Proceedings of the I Congress PIIISA celebrado en la Estación Experimental del Zaidín (Granada), en mayo de 2013.Seedless triploid varieties of watermelon (Citrullus lanatus var. lanatus) are very appreciated
by consumers, but its production is limited because pollen donor diploid plants and insectassisted
pollination is required. To improve this process it is necessary to better study pollen
biology aspects such as pollen viability and germinability during long-term storage, stigma
receptivity period, etc. In this work we have compared the morphology and ultrastructure of
triploid and diploid plant-derived pollen grains in commercial varieties using diverse
microscopy techniques. We have not detected at this stage key macroscopic morphological
differences between diploid and triploid flowers. Anther development within the triploid
flower is highly asynchronous. Microspores from triploid plants are larger than those from
diploid plants and showed symptoms of cytoplasmic degeneration. Pollen grains from
triploid plants present different morphologies, contain three isodiametric pores but colpi are
sometimes not well developed. Moreover, and also depending on the hydration stage, the
pollen surface is sometimes smooth, without the characteristic reticulate pattern present in
pollen grains from diploid plants. All these developmental features may lead to infertility of
triploid plant-derived pollen.This work was supported by ERDF-co-financed projects BFU2011-22779 (Spanish Ministry of
Science and Innovation), P2010-AGR-6274, P2010-CV-I5767, and P2011-CVI-7487 (Junta de
Andalucía), and RECUPERA2020 3.1.4 (Spanish Ministry of Economy and Competitiveness/
CSIC).Peer reviewe
