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A new protocol for the production of transgenic pineapple plants was developed. Adventitious buds were induced directly from Agrobacterium-infected leaf bases and stem discs of in vitro plants, bypassing the establishment of callus cultures. Non-chimeric transgenic plants were obtained by multiple subculturing of primary transformants under increasing levels of selection. A total of 42 independent transgenic lines were produced from two cultivars with two different constructs: one containing a modified rice cystatin gene (Oc-IΔD86) and the other with the anti-sense gene to pineapple aminocyclopropane synthase (ACS). GUS histochemical staining provided the first evidence of the non-chimeric nature of the transformed plants. Their non-chimeric nature was further demonstrated by PCR analyses of the DNA extracted from individual leaves of a primary transformed plant and also from multiple plants propagated from a single transformation event. Southern hybridization confirmed random integration patterns of transgenes in the independent lines. For the Oc-IΔD86 gene, the expression at the mRNA level was detected via RT-PCR and its translation was detected by protein blot. Agronomic evaluation and bioassays of the transgenic plants will further validate the utility of this new tool for pineapple improvement.

Taro [Colocasia esculenta (L.) Schott] corms from 57 vegetatively propagated cultivars were evaluated for yield, physical and chemical characteristics, and either microwaved, microwaved and ground into poi, or fried. Poi color ranged from purple to orange or yellow and the dry matter content from 18.3 to 48%. The taste panel preferred poi made from a number of other cultivars than that made from the most common cultivar `Lehua Maoli' used in Hawaii, and a darker bluish-red poi was preferred. Corm total soluble solids were positively correlated to corm specific gravity and dry matter, and to the taste preference of microwaved corm and poi. The fried cultivars varied widely in yield and corm color varied from cream to white. Additionally, some cultivars did not have purple vascular bundles, and others were acrid after frying. Chip oil content was negatively correlated to corm weight, dry weight, and chip yield. The `Bin Liang' cultivar was judged the best overall in fried chip taste. Considerable variation in corm yield and quality characteristics existed in this widely cultivated vegetatively propagated tropical crop.

No abstract

The sugar-to-acid ratio of pineapple (Ananas comosus L.) contributes toward giving the fruit its unique flavor. This ratio is an important indicator of both commercial and organoleptic ripeness, and it is useful in determining a harvest date. Citric acid is the major acid in pineapple and usually is determined by titration to a specific pH endpoint, while sugars are determined as total soluble solids by refractometry. Both acid and sugar levels vary with the season in the year-round production cycle. Acid titration is slow and difficult to perform in the field. A digital acidity meter based upon diluted juice conductivity was evaluated for potential field use. The readings obtained from the meter varied with clone and fruit potassium concentration. The meter had utility for field use to evaluate fruit quality and harvest date. Because fruit potassium levels can vary between harvests, the meter should be recalibrated on a regular schedule to adjust for potential crop management and seasonal effects.