Genotypic differences among maize cultivars in response to PEG and phosphate stresses

IntroductionAbiotic stresses can disrupt future food security, which simultaneously implies the importance of genotype screening in stressed environments. Drought and phosphorus stresses have great effects on the growth and development of maize. Soil dryness and phosphorus deficiency cause similar effects and illicit similar defence mechanisms in plants (Xia et al., 2021a). Drought and phosphorus stresses in the root zone can cause active oxygen accumulation in plants. In order to deal with excessive accumulation of active oxygen, plants activate their oxidative defence mechanisms through enzyme or non-enzymatic routes. Oxidative stress caused by excessive accumulation of reactive oxygen species is one of the important physiological factors affecting plant growth and development under stress conditions. The sensitivity of genotypes to water deficit is different and they can be classified into two groups, tolerant or sensitive. Maize (Zea mays L.) is one of the most important crops in the world for food security, as it feeds millions of people. Abiotic stress can create significant challenges in maize production. The present study aimed to determine the effects of phosphate and PEG stresses on the physiological and biochemical traits in the maize cultivars.Materials and methodsMeasured traits in leaf and root tissues were analysed among five maize cultivars under PEG and phosphate stresses. Also, analysis of biochemical traits such as chlorophyll a/b and carotenoids in maize seedlings under PEG 20% and low phosphate were analysed. The five maize cultivars were exposed to PEG 20% and low phosphate stresses and sampled at two-time points after treatment (24 and 48 h). This experiment was carried out as a factorial experiment in the form of a completely randomized design with three replications. In this study, antioxidant enzymes such as catalase, ascorbate peroxidase, and peroxidase activity were measured in leaf and root tissues. Further, PCA, dandraogram and correlation of physiological traits, biochemical and morphological traits were analysed. Statistical analysis was performed using SPSS. Differences across tissues were analysed using one-way ANOVA. Duncan’s test was used to compare the treatment means at P<0.05. Values represent the means of three replications per treatment. Principal Component Analysis (PCA) and correlations were performed using SPSS 22.Results and discussionBased on the cluster analysis, the cultivars were grouped into three classes. The cluster I included Fajr, Paya, and Dehghan whereas, Kosha and Taha cultivars were placed in the clusters II and III, respectively. Also, there was a significantly positive correlation at the probability level of one percent between the content of chlorophyll a/b and root anthocyanin and total chlorophyll content. Correlation between biochemical and physiological traits is shown in Figure 2. The chlorophyll a showed a positive and significant correlation with total chlorophyll and carotenoid contents. The chlorophyll b showed a positive and significant correlation with total chlorophyll content and root anthocyanin. PCA was performed on physiological and biochemical traits to fully investigate the various factors that play essential roles in the drought indices. The cumulative contribution rate of the total changes of PC3 reached 97%. According to PCA analysis measured by correlation matrix and biplot analysis method, it was found that these parameters can be used to evaluate the response of maize genotypes to abiotic stresses under different environments. The relationships between biochemical traits and genotypes is shown graphically in two segments of PC1 and PC2.ConclusionPrincipal component analysis (PCA) and measured traits showed that Fajr, Paya, and Kosha cultivars can show high performance under studied stress conditions. In the present study, the Kosha cultivar was shown to be relatively water stress and low phosphate tolerant due to improved antioxidant, chlorophyll, and carotenoids activities under abiotic stresses.