Search Results
among 25 different species of Ruellia were conducted at the University of South Florida by Long (1975) . Among these, R. simplex (as R. brittoniana ) and three varieties of R. caroliniensis were included in crossing studies. Only a cross between
. Eleven of the interspecific clones were in Cluster 1, whereas four were in Cluster 2. NAT, MUS and SAR, the only three interspecific hybrids resulting from a direct cross between L. indica and L. fauriei ( Egolf, 1981a ), clustered together in the
142 ORAL SESSION (Abstr. 666-672) CROSS-COMMODITY BIOTECHNOLOGY II/RFLPs
, breeding lines, and genetic stocks are preserved at 5 locations in the U.S. ( Anonymous, 2004 ). These resources offer valuable germplasm for improvement of all types of lettuce. Use of interspecific crosses of L. sativa with other related lettuce species
Combining ability for transmission of juvenile period duration was studied in a large pear breeding population. The 92 parents, consisting of cultivars and selections of Pyrus communis L. and its interspecific hybrids with P. pyrifolia (Burm.) Nakai and P. ussuriensis Maxim., as well as genotypes of P. calleryana Decne., were crossed in 298 combinations. General combining ability was highly significant and of much larger magnitude than specific combining ability, indicating that juvenile period length was under predominantly additive genetic control. Selection of parents based on their juvenile period or their combining ability constants is likely to result in significant reduction in mean juvenile period.
Powdery mildew is a fungal disease of crucifers, caused by Erysiphe polygoni D.C. and it can be problematic during seed increase in green-houses. Crosses were made between Brassica carinata (Ethiopian mustard) accession (PI 360883) and B. oleracea cultivars `Titleist' and `Cecile' to transfer resistance to powdery mildew to B. oleracea germplasm. It was not possible to obtain interspecific hybrids between Ethiopian mustard and B. oleracea through natural seed set. However, interspecific hybrids and backcross one (BC1) progenies were produced via embryo rescue following sexual crosses. Four interspecific hybrid plants were produced with the aid of embryo rescue from cultured pistils with B. carinata as the maternal parent, and their interspecific origin was confirmed through plant morphology and analysis of RAPD polymorphisms. No interspecific hybrids were obtained when `Titleist' was used as a maternal parent. Interspecific hybrid plants were male sterile and they were used as maternal parents to produce BC1 plants. Twenty one BC1 plants were obtained through natural seed set and embryo rescue, although embryo rescue was not necessary to produce first backcross generation plants. When tested in greenhouse with powdery mildew, all interspecific hybrids and eight of the BC1 plants were resistant to the disease. Crosses are being made to produce BC2 plants with 2n = 18 chromosomes for introgression of the resistance in B. oleracea.
It is well known that crossability within section Batatas is a complex phenomenon because of genetic, cytogenetic and physiological implications. During 1988 to 1991 we investigated the factors involved in crossability. In the 1st stage, self-compatibility was determined/verified in I. cynanchifolia (2x), I. grandifolia (2x), I. triloba (2x), I. x leucantha (2x), I. lacunosa (2x), I. tenuissima (2x), I. ramosissima (2x) and I. cordato-triloba (2x). Additionally, self-incompatibility was verified in I. trifida (2x), I. tiliacea (4x) and I. batatas (4x,6x). It is postulated that sexual compatibility is related to a multiallelic sporophytic incompatibility system. In the second stage, 4,162 cross pollinations between 11 species were performed at La Molina and San Ramon, and 76 interspecific combinations from 110 possible theoretic combinations in a diallelic 11 × 11 design were obtained. Of 76 interspecific combinations, 38 succeded with a crossability rate ranging from 0.01 to 1.00 at La Molina. In San Ramon, of 17 interspecific combinations, 11 were succesfull when estimating crossability from 0.01 to 0.71. Considering the factors affecting crossability, it was found that latitude influences flowering synchrony in progenitors, and in the germination process, and the early death of seedlings is related to an unbalanced genome (embryo/endosperm) relationship. In interspecific crosses, it was shown that I. trifida and I. x leucantha act as “bridge species”.
. brachycera ‘Berried Treasure’ TM × US 2520-A. The hybrid is three-quarters G. brachycera and one-quarter G. dumosa . Flow cytometry. Previous interspecific crosses within Ericaceae have sometimes produced unexpected triploids and tetraploids
149 POSTER SESSION 6A (Abstr. 316–328) Breeding & Genetics–Cross-commodity
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.