Ameliorative Effects of Foliar Application of Ascorbic Acid on Agronomic Characteristics, Paste Quality, and Gene Expression Related to Ripening in Tomato

Abstract

This study aimed to compare determinate local varieties with commercial hybrid cultivars, under the hypothesis that applying ascorbic acid (AsA) at different growth stages would enhance the quality of both tomato fruits and paste. Four local varieties (Soran, Gwer, Khabat, and Ankawa) and four commercial cultivars (SV1521, SV6714, Marwaa F1, and FDR8565) were cultivated in an open farm during the 2021 growing season. To evaluate the influence of AsA on growth and development, a number of morphological, physiological, and molecular analyses were performed on both tomato fruit and paste. AsA promoted a progressive improvement in all morphological and biochemical parameters, along with certain quality attributes of the tomato paste, across both varieties and cultivars, relative to the control group. It was found that the properties of tomato paste, such as its dry matter (DMP), total soluble solids (TSS_P, 0Brix), pH, titratable acidity (TA), and taste index (TI), were the same for both commercial and local cultivars. In terms of morphological features, 1.5 mM AsA resulted in an increase ranging from 21.60 % to 83.90 % relative to untreated plants, whereas 2.5 mM AsA elevated these ratios between 22.20 % and 71.90 %. Lycopene and /3-carotene exhibited a substantial increase at 1.5 and 2.5 mM AsA concentrations compared to the control. 1.5 mM AsA yielded the highest enhancement of TSS_F, measuring 5.03 degrees Brix, while 2.5 mM AsA resulted in the greatest increase in ascorbic acid (AsA) in the fruit, quantified at 11.47 mg per 100 g of fresh weight (FW). The findings of gene expression revealed that the SlFSR (fruit shelf-life regulator) was overexpressed in the Ankawa and Marwaa F1 (4.64 and 3.88, respectively), but the RIN (ripening inhibitor) was overexpressed in SV6714 (4.51). Furthermore, the E8 (ethylene-related gene) exhibited overexpression in SV1521TD (4.24).