the advent of the common bean genome sequence, SNP markers, and tools such as mutagenesis populations and TILLING ( Porch et al., 2009 ), novel methods are available for identifying genes of interest. Although the genetics of Cl have been studied
Petunia hybrida Vilm. is one of the major bedding plants grown worldwide, and, like most bedding plants, is grown primarily for its seasonal floral display. While increased floral and reflowering capacity have been the focus of breeding programs for many ornamental species, floral longevity has received little direct attention. Increased floral longevity would enhance the value of any crop grown for floral effect. In this study, four parental genotypes (two with short flower life, two with long flower life) were crossed in a partial diallel mating design to create six F1 families. The F1 individuals were then selfed and backcrossed to the appropriate parents to create F2 and backcross families. Data from parental and F1 genotypes were analyzed to determine general and specific combining ability for floral longevity in petunia. Results indicated the presence of significant additive gene effects and nonsignificant nonadditive gene effects for floral longevity in this germplasm. However, aberrant F2 and backcross family means were observed in all families. For each family, F2 and backcross means were lower than expected given normal Mendelian segregation. Further experiments will be necessary to elucidate the causes for the deviate F2 and backcross family means before specific recommendations for selecting for increased floral longevity in petunia can be made.
Parents and progeny of four biparental crosses were analyzed for RAPD marker segregation. A range of 57 to 122 primers were tested in each cross, with an average of 82. Average polymorphic primers and band numbers were 22 and 53, respectively. Of the 212 polymorphic bands, phenotypic segregation ratios were as follows: 133 fitted 1 dominant: 1 recessive, 58 fitted 3:1, 11 fitted ratios 4:1 to 19:1 and 10 were distorted. The 1:1 and 3:1 ratios were expected for either diploid or hexaploid segregation, and the 4:1 to 19:1 are exclusive to hexploid. A total of 14 pairs of markers were linked at map distances ranging from 2.1 to 36.5 cM. One common pair of linked markers was found in two separate crosses.
Sarracenia L. is a genus of insectivorous plants confined to wetlands of the United States and Canada. Green mutants, lacking red pigmentation in the leaves, flowers, and growing point, have been found in most Sarracenia species. Controlled crosses were made using green mutants from S. rubra Walter ssp. gulfensis Schnell, S. purpurea L., S. psittacina Mich., and S. leucophylla Raf. Self-pollination of mutant green individuals in four different species resulted in green offspring, whereas reciprocal crosses with respective wild-types resulted in red offspring. Three of six self-pollinated heterozygous S. rubra ssp. gulfensis yielded offspring exhibiting a 3 red : 1 green ratio. Progeny from a testcross and two self-pollinated heterozygous plants of S. purpurea fit the expected ratios, whereas offspring from two S. purpurea crosses had significant deviations in field and laboratory sowing experiments. Offspring from testcrosses with S. rubra Walter ssp. jonesii (Wherry) Wherry met expected ratios under field conditions. Interspecific crosses between green individuals resulted in green offspring. These results suggest that anthocyanin pigmentation is controlled by two alleles at a single locus, with red dominant to green.
Plants exist as integrations of their many parts and processes. Each part is conditioned by a distinct collection of genes that interact and integrate with the genes that condition other plant parts or processes (44). Root characteristics are conditioned by about 30% of the plant genome, and one-third of these (10% of the total) condition only root characteristics (39). This level of control for a single plant organ is in agreement with that of other plant organs (25) and implies that root characteristics are as amenable to genetic manipulation as the characteristics of any other plant organ or tissue. Root characteristics are not normally emphasized in plant breeding programs because of the difficulty in observing them in situ, rather than because of a reduced potential for improvement. The level of genetic control described (39) should allow the development of isogenic root mutants that have modified physiological and developmental controls to be used for precise experimentation. Data derived from experimentation with these isogenic root mutants would provide a sound basis for developing and testing hypotheses leading, ultimately, to genetic improvement of vegetable root systems.
The objective of this study was to elucidate the genetic control of the semideterminate growth habit in tomato (Lycopersicon esculentum Mill.). A semideterminate tomato line was crossed with determinate and indeterminate lines; their F1, F2, and backcrosses were grown; and the growth habit recorded and analyzed. Plants with six or more inflorescences on the main stem were defined as semideterminate, while those with fewer were defined as determinate. The F2 and backcross to determinate were bimodal, indicating a single recessive gene for semideterminate, which was denoted as sdt. The goodness-of-fit chi square for a single recessive gene model was 88% and 69% for F2 and backcross generations, respectively. In the cross between semideterminate and indeterminate types, the results indicated control by two genes, sp and sdt, with the sp+ indeterminate type epistatic over semideterminate. The goodness-of-fit to this model was 70% and 82% for F2 and backcross generations, respectively.
We have used isozyme techniques (SGE) to assess variation and begin construction of a genetic map of the Asparagus officinalis genome. Isozyme extraction buffers, electrophoretic buffer systems, and isozyme stability during storage were evaluated. Isozyme expression under different environmental conditions was also examined. Thirty-four enzymes were evaluated for their usefulness as genetic markers in A. officinalis. Of these 34, 13 had sufficient activity and resolution on the gels for isozyme analysis. Of the 13 enzyme systems resolved, polymorphisms were observed in aconitase, endopeptidase, malate dehydrogenase, phosphoglucomutase, and shikimate dehydrogenase. Segregation of putative alleles is presented for ACON, END, MDH, PGM and SKDH isozymes. Co-segregation data showed linkage between a SKDH locus and a PGM locus. The isozyme analysis also included Asparagus densiflorus `Sprengeri' and revealed that aspartate aminotransaminase, endopeptidase, and triosephosphate isomerase would be potentially useful for verification of cell fusion products between the two species.
Two new lettuce (Luctuca sativa L.) genes are described and named truncated leaf (tn), and sickly (si). A gene for reflexed involucre is identical to that previously described in wild lettuce (L. serriola L.). Mosaic reaction (me) and light green (lg) are linked, with P = 0.448. Six gene pairs tested for linkage are independently inherited. Sickly is epistatic to light green.