Adventitious regeneration in vitro occurs across a wide spectrum of squash (Cucurbita pepo) genotypes

Abstract

Cucurbita pepo L. (squash, pumpkin) is a highly polymorphic vegetable species of major importance. Our study characterized a spectrum of C. pepo germplasm for the ability to regenerate in vitro by direct organogenesis from cotyledon explants. Cultivars tested included both cultivated subspecies, texana and pepo, and nearly all of their respective cultivar-groups. Direct shoot regeneration occurred in all accessions, and was generally high (56-94%), with a single exception of 22% ('Bolognese'). There was no significant difference between the percentage regeneration of the two subspecies. Shoot regeneration per responding explant was uniform (1.2-1.6 shoots per explant). Only 'True French' produced statistically more shoots (3.9 per explant) than other accessions. The morphology of regeneration varied. Most cultivars produced long shoots, often fasciated, amid a few small buds. Some subspecies pepo cultivars (Beirut, Yugoslavia 7, Ma'yan and True French) produced short, massive, hollow shoots, sometimes accompanied by shoots that were more normal. Two subspecies texana cultivars (Creamy Straightneck and Small Bicolor) produced single (sometimes double) shoots without other buds. The production of chimeric (mixoploid) regenerants varied and there was a tendency to regenerate chimeric plants from the widest-fruited accessions (i.e. lowest length-to-width ratio) in each subspecies. Subspecies pepo Pumpkin Group 'Tondo di Nizza' showed significantly greater production of chimeric regenerants. In comparison with the great range of variation observed in fruit shape, the variation of in vitro responses (mostly less than 2-fold in regeneration and shoot production) was less than expected.

Simplified in vitro propagation protocol for Tacca leontopetaloides (L.) Kuntze and assessment of genetic uniformity of regenerated plantlets

“…Analysis of ploidy level variation is a useful complementary approach to molecular analysis, which only enables revealing mutations linked to these markers; whilst genomic changes might remain undetected (Jin et al, 2008;Raimondi et al, 2001). Variation in ploidy level after in vitro propagation was detected in many species, e.g., in Titanotrichum oldhamii (Takagi et al, 2011), Cucurbita pepo (Kathiravan et al, 2006), and in Populus x beijingensis (Huang et al, 2015). Thus, development of an efficient system for assessment of in vitro regenerants, making it possible to reveal both molecular and genomic changes, seems to be highly advisable.…”

Direct shoot regeneration via organogenesis in chieh-qua (Benincasa hispida Cogn. var. Chieh-qua How)

“…The explant type, plant genotype, seedling age, culture medium, concentration, and a combination of PGRs were the key factors that influenced shoot organogenesis and subsequent plant regeneration (Niederwieser and Staden, 1990;Dabauza and Peña, 2001;Ashrafuzzaman et al, 2009;Prakash and Gurumurthi, 2010). Basal MS medium has been found to be the most effective for adventitious shoot organogenesis in Cucurbitaceous cotyledon explants (Kathiravan et al, 2006;Haque et al, 2008;Zhang et al, 2011). Many reports have indicated that 6-BA alone or in combination with auxin is useful for shoot differentiation (Dong and Jia, 1991;Sarowar et al, 2003).…”

“…Thomas and Sreejesh (2004) have reported that the addition of 0.2 μM NAA with 4 μM 6-benzylaminopurine (BAP) was beneficial for adventitious shoot regeneration in the cotyledon-derived callus of ash gourd. When compared with cucumber (Vasudevan et al, 2004;Vasudevan et al, 2007b), watermelon (Sultana and Bari, 2003;Sultana et al, 2004), melon (Curuk et al, 2002;Muruganantham et al, 2002) and squash (Ananthakrishnan et al, 2003;Kathiravan et al, 2006), chieh-qua also needed a high concentration of 6-BA for shoot induction. Such a high concentration may influence shoot proliferation as well as elongation, and could be one of the reasons for the difficulty of regeneration of chieh-qua.…”

“…Many studies have demonstrated in vitro that low-salt, ½ and ¼ MS media promote shoot rooting in cucurbits (Lee et al, 2003;Han et al, 2004;Thomas and Sreejesh, 2004). Auxin is also widely used for root induction in cucurbits, including IAA (Han et al, 2004), NAA (Kathiravan et al, 2006;Kim et al, 2010) and IBA (Sarowar et al, 2003;Krug et al, 2005). All these observations revealed that the shoot rooting response may be affected by the growth medium composition.…”

“…Up to now, some efficient plant regeneration protocol has been established in some crops of Cucurbitaceae (Chaturvedi and Bhatnagar, 2001;Soniya and Das 2002;Kintzios et al, 2002;Curuk et al, 2002;Lee et al, 2003;Ananthakrishnan et al, 2003;Sultana et al, 2004;Akasaka-Kennedy et al, 2004;Thomas and Sreejesh, 2004;Kathiravan et al, 2006;Selvaraj et al, 2007;Vasudevan et al, 2007a;Suratman et al, 2010). However, the regeneration of Cucurbitaceae crops is not accomplished like other model plants.…”