Abstract
Evolved in South Africa and released to market in 2009, the ‘African Rose’ plum has been introduced and grown under the Egyptian semi-arid conditions since 2010. Within that time, this cultivar has faced significant fruit quality issues, mainly poor color and low total soluble solids (TSS). Several trials using foliarly applied growth regulators have been conducted, but with little conspicuous results on fruit yield and quality. There is very limited information about the relationship between irrigation regime and fruit quality for this cultivar. Therefore, a field experiment was conducted to study the effect of deficit irrigation on the quality of the ‘African Rose’ plum during the 2019 and 2020 seasons. Five-year-old hedge growing trees were subjected to three deficit irrigation regimes: 100% (control), 80%, and 60% of the crop evapotranspiration (ETc) after the pit hardening stage until the end of the harvest season (May to June period) were evaluated. Results indicated that deficit irrigation positively enhanced the levels of abscisic acid (ABA), total phenols, and anthocyanins with improved fruit TSS and maturity index, although fruit yield, acidity, size, and firmness were decreased. Deficit irrigation could be suggested as a sustainable novel solution to improve the fruit quality of the ‘African Rose’ plum grown under the semi-arid conditions of Egypt. Although the total yield and some quality characteristics were not improved, the early harvested fruit with enhanced color and taste could be a good start for additional research to solve other quality-related issues under such conditions.
Highlights
Domesticated in China more than 200 years ago, the plum, a member of the Rosaceae family, is one of the most widely distributed deciduous fruit tree in the world [1]
Due to the limited reports on the environmental and cultural requirements of this cultivar, the objective of this research was to determine whether deficit irrigation could be used as a sustainable novel tool to improve fruit quality, instead of commonly used methods such as foliar spray of growth regulators, which did not show much improvement in fruit quality, those used as harvest indices like fruit color and total soluble solids (TSS) [4]
Results of the current study showed that under deficit irrigation conditions, there was an increase in fruit total phenols, anthocyanins (Table 7), and abscisic acid (ABA) (Figure 4), which were observed following two successive seasons of water deficit (2019 and 2020) (Table 7 and Figure 4)
Summary
Domesticated in China more than 200 years ago, the plum, a member of the Rosaceae family, is one of the most widely distributed deciduous fruit tree in the world [1]. Under the South African conditions, trees are generally moderate in vigor, semi spreading, bear on both spurs and one-year shoots, and have low-to-moderate chilling requirements (200 to 400 infruitec chilling units); this cultivar is recommended for cultivation in early maturing areas like deserts. Personal observations with plum growers indicated that under the Egyptian conditions, fruit have shown poor peel color, low sugar, and high acidity contents. This might be due to the hot and dry growing season, which requires sufficient rates of irrigation during fruit ripening to avoid heat stress and preharvest fruit abscission [5]. Most growers of ‘Crimson Seedless’ grapes in Egypt irrigate their vineyards well to ensure adequate water supply during the ripening stage due to hot summer; they experience poor berry color and low TSS, but deficit irrigation has improved berry maturation with good color and TSS [12]
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