Despite the agronomical importance and high synteny with other Prunus species, breeding improvements for cherry have been slow compared to other temperate fruits, such as apple or peach. However, the ...recent release of the peach genome v1.0 by the International Peach Genome Initiative and the sequencing of cherry accessions to identify Single Nucleotide Polymorphisms (SNPs) provide an excellent basis for the advancement of cherry genetic and genomic studies. The availability of dense genetic linkage maps in phenotyped segregating progenies would be a valuable tool for breeders and geneticists. Using two sweet cherry (Prunus avium L.) intra-specific progenies derived from crosses between 'Black Tartarian' × 'Kordia' (BT×K) and 'Regina' × 'Lapins'(R×L), high-density genetic maps of the four parental lines and the two segregating populations were constructed. For BT×K and R×L, 89 and 121 F(1) plants were used for linkage mapping, respectively. A total of 5,696 SNP markers were tested in each progeny. As a result of these analyses, 723 and 687 markers were mapped into eight linkage groups (LGs) in BT×K and R×L, respectively. The resulting maps spanned 752.9 and 639.9 cM with an average distance of 1.1 and 0.9 cM between adjacent markers in BT×K and R×L, respectively. The maps displayed high synteny and co-linearity between each other, with the Prunus bin map, and with the peach genome v1.0 for all eight LGs (LG1-LG8). These maps provide a useful tool for investigating traits of interest in sweet cherry and represent a qualitative advance in the understanding of the cherry genome and its synteny with other members of the Rosaceae family.
Profiles of S-substituted cysteine flavor precursors were determined in 42 Alliaceae species native to South Africa and South America. It was found that the pool of cysteine derivatives present in ...these plants is remarkably very simple, with S-((methylthio)methyl)cysteine 4-oxide (marasmin) being the principal flavor precursor, typically accounting for 93-100% of the pool. Out of the other cysteine derivatives, only minor quantities of methiin were present in some species. The marasmin-derived thiosulfinate marasmicin (2,4,5,7-tetrathiaoctane 4-oxide), a major sensory-active compound of the freshly disrupted plants, was isolated, and its organoleptic properties were evaluated. Furthermore, sulfur-containing volatiles formed upon boiling of these alliaceous species were studied by GC-MS. The profile of the volatiles formed was relatively simple, with 2,3,5-trithiahexane and 2,4,5,7-tetrathiaoctane being the major components. Despite the traditional belief, ingestion of the marasmin-rich plants was always accompanied by development of a strong "garlic breath". We believe that especially several Tulbaghia species deserve to attract much greater attention from the food industry thanks to their pungent garlicky taste and unusual yet pleasant alliaceous smell.
The Chilean endemic genus Conanthera is comprised of five species of herbaceous cormous geophytes. They have ornamental value due to their bell-shaped flowers, which are blue, violet or white. ...Previous germination studies of Conanthera campanulata and Conanthera trimaculata were carried out at 22 degreesC, and manual mechanical scarification improved germination. Based on these results, it was suggested that physical dormancy is present in the non-scarified seeds. However, an improvement in germination after scarification is not enough evidence to conclude that the seed is non-permeable to water and thus has physical dormancy. The objective of the present study was to assess the testa water permeability via an imbibition test and to identify the optimum germination temperature in C. campanulata and C. trimaculata. Using 6-mo-old seeds, data from the imbibition tests showed that neither the seeds of C. campanulata nor C. trimaculata have physical dormancy. In the germination experiments, the temperature range for achieving high germination percentages was 10 to 15 degreesC, where germination reached 90% in less than 28 d. Temperature of 20 degreesC can be considered supra-optimal, while 5 and 25 degreesC inhibited germination. Manual mechanical scarification did not affect germination results at the range of 10 to 15 degreesC. However, at the supra-optimal temperature of 20 degreesC manual mechanical scarification increased germination, although levels were never higher than 25%. Key words: Conanthera campanulata, Conanthera trimaculata, germination temperature, imbibition, scarification, seed dormancy.
A large recombinant inbred population of soybean has been characterized for 220 restriction fragment-length polymorphism (RFLP) markers. Values for agronomic traits also have been measured. ...Quantitative trait loci (QTL) for height, yield, and maturity were located by their linkage to RFLP markers. QTL controlling large amounts of trait variation were analyzed for the dependence of trait variation on particular alleles at a second locus by comparing cumulative distributions of the trait for each genotype (four genotypes per pair of loci). Interesting pairs of loci were analyzed statistically with maximum likelihood and Monte Carlo comparison of additive and epistatic models. For each locus affecting height, variation was conditional upon the presence of a particular allele at a second unlinked locus that itself explained little or no trait variation. The results show that interactions between QTL are frequent and control large effects. Interactions distinguished between different QTL in a single linkage group and between QTL that affect different traits closely linked to one RFLP marker--i.e., distinguished between pleiotropy and closely linked genes. The implications for the evolution of inbreeding plants and for the construction of agronomic breeding strategies are discussed
Breeding soybean Glycine max (L.) Merr. cultivars for resistance to both the soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) and Fe-deficiency chlorosis (IDC) is an important objective for ...growing soybean on some calcareous soils. PI 437654 has the highest level of SCN resistance known in soybean; our objective was to investigate its level of IDC resistance. For this purpose, PI 437654 was evaluated along with eight soybean genotypes, including the highly resistant A13 and the highly susceptible T203. The test was conducted on calcareous Harps soils (fine-loamy, mesic Typic Calciaquolls) at Ames, IA, in 1989, and at Ames and Humboldt, IA, during 1990. The IDC symptoms were visually rated on the scale 1 = no yellowing to 5 = severe yellowing and some necrosis. 1703 had an average score of 4.9 and A13 had an average score of 1.4. PI 437654 had an average score of 1.7. Thus, PI 437654 is a good source for resistance to Fe-deficiency chlorosis as well as soybean cyst nematode
Genetic variability fuels crop improvement and has sustained crop
evolution and adaptation for thousands of years. It is a vital resource
for humanity's future survival given that increases in crop ...production
will most likely come from higher yields per unit area rather than from
new crop lands. Intensive plant breeding using scientific methods
during much of the 20th century has led to significant gains in
productivity for most major world crops. However, the cost of these
achievements has been narrower genetic variability within the elite
gene pool, increased genetic uniformity and vulnerability in crops, and
erosion of native genetic resources (Lee, 1998). The consequences of
narrow genetic pools have been disastrous in the past. Examples abound:
the infamous Irish famine of 1850 caused by a genetically uniform
potato crop susceptible to blight; the famine triggered in India in
1943 by the brown spot disease of rice. More recently the Southern corn
blight that struck the United States corn industry in 1970 caused over
a billion dollars worth of damage (Horsfall, 1972). Future consequences
will be harsh unless steps are taken to reverse the dangerous trend in
genetic erosion of our main sources of food. Furthermore, it is
suspected that reduced genetic variability in most major crops is
responsible for the decrease in genetic gain for yield (Lee, 1998).
Among the important causes for this narrow genetic base is that crop
species have undergone genetic bottlenecks during the domestication and
breeding processes (Tanksley and McCouch, 1997). In the past it has
been difficult to use exotic germplasm because useful genes are often
linked to genes controlling undesirable traits and there were no tools
to go after specific genes or genomic regions. The development of
densely populated genetic linkage maps, marker assisted selection,
expressed sequence tags, chromosome walking and gene cloning, have
changed the scenario and it is now possible to transfer specific genes
or loci to cultivated plants. In developed countries, like the United
States, major efforts are underway to use these tools to mine, capture
and transfer useful genes from exotic germplasm to crop plants
(Tanskely and Nelson, 1996; Tanksley and McCouch, 1997). Also the
completion of the Arabidopsis genome sequencing project will result in
a number of new techniques (Sommerville and Dangi, 2000) that will
enhance our understanding of genomes and, therefore, our ability to
exploit exotic genetic resources. Not surprisingly increased research
and gene discovery will correspondingly increase the value of exotic
germplasm, meaning land races and wild ancestors of cultivated plants.
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