Morpho-physiological effects of environmental stress on yield and quality of sweet corn varieties (Zea mays L.)

Abstract

Sweet corn is cultivated in different climatic regions of the world, and consumed either fresh or processed. Morpho-physiological effects of environmental stress on yield, yield components and quality of some sweet corn varieties were investigated in field experiments conducted at Southeastern Anatolia Region of Turkey during 2019 and 2020 growing seasons. The experimental lay out was randomized blocks with three replicates. Eight candidates and two control sweet corn varieties classified as moderate maturity (FAO 650-700) were used in field experiment. Mean values of pollen fertility rate (PFR, %), total soluble solids (TSS, °Brix), abscisic acid (ABA, nmol/g DW), ear length (EL, cm), plant height (PH, cm), number of grains per cob (CGN, grain) and fresh cob yield (FCY, t ha^-1) were significantly different between years and sweet corn varieties. The PFR, TSS, ABA, EL, PH, CGN and FCY ranged from 40.29-67.65%, 13.24-20.09 °brix, 7.74-21.04 nmol/g DW, 9.69-15.98 cm, 97.80-171.34 cm, 289.15-420.33 grain and 4.15-10.23 t ha^-1 respectively. The FCY, yield components and PFR values in the second year that had a higher temperature and lower relative humidity were lower compared to the first year, while ABA and TSS values were higher in the second year. Statistically significant correlations were recorded between the parameters investigated except FCY and TSS. The FCY and other parameters of sweet corn varieties, which produced high ABA phytohormone, were high, and the ABA hormone significantly contributed to plant growth under stress conditions. The results revealed that the PFR physiological parameter and ABA hormone in the plants provide important information about stress level and stress tolerance level of the cultivars, respectively. Despite adverse environmental stress conditions, the FCY of ŞADA-18.7 variety, one of the candidate varieties, was higher than that of the control and the mean value of the experiment.

Keywords: Abscisic acid; Heat stress; Pollen fertility; Sweet corn.

Figure 1. Geographical position of the study area.

The location having the hottest and driest climatic conditions on the Syrian border of Turkey was selected in both years of the experiment. Map data: Google, © 2021 CNES/Airbus, Maxar Technologies.

Figure 2. Mean daily temperature values during the tasseling period in both years of the study.

The climate data used in the experiment were obtained daily from the climate station in the area where the experiment was conducted.

Figure 3. The ABA level of leaf samples was determined using Enzyme-Linked Immuno Sorbent Assay (ELISA)method.

Stages such as homogenization process of 100 mg leaf tissue (A) and transfer of homogenates to 15 ml falcon tubes (B) and the falcon tubes with mixtures of 1st and 2nd supernatants (C) and microplate which is consisting of 96-well for ABA readings (D) of ABA analysis in sugar corn leaves.

Figure 4. The mean values in both years of Some parameters such as polen fertility rate (PFR, %), Absisic asit (ABA, nmol/g DW), Total soluble solids (TSS, °brix) and Fresh cob yield (FCY, t ha⁻¹) (P ≤ 0.05).

The sweet corn varieties investigated in the study showed different physiological and biochemical responses under stress conditions such as severe temperature and low relative humidity.

Figure 5. Pollen fertility (A) and pollen infertility (B) images of ŞADA-18.7 from sweet corn varieties under light microscope.

Pollen grains were counted under a light microscope to determine the viability rate of the dyed pollens. Pollen grains not dyed with TTC (dark red or brown color) were considered not viable, while pollen grains dyed with orange or bright red color were evaluated as viable.