Onion germplasm interacts with sulfur fertility for plant sulfur utilization and bulb pungency

Abstract

Sixty-two onion (Allium cepa L .) entries grown under high (4 .0 mequiv .liter -1 ) and low (0 .1 mequiv .liter -1 ) S fertility were evaluated for foliar and bulb S utilization, and pungency . Significant differences were detected among entries at both S fertility levels for foliar and bulb %S, and enzymatically developed pyruvate (pungency) in bulb tissue . Correlations between foliar %S and enzymatically developed pyruvate and between bulb %S and enzymatically developed pyruvate were poor suggesting that S is differentially partitioned into flavor and non-flavor compounds in the bulbs of onion germplasm . Significant S by entry interactions were found for all variables tested indicating that selection for S utilization and bulb pungency in onions be conducted at S fertility levels indicative of targeted production areas .

Pungency of Spring Onion as Affected by Inoculation with Arbuscular Mycorrhizal Fungi and Sulfur Supply

“…These results were expected and similar results have been reported for onion plants by other investigators (Randle and Lancaster, 2002). Shoot total sulfur concentrations in spring onion ranged from 0.15 to 0.44 %, which falls within the range of S concentrations in onion leaves and bulbs as reported by Randle (1992). The results lead further evidence for the importance of S fertility in the S metabolism, and eventually the flavor intensity, of Allium plants.…”

“…Root samples (0.5 g fresh weight) were cut into 1 cm-long segments to determine the proportion of root length colonized by AM fungi as described by Giovannetti and Mosse (1980). Pungency as an indicator of onion flavor was determined by the pyruvic acid method (Randle, 1992;Randle et al, 1995), i.e., by measuring enzyme produced pyruvate (EPY). Briefly, the reaction of 2,4-dinitrophenylhydrazine (DNPH) with NaOH was used to detect the presence of pyruvic acid (enzymatically formed pyruvate).…”

“…Studies have shown that water supply (Freeman and Mossedeghi, 1973), temperature (Randle et al, 1993), harvest time (Bloem et al, 2004), S supply (Randle, 1992;Randle et al, 1999), the amount (Coolong et al, 2004) and the forms of nitrogen (N) supplied (Gamiely et al, 1991), and N and S interactions (Coolong and Randle, 2003;Bloem et al, 2004;McCallum et al, 2005) can affect plant growth, maturity, yield, flavor attributes, and bulb firmness. However, S supply in the substrate is considered to be the primary factor because S is directly involved in the synthesis of the ACSOs and is a major constitutent of the flavor compounds.…”

“…However, S supply in the substrate is considered to be the primary factor because S is directly involved in the synthesis of the ACSOs and is a major constitutent of the flavor compounds. Higher available S in the substrate generally results in greater gross flavor intensity (Randle, 1992;Randle et al, 1999) and alters the composition of the ACSOs and the biosynthetic intermediates in onion plants (Randle et al, 1995;Coolong and Randle, 2003).…”

Interactions among genotype, environment and agronomic practices on production and quality of storage onion (Allium cepa L.) - A review

“…Notably, the concentration and lachrymatory factor of thiosulfonates linearly increases as the S content in the soil increases (Randle 1992a;Randle, Bussard 1993;Randle et al 1994), but pungency is not affected by high sulphur content in the soil (Hamilton et al 1997;Lee et al 2009b) and it is not correlated with S level from 16 to 97 p.m. (Yoo et al 2006). Moreover, the transcript levels of the gene associated to ferredoxin-sulphite reductase in plant roots are enhanced under sulphur sufficiency in pungent cultivars but not in the less pungent ones; moreover, the activity of ferredoxin-sulphite reductase significantly increases in response to sulphur fertilization, in the leaves of pungent cultivars but not in less pungent cultivars (McManus et al 2012).…”