Abstract
The characterization and viability of pollen grains are useful tools to guide crosses in breeding programs. The objective of this study was to describe the morphological patterns and viability of pollen grains from five accessions of Passiflora edulis f. flavicarpa O. Deg. and five accessions of Passiflora setacea DC. Pollen morphology descriptions were made using light microscopy and scanning electron microscopy, whereas the viability analysis was performed by in vitro germination and histochemical analysis (Lugol's solution and 2,3,5-triphenyltetrazolium chloride). Pollen grains assessed for germination were inoculated in culture medium containing Ca(NO3).4H2O (0.03%), Mg(SO4).7H2O (0.02%), KNO3 (0.01%), H3BO3 (0.01%), sucrose (15%) and agar (0.8%). Although P. edulis and P. setacea showed the same shape and type of pollen aperture, the two differed in terms of their morphology and exine ornamentation pattern. In vitro analysis showed that one of the P. edulis f. flavicarpa accessions (designated BGP 330) presented the highest germination rate (53.98%) and longest pollen tube (2.18 mm). The histochemical analysis overestimated pollen viability when compared with the in vitro results. The results of this study contribute to the breeding of Passiflora species by increasing the understanding of their morphology and pollen grain viability.
Highlights
Passiflora is the largest of the Passifloraceae genera, with approximately 530 different species (Feuillet & MacDougal 2007)
Pollen grains were collected during the anthesis period of five accessions of P. edulis f. flavicarpa, and five accessions of P. setacea (BGP 237, BGP 238, BGP 240, BGP 242 and BGP 272) from the Passion Fruit Germplasm Bank stored at Embrapa Mandioca e Fruticultura, located in the city of Cruz das Almas, in the State of Bahia, Brazil
The morphometric data used for determining the shape and size of the Passiflora edulis f. flavicarpa and P. setacea pollen grains is displayed in Tab. 1 and illustrated in Figs. 1 and 2
Summary
Passiflora is the largest of the Passifloraceae genera, with approximately 530 different species (Feuillet & MacDougal 2007). Many of these species are appreciated on a global basis for their ornamental properties, their seeds being widely sold and marketed, mainly in North America and Europe (Ulmer & MacDougal 2004). The enhanced process of collecting and conserving Passiflora germplasm is an important phase in the formation of germplasm seed banks, it is still being necessary to invest heavily in research involving stored genetic variations, especially in wild species. These species have huge potential for ornamental cultivation due to the aesthetic attributes of their flowers and leaves, as well as the sheer quantity of flowers they produce (Abreu et al 2009). Extraction of these genetic resources makes for better understanding of the biological and genetic aspects of these species, for subsequent inclusion in genetic improvement programmes
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