Everton Hilo de Souza

Viability of pollen grains of tetraploid banana

Obtaining banana tetraploid cultivars from triploid strains results in total or partial reestablishment of fertility, allowing the occurrence of some fruits with seeds, a feature that is undesirable from a marketing perspective. The objective of this study was to assess the viability of pollen of 12 banana tetraploid hybrids (AAAB) by means of in vitro germination and two histochemical tests (acetocarmine and 2,3,5-triphenyltetrazolium chloride). The pollen tube growth was evaluated by germinating grains in three culture media — M1: 0.03% Ca(NO3)∙4H2O, 0.02% Mg(SO4)∙7H2O, 0.01% KNO3, 0.01% H3BO3 and 15% sucrose; M2: 0.03% Ca(NO3)∙4H2O, 0.01% KNO3, 0.01% H3BO3 and 10% sucrose; and M3: 0.015% H3BO3, 0.045% Ca3(PO4)2 and 25% sucrose. The acetocarmine staining indicated high viability (above 80%), except for the genotypes YB42-17 and Caprichosa, which were 76 and 70%, respectively. However, the in vitro germination rate was lower than 50% for all the genotypes, except for the hybrids YB42-17 (M1) and YB42-47 (M1). The medium M1 provided the greatest germination percentage and pollen tube growth. Among the genotypes assessed, YB42-47 presented the highest germination rate (61.5%) and tube length (5.0 mm). On the other hand, the Vitoria cultivar had the lowest germination percentage (8.2%) in medium M1. Studies of meiosis can shed more light on the differences observed in the evaluated tetraploids, since meiotic irregularities can affect pollen viability.

Cryopreservation of Pollen Grains of Pineapple and Other Bromeliads

Cryopreservation of pollen grains is an efficient technique to overcome asynchronous flowering and to support actions for genetic improvement and conservation of important alleles. It can be used both by germplasm curators and plant breeders. In the case of Bromeliaceae, a family with wide diversity but also high vulnerability, the form of conservation can be crucial to prevent the increasing problem of genetic erosion. This chapter describes a method of cryopreservation of pollen grains of different Bromeliaceae species, including pineapple, after dehydration with silica and subsequent immersion in liquid nitrogen. The efficiency of this protocol has been demonstrated by the high pollen viability percentage and production of seeds after in vivo pollination with cryopreserved grains. The protocol can be used for cryopreserving pollen of many species of bromeliads and is easy to perform.

Cryopreservation of Pineapple Shoot Tips by the Droplet Vitrification Technique

Cryopreservation is a technique that allows the conservation of many species for long periods. Among the protocols used for cryopreservation, droplet vitrification has shown efficient results in preserving shoot tips of various wild and cultivated pineapple genotypes. The method consists of extraction of shoot tips from plants grown in vitro, dehydration for a period of 48 h in a preculture medium supplemented with a high concentration of sucrose, treatment in a plant vitrification solution (PVS2), and immersion in liquid nitrogen. The method described in this chapter has produced survival and regeneration indices of around 70%, depending on the genotype and physiological conditions of the initial explants. The objective of this chapter is to describe in detail a droplet vitrification protocol for shoot tips that is easy to perform for cryopreservation of pineapple germplasm.

Comparative pollen morphological analysis in the subgenera Passiflora and Decaloba

The genus Passiflora is the most diversified of the Passifloraceae, and its palynology presents wide morphological variability. The objective of the study was to evaluate the pollen morphology of 18 Passiflora species in order to identify informative pollinic characteristics to contribute to the taxonomic classification of the genus. The morphology of the pollen grains and the exine structure were investigated using light microscopy and scanning electron microscopy. Differences in the pollen morphology were found in the studied species, mainly in terms of shape, pollen aperture and ornamentation pattern of the exine. Most of the species belonging to the subgenus Passiflora presented ornamented 6-syncolpate pollen grains with an oblate-spheroidal shape and an exine with large lumens. In the subgenus Decaloba the pollen grains were 6-colporate, 12-colpate and 12-colporate, with subprolate to prolate-spheroidal shape, as well as an exine with smaller lumen size and few ornamented. The pollen morphology of the species of the subgenera Passiflora and Decaloba has shown palynological characteristics that have specific diagnostic value, thus allowing a better understanding of the taxonomy of the genus Passiflora.