Cell Wall Polysaccharide Composition of Grafted ‘Liberty’ Watermelon With Reduced Incidence of Hollow Heart Defect

Abstract

Grafting watermelon scions to interspecific squash hybrids has been found to increase fruit firmness. Triploid (seedless) watermelon are prone to hollow heart (HH), an internal fruit disorder characterized by a crack in the placental tissue expanding to a cavity. Although watermelon with lower tissue firmness tend to have a higher HH incidence, associated differences in cell wall polysaccharide composition are unknown. Grafting “Liberty” watermelon to “Carnivor” (interspecific hybrid rootstock, C. moschata × C. maxima) reduced HH 39% and increased tissue firmness by 3 N. Fruit with and without severe HH from both grafted and non-grafted plants were analyzed to determine differences in cell wall polysaccharides associated with grafting and HH. Alcohol insoluble residues (AIR) were sequentially extracted from placental tissue to yield water soluble (WSF), carbonate soluble (CSF), alkali soluble (ASF), or unextractable (UNX) pectic fractions. The CSF was lower in fruit with HH (24.5%) compared to those without HH (27.1%). AIRs were also reduced, hydrolyzed, and acetylated for GC-MS analysis of monosaccharide composition, and a portion of each AIR was methylated prior to hydrolysis and acetylation to produce partially methylated alditol acetates for polysaccharide linkage assembly. No differences in degree of methylation or galacturonic and glucuronic acid concentrations were found. Glucose and galactose were in highest abundance at 75.9 and 82.4 μg⋅mg–1 AIR, respectively, followed by xylose and arabinose (29.3 and 22.0 μg⋅mg–1). Mannose was higher in fruit with HH (p < 0.05) and xylose was highest in fruit from grafted plants (p < 0.05). Mannose is primarily found in heteromannan and rhamnogalacturonan I side chains, while xylose is found in xylogalacturonan or heteroxylan. In watermelon, 34 carbohydrate linkages were identified with galactose, glucose, and arabinose linkages in highest abundance. This represents the most comprehensive polysaccharide linkage analysis to date for watermelon, including the identification of several new linkages. However, total pectin and cell wall composition data could not explain the increased tissue firmness observed in fruit from grafted plants. Nonetheless, grafting onto the interspecific hybrid rootstock decreased the incidence of HH and can be a useful method for growers using HH susceptible cultivars.

Biostimulatory Action of Vegetal Protein Hydrolysate and the Configuration of Fruit Physicochemical Characteristics in Grafted Watermelon

“…It is very possible that, in our current study, the phyto-hormonal potential of protein hydrolysate biostimulant was masked by the pronounced rootstock effect on pulp firmness. A plethora of studies have identified pulp firmness as the quality trait most frequently and consistently improved by grafting commercial watermelon cultivars onto inter-specific hybrid rootstocks [22,35]. This effect is associated with increased fruit cell density and altered cell wall characteristics, and it is possibly related to the grafting-mediated differentiation of scion gene expression, which encompasses the over-regulation of cytokine and other metabolites of primary and secondary metabolism [36][37][38][39].…”

Blueberry Cell Wall Polysaccharide Composition of Three Distinct Fruit Firmness Phenotypes

“…Determining composition via linkage assembly offers a means to identify the primary cell wall polysaccharides using linkage residue data. , The plant cell wall is composed of a load-bearing network with cross-linking interactions via covalent and noncovalent contacts among sugar linkage residues. Elucidating the physical cross-linking allows for the development of cell wall models and determination of polysaccharide classes .…”

“…All samples and sugar standards were injected into an Agilent 7890A GC coupled to a 5975C VL MSD mass spectrometer (Agilent, Santa Clara, CA). GC-MS system and injection methods followed Trandel et al and Pettolino et al , Data were integrated/quantitated via a 5975C Data Analysis MSD Chemstation (Agilent, Santa Clara, CA). Neutral sugars, galacturonic and glucuronic acids, and the degree of methylation (%methylation) were estimated following Pettolino et al To calculate %methylation, the single and double deuterated galactose peak areas of m / z = 117 were used.…”

“…Quantitative Cell Wall Extraction. Methods for comprehensive cell wall polysaccharide analysis were adapted from Trandel et al and Pettolino et al 32,33 Twelve sugar standards and myo-inositol (internal standard) were used. All sugars were oven-dried, and a stock sugar solution (0.1 M) of standards excluding the internal standard was diluted to generate a calibration curve.…”

Clinical Efficacy Of Medical Dextrose Tincture Liquid In The Treatment Of Facial Photoaging

“…Dextran is a kind of branched dextran polymer with molecular weight ranging from 1 kDa to 2000 kDa. The side chain degree of dextrose differs according to molecular weight [ 17 ]. The smaller the molecular weight, the lower the side chain degree.…”