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Notes on Citrullus spp.: Pollen Morphology, C Values, and Interspecific Hybridizations with the Gemsbok Cucumber
Author(s) -
Jarret Robert L.,
Bauchan Gary R.,
Oswald W. Wyatt,
Arumuganathan Kathiravetpillai,
Shields John P.
Publication year - 2017
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2016.08.0717
Subject(s) - biology , pollen , botany , cucurbitaceae , reticulate , citrullus lanatus
Scanning electron and light microscopy were used to examine pollen of the currently recognized species (and forms) within the genus Citrullus (Cucurbitaceae). Materials examined included: C. lanatus (Thunb.) Matsum. & Nakai, the citron ( C. amarus Schrad.), the egusi [ C. mucosospermus (Fursa) Fursa], C. colocynthis (L.) Schrad., C. rehmii De Winter, C . ecirrhosus Cogn., and the gemsbok cucumber [ C. naudinianus (Sond.) Hook. f.]—also referred to in the literature as Acanthosicyos naudinianus (Sond.) C. Jeffrey. Pollen of all species were similar in shape differing slightly in their polar (P) and equatorial (E) axes and P/E. In general, all were characterized as prolate and tricolpate with a small polar area and reticulate ornamentation. Flow cytometry revealed C values for the taxa examined as ranging from 0.8 to 1.04 pg DNA per 2C nuclei. A mutant affecting pollen ornamentation was identified in PI 482261, a C. amarus citron from Zimbabwe. Pollen ornamentation on PI 482261 was rugulate. An examination of 15 additional accessions from neighboring areas in Zimbabwe revealed a second rugulate type in PI 482312, while the remaining 14 C. amarus accessions were reticulate. Successful hybridizations were made between C. colocynthis (PI 652554) and C. naudinianus (GRIF 14032), and between C. rehmii (PI 670011) and C. naudinianus (GRIF 14032). The F 1 hybrids of both crosses were extremely vigorous and exhibited some characteristics (i.e., branching and storage root formation) associated with the male parent. Other characteristics such as tendril length and shape, and leaf size and shape, were intermediate between the parents. To date, the interspecific F 1 hybrids have produced only shrunken (nonviable) pollen.