Linear growth rates of strains representing 10 Neurospora species

Linear growth rates of strains representing 10 Neurospora species This regular paper is available in Fungal Genetics Reports: https://newprairiepress.org/fgr/vol33/iss1/13 GENETIC ANALYSIS AND CONVENTIONS 36. Cleaning up new mutants. Before being subjected to extensive genetic or phenotypic analysis, new mutant strains from mutant hunts or other sources should be monitored for the presence of (1) secondary mutations or modifiers (by crossing by standard wild type and recovering the single mutant as an f1), and (2) chromosome rearrangements (by examining ascospores in a cross of the mutant by fluffy or another standard tester). 37. Gene order and map distance. Whenever possible, establish gene order using 3-point data in preference to combining 2-point data from separate crosses. rec genes are polymorphic in stocks of different parentage, and these can result in local differences up to 10 or 20 fold in recombination in specific regions, depending on differences in rec genotype. (For example, see Catcheside 1973 Aust. J. Biol. Sci. 26, p. 1342). Don't base gene order just on the 'distance' apparent in your cross from markers in a "standard" published map. There is no 'standard' map so far as distances are concerned, because the maps are based on crosses which were highly heterogenous with respect to rec genotypes. In contrast, gene order from 3-point or multiple-point crosses is reliable and doesn't depend on absolute values. In calculating recombination values (map distances) from 3-point data, double cross-overs contribute to each component interval. One must add the double crossovers to the single crossovers to obtain the value for each segment. 38. Nomenclature and conventions. With new mutants, assign a unique allele (isolation) number to each occurrence. Allele numbers should be preceded by a letter or letters indicating your name or institution, e.g. CB1, CB2, etc. if your name were Charley Brown. Choose a combination not already preempted (see FGSC stocklist for list of prefixes in use. Allele numbers of markers should be recorded for all stocks maintained or sent to others. Do not confuse allele (isolation) number (e.g. CB513) with locus number (e.g., in al-2), or with accession (stock or strain) number (e.g., FGSC no. 2583). Assign new locus numbers (e.g. al-4) only when allelism with previously established loci (al-1, al-2, al-3) has been excluded. For summary and references on nomenclature see Compendium pp. 427-428 and Barratt et al. 1965 N.N. 8:23-24. Department of Biological Sciences, Stanford University, Stanford, California 94305 Perkins, D.D. and Virginia C. Pollard The method of measuring linear growth rate on agar medium in long tubes devised by Francis Linear growth rates of strains reRyan in 1941-1942 is simple, precise, and reproducible. These "race tubes" have been widely presenting 10 Neurospora species. used for many purposes, such as to define optimal conditions for growth (Ryan et al. 1943 Am. J. Bot. 30:784-799), to measure complementation and assay the effect of varying nuclear ratios in heterokaryons (Davis 1966, in Ainsworth/Sussman (eds.), The Fungi, an Advanced Treatise 2:567-588), to study circadian rhythms (Sargent et al. 1966 Plant Physiol 41:1343-1349, Feldman et al. 1983 Photochem. Photobiol. Rev. 7:319-368), and to determine changes in growth rate that accompany decreases or increases in the number of genes specifying ribosomal RNA (Rodland et al. 1983 Curr. Genet. 7:379-384). Race tubes have also been used to detect and study senescence and mitochondrion-based stopper mutations in laboratory strains, and the stop-start growth shown by classes of mutagen-sensitive and DNA-repair deficient mutants (e.g. Sheng 1951 Genetics 36:199-212; Bertrand et al. 1976 Can. J. Genet. Cytol. 18:397409; Newmeyer 1984 Curr. Genet. 9:65-74). In a survey of wild-collected strains, race tubes led to the discovery in one wild population of senescence due to mitochondrial defects (Rieck et al. 1982. Can. J. Genet. Cytol. 24:741-759. Ryan et al. determined growth rates of representative strains of N. crassa and N. sitophila. Rieck et al. have measured the rate for N. intermedia. To our knowledge, linear growth rates have not been reported for N. tetrasperma or for the five homothallic species. We were prompted to compare linear growth rates by the discovery of a fourth heterothallic species, which is being described and named N. discreta. Sexually compatible strains of N. discreta are highly fertile among themselves, but are genetically isolated from all the other species by sterility barriers. In preparing a species description it seemed of interest to compare growth rates of N. discreta with the other species. The results are summarized in Table 1, where rates are also shown graphically.

Perkins, D.D. and Virginia C. Pollard The method of measuring linear growth rate on agar medium in long tubes devised by Francis Linear growth rates of strains re-Ryan in 1941re-Ryan in -1942 is simple, precise, and reproducible. These "race tubes" have been widely presenting 10 Neurospora species.
used for many purposes, such as to define optimal conditions for growth (Ryan et al. 1943 Am. J. Bot. 30:784-799), to measure complementation and assay the effect of varying nuclear ratios in heterokaryons (Davis 1966, in Ainsworth/Sussman (eds.), The Fungi, an Advanced Treatise 2:567-588), to study circadian rhythms (Sargent et al. 1966Plant Physiol 41:1343-1349, Feldman et al. 1983, and to determine changes in growth rate that accompany decreases or increases in the number of genes specifying ribosomal RNA (Rodland et al. 1983 Curr. Genet. 7:379-384).
Race tubes have also been used to detect and study senescence and mitochondrion-based stopper mutations in laboratory strains, and the stop-start growth shown by classes of mutagen-sensitive and DNA-repair deficient mutants (e.g. Sheng 1951 Genetics 36:199-212;Bertrand et al. 1976 Can. J. Genet. Cytol. 18:397-409;Newmeyer 1984 Curr. Genet. 9:65-74). In a survey of wild-collected strains, race tubes led to the discovery in one wild population of senescence due to mitochondrial defects (Rieck et al. 1982 We were prompted to compare linear growth rates by the discovery of a fourth heterothallic species, which is being described and named N. discreta. Sexually compatible strains of N. discreta are highly fertile among themselves, but are genetically isolated from all the other species by sterility barriers. In preparing a species description it seemed of interest to compare growth rates of N. discreta with the other species. The results are summarized in Table 1, where rates are also shown graphically. Linear growth of strains representing all the known Neurospora species. Rate is mm/h at 25°C on minimal medium N in 30 cm long growth tubes. Each value is based on the linear phase of growth in a single tube.  Rather than prepare tubes in duplicate or triplicate for individual tests, only a single race tube was used for each strain, and rates were determined using several different strains to represent each species. This could not be done for the homothallic species where only a single isolate was available. N. crassa, N. intermedia, N. sitophila, and N. tetrasperma differ little in rate of linear growth. An apparent exception is the yellow ecotype of N. intermedia (represented by P60, P201) which is found characteristically on nonburned substrates in the Eastern hemisphere.

SPECIES
In contrast, the five homothallic species grow at only half the speed of the heterothallics, or less. The slowest species, N. terricola, from soil in Wisconsin, is also set off from the others morphologically by having rounded ascospores with a single germ pore. Strain D301 from Dominica, West Indies, has been diagnosed as a variety of N. galapagosensis (H.L. Huang, personal communication). All the homothallic strains are devoid of conidia.
Representative strains of the new species N. discreta are also distinctly slower than the other heterothallic species. The Kirbyville isolates from Texas are slowest. P390 (Florida) and P755 (Guatamala) are somewhat faster.
Our growth-rate determinations based on single tubes are certainly not definitive. However, these results agree well with the more extensive data of other workers for species tested previously. Our 25° C rates compare with those of Ryan et al. (1943)