Daniele Rosellini

Bacterial citrate synthase expression and soil aluminum tolerance in transgenic alfalfa.

Alfalfa is very sensitive to soil acidity and its yield and stand duration are compromised due to inhibited root growth and reduced nitrogen fixation caused by Al toxicity. Soil improvement by liming is expensive and only partially effective, and conventional plant breeding for Al tolerance has had limited success. Because tobacco and papaya plants overexpressing Pseudomonas aeruginosa citrate synthase (CS) have been reported to exhibit enhanced tolerance to Al, alfalfa was engineered by introducing the CS gene controlled by the Arabidopsis Act2 constitutive promoter or the tobacco RB7 root-specific promoter. Fifteen transgenic plants were assayed for exclusion of Al from the root tip, for internal citrate content, for growth in in vitro assays, or for shoot and root growth in either hydroponics or in soil assays. Overall, only the soil assays yielded consistent results. Based on the soil assays, two transgenic events were identified that were more aluminum-tolerant than the non-transgenic control, confirming that citrate synthase overexpression can be a useful tool to help achieve aluminum tolerance.

Variation for Agronomic and Essential Oil Traits Among Wild Populations of Chamomilla recutita (L.) Rauschert from Central Italy

SURMMARY In Italy, Chamomile is widely used for flower-head infusion but is almost totally imported. Wild populations are easily found, especially in disturbed soils and as weeds of cereal crops. Eleven chamomile populations were collected in Central Italy with the purpose of estimating the diversity and potential economic value of wild germplasm from this area. The eleven populations, together with two previously collected wild populations from North Italy, the Slovak variety Bona and an Italian selection (Syn1) were compared in a spaced-plant trial in 1999. High diversity was found for both agronomic and quality traits, and some wild populations appeared to be better than the best check (Bona) for flower head and essential oil yield. As for the essential oil composition, the populations were tentatively grouped into four previously defined chemotypes and a new one. Four wild populations appeared equal or better than Bona for α-bisabolol (43–55%) or chamazulene (16.3–22.5%) content, and can be useful for developing high oil quality varieties. A significant negative correlation was found between flower head weight and α-bisabolol content.

An Insight into T-DNA Integration Events in Medicago sativa

The molecular mechanisms of transferred DNA (T-DNA) integration into the plant genome are still not completely understood. A large number of integration events have been analyzed in different species, shedding light on the molecular mechanisms involved, and on the frequent transfer of vector sequences outside the T-DNA borders, the so-called vector backbone (VB) sequences. In this work, we characterized 46 transgenic alfalfa (Medicago sativa L.) plants (events), generated in previous works, for the presence of VB tracts, and sequenced several T-DNA/genomic DNA (gDNA) junctions. We observed that about 29% of the transgenic events contained VB sequences, within the range reported in other species. Sequence analysis of the T-DNA/gDNA junctions evidenced larger deletions at LBs compared to RBs and insertions probably originated by different integration mechanisms. Overall, our findings in alfalfa are consistent with those in other plant species. This work extends the knowledge on the molecular events of T-DNA integration and can help to design better transformation protocols for alfalfa.