<b>Developing an <i>in vitro</i> optimized protocol to sweet potato landraces conservation

Abstract

This study aimed to develop a protocol for the in vitro conservation of 30 accessions of sweet potato collected in the northern region of Rio de Janeiro State, Brazil, aiming to extend the period between subcultures for this species. An in vitro minimal growth experiment was established with accession UENF 1931 in a factorial arrangement consisting of four concentrations of mineral salts in MS medium and four concentrations of sucrose, at two temperatures. The others accessions were grown in medium containing 100% MS salts and 2% sucrose, which was the medium that allowed the in vitro conservation of accession UENF 1931 for a longer time period. For this second experiment, 30 accessions of sweet potato and two temperatures were used. Plant height, number of leaves, and survival rate were measured every 30 days for 12 months, in both experiments. In the last stage, the sweet potato plantlets originating from in vitro minimal growth were acclimatized and exhibited 100% survival. The recommended in vitro minimal growth conditions for the studied accessions are MS medium with 100% concentration of mineral salts and 2% sucrose, at a temperature of 27±2°C, with subculture performed every 180 days.

Optimization of media formulation for axillary shoot multiplication of the red-peeled sweet potato (Ipomoea batatas [L.] Lam.) &#8216;Abees&#8217;

“…For example, nodal explants were used for the micropropagation of 'Carmen Rubin' and 'White Triumph' (Dolinski and Olek, 2013), 'Gaozi No. 1' (Gong et al, 2005), 'Naruto Kintoki' (Teixeira da Silva et al, 2007), 'KSP 36' and 'KEMB 36' (Mvuria and Ombori, 2014), and 30 accessions from the northern region of Rio de Janeiro, Brazil (Vettorazzi et al, 2017). However, little is known about the micropropagation of 'Abees' sweet potato.…”

Responses of Different Explants of Sweet Potato on Modified MS and LS Based Nutrient Media in vitro

“…Preliminary study carried out indicated that calli induction on modified MS medium containing 2, 4-D on similar explants as reported by [3] under the culture conditions was difficult, if not impossible, with the PNG cultivars tested. In addition, [6] reported that embryogenic calli was induced on LS-based medium supplemented with 1 mgL -1 picloram and more than 50% of the embryogenic calli of 11 genotypes cultured produced shoots.…”

“…Reports of similar research by others [3,6,10] showed that sweet potato is recalcitrant to every in vitro culture treatment and occur at low frequencies for various explants. In fact, shoots can easily be regenerated from explants of stems, petioles, leaves and roots but callus induction and shoot regeneration is difficult, if not impossible [11].…”

“…Leaf explants that were 14-21 days old responded to MSP.8 medium more quickly than explants of 21-28 days old. Contrarily, [3] reported callus induction and somatic embryogenesis initiation on leaf discs and stems on MS based-medium containing 2, 4-D.…”

“…Several other investigators have also shown that sweet potato somatic embryogenesis is initiated from leaf disc, petiole fragment, nodal segment, internodal fragment and root portions [2]. Many of these groups reported in vitro stock cultures as the ideal source of explants for inducing callus and direct shoot regeneration [3]. Additionally, callus was induced from auxenic leaf explants containing 4-5 pairs of leaf primodia, stem segments, internodal section directly behind the apex and freshly harvested roots on basal MS [4] based-medium supplemented with 60 gL -1 sucrose and 0.5-4 mgL -1 2, 4-dichlorophenoxy acetic acid (2, 4-D) and solidified with 7 gL -1 agar [2].…”