Does chitosan affect bulb yield and quality of sweet onion (Allium cepa L.)?

Abstract

ABSTRACT Chitosan, a polymer derived from shellfish, may enhance plant health and have antimicrobial properties. Effects of chitosan applications to sweet onion (Allium cepa L.) in the field on bulb yield and quality were evaluated. The study was conducted in Tifton (sandy loam) and Reidsville (loamy sand), GA, during the 2015–2016 and 2016–2017 winter seasons (Dec. to May). “Century” sweet onion seedlings were transplanted to beds (1.8-m centers) in mid-December. Treatments were chitosan (117 mg·L−1) applied before transplanting plus monthly applications at 0, 1, 2, 3, and 4 months after transplanting, and an untreated control (water). Harvested bulbs were stored for 3 mo [2.0°C, 80% RH, 0.586 kPa of vapor pressure deficit, 4% CO2, and 10% O2]. Chitosan did not affect bulb marketable and total number and weight, individual bulb weight, and incidence of bulb sour skin (caused by Burkholderia cepacia). Immediately after harvest, chitosan did not influence bulb dry matter, soluble solids concentration, pungency, and total phenols concentration. However, after 3 months of storage, bulb SSC and total phenols decreased, and bulb dry matter and pungency increased. In conclusion, chitosan applications before and during sweet onion production did not affect marketable or total bulb yield, bulb sour skin incidence, or bulb chemical composition.