fungi is given in which it is brought out that the major criteria for delimiting the species are (i) dimensions, wall thickness, number of germ pores and their distribution, for uredospores, (ii) dimensions, thickness of wall and pore cap, and wall sculpturing of the teleutospores, (iii) host specialisation, and (iv) length of life cycle. 3, 76 herbarium specimens along with the locally occurring member of the U. pisi group were examined from these stand-points, and the relative desoxy-ribose nucleic acid (D.F. A) content per nucleus of U. pisi. U. punctatus and U. loti was determined. 4. It was found that the species of the group could be separated by statistically analysing the spore measurements. Only U. jordianus could be separated by the number of germ pores of its uredospores, and both spore types of all the Species had approximately the same wall thickness. It is shown that the sculpturing of the teleutospore wall varies within each species and shows a gradation from a weakly punctate, to a definitely punctate-striate condition. A review of the literature on host specialisation and life cycle is given for each species, and a host list and synonym list has been compiled for each. From this review it is pointed out that, (1) it is difficult to separate certain of the species of the U. pisi group by host reaction and (ii) biological races exist in some of the heteroecious species. 6. Inoculation experiments were carried out with the locally occurring U. punctatue on Astragalus danicus, and it was found that the rust could infect 9 other species of Astragalus and one of Medicago. Attempts to geminate the teleutospores by various chemical stimulants failed with the exception of one teleutospore. Observation and experiment showed that U. punctatus could overwinter by means of uredospores. Inoculation experiments were carried out on the aecidial host, but no infection ensued after four years. It is concluded that U.punetatus at St, Andrew has lost the ability to infect the aecidial host and that this is due to, (i) the absence of the aecidia host over a period of years leading to adaptation to the uredo host, and (ii) various climatic factors. 7. Inoculation experiments carried out with the local specimens of U. pisi on Lathyrus pratensis and U. loti on Lotus corniculatus, showed that these rusts were narrowly specialised on their resptective hosts. Other closely related rusts which exist in the Hemi- form and are highly specialised with regard to host selection, are described and it is suggested that these rusts have probably arisen from specialised races of the heteroecious members of the group. 9. The ecology and geographical distribution of the group is discussed. The number of leguminous rusts in Britain is less than the number on the Continent. With the exception of U. pisi, heteroecism in the group is confined to Central and S. Europe. Outside this region the heteroecious species adopt the Hemi- form, and can overwinter in the uredo stage. In this condition they 'become more specialised. The number of possible British hosts is greater than the actual number parasitised, except. U. loti and U. laburni where the actual numbers are the same as the possible numbers of hosts. In considering these points it is suggested that the absence of the aecidial hosts from the region outside central S. Europe, has led to the species adopting the Hemi-form and becoming more specialised. Also in this region the climate is not favourable to the development of the aecidium. 10. It is suggested on this evidence, that the members of the group probably have a common ancestor.

The development of our knowledge of the metabolism, nutrition., and physiology of the rust fungi has been restricted because of our inability to grow these fungi in axenic culture. Most of the physiological and biochemical investigations on rust fungi have been limited to studies of the germination and development of germ tubes. It is not known, whether failure of the rusts to grow axenically is associated with a metabolic block in essential biochemical pathways. The uredial stage of an Australian isolate (ANZ 126-6, 7) of wheat stem rust was grown on a relatively simple medium. Successful in vitro growth was obtained on a medium containing Czapek's minerals, glucose and an organic nitrogen source viz. yeast extract, peptone or BSA. Vegetative growth producing a discrete colony appeared to be dependent upon high density seeding, when conventional dry seeding techniques were followed. When a spore suspension in gelatin was used for inoculation consistent, reproducible vegetative growth at low density seeding was obtained. Water spore suspensions failed to support any growth on the same series of media, under identical conditions. Sodium citrate, host extract, and host protein fractions in general inhibited growth whereas pectin increased the lag phase. Spore-like bodies were obtained inside the colony, which were devoid of any pigmentation. It is suggested that the combination of physical and chemical factors surrounding the germinating spore play an important role in the in vitro development of rust fungi. / Land and Food Systems, Faculty of / Graduate

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Thesis--University of Michigan, 1939. / Cover title. "Papers from the Department of Botany of the University of Michigan, no. 693." "Reprinted from the American journal of botany, vol. 26, no. 8 ... October, 1939." "Literature cited": p. 608-609.

Wheat is one of the major food crops consumed by man and is grown in a wide range of environments. One constraint in the production of wheat is the different diseases attack the crop. One such a diseases is leaf rust. Leaf rust is caused by Pucdnia recondita f.sp. trifid and is the most widespread and regularly occurring rust on wheat. Researchers are continually searching for new resistance genes and to date 47 leaf rust resistance genes (Lr) have been designated in wheat. Three molecular techniques RAPDs (random amplified polymorphic DNA), AFLPs (amplified fragment length polymorphism) and SSRs (microsatellites) were used to identify and analyse the distances between different cereal genotypes. Four RAPD primers, three AFLP primers and two SSR primers were used to analyse the wheat genotypes, x-tritosecale and rye. The average polymorphisms obtained from the AFLPs were 100 polymorphisms per AFLP primer combination, and is much higher than with the RAPD primers (11-16 polymorphic loci). The four RAPD primers failed to identify unique molecular markers for the wheat genotypes. The AFLP primers were able to distinguished between the 'Kiewiet', rye, 'SA463/*4Palmiet', 'SA684', TA2460' and 'KG90WGRClO' genotypes. The SSR primer pair XGWM122150 was able to amplify a fragment from the A or B genome. The pairwise distances between the genotypes revealed that the wheat genotypes were genetically very close, with an average distance value of 0.29 between the genotypes. The genotypes, 'TA2460', 'TAMI07' and 'KS90WGRCI0', were not closely related to the South African wheat genotypes and were genetically very close to each other. The rye and 'Kiewiet' genotypes were grouped as an outgroup by the UPGMA analysis and were the least closely related to the cereal genotypes. RAPD (Random amplified polymorphic DNA) and AFLP (amplified fragment length polymorphism) analysis were used to identify molecular markers linked to leaf rust resistance gene Lr41. Bulk and parental lines were screened with 380 RAPD primers and 64 AFLP primer combinations. A total of 3190 RAPD and 1859 AFLP loci, respectively were screened for linkage to the resistance gene. Twelve fragments (seven RAPD and five AFLP), nine in coupling phase and three in repulsion phase, were identified as putative markers for the leaf rust resistance gene Lr41. Segregation analysis of these markers in a BC2F2 population revealed varying linkage distances that ranged from 2.8 to 33 cM. The coupling phase AFLP marker E-AAG:M-CTA300 was converted into a sequence characterised amplified region (SCAR) marker. AFLP markers have potential for marker assisted selection breeding programs, provided it can be converted into SCARs or equivalent marker typed systems. / Dissertation (MSc (Genetics))--University of Pretoria, 2007. / Genetics / unrestricted