Germination of Cas (Psidium friedrichsthalianum L.) Seeds with Different Extraction Methods, Temperatures, and Storage Periods.

Cas or Costarican guava (Psidium friedrichsthalianum L.) is used in some Latin American countries for fresh consumption and as a rootstock for guava commercial production. However, little is known about seed germination and storability. The objective of this research was to evaluate germination of cas seeds, extracted manually or by using a pectinase enzyme, from ripe and overripe fruits, under different temperatures (20ºC, 25ºC, and 30ºC), and storage periods (0, 2, 4, 8 and 12 weeks). The variables evaluated were: percentage of germination, microorganism incidence, and seedling height. The first experiment was arranged in a factorial split split plot design with three repetitions, with temperature as a whole plot treatment, extraction method as the split plot factor, and type of fruit as the split split plot factor. Average seed germination was 78 %, 80 %, and 0 % for the 20°C, 25°C and 30°C treatments, respectively. Pectinase extraction method increased germination speed and decreased fungal growth on seeds. Fruit ripeness had no effect on seed germination. The germination inhibiting effect of 30^oC was further confirmed when seeds placed to germinate at 25°C for three days and then placed at 30^oC, showed a delay in germination. For the second experiment, seed enzymatic extraction was used and seeds were stored at 5^oC in glass Petri dishes. The experiment had three repetitions and was arranged as a complete randomized design. Seeds were stored for up to 12 weeks and germination tests were run weekly after imbibition. Independently of the storage period, a decreased germination velocity was observed, without affecting the final germination percentage, with an average of 90 %.