Search Results

You are looking at 1 - 10 of 131 items for :

  • "transgenes" x
Clear All
Free access

Jude W. Grosser

32 COLLOQUIUM 1 (Abstr. 632–635) Genetic Stability of Transgenes under Field Conditions

Free access

Guo-qing Song, Hideo Honda and Ken-ichi Yamaguchi

( Otani and Shimada, 2002 ; Otani et al., 2003 ; Wakita et al., 2001 ). To obtain sufficient expression levels of transgenes in target tissues of genetically engineered sweetpotato plants, the selection of promoters is crucial. To date, few tissue

Free access

Richard M. Manshardt, Cathy Mello, Sharon D. Lum and Leanne Ta

Genetically engineered (GE), virus-resistant papaya cultivars in Hawaii are easily identified by a colorimetric assay for the β-glucuronidase (GUS) marker transgene. We used GUS to track pollen movement from a central 1-acre plot of gynodioecious GE `Rainbow' plants into seeds on surrounding border rows of non-GE `Sunrise' papaya. GUS evidence of cross-pollination occurred in 70% of female plants (43% of assayed seeds), compared with only 13% of the predominantly self-pollinating hermaphrodite plants (7% of seeds) segregating in the gynodioecious `Sunrise' border rows. The percentage of GUS+ seeds in border row plants showed a weak negative correlation (r = –0.32) with distance from the nearest GE tree (30 m maximum). In a non-GE papaya field located less than a mile downwind from the `Rainbow' source, no evidence of GUS was found in 1000 assayed seeds. In a separate study, the origin of GUS+ seed discovered in papaya fruits from an organic farm was investigated. Leaf GUS assays revealed that 70% of trees were GE, indicating that the grower had planted GE seed. The impact of pollen drift from GE trees in the same field was determined by screening seed samples from 20 non-GE hermaphrodites for GUS expression. Only three hermaphrodites (15%) showed GUS+ seeds, at low levels ranging from 3% to 6% of contaminated samples. These data indicate that the major source of GE contamination in organic fields is seeds of unverified origin, rather than pollen drift from neighboring GE fields. Organic growers are advised to: 1) plant only seed that is known to be non-GE, preferably obtained by manual self-pollination of selected non-GE hermaphrodites; 2) avoid open-pollinated seed; and 3) grow only hermaphrodite (self-pollinating) trees, removing any female or male plants from production fields.

Free access

Manoel T. Souza Jr., Paula F. Tennant and Dennis Gonsalves

Line 63-1 is a `Sunset'-derived transgenic papaya expressing the coat protein (CP) gene from a mild mutant of a Hawaiian isolate of Papaya ringspot virus (PRSV). Previous work showed that line 63-1 R1 plants exhibited a range of resistance to severe PRSV isolates from Hawaii (HA), Jamaica (JA), Thailand (TH), and Brazil (BR). Genetic and molecular data obtained in this study confirm that line 63-1 has two CP transgene insertion sites; segregation analysis shows that the CP and the npt II genes are present at both loci. To study the potential effect of gene dosage on resistance, various populations of R1, R2, and R3 seedlings were challenged by PRSV HA, BR, and TH. A R1 population obtained by self-pollination of line 63-1 hermaphrodite R0 plant exhibited resistance to all three isolates. The percentage of plants resistant to all three PRSV isolates increased in 63-1-derived populations as a result of recurrent selection. Additional genetic studies demonstrate that the number of resistant plants in a 63-1-derived population is directly correlated with the number of plants with multiple transgene copies. We conclude that transgene dosage plays a major role in affecting the resistance of 63-1 to PRSV isolates from various geographical locations.

Free access

C.S. Prakash, O. Zheng and A. Porobodessai

Stable, transgenic, sweetpotato plants have been developed using an improved somatic embryogenesis consisting of l) stage I—explants incubated in darkness for 14 days on MS medium with 2,4D (2.5 mg·liter–1) and 6-BAP (0.25 mg·liter–1) and 2) stage II—culture in light for 14 to 28 days on MS medium with ABA (2.5 mg·liter–1). Petiole or leaf explants of the genotype PI318846-3 were co-cultivated with Agrobacterium tumefaciens EHA 101 containing gusA::nptII fusion gene. Transgenic somatic embryos were selected on a kanamycin medium (100 mg·liter–1). The PCR analysis of the transgenic sweetpotato plants showed the presence of foreign genes in the sweetpotato genome. About 100 transgenic plants are being maintained under laboratory and greenhouse conditions. All the transgenic plants showed a strong expression of gusA gene in the histochemical GUS assay but showed quantitative differences in the chemiluminescent assay. The CaMV35S promoter shows a differential expression because there was some degree of tissue- and organ-specificity in the gusA expression. All transgenic plants appear normal with no phenotypic aberrations and are being tested for productivity traits.

Free access

William R. Woodson

69 WORKSHOP 11 Variation in Expression and Stability of Transgenes in Horticultural Crops

Free access

Monique Guis, Rinaldo Botondi, Mohamed Ben-Amor, Ricardo Ayub, Mondher Bouzayen, Jean-Claude Pech and Alain Latché

Transgenic Cantaloupe Charentais melons (Cucumis melo var. cantalupensis Naud. `Védrantais') exhibiting strong inhibition of ethylene production were used as a model to discriminate between ethylene-regulated and ethylene-independent ripening pathways. Compared to wild-type fruit, transgenic fruit did not undergo significant yellowing of the rind and softening of the flesh. However, these effects were completely reversed by treating transgenic fruit with 50 μL·L-1 exogenous ethylene. Pigmentation of the flesh occurred early before the onset of the climacteric and was thus unaffected by ethylene inhibition in transgenic fruit. Total soluble solids accumulated at the same rate in both types of fruit until 38 days after pollination when wild-type fruit abscissed. However, as ethylene-inhibited fruit failed to develop a peduncular abscission zone, they remained attached to the plant and accumulated higher amounts of sugars, mainly sucrose. Harvesting transgenic fruit resulted in a small but significant increase of internal ethylene associated with softening of the flesh.

Free access

Richard Manshardt and Dennis Gonsalves

32 COLLOQUIUM 1 (Abstr. 632–635) Genetic Stability of Transgenes under Field Conditions

Free access

Richard Meilan, Caiping Ma and Steven H. Strauss

32 COLLOQUIUM 1 (Abstr. 632–635) Genetic Stability of Transgenes under Field Conditions