The recessive leaf trait, fused vein (fv), in Cucurbita pepo L. is expressed by the sixth leaf stage and then throughout vegetative growth. It is characterized by the partial fusion of the lateral leaf veins to the main central vein. Consequently, the dorsal leaf surface is distinctively puckered. Use of fv as a genetic marker in hull-less seeded pumpkin lines is hampered, however, by a low recovery of fv plants in segregating populations. Homogeneity Chi Square analysis of 11 F2 (3:1 X2 = 72.05 P < 0.005) and 16 BC (1:1 X2 = 120.12 P < 0.005) populations indicated significant heterogeneity between populations for fv recovery. Recovery ranged from 0 to 35.5% for 11 F2 populations and from 6.8 to 75.4% for 16 BC populations. There was a significant reduction, 35%, in seed yield/fruit when fv pollen was used to hand pollinate fv, normal (N), and F1 flowers as compared to pollinations with N pollen. In pollen competition studies, reduced competition at low levels of F1 or 50:50 fv/N pollen increased fv recovery in F2 and BC populations. These results are consistent with the hypothesis that the fv trait confers gametic subvitality resulting in distorted Mendelian segregation.
R. Bruce Carle and J. Brent Loy
Ryan N. Contreras, John M. Ruter, and David A. Knauft
American beautyberry (Callicarpa americana) is a deciduous shrub native to the southeast United States and is grown primarily for its metallic-purple fruit that develop in the fall. There are also pink- and white-fruiting and variegated forms but these traits are rare in nature and there is no information available regarding their inheritance. Also, there is confusion regarding self-compatibility and the presence of apomixis in Callicarpa L. Crosses were performed to investigate the genetics of fruit color, self-compatibility, and apomixis in american beautyberry. Test crosses between C. americana (CA) and C. americana ‘Lactea’ (CAL) suggested that white fruit is recessive to purple. White fruit appears to be controlled by a single recessive gene for which we propose the name white fruit and the gene symbol wft. Although there were only a limited number of progeny grown, crosses between CA and ‘Welch’s Pink’ suggest that purple is dominant to pink. Test crosses between CAL and ‘Welch’s Pink’ are needed to draw conclusions; however, we propose that purple, pink, and white fruit are controlled by an allelic series for which we suggest the gene symbols Wft > wft p > wft. Segregation ratios suggested that all progeny in the study developed through sexual hybridization. All genotypes used in the current study were self-compatible.
Chunxian Chen and William R. Okie
Several new peach (Prunus persica) flower types were discovered in an F2 segregating population from an open-pollinated, non-showy-flowered F1 seedling of ‘Helen Borchers’, a double-flowered ornamental cultivar. The novel flower types were white and red single-flowered, non-showy blooms, as well as double-flowered, non-showy red, pink, white, and yellow phenotypes. The double, non-showy flowers were very attractive, and resembled pom-pom chrysanthemums. Yellow flower color is unknown in peach. Flower type in the F2 family segregated ≈3:1 for non-showy (Sh_) vs. showy (shsh), for anthocyanin-present vs. anthocyanin-absent, and for pink (R_) vs. red (rr), independently. Flower petal number segregated at about 9:3:4 for classes single:semi-double:double. Although both parents were late flowering, the F1 was not. The F2 seedlings showed a wide range in time of flowering. Higher petal number was correlated with later bloom, although it is unclear whether this is due to linkage or developmental differences in the flowers with extra petals. These novel flower types might be useful as ornamentals, and for use in genetics and breeding studies. Microsatellite analysis of possible pollen donors revealed that ‘Oldmixon Free’, a non-showy-flowered peach cultivar, was likely the pollen parent of the F1.
Hongmei Ma, Richard Olsen, Margaret Pooler, and Matthew Kramer
. Table 3. Inheritance of SSR markers in Prunus hybrids from controlled interspecific crosses showing expected Mendelian inheritance and nonparental bands (in bold) in the progeny. Only a partial data set is included for brevity. All species in this
Liang L. Hong and Paul G. Thompson
Random amplified polymorphic DNA (RAPD) markers were analyzed in parents and progeny of four sweetpotato crosses. An average of 69 primers were tested and 23.5% produced well resolved polymorphic banding patterns. Each polymorphic primer had an average of 1.9 polymorphic bands resulting in 0.45 polymorphic fragments per primer tested. Phenotypic segregation ratios of 88% of polymorphic fragments fit those expected for hexaploid Mendelian inheritance. Numbers of linked polymorphic fragments and numbers of linkage groups were 13 and 5 for Cross A, 0 and 0 for Cross B, 23 and 3 for Cross C and 16 and 6 for Cross D. Those results indicated that RAPD markers have potential for a genetic linkage map in sweetpotato; however, many primers must be screened.
V. V. Meglic, T. F. Horejsi, J. E. Staub, and J. D. McCreight
The genetic diversity of 400 U.S. melon germplasm plant introductions was assessed using 35 enzyme systems. Polymorphisms were observed at 24 putative loci (Ac, Acp1, Acp4, Ak2, Ak3. Ak4, Fdp1, Fdp2, Fdp4, Gpi, Idh, Mdh2, Mdh4, Mdh5, Mdhb, Mpi1, Mpi2, Pgd1, Pgd2, Pgm, Pep-g1, Pep-1a, Pep-pap, Skdh) representing 17 different enzymes. Sixteen loci demonstrated simple Mendelian inheritance. Multivariate analyses aided in reduction of data using 16 loci and linkage relationships were observed among the plant introductions. Two of 16 loci (Pgd1 and Acp1) segregated independently. Fourteen loci were assigned into three linkage groups (A-C): A Fdp1, Fdp2, Acp4, Skdh; B Mdh2, Mdh4, Mdh5, Mdh6, Pep-g1, Pgm; C Mpi2, Ac, Idh.
J.D. Cheung, Y.S. Cha, and B.S. Kim
Bacterial wilt caused by Ralstonia solanacearum is sporadically causing damage to pepper in Korea. We put efforts in analyzing the genetics of resistance to bacterial wilt and in subsequent breeding for resistance by selection. Two Korean cultivars, Subi and Chilsung, were crossed with a resistant source, MC-4, which was kindly provided by Lopes in Brazil. In addition, four breeding lines bred for resistance to Phytophthora blight were crossed with another resistance source, PBC631, which we received from AVRDC. F2 and backcross populations of the crosses were developed and tested by inoculation by dipping the roots of the seedlings before transplanting 25 days after seeding. Segregation in the F2 and backcross populations did not fit any mode of simple Mendelian inheritance, but appeared inheriting in a quantitative mode with relatively low heritability. Selection was practiced in the subsequent F3, BC1F2, F4, and BC1F3 generations and a few resistant selections were obtained.
Marie C. Pairon and Anne-L. Jacquemart
Tetraploid black cherry (Prunus serotina) is the only Prunus L. species that has commercial importance as a timber tree in North America and is well known in Europe for its invasive behavior. Inheritance studies have never been performed and it is not known whether the species is allo or autotetraploid. Six microsatellite nuclear markers were used to test the inheritance in progenies of controlled crosses. Inheritance was proven to be disomic at all loci and a typical diploid mendelian inheritance was found at two loci. A first screening of a population in the invasive range showed high number of alleles per locus (ranging from 6 to 16) and high level of observed heterozygosity (0.75 to 1). Knowing that inheritance is disomic at six microsatellite loci and that at least two of them can be treated as codominant, diploid markers will be beneficial for future genetic studies.
M. Hockenberry Meyer and Donald B. White
Starch gel electrophoresis was used to screen 10 enzyme systems for variation in fountain grass, Pennisetum alopecuroides (L.) Spreng. plants exhibiting four different growth habits: dwarf(d), mound(m), prostrate(p), and upright (u). Only phosphoglucoisomerase (PGI; E.C. 18.104.22.168) was found to be polymorphic at one locus, PGI-2, and was expressed as two alleles, which appeared to be associated with growth habit. The dwarf form expressed one slow band (SS), the mound and prostrate forms exhibited one fast band (FF), and the upright form carried triple bands indicating a heterodimer (FS). Hybrids between FF and SS parents were detected as triple bands (FS). Three generations of progeny resulting from 16 crosses and selfs of these growth habits all followed the expected segregation ratios for typical Mendelian inheritance of this isozyme.
Samir Mhameed, Dror Sharon, Jossi Hillel, Emanuel Lahav, Daniel Kaufman, and Uri Lavi
To estimate heterozygosity level in the avocado (Persea americana Mill.) genome, two types of variable number of tandem repeat (VNTR) markers were used. Multilocus DNA fingerprints (DFPs) were analyzed on avocado progeny resulting from either crosses or selfing of cultivars. In five crosses, heterozygosity was 100%, while in two self-pollinated families, heterozygosity was 90% and 94%. Single locus, simple sequence repeat (SSR) DNA markers were analyzed by typing 59 loci on five avocado cultivars. Average heterozygosity varied from 0.50 to 0.66, while gene diversity varied from 0.42 to 0.66. Heterozygosity varied from 38% to 70%. The percentage of fragments that exhibited Mendelian inheritance was 62.5% to 85% (P < 0.05) for the DFP fragments and 85% for the SSR alleles.