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Bahiagrass ( Paspalum notatum Flüggé) is the predominant forage grass in the southeastern US. The commercially important bahiagrass cultivar ‘Argentine’ is preferred for genetic transformation over sexual diploid cytotypes, since it produces uniform seed progeny through apomixis. Pseudogamous apomictic seed production in Argentine bahiagrass may contribute to transgene confinement. It is characterized by embryo development which is independent of fertilization of the egg cell, but requires fertilization with compatible pollen to produce the endosperm. Pollen-mediated gene transfer from transgenic, glufosinate-resistant apomictic bahiagrass as pollen donor at close proximity (0.5–3.5 m) with non-transgenic sexual or apomictic bahiagrass cultivars as pollen receptors was evaluated under field conditions. Hybridization frequency was evaluated by glufosinate herbicide resistance in >23,300 seedlings derived from open-pollinated (OP) pollen receptor plants. Average gene transfer between transgenic apomictic, tetraploid and sexual diploid bahiagrass was 0.03%. Herbicide-resistant hybrids confirmed by immuno-chromatographic detection of the PAT protein displayed a single copy bar gene identical to the pollen parent. Hybrids resulting from diploid pollen receptors were confirmed as triploids or aneu-triploids with significantly reduced vigor and seed set as compared to the parents. Transmission of transgenes to sexual bahiagrass is severely restricted by the ploidy difference between tetraploid apomicts and diploid sexual bahiagrass. Average gene transfer between transgenic apomictic tetraploid and non-transgenic, apomictic tetraploid bahiagrass was 0.17%, confirming a very low frequency of amphimixis in apomictic bahiagrass cultivars. While not providing complete transgene containment, gene transfer between transgenic apomictic and non-transgenic bahiagrass occurs at a much lower frequency than reported for other cross-pollinating or facultative apomictic grasses. [ABSTRACT FROM AUTHOR]

Bahiagrass ( Paspalum notatum Flugge) is a prime candidate for molecular improvement of turf quality. Its persistence and low input characteristics made it the dominant utility turfgrass along highways in the south-eastern USA. However, the comparatively poor turf quality due to reduced turf density and prolific production of unsightly inflorescences currently limits the widespread use of bahiagrass as residential turf. Alteration of endogenous gibberellin (GA) levels by application of growth regulators or transgenic strategies has modified plant architecture in several crops. GA catabolizing AtGA2ox1 was subcloned under the control of the constitutive maize ubiquitin promoter and Nos 3’UTR. A minimal AtGA2ox1 expression cassette lacking vector backbone sequences was stably introduced into apomictic bahiagrass by biolistic gene transfer as confirmed by Southern blot analysis. Expression of AtGA2ox1 in bahiagrass as indicated by reverse transcription–polymerase chain reaction and Northern blot analysis resulted in a significant reduction of endogenous bioactive GA1 levels compared to wild type. Interestingly, transgenic plants displayed an increased number of vegetative tillers which correlated with the level of AtGA2ox1 expression and enhanced turf density under field conditions. This indicates that GAs contribute to signalling the outgrowth of axillary buds in this perennial grass. Transgenic plants also showed decreased stem length and delayed flowering under controlled environment and field conditions. Consequently, turf quality following weekly mowing was improved in transgenic bahiagrass. Transgene expression and phenotype were transmitted to seed progeny. Argentine bahiagrass produces seeds asexually by apomixis, which reduces the risk of unintended transgene dispersal by pollen and results in uniform progeny. [ABSTRACT FROM AUTHOR]

Bahiagrass ( Paspalum notatum Flugge) is a popular low-input turfgrass in subtropical regions. However, its turf quality and widespread use as residential turf is limited by up to 60-cm-tall seedheads and its open, sparse-looking growth habit. Plant growth retardants (PGRs) are being used in bahiagrass for the suppression of seedheads and leaf growth since a dwarf bahiagrass cultivar is not available and mowing costs are increasing. However, PGRs have to be applied frequently and may result in phytotoxicity. The improvement of turf quality by genetic engineering represents a promising alternative to the application of PGRs. The data presented here indicate that over-expression of the Arabidopsis ATHB16 transcription factor in bahiagrass significantly changes plant architecture of this important low-input turfgrass. All transgenic plants investigated produced significantly more vegetative and fewer reproductive tillers, shorter leaves and shorter tillers. Over-expression of ATHB16 resulted in a proportional reduction of leaf width and leaf length. The formation of seedheads under natural photoperiod was delayed in some transgenic lines for approximately 4 weeks. Total root or shoot biomass and seed set were not compromised in semi-dwarf bahiagrass plants over-expressing ATHB16. Our findings are consistent with the proposed function of ATHB16 as a suppressor of cell expansion and demonstrate its conserved role in grasses with direct practical implications for enhancing turf quality. [ABSTRACT FROM AUTHOR]

A system for the genetic transformation of rye by co-cultivation with Agrobacterium tumefaciens is described. A total of 45 independent transgenic plants were regenerated with a transformation efficiency of 1 to % of the inoculated explants. The co-cultivation of Agrobacterium-strain AGL0, harboring plasmid pJFnptII and rye im-mature embryos in liquid medium allowed a high throughput and facilitated washing of the cultures to avoid Agrobacterium overgrowth. Transgenic plants were phenotypically normal and fully fertile, which might be a consequence of the short time in tissue culture. The selection with paromomycin exclusively during the regen-eration allowed the efficient recovery of transgenic events without interfering with somatic embryogenesis. Southern blot analysis confirmed the independent nature of the analyzed plants and indicated single copy inserts in more than 50% of them. Segregation analysis confirmed single locus integration and stable transgene expression in most of the lines, while one line with multiple locus integration was also observed. The analysis of T-DNA:: plant DNA boundary sequences revealed examples of exclusion of vector sequences, deletion of a few bases of the T-DNA or insertion of up to 29 bases of the vector backbone. This stresses the importance of detailed analysis of the inserted transgenes in order to identify events with the desired integration profile. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is a key crop for the global food supply. Its complex polyploid genome and recalcitrance to tissue culture pose challenges for genetic transformation, especially for elite cultivars. This study aimed to improve transformation efficiency in elite Korean wheat cultivars by integrating morphogenic regulator genes (GRF4–GIF1), using an engineered Agrobacterium tumefaciens strain. By integrating speed breeding to accelerate donor plant growth, we also reduced the time required to generate transgenic plants. Modifying the resting period and incorporating GRF4–GIF1 significantly improved the outcomes, leading to a transformation efficiency of 4.46% ± 0.93% in Bobwhite cultivar. Application of these methods to Korean elite cultivars also successfully yielded transformations with Keumkang and Baekkang cultivars. Furthermore, using a T3SS AGL-1 strain expressing the type III effector AvrPto enhanced the transformation efficiency in Baekkang cultivar by 2.27 times (17.7%) compared to the standard AGL-1 strain. Using the protocol as described here, we successfully developed stable transgenic lines of the Korean wheat cultivar, marking a pioneering achievement in Korean wheat molecular breeding. The modified protocol can contribute to wheat genetic research and breeding programs in Korea. [ABSTRACT FROM AUTHOR]