INHERITANCE OF SPORE COLOUR IN PUCCINIA HELIANTHI

Abstract

A mutation for loss of wall pigment in urediospores and teliospores of Puccinia helianthi Schw, is described. The mechanism of inheritance of spore colour could not be established precisely. Wall pigment appeared to be determined by one or a small number of genes, whereas pigment of the cytoplasm was unstable and influenced by environmental factors. Evidence for multiple fertilizations in single aecial cups supported earlier reports that the aeciospore should be considered the unit of fertilization in the rusts. Somatic segregation for colour was observed in F, cultures. IntroduotionInheritance of urediospore colour in Puccinia graminis f. sp. tritici Erikss. & Henn. has been shown to be controlled by two genes: one determining carotenoid pigment in the cytoplasm and the other, brown pigment in the spore wall (Johnson, Newton and Brown, 1934;Green, 1964). A mutation for spore colour in P. helianthi Schw. was described by Brown (1940). It affected pycnia and aecia as well as uredia and telia. The genetic basis of the colour change was not established. Spore size, shape and echinulation, viability, host range and temperature tolerance were also affected and Brown suggested that more than one gene was probably involved.Colour mutants have been extensively used as genetic markers in the cereal rusts. Studies on P. helianthi have lagged behind those on other species in this respect. A spontaneous mutation for loss of wall pigment in a culture of sunflower rust at Macdonald College afforded an opportunity to extend genetic studies on P. helianthi which have so far met with little success (Miah and Sackston, 1970). Besides determining the mechanism of spore colour inheritance in P. helianthi, it was hoped that this study would help to resolve the controversy over the unit of fertilization in the rusts (Dinoor, Khair and Fleischmann, 1968) which has been a fundamental difficulty in studies on the inheritance of pathogenicity in the rusts. M'aterials and MethodsA yellow-spored mutant of P. helianthi arose spontaneously from a culture of "Canadian" race 2 on a single leaf in an otherwise normal detached leaf culture growing at 10°C. Two of the five pustules found were cultured (as Y1 and Y2) for further study. Urediospores from the others, when transferred to susceptible leaves, failed to induce infections.Single spore isolates of these cultures were maintained on detached sunflower leaves on moist filter paper in Petri plates in controlled environment growth chambers at 22 + 2°C day and 20 -+ 2°C night temperature, daylength of 16 hr and light intensity at plant level of 13200 -+ 2200 lux (1200 2 200 ft-c) from cool white VHO fluorescent tubes supplemented with incandescent bulbs, giving approximately 4400 lux at leaf surface within the plates. Cultures were also grown on plants in the greenhouse (22 to 25°C) isolated beneath plastic covers.

High-throughput RNA sequencing reveals differences between the transcriptomes of the five spore forms of Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen

“…Teliospores are dark yellowish-brown, basidiospores and pyciniospores are hyaline, and aeciospores and urediniospores are yellow-orange. The yellow-orange color is due to carotenoid pigments, whereas the dark yellowish-brown color of teliospores may result from an accumulation of diphenol/urishiol (multi-copper) oxidase or laccase (Hennessy & Sackston 1972 ; Xu, et al 2011 ). In the present study, we checked the variation of gene expression related to carotenoid biosynthesis and diphenol/urishiol (multi-copper) oxidase or laccase.…”

“…The yellow-orange rust color of urediniospores and aeciospores can be attributed to carotenoid pigments accumulating in lipid droplets within the cytoplasm as well as pigments associated with the cell wall (Hennessy and Sackston 1972 ). Basidiospores and pycniospores, however, are hyaline.…”

Hyperspectral signal decomposition and symptom detection of wheat rust disease at the leaf scale using pure fungal spore spectra as reference

“…Rust diseases are widespread and highly host‐specific (Dracatos et al ., ), and rust fungi are obligate biotrophic pathogens (Mendgen & Hahn, ). The pigmentation of rust spores is due to the presence of carotenoids (Hennessy & Sackston, ). Four different types of carotenoids have been found in rust fungi, with γ‐ and β‐carotenes appearing in most species (Smits & Mitchell, ).…”

“…It is assumed that carotenoids play a protective role against UV radiation and oxidative stress, and could act as virulence factors (Butler & Day, ; Avalos & Carmen Limón, ). The colour of rust spores is correlated to the content and composition of these carotenoids, which are located in the cell wall and as lipid droplets in the cytoplasm (Hennessy & Sackston, ; Wang et al ., ). In the case of yellow rust and brown rust, differences in the pigmentation due to carotenoids can be observed by the naked eye.…”