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Isozyme staining and SDS-PAGE of soluble proteins were performed using leaf homogenates from 6- to 8-month-old field-grown seedlings resulting from the cross of either `Heritage' or `Nova' raspberry with ARK-577 diploid blackberry, the latter used as the pollen-donor parent. Four enzyme systems were tested: ADH, PGM, MDH, and PGI. Of these, ADH and PGM did not show any activity; MDH was monomorphic in both raspberry and blackberry parents, with activity at the same migration distance. PGI was polymorphic in the two raspberry cultivars, showing three dimeric bands, but monomorphic in blackberry; the allele for PGI in blackberry being common to that allele coding for the most cathodal band in raspberry. This phenomenon, in addition to poor resolution of bands (due, perhaps to low enzyme activity) and evidence of accidental self-pollination in our populations, prevented us from positively identifying the hybrid offspring using isozymes. By SDS-PAGE of soluble proteins, two bands were detected that seemed to be unique to ARK-577 blackberry and were also expressed in some of the offspring, suggesting a hybrid origin of these seedlings. Morphological comparisons indicated that those seedlings possessing the two unique bands highly resemble the blackberry male parent, greatly supporting their hybrid origin. Unless additional analysis shows otherwise, SDS-PAGE can be used to identify Raspberry–Blackberry hybrids during their vegetative stage of development, and might prove applicable to other interspecific hybrids of Rubus.
Oviposition and feeding of Scrobipalpuloides absoluta was studied on plants of seven different genotypes with varying 2-tridecanone (2-TD) foliage concentrations: Lycopersicon esculentum var. glabratum PI 1344417 (GLA), L. esculentum TSWV-547 (ESC), F1 (ESC × GLA), and four F2 genotypes—two with high 2-TD (HI1, HI2) and two with low foliage 2-TD concentrations (LO1, LO2). GLA, HI1, and HI2 showed 2-TD concentrations above 185 × 10–12 mol·cm2, while ESC, LO1 and LO2 had 2-TD below 40 × 10–12 mol·cm2; F1 had intermediary levels of 2-TD (83.5 × 10–12 mol 2-TD/cm2). Ovipositioning was substantially higher in the low 2-TD than on either the high 2-TD genotypes or in the F1, especially in the upper portion of the plants. Scores for leaf lesion type (LLT), overall plant damage (OPD) and percent leaflets attacked (PLA) were substantially higher for the low 2-TD than for either the high 2-TD genotypes or the F1. The results indicate that 2-TD mediates resistance to Scrobipalpuloides absoluta in the interspecific cross, and strongly suggest that 2-TD acts as both an ovipositioning and feeding deterrent for this insect.
The genus Alstroemeria L. is endemic in South America, mainly in Chile and Brazil. Crossing barriers of mainly postfertilization origin hampered widely inter-specific hybridization. Culturing the ovules 2 days after pollination in an hormone-free MS medium with 9% saccharose for 6 weeks and hereafter transfer to a MS medium with 3% saccharose gives germination of the fertilized ovules. In a diallel cross with 5 Chilean and 2 Brazilian species 39 combinations failed, whereas after early ovule culture hybrid plants were obtained in 27 of the incongruous combinations. The rate of success varied between 0.4%–22.5% depending on the species combination. The hybrids were tested in in vitro stage for their true hybridity using isozyme analysis and/or genomic in situ hybridization of chromosomes (GISH). This method can easily be applied in hybrids between Chilean and Brazilian species. Backcrosses were made using the ovule culture again and in the combination (A. aurea × A. inodora) × A. inodora plants were obtained although the pollen fertility was very low (1%–5%). By using species-specific repetitive probes in in situ hybridization (FISH) chromosome specific patterns were obtained enabling us characterizing the backcross hybrids for their chromosome constitution. By this method we can identify our breeding material for special traits linked with identified chromosomes.
Callus cultures were established from intraspecific lines of Allium cepa L., interspecific F1 progeny of A. cepa crossed to A. fistulosum L. and to A. galanthum L., advanced generations of A. fistulosum x A. cepa backcrossed to A. cepa, and lines of A. fistulosum and A. galanthum. These genotypes had been identified as susceptible, resistant, or partially resistant tester lines based on prior seedling and field nursery screenings using the pink-root pathogen Pyrenochaeta terrestris (Hansen) Gorenz, Walker and Larson. Tester line calli were challenged in vitro with culture filtrates of the fungal pathogen and were assessed by visible damage ratings expressed as the percentage of pigmentation in response to the filtrate. The degrees of callus sensitivity to the filtrate observed in vitro corresponded well with the in vivo tester line classifications. These results eliminated the possible confounding influence of using various species of Allium for in vitro screening. Our results indicated the suitability of the in vitro screening approach for the possible identification of useful segregants or somaclonal variants possessing pink-root resistance. However, in vivo pathogenicity may involve mechanisms in addition to sensitivity to the putative toxins present in the filtrate.
Hardened and nonhardened whole plants of three potato species, Solanum tuberosum L., S. acaule Bitt., and S. commersonii Dun., and one interspecific cross, `Alaska Frostless' (S. tuberosum x S. acaule) were placed in a low-temperature chamber capable of maintaining -4 ± 0.5C for 6 or 12 hours. The chamber was designed to control the root temperature independently from the rest of the plant. Cold acclimation did not affect the ability of any of the potatoes tested to undercool (supercool). Solanum tuberosum and `Alaska Frostless' did not undercool for the times and temperatures tested and in all cases were killed. Whole plants of S. acaule and S. commersonii undercooled, in some cases, for up to 12 hours. When plants of S. acaule froze, they were severely injured, although their hardiness levels were reported to be lower than the temperature to which they were exposed in this study. Whenever leaves and stems of S. commersonii were frozen they were not injured. Once the soil was allowed to freeze, all plants, in all cases, were frozen.
Resistance to the Colorado potato beetle (CPB) and green peach aphid (GPA) would be valuable if it could be effectively transferred from wild potato species to the cultivated potato. Eighteen diploid interspecific hybrids have been developed using Solanum tuberosum Gp. Tuberosum haploids (2n = 2x = 24) and the diploid wild species S. berthaultii (ber), S. chacoense (CHC), S. jamesii (jam), and S. tarijense (tar). Twenty-five genotypes per family were screened for resistance to CPB and GPA. Feeding trials were carried out on intact leaves. The degree of resistance to CPB was determined by the stage of instar development and weight of larvae after a four day feeding period; resistance to GPA was evaluated by aphid reproduction and survival after a fifteen day feeding period. Highly CPB or GPA resistant clones, compared to `Norgold Russet',, have been identified thus far. Some clones express high levels of resistance to both CPB and GPA. Crosses between resistant clones and S. tuberosum will be carried out at the diploid level in an attempt to combine resistance with good tuberization qualities.
The edible Alliums are economically important world-wide. The bulb onion (Allium cepa) is the most widely grown. The Japanese bunching onion (A. fistulosum) has many desirable characters, e.g., resistance to pink root, Thrips, smut, maggot, and Botrytis. Transfer of pink root resistance from A. fistulosum into A. cepa has been attempted for over 60 years. However, sterility of the F1 hybrid is a barrier and there is little evidence of gene introgression during backcrossing to A. cepa. Dr. Corgan has made crosses between A. fistulosum as the seed parent and A. cepa. He backcrossed the F1 hybrids to A. cepa and generated BC2 progenies which showed excellent pink root resistance. RFLPs in the chloroplast genome showed all BC2 progenies had either the normal or sterile cytoplasm of A. cepa. This may be due to not strictly maternal inheritance of the chloroplast DNA or a seed mixture during backcrossing. Other interspecific hybrids and their BC1 progenies had the cytoplasm of A. fistulosum. Nuclear RFLPs show hybrid patterns in the F1 plants. BC1 progenies possess some A. fistulosum markers as evidence of DNA introgression from A. fistulosum into the backcross progenies.
Thermal analysis of Forsythia × intermedia `Spectabilis' flower buds had previously detected the occurrence of low temperature exotherms (LTE) during freezing. The LTE apparently resulted from the freezing of supercooled water and corresponded to the death of the florets. The genus Forsythia encompasses a wide array of species and interspecific crosses ranging in flower bud hardiness and floret size. The ability of buds to supercool, the relationship between the LTE and flower bud hardiness, and the extent to which floret size affects both were studied in flower buds of the following Forsythia species: F. × intermedia `Spectabilis', F. × intermedia `Lynwood', F. `Meadowlark', F. suspensa var. fortunei, F. `Arnold Dwarf, F. europaea, F. giraldiana, F. × intermedia `Arnold Giant', F. japonica var. saxatilis, F. mandshurica, F. ovata, and F. viridissima. Flower buds used for thermal analysis were also used in subsequent size determinations. Hardiness evaluations were conducted using controlled freezing tests, and the sampling interval defined using the temperature range of the LTEs. Initial evaluation indicated a high degree of correlation (α>.50) between mean LTEs and mean killing temperatures. The Forsythia genus, with its broad range of bud hardiness and size provides an excellent system in which to study the mechanisms of supercooling. Thermal analysis of cultivars which exhibit LTEs can accurately assess bud hardiness with minimal plant material.
This study was carried out to investigate the distribution, morphological and ecological characteristics, cross fertility and peroxidase banding pattern in floral buds of wild Prunus yedoensis var. nudiflora and its putative parents, P. subhirtella and P. donarium growing at Haenam districts in Korea. P. yedoensis was distributed 200-250 m elevation and showed extensive variations in sterility and morphological variations. The morphological characteristics of P. yedoensis are judged to be intermediate between P. subhirtella and P. donarium. P. subhirtella and P. donarium were naturally found 150-350 m and 150-900 m elevation. Flowering date of p. subhirtella, P. donarium and p. Yedoensis were early April, mid-to-late April and around April 8, respectively. The floral morphology of p. yedoensis showed greater variations than that of p. subhirtella. It is proved that p. yedoensis is an interspecific hybrid between P. subhirtella and P. donarium considering the intermediate characteristics of flower, leaf and peroxidase banding pattern of the floral buds by isoelectric focusing electrophoresis.
The genus Rhododendron is widely distributed and diverse, consisting of over 900 species. Although this diversity has been exploited by hybridizers for over 100 years, few single gene traits have been genetically characterized. In order to develop genetic markers useful for biological, breeding, and commercial applications, we are investigating allelic variability and mode of inheritance at enzyme loci using starch gel electrophoresis. Thus far, allozyme segregation data at 4 enzyme loci (Pgi-2, Idh-1, 6Pgd-2, Est-1) fit the Mendelian model for single gene inheritance at the diploid level. An additional 4 polymorphic loci are presently being characterized: Pgm-2, Mdh-1, Mdh-2, and 6Pgd-1. Disomic inheritance appears to be consistent across a wide array of genetic backgrounds in these crosses, most involving parents with interspecific pedigrees. Variability at these loci is fairly abundant within the Leach breeding population. This should enable us, as an initial application, to genetically `ID' many of the Leach hybrids on the basis of their electrophoretic phenotypes.