Regeneration of Tetraploid Muskmelons from Cotyledons and Their Morphological Differences from Two Diploid Muskmelon Genotypes

Abstract

<jats:p>`Gulfstream' and `Charentais' muskmelons <jats:italic>(Cucumis melo.</jats:italic> L.) plants were regenerated by in vitro culture to increase their genetic variability for resistance to root-knot nematodes <jats:italic>(Meloidogyne</jats:italic> spp.). While no genetic variability for root knot resistance was found, regenerated plants exhibited other traits that varied from the donor cotyledons. Chromosome counts confirmed that &gt;75% of the somaclonal variants were tetraploid (2n = 24; 4n = 48). Tetraploids consistently exhibited micro- and macroscopic morphological changes that enabled distinction between tetraploids and diploids without chromosome counts; tetraploids contained enlarged stomates with more chloroplasts in the guard cells and pollen with a high percentage of square-appearing shapes. Tetraploids exhibited distinctive macroscopic morphological changes, including differences in leaf structure, fruit shape, blossom-end scar, number of vein tracts, and seed size.</jats:p>

High frequency shoot regeneration from leaf explants of muskmelon

“…Tetraploidy has been reported frequently for melon plants regenerated from cotyledons (Ezura et al, 1992;Fassuliotus and Nelson, 1992;Yadav and Grumet, 1994;Gonsalves et al, 1994). As observed by Kathal et al (1992) tetraploidy also occurred in some of the leaf derived regenerants.…”

“…Rooted plantlets were transplanted into 10 cm pots with Baccto mix, acclimatized for a week in the growth chamber and then moved to the greenhouse. Ploidy levels of regenerated plants were examined by pollen morphology as described by Fassuliotus and Nelson (1992).…”

Identification of tetraploid regenerants from cotyledons of diploid watermelon cultured in vitro

“…Polyploid regenerants have been identified from tissue cultures of melon, Cucumis melo L . (Bouabdallah & Branchard, 1986 ;Ezura et al ., 1992a, b ;Fassuliotis & Nelson, 1992), another cucurbitaceous species, as well as asparagus, Asparagus ofcinalis L. (Odake et al ., 1993), beet, Beta vulgaris L . (Hansen et al ., 1994), maize, Zea mays L .…”

“…Ploidy of regenerated plants has been determined by performing somatic chromosome counts (Karp et al ., 1982), but can be more easily estimated by counting the number of chloroplasts per guard cell pair of leaf epidermal cells . This technique has been used to differentiate between diploid and tetraploid regenerants of melon (Fassuliotis'& Nelson, 1992), potato, (Cardi et al, 1993) and tomato (Compton & Veilleux, 1991 ;Jacobs & Yoder, 1989), and to distinguish between diploid and tetraploid watermelon plants obtained following treatment of diploid seedlings with colchicine (McCuistion & Elmstrom, 1993) . The purpose of this study was to investigate whether adventitious shoot regeneration from cotyledons of diploid watermelon could be used to produce fertile, non-chimeric tetraploid plants for use in breeding triploid hybrids .…”

Induction of tetraploidity with antimicrotubule agents in oriental melon (Cucumis melo var. Makuwa)

“…In addition, tetraploid plants of fruit crops are used as breeding parents to produce triploid plants (Jaskani & Khan 2000). Previous studies of tetraploid melons focused on the muskmelon or honeydew melon (Batra 1952;Fassuliotis & Nelson 1992;Zhang et al 2010;Ren et al 2013). However, limited research has been conducted on C. melo var.…”