Ethrel-induced release of fresh seed dormancy causes remodelling of amylase activity, proteomics, phytohormone and fatty acid profile of groundnut (Arachis hypogaea L.).

It is important to have a short period of fresh seed dormancy in some of the groundnut species to counter pre-harvest sprouting (PHS). One of the main causes of PHS is the activation of ethylene-mediated pathways. To determine the effect of ethylene, the study was conducted and alterations in amylase, proteins and fatty acids were observed at the 0, 6, 12, and 24 h stages after ethrel administration. The result showed an increase in amylase activity, and the fatty acids profile showed a unique alteration pattern at different germination stages. Two-dimensional gel electrophoresis (2DGE) revealed differential expression of proteins at each stage. The trypsin digestion following spectral development through UPLC-MS/MS enabled identification of number of differentially expressed proteins. A total of 49 proteins were identified from 2DGE excised spots. The majority were belonged to seed storage-related proteins like Arah1, Arah2, AAI- domain containing protein, conglutin, Arah3/4, arachin, glycinin. Expression of lipoxygenase1, lipoxygenase9 and Arah2 genes were further confirmed by qRT-PCR which showed its involvement at transcript level. Up-regulation of lipoxygenase9 is correlated with decreased content of fatty acids during germination. Phytohormone detection revealed decrease in ABA, SA and JA content which are generally inhibitor of seed germination while GA, IAA and kinetin concentration increased revealing positive regulation of seed germination. We present an integrated view of proteomics, phytohormone profile, carbohydrate and lipid metabolism to unravel mechanism of fresh seed dormancy. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01332-6.

Accumulation of resveratrol, ferulic acid and iron in seeds confer iron deficiency chlorosis tolerance to a novel genetic stock of peanut (Arachis hypogaea L.) grown in calcareous soils.

Peanut is mostly grown in calcareous soils with high pH which are deficient in available iron (Fe2+) for plant uptake causing iron deficiency chlorosis (IDC). The most pertinent solution is to identify efficient genotypes showing tolerance to limited Fe availability in the soil. A field screening of 40 advanced breeding lines of peanut using NRCG 7472 and ICGV 86031 as IDC susceptible and tolerant checks, respectively, was envisaged for four years. PBS 22040 and 29,192 exhibited maximum tolerance while PBS 12215 and 12,185 were most susceptible. PBS 22040 accumulated maximum seed resveratrol (5.8 ± 0.08 ppm), ferulic acid (378.6 ± 0.31 ppm) and Fe (45.59 ± 0.41 ppm) content. Enhanced chlorophyll retention (8.72-9.50 µg ml-1), carotenoid accumulation (1.96-2.08 µg ml-1), and antioxidant enzyme activity (APX: 35.9-103.9%; POX: 51- 145%) reduced the MDA accumulation (5.61-9.11 µM cm-1) in tolerant lines. The overexpression of Fe transporters IRT1, ZIP5, YSL3 was recorded to the tune of 2.3-9.54; 1.45-3.7; 2.20-2.32- folds respectively in PBS 22040 and 29,192, over NRCG 7472. PBS 22040 recorded the maximum pod yield (282 ± 4.6 g/row), hundred kernel weight (55 ± 0.7 g) and number of pods per three plants (54 ± 1.7). The study thus reports new insights into the roles of resveratrol, ferulic acid and differential antioxidant enzyme activities in imparting IDC tolerance. PBS 22040, being the best performing line, can be the potent source of IDC tolerance for introgression in high yielding but susceptible genotypes under similar edaphic conditions. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01321-9.

Metabolic profiling for dissection of late leaf spot disease resistance mechanism in groundnut.

Late leaf spot (LLS) caused by fungi Passalora personata is generally more destructive and difficult to control than early leaf spot. The aim of this study was to decipher biochemical defense mechanism in groundnut genotypes against P. personata by identifying resistance specific biomarkers and metabolic pathways induced during host-pathogen interaction. Metabolomics of non-infected and infected leaves of moderately resistant (GPBD4 and ICGV86590), resistant (KDG128 and RHRG06083) and susceptible (GG20, JL24 and TMV2) genotypes was carried out at 5 days after infection (65 days after sowing). Non-targeted metabolite analysis using GC-MS revealed total 77 metabolites including carbohydrates, sugar alcohols, amino acids, fatty acids, polyamines, phenolics, terpenes and sterols. Variable importance in projection (VIP) measure of partial least squares-discriminant analysis (PLS-DA) showed that resistant and moderately resistant genotypes possessed higher intensities of ribonic acid, cinnamic acid, malic acid, squalene, xylulose, galactose, fructose, glucose, ß-amyrin and hydroquinone while susceptible genotypes had higher amount of gluconic acid 2-methoxime, ribo-hexose-3-ulose and gluconic acid. Heat map analysis showed that resistant genotypes had higher intensities of ß-amyrin, hydroquinone in non-infected and malic acid, squalene, putrescine and 2,3,4-trihydroxybutyric acid in infected leaves. Dendrogram analysis further separated resistant genotypes in the same cluster along with infected moderately resistant genotypes. The most significant pathways identified are: linoleic acid metabolism, flavone and flavonol biosynthesis, cutin, suberin and wax biosynthesis, pentose and glucuronate interconversions, starch and sucrose metabolism, stilbenoid biosynthesis and ascorbate and aldarate metabolism. Targeted metabolite analysis further confirmed that resistant genotypes possessed higher content of primary metabolites sucrose, glucose, fructose, malic acid and citric acid. Moreover, resistant genotypes possessed higher content of salicylic, coumaric, ferulic, cinnamic, gallic acid (phenolic acids) and kaempferol, quercetin and catechin (flavonols). Thus metabolites having higher accumulation in resistant genotypes can be used as biomarkers for screening of LSS resistant germplasm. These results unravel that higher amount of primary metabolites leads to stimulate the accumulation of more amounts of secondary metabolites such as phenolic acid, flavanols, stilbenes and terpenoids (squalene and ß-amyrin) biosynthesis which are ultimately involved in defense mechanism against LLS pathogen. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-00985-5.