Pre- and postharvest development of carrot yield and quality

Abstract

Storage is a prerequisite for a year-round supply of domestic vegetables.The quality of vegetables after long-term storage is primarily determined during the growing season, and storage conditions can only help to maintain the quality as long as possible.Similarly, the quantity of the marketable yield is determined by conditions during the growing season, and loss during storage is affected by both pre-and postharvest factors.This study aimed to show how the quality and quantity of carrot at harvest and after storage can be better controlled.The main emphasis was on the effects of harvest time on yield, storability and sensory quality, with the aim of optimising the timing of harvest.In addition, development of the carrot plant during the growing season was investigated to characterise the determinants of yield production.The sugar composition of carrot storage root was studied as a possible descriptor of the plant's stage of development.Field experiments were conducted at the Vegetable Experimental Site of the Agricultural Research Centre of Finland and on vegetable farms in 1995-1998.Two cultivars, 'Fontana' and 'Panther', were used, and there were 3-6 harvests in September-October.Despite the large variation in average yield at different growing sites, the yield increase generally ceased in early October.On average, 10-36% of the total yield at the final harvest was produced after early September, when the weather was already less favourable for growth.This suggests that carrot still has considerable potential for yield production late in the growing season.The yield increase during the harvest period can be estimated on the basis of thermal time.Delaying the harvest improved storability up to late September or early October; thereafter storability remained at the same level.Only a prolonged period of frost injured the plants so severely that their storability declined.The effect of harvest time was similar irrespective of cultivar, growing site, year and storage conditions.Weather conditions did not account for the improved storability.It is hypothesised that the concentration of antifungal substances increases at the end of the growing season, which makes the storage roots more resistant to storage pathogens.Healing at 10C for 7 days was effective in decreasing the incidence of infections caused by Mycocentrospora acerina.Changes in sugar content and composition during the harvest period were dependent on the year and growing site, and do not provide evidence for the existence of any developmental stage definable as maturity.Neither do changes during storage