Field performance of micropropagated,macropropagated, and seed-derived propagules of three Eucalyptus grandis ortets

Tree size, survival, and coppicing of micropropagated plantlets, macropropagated cuttings, and seedlings of Eucalyptus grandis Hill ex Maiden were monitored through 57 months in a study in southern Florida to assess propagation options. Two plantlet lines developed by direct micropropagation and orchard open-pollinated seedlings from three ortets were compared in the main study. Rooted cuttings from up to four ramets of each of the three ortets and another ortet were examined in an adjacent supplemental study. Freezes at six and 16 months killed most initial and first-coppice stems to the ground. Most developmental differences in the main study were consistent from ages 2 to 57 months. Propagation by ortet interactions were observed beginning at 21 months, due to the poor performance of seedlings of one ortet after the second freeze. At 57 months, no differences in tree height, DBH, volume, or survival were detected between plantlet lines and between rooted cuttings and plantlets, but seedlings were inferior to plantlets and cuttings. Vegetative propagules had more uniform tree size at every age, with typically less than one-half the variability observed among seedlings. Even though plantlets and cuttings may be more expensive to produce, they have numerous advantages over seedlings for E. grandis plantation establishment in Florida.     

Quantitative cytology of the alfalfa generative cell and its relation to male plastid inheritance patterns in three genotypes

Summary Studies utilizing restriction analysis of plastid DNA, as well as those employing chlorophyll-deficient mutants, have shown a high frequency of paternal plastid transmission in alfalfa. Recent research has also shown that plastid inheritance patterns among alfalfa genotypes and are under genetic control. In a previous study we were unable to detect any correlations between qualitative, three-dimensional ultrastructure of generative cells and male plastid transmission strength in certain genotypes. In the present study we used serial ultrathin sectioning, computerized reconstruction and quantitation, and stereology to further analyze generative cells within mature pollen. Measurements included volumes and surface areas of cells, nuclei, and organelles, as well as organelle number and distribution. Three genotypes were investigated, one that is a strong transmitter of male plastids (genotype 301), one that is a weaker transmitter of male plastids (genotype 7W), and a third that is an even weaker male plastid transmitter (genotype MS-5). Our results show that genotype MS-5 has significantly fewer plastids/generative cell than either of the other genotypes, which may account for it being a relatively poor transmitter of male plastids. However, plastid number does not explain known differences in male plastid inheritance between genotypes 301 and 7W, since plastid number does not differ significantly between these two genotypes. Regarding the other features of generative cells measured in this study, no consistent correlations were found that might account for differences in male plastid inheritance patterns between genotypes. Plastid distribution is equal in each end of the spindle-shaped generative cell in all genotypes studied. Similar relative results were found with regard to mitochondria within generative cells; however, comparative genetic data are not available on mitochondrial transmission patterns in alfalfa genotypes.     

High transmission of paternal plastid DNA in alfalfa plants demonstrated by restriction fragment polymorphic analysis

Summary A high frequency of paternal plastid transmission occurred in progeny from crosses among normal green alfalfa plants. Plastid transmission was analyzed by hybridization of radiolabeled alfalfa plastid DNA (cpDNA) probes to Southern blots of restriction digests of the progeny DNA. Each probe revealed a specific polymorphism differentiating the parental plastid genomes. Of 212 progeny, 34 were heteroplastidic, with their cpDNAs ranging from predominantly paternal to predominantly maternal. Regrowth of shoots from heteroplasmic plants following removal of top growth revealed the persistence of mixed plastids in a given plant. However, different shoots within a green heteroplasmic plant exhibited paternal, maternal, or mixed cpDNAs. Evidence of maternal nuclear genomic influence on the frequency of paternal plastid transmission was observed in some reciprocal crosses. A few tetraploid F₁ progeny were obtained from tetraploid (2n=4x=32) Medicago sativa ssp. sativa x diploid (2n=2x=16) M. sativa ssp. falcata crosses, and resulted from unreduced gametes. Here more than the maternal genome alone apparently functioned in controlling plastid transmission. Considering all crosses, only 5 of 212 progeny cpDNAs lacked evidence of a definitive paternal plastid fragment.Contribution No. 89-524-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan     

Interspecific brood-mixing in Tanganyikan cichlids

Synopsis We collected schools of young, guarded by parents, of six common cichlid species to investigate the frequency and origin of interspecific brood-mixing. The main host species were a piscivore Lepidiolamprologus elongatus and a scale-eater Perissodus microlepis; more than half of their schools included heterospecific young, accounting for 20–40% of the total young. Most of the foreign young belonged to four biparental mouth-brooders whose parents have a habit of carrying their young in their mouths. Many of these young were smaller than the largest young brooded by their own parents. We concluded that adoption of young before independence results from farming-out, a behavior by which parents actively transfer their young to foster parents.     

First controlled progenies checked by isozymic markers in cultivated yams Dioscorea cayenensis-rotundata

As tested progeny have never been obtained, breeding studies on African yams (Dioscorea cayenensisrotundata) are scarce. We report here the first progenies checked by isoenzyme markers. This was made possible by the choice of well-known genitors [one male (cv Zrezrou) and three females (cvs Sopéré, Dahomey and C 20)] and special hybridization conditions. Six enzymatic systems [esterase (EST), isocitrate dehydrogenase (ICD), malate dehydrogenase (MDH), 6-phosphogluconate dehydrogenase (6PGD), shikimate dehydrogenase (SDH), and phosphoglucoisomerase (PGI)] were used to check the progenies and detect outbreeding. Despite the small number of progeny, it was possible to provide information on the genetics of the isoenzymatic systems.     

INBREEDING DEPRESSION IN TWO MIMULUS TAXA MEASURED BY MULTIGENERATIONAL CHANGES IN THE INBREEDING COEFFICIENT

In mixed-mating plant populations, one can estimate the relative fitness of selfed progeny w by measuring the inbreeding coefficient F and selfing rate s of adults of one generation, together with F of adults in the following generation (after selection). In the first application of this multigenerational method, we estimated F and s for adults over three consecutive generations in adjacent populations of two annual Mimulus taxa: the outbreeding M. guttatus and the inbreeding M. platycalyx. This gave estimates of w for the last two generations. Although average multilocus selfing rates were high in both taxa (0.63 in M. guttatus; 0.84 in M. platycalyx), the relative fitness of selfed progeny averaged only 0.19 in M. guttatus and 0.32 in M. platycalyx. An alternative estimator for w that incorporates biparental inbreeding gave even lower estimates of w. These values are significantly below the 0.5 threshold thought to favor selfing, and show that partially selfing populations can harbor substantial genetic load. In accordance with the purging hypothesis, the more highly selfing M. platycalyx showed marginally lower inbreeding depression than M. guttatus in both years (P = 0.08). Inbreeding depression and selfing rates also varied among years in concert among taxa. Several sources of bias are discussed, but computer simulations indicate it is unlikely that w is biased downwards by linkage of marker loci to load loci.     

Cytological evidence of biparental inheritance of plastids and mitochondria inPelargonium

Summary Based on the organelle differences between egg and sperm cells inPelargonium hortorum, the zygote, proembryo, and endosperm were examined under the transmission electron microscope. Plastids and mitochondria in the egg cell are significantly different from those of the sperm cell. Egg plastids are starch-containing and less electron dense. They appear circular, elliptical irregular elongate in sections. Sperm cell plastids are relatively electrondense, mostly cup-shaped or dumbbell and devoid of starch granules. Mitochondria of the egg cell are giant and mostly cup-shaped while sperm mitochondria are smaller and usually circular in section. Double fertilization is completed by 24 h after pollination and the pollen tube can be seen in the degenerated synergid. In the zygote, plastids and mitochondria from male and female gametes can be distinguished by their characteristic differences. Moreover, paternal and maternal organelles appear to be distributed at random in the zygote. Aside from the pollen tube and its released starch granules, there is no enucleated cytoplasmic body in the degenerated synergid. Two days after pollination, the zygote undergoes one transverse division to form a 2-celled proembryo which consists of one larger vacuolated basal cell and one smaller densely cytoplasmic apical cell. Paternal and maternal organelles can be detected in both cells of the proembryo and also in the endosperm at this stage. From these results, it can be concluded that plastids and mitochondria from both male and female gametes have been transmitted into the apical cell of the proembryo and most probably to the following generation.Abbreviations TEM transmission electron microscope - DAPI 4,6-diamidino-2-phenylindole - RFLP restriction fragment length polymorphism     

Experimental analysis of some factors affecting parental expenditure and investment inCichlasoma nigrofasciatum (Cichlidae)

Synopsis Parental investment is the cost of providing parental care. The short-term cost of parental care was measured in the biparental substrate nesting cichlid,Cichlasoma nigrofasciatum, by comparing the expected future survival (measured indirectly as energy content of the body), time taken to breed again and, among females, the number of eggs produced at a subsequent spawning of parental and non-parental pairs. In comparison with non-parental pairs, parental pairs took significantly longer to respawn. Body condition and female fecundity were unaffected after a single parental cycle. The effect on parental cost and expenditure of factors likely to stress the parental fish was also investigated. Removing the male parent had no effect on female parental cost. Exposing pairs to potential predators of offspring increased the time taken by pairs to respawn. In parental males, reducing the level of feeding gave rise to a reduction in some care behaviours.     

Identification,cloning and sequence analysis of a dwarf genome-specific RAPD marker in rubber tree [<Emphasis Type="Italic">Hevea brasiliensis</Emphasis> (Muell.) Arg.]

High-yielding dwarf clones of Hevea brasiliensis are tolerant to wind damage and therefore useful for high-density planting. The identification of molecular markers for the dwarf character is very important for isolating true-to-type high-yielding dwarf hybrid lines in the early stage of plant breeding programs. We have identified a dwarf genome-specific random amplified polymorphic DNA (RAPD) marker in rubber tree. A total of 115 random oligonucleotide 10-mer primers were used to amplify genomic DNA by PCR, of which 19 primers produced clear and detectable bands. The primer OPB-12 generated a 1.4-kb DNA marker from both natural and controlled F₁ hybrid progenies (dwarf stature) derived from a cross between a dwarf parent and a normal cultivated clone as well as from the dwarf parent; it was absent in other parent (RRII 118). To validate this DNA marker, we analyzed 22 F₁ hybrids (13 with a dwarf stature and nine with a normal stature); the dwarf genome-specific 1.4-kb RAPD marker was present in all dwarf-stature hybrids and absent in all normal-stature hybrids. This DNA marker was cloned and characterized. DNA marker locus specificity was further confirmed by Southern blot hybridization. Our results indicate that Southern blot hybridization of RAPD using probes made from cloned DNA fragments allows a more accurate analysis of the RAPD pattern based on the presence/absence of specific DNA markers than dye-stained gels or Southern blot analysis of RAPD blots using probes made from purified PCR products. Detection of RAPD markers in the hybrid progenies indicates that RAPD is a powerful tool for identifying inherited genome segments following different hybridization methods in perennial tree crops.     

INBREEDING DEPRESSION IN GYNODIOECIOUS LOBELIA SIPHILITICA: AMONG-FAMILY DIFFERENCES OVERRIDE BETWEEN-MORPH DIFFERENCES

If inbreeding depression is caused by deleterious recessive alleles, as suggested by the partial dominance hypothesis, a negative correlation between inbreeding and inbreeding depression is predicted. This hypothesis has been tested several times by comparisons of closely related species or comparisons of populations of the same species with different histories of inbreeding. However, if one is interested in whether this relationship contributes to mating-system evolution, which occurs within populations, comparisons among families within a population are needed; that is, inbreeding depression among individuals with genetically based differences in their rate of selfing should be compared. In gynodioecious species with self-compatible hermaphrodites, hermaphrodites will have a greater history of potential inbreeding via both selfing and biparental inbreeding as compared to females and may therefore express a lower level of inbreeding depression. We estimated the inbreeding depression of female and hermaphrodite lineages in gynodioecious Lobelia siphilitica in a greenhouse experiment by comparing the performance of selfed and outcrossed progeny, as well as sibling crosses and crosses among subpopulations. We did not find support for lower inbreeding depression in hermaphrodite lineages. Multiplicative inbreeding depression (based on seed germination, juvenile survival, survival to flowering, and flower production in the first growing season) was not significantly different between hermaphrodite lineages (δ = 0.30 ± 0.08) and female lineages (δ = 0.15 ± 0.18), although the trend was for higher inbreeding depression in the hermaphrodite lineages. The population-level estimate of inbreeding depression was relatively low for a gynodioecious species (δ = 0.25) and there was no significant inbreeding depression following biparental inbreeding (δ = 0.01). All measured traits showed significant variation among families, and there was a significant interaction between family and pollination treatment for four traits (germination date, date of first flowering, number of flowers, and aboveground biomass). Our results suggest that the families responded differently to selfing and outcrossing: Some families exhibited lower fitness following selfing whereas others seemed to benefit from selfing as compared to outcrossing. Our results support recent simulation results in that prior inbreeding of the lineages did not determine the level of inbreeding depression. These results also emphasize the importance of determining family-level estimates of inbreeding depression, relative to population-level estimates, for studies of mating-system evolution.