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Pineapple, Ananas comosus L. Merr., cultivars differing in resistance to fusariose were examined for the phytotoxic effect of culture nitrate (CF), and fusaric acid (FA) isolated from Fusarium subglutinans (Wollew & Reinking) Nelson, Toussoun & Marasas. The possibility of using these substances on F1 hybrids as selection agents for resistance was also evaluated. The phytotoxic effect of these substances was assessed in pineapple plantlets from tissue culture by placing them on wounded leaf segments. The resistance level of the F1 hybrids and cultivars under natural conditions was measured in greenhouse field tests. The susceptible cultivars proved to be the most sensitive in each test, whereas resistant cultivars showed resistance to CF. FA affected all the cultivars independently of the degree of resistance of the cultivars The presence of other metabolites in CF was responsible for the screening effect between the varieties. Using CF as selection criteria allowed the selection of resistant plants with behaviour quite similar to plants where the fungus itself was used as the selection agent.

Evaluations were made during 30 days of in vitro-plantlet hardening. Transformed (bar, chitinase, ap24 transgenes) and non-transformed plantlets were compared. Both groups of plantlets were similar in regard with plant height and weight and peroxidase activity. However, statistical significant changes, caused by transformation, were recorded in levels of malondialdehyde, other aldehydes, chlorophyll (a, b, total), phenolics (free and cell wall-linked) and proteins.

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Pineapple is one of the most important tropical fruits, but the availability of planting material is insufficient to agricultural demands. Therefore, several pineapple micropropagation protocols have been developed. However, acclimatization of in vitro plants continues to take a prolonged period. Biofertilizers have been found as safe alternatives to improve the agricultural performances of many crops. This study highlights some of the effects of the application of Azotobacter chroococcum (INIFAT5 strain) on in vitro pineapple plants during acclimatization. The bacteria were sprayed immediately after transplanting to the ex vitro environment; the plants were then sprayed every 4 wk. A control group of plants was established. Subsequently, after 5 mo, the evaluated variables included fresh and dry plant weight, plant height (cm), and root length (cm). The anatomy of middle-aged leaves and roots was also studied: transversal thickness and width of cuticle, epidermis, hypodermis, aquiferous parenchyma, and photosynthetic parenchyma. Thickness of root exoderm, external cortex, internal cortex, and stele were also evaluated. In general, the INIFAT5 strain improved the plant development. Results showed that the bacteria significantly provoked changes in the plant fresh weight, the thickness of the leaf abaxial and adaxial cuticles, and the root exoderm width. Contrastingly, A. chroococcum did not affect the thickness of the leaf photosynthetic parenchyma.