Effects of Metabolites and Antlmetabolites on the Sporulation of Peronospora Tabaoina Adam. On Tobacco Leaf Disks

Abstract

Summary.The effects of 148 metabolites and a~tinietabolites on the sporulation or"Peronospora tabacina Adam. on leaf disks of Nieotiand tubacum cv. Virginia Gold.have been determined.(1) Normal metabolites, with the exception of flavin adenine dinucleotide, had slight althoU:gh statistically significant effects on sporulation intensIty, which suggests that inhibition-nutri tion phenomena play no part in the sporulation process of P. tabacina.(2) Seven uracil analogues had an inhibitory effect on sporulation, and the reversal of inhibition by uracil suggests the active involvement of this compound in the sporulation process.(3) Canavanine at a final concentrat.ion of 120 ftgjml showed complete inhibition of sporulation. The reversal of the canavanine inhibition of sporulation by arginine, citrulline, and ornithine suggests the involvement of arginine and the functioning of an ornithine cycle in the sporulating system.(4) White, instead of the normal blue, conidia were produced in the presence of a number of sUlphur-contain ing compounds. It is suggested that this phenomenon depends on the chelating properties of these compounds towards copper ions, with the subsequent inactivation of tyrosinase activity in the conidia.(5) Sporulation intensities of 68 X 10'-}53 X 10 4 conidia per sqnare centimetre of leaf area were observed during the present study.

Interacting Effects of Light and Temperature on Sporulation of Peronospora tabacina on Tobacco Leaves

“…Maximal spore yield of P. tabacina per unit area is obtained at 20°C in the dark. Consequently, most if not all studies related to light effects upon sporulation were conducted at this temperature (Cruickshank 1963;Shepherd and Mandryk 1964;Uozumi and Krober 1967). The following results indicate that light can strongly suppress spore formation at 20°C or above but not below this temperature.…”

“…Sporulation of Peronospora tabacina Adam on tobacco leaves has been investigated in detail by various workers (e.g. Cruickshank 1963;Shepherd and Mandryk 1964;Uozumi and Krober 1967;Rotem and Cohen 1970). Sporulation of this pathogen, as of some other fungal plant pathogens of the Peronosporales, is controlled by light in a dual way: light is an ultimate prerequisite (for host photosynthesis) before sporophore emergence (Cohen and Rotem 1970), and it is a strong inhibitor if applied during the wet sporulation period (Cruickshank 1963;Jadot 1966;Uozumi and Krober 1967).…”

The Effect of Some Protein and Non‐Protein Amino Acids on the Growth of Cladosporium herbarum and Trichothecium roseum

“…1-25%, ++ growth 25-50%, +++ growth ,50-75%, ++ + + growth 75-100%of that witii the best amino add used in the experiment. (Shepherd and Mandryk 1964). The aim of the present study was to discover whether Cladosporium herbarum and Trichothecium roseurUj which are…”

Factors Affecting Viability of Spore Inooulum In Peronospora Tabacina Adam and Lesion Produotion In tobaooo Plants

“…Spore production in P. tabacina was investigated by Cruickshank (1961aCruickshank ( , 1961bCruickshank ( , 1963, Rider, Cruickshank, and Bradley (1961), and Shepherd and Mandryk (1964); spore survival by Hill (1962), Krober (1965), Bromfield and Schmitt (1967), Jankowski (1967), and others; germination in vitro by Cruickshank (1961a) and Shepherd (1962), and in vivo by . Although single spore transfers to leaves have resulted in lesions (Shepherd, Stuart, and Mandryk 1963) very little has been done to relate spore viability and spore number to lesion production.…”