Table 1.
Strains of Neurospora used in this study.
Figure 1.
Maternal fitness of sequentially mated Neurospora.
To determine the effect of hybrid matings on subsequent conspecific matings, receptive N. crass NcC-India cultures were initially fertilized in four different ways: distilled water as a negative control (A, E, K, O); N. crassa NcC-India as a conspecific positive control (B, F, I, L); N. intermedia allopatric to N. crassa NcC-India (C, G, J, M); N. intermedia sympatric to N. crassa NcC-India (D, H, N, P). In all experiments, the second fertilizing strain was an N. crassa NcC-India. The photographs show: whole plates (A–D), typical fruitbody development (E–H, K–N; bar = 500 µm) and ejected ascospores, if any (I, J, O, P; bar = 50 µm), resulting from the first and second fertilizations. Note that the conspecific second fertilizations resulted in ascospore production only when the initial heterospecific partner was a sympatric strain or when the initial fertilization was a water control (P and O, respectively). Second-fertilization sexual development was completely inhibited after initial fertilization by allopatric heterospecifics or by the conspecific postitive control (M and L, respectively). The clear ascospores in J are inviable hybrid progeny typical of crosses between allopatric strains of N. crassa and N. intermedia.
Table 2.
The effect of initial fertilization on subsequent maternal fertility in sequentially fertilized Neurospora crassa (NcC-India) colonies.
Table 3.
Proportional hazards model of how initial fertilization affects subsequent maternal fertility of Neurospora colonies.
Table 4.
Summary of hybrid fruitbody development phenotypes analyzed by QTL mapping.
Figure 2.
The N. crassa clade NcA × clade NcC genetic map.
Markers are mapped to seven linkage groups reflecting the seven chromosomes of N. crassa. For each marker, its genetic position (cM) relative to the linkage group's leftmost marker is given. Marker names indicate the nature of each marker as follows: AFLP markers are named with a three-letter prefix and the estimated length of the fragment in base pairs. The prefixes “cr” and “tn” indicate whether the AFLP fragment was present in the NcA or NcC parent, respectively. The third letter in the prefix (a–h) indicates which selective primers were used to obtain the fragment. Microsatellite markers are named with the prefix “nc” followed by the number of the linkage group and (1–7) and an alphanumeric identifier preceded by “L” or “R” to reflect whether the microsatellite was targeted to the left arm or the right arm of the chromosome.
Table 5.
Primer sequences for preselective and selective AFLP primers.
Table 6.
Primer pairs for preselective and selective AFLP reactions.
Table 7.
Microsatellite targeted markers on the Neurospora crassa linkage map.
Figure 3.
Segregation of mapped markers in the N. crassa NcA × NcC mapping population.
Genetic markers showing distorted (closed circles) or undistorted (open circles) segregation are ordered according to their position within the seven linkage groups on the x-axis. The size of each circle is proportional to the number of individuals in the mapping population that was genotyped for that marker, and the frequency of the NcA allele is shown on the y-axis. Four markers from linkage group VI (nc6L2, nc6L6, nc6L13, and nc6L15) were excluded because they were selectively genotyped for finer mapping.
Table 8.
Pairs of unlinked loci showing significant non-random associations.
Figure 4.
Genetics of hybrid fruitbody development in N. crassa.
a. Chromosomes with QTLs are shown. Genome-anchored markers are labeled. Height of QTL rectangle indicates 1-LOD confidence interval; width is proportional to percent variance explained (range, 1.9%–11.0%). A = sympatric maternal; C = allopatric maternal; D = allopatric paternal; * = NcC-allele with positive effect. b. Rejection of neutral evolution for hybrid fruitbody abortion. The probability of observing a genetic architecture as or more biased toward negative alleles than NcC (arrow) is 0.0099. Allele bias was determined in 10,000 replicates of a neutral evolution model, assuming phenotypic disparities at least as great as in parental sympatric maternal fruitbody development, 11 QTLs, and genetic effects magnitudes distributed as in observed QTLs.
Figure 5.
Composite interval mapping of hybrid fruitbody development in crosses between N. crassa and N. intermedia.
The y-axes show the likelihood ratio statistic determined by composite interval mapping under the hypothesis that a QTL exists versus the null hypothesis that no QTL exists. The critical likelihood ratio threshold (horizontal line) reflects a Type I error of 0.05. The x-axis represents the seven linkage groups of the N. crassa genetic map (cM) generated in this study. Solid black circles indicate the positions of significant QTLs whose NcC alleles have negative effects on hybrid fruitbody development and open circles indicate QTLs whose NcC alleles have a positive effect on fruitbody development. Results for four traits are pictured: row 1, trait A—maternal influence on fruitbody development in N. crassa fertilized by sympatric N. intermedia from Tamil Nadu; row 2, trait B—paternal influence on fruitbody development by sympatric N. intermedia from Tamil Nadu fertilized by N. crassa from the mapping population; row 3, trait C—maternal influence on fruitbody development by N. crassa fertilized by allopatric N. intermedia from Africa; row 4, trait D—paternal influence on fruitbody development on allopatric N. intermedia from Africa fertilized by N. crassa from the mapping population.
Table 9.
QTLs for hybrid fruitbody development in crosses between N. crassa and N. intermedia.