Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and on the fruit shelflife regulator (SIFSR) gene expression under elevated CO2 condition

Abstract

The study entitled “Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and the Fruit Shelflife Regulator (SlFSR) gene expression under elevated CO2 condition” was undertaken with the objective of elucidating the effects of biofertilizers and nutrients on the quality and shelf-life of tomato and the Fruit Shelf-life Regulator (SIFSR) gene expression under elevated CO2 condition. The experiment was conducted using the Open Top Chamber (OTC) system facility in the Department of Plant Physiology, College ofAgriculture, Vellayani during 2022-2023. In the experiment, quality and shelf-life of tomato under elevated CO2 environment, as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out in CRD consisting 5 treatments with three replications under ambient and elevated conditions. The treatments comprised of T1: POP, KAU+AMF, T2: POP, KAU+ PGPR Mix-1,T3: POP, KAU+Azolla T4: POP, KAU+50 ppm B + 50 ppm Zn+60 ppm Ca water spray (40, 55 and 70 DAS.) and T5: POP,KAU Control. The experimental results revealed, plant height after 75 days of sowing, specific leaf area and total dry matter increased significantly under elevated CO2 condition. Foliar spray with 50 ppm B + 50 ppm Zn + 60 ppm Ca along with POP, KAU recommendation recorded the highest plant height at 75 DAS. AMF treated plants were found to improve specific leaf area at 60 DAS and 75 DAS. Root to shoot ratio was reduced under elevated CO2 condition compared to ambient condition. Among the treatments, soil incorporation of PGPR before transplantation of seedlings resulted in the highest accumulation of dry matter. Among the physiological and biochemical parameters, total chlorophyll content, total carbohydrate content and chlorophyll stability index recorded higher values under elevated CO2 compared to open condition. However, a significant reduction was noted in total soluble protein content under elevated CO2 compared to open condition. PGPR mix 1 treated plants had recorded the highest chlorophyll and total carbohydrate content but plants foliar sprayed with 50 ppm B+50 ppm Zn+60 ppm Ca recorded the best results with respect to chlorophyll stability index. Exposure to elevated CO2 was found to increase the days for first flowering. Application of biofertilizers and nutrients reduced the days to flowering significantly. Plants came to flowering 40 DAS in the cases of PGPR mix-1 treated plants under eCO2 and AMF treated plants under aCO2. Due to high temperature associated with CO2 enrichment, pollen viability was lost and there was no fruit production inside OTC. Yield parameters such as number of fruits, fruit weight, fruit setting percentage and yield per plant showed significant difference among treatments. Among the treatments, PGPR mix-1 treated plants recorded significant increase in fruit weight, number of fruits and yield. Application of biofertilizers and nutrients had significant impact on quality of fruit and the most effective treatment was incorporation of PGPR mix-1 along with POP, KAU in terms of increased accumulation of lycopene, β-carotene, vitamin C, total sugars, pectin, moisture content, shelf-life and reduced physiological loss in weight. Foliar spray had the same impact as that of PGPR mix-1 treatment in the cases of vitamin C and beta carotene contents. Though AMF was found to increase P content of the fruits significantly, Fe content in fruits was influenced by foliar sprayed and PGPR mix-1 treatment.CO2 enrichment was found to have no influence on expression levels SlFSR gene in leaf tissues but the application of biofertilizers and nutrients was found to affect expression levels in fruits. Lowest level of expression was noted in fruits collected from azolla treated plants under ambient condition. The increase in atmospheric temperature due to increasing CO2 concentration can hasten perishability in the case of farm products. Efforts towards shelf-life extension to make fruit safe for long periods, keeping its original quality is of paramount importance today. The present programme clearly indicates that the shelf-life of tomato variety Vellayani Vijay can be enhanced by 85% through the soil incorporation of PGPR mix-1 before transplanting. This is a great achievement considering the higher perishability of tomato. Application of the biofertilizer, azolla which resulted in the 22.22% increase in shelf-life lead to down regulation of the GRAS transcriptional factor, SlFSR which controls fruit shelf-life by regulating expression of cell wall modifying genes and metabolism of pectin and cellulose. The significant extension of shelf-life achieved through the application of PGPR and AMF could be mediated through the down regulation of ethylene biosynthesis and cell wall degrading enzyme activities. Combined application of calcium, boron and zinc contributes towards firmness of fruit tissues and extended shelf-life to the same degree. The findings of the present programme revealed that application of azolla, PGPR mix-1 and AMF and combined application of calcium, boron and zinc improved the quality and shelf-life of tomato significantly. The result also proves SlFSR gene as a potential biotechnological target for the control of fruit shelf-life. The outcome of the programme will help to develop agricultural practices for improving the shelf-life and quality of tomato which is of paramount importance in the scenario of increasing atmospheric temperature and climate change.