Seed priming improves chilling tolerance in chickpea by modulating germination metabolism, trehalose accumulation and carbon assimilation.

Chilling stress is one of the major abiotic stresses affecting chickpea productivity worldwide. This study evaluated the potential role of seed priming in improving resistance to chilling stress in chickpea (cv. Punjab, 2008). The priming treatments involved soaking seeds of chickpea cultivar Punjab 2008 in either water for 8 h (on-farm priming), aerated water (hydropriming) for 18 h, or CaCl2 solution (ψs -1.25 MPa; osmopriming) for 18 h. Primed and untreated seeds were grown either at 18/15 °C (control) or 13/10 °C (chilling stress). Chilling stress suppressed the growth of chickpea while seed priming mitigated the adverse effects of chilling stress by improving stand establishment, growth, water relations, photosynthesis, α-amylase activity, sugar metabolism, antioxidant enzyme activity, membrane stability, and leaf accumulation of proline, nitrogen, potassium and soluble phenolics. Seed priming also improved the performance of chickpea under optimal (control) conditions. The overall order of improvement in resistance to chilling by using seed priming was osmopriming > hydropriming > on-farm priming. Osmopriming improved seedling dry weight, specific leaf area, leaf CO2 net assimilation rate, maximal photochemical efficiency of PSII, α-amylase activity, trehalose content and leaf relative water content by 10, 22, 17, 20, 73, 48 and 7%, respectively, relative to the non-primed control under chilling stress. Under optimal temperature conditions, the corresponding values were 30, 32, 16, 10, 83, 75 and 5%, respectively. Sugar metabolism, especially trehalose content, was strongly linked with stand establishment, photosynthesis, antioxidant potential (under chilling stress) and plant biomass. Overall, seed priming improved chickpea performance under both optimal temperature conditions and chilling stress through better germination metabolism and the accumulation of trehalose, which protected from oxidative damage and helped to maintain carbon assimilation and seedling growth.

Farooq M ，Hussain M ，Nawaz A ，Lee DJ ，Alghamdi SS ，Siddique KHM ... -  《-》

Desi chickpea genotypes tolerate drought stress better than kabuli types by modulating germination metabolism, trehalose accumulation, and carbon assimilation.

Chickpea is mostly grown in rainfed environments and, consequently, its growth is affected by drought stress. This study comprised two independent experiments to investigate the physiological basis of drought tolerance in desi and kabuli chickpea genotypes. In Experiment 1, six genotypes each of desi and kabuli types were planted in soil-filled pots under natural conditions. Ten days after planting, soil moisture was maintained at 75% water holding capacity (well-watered) or 50% water holding capacity (drought stress). Drought stress significantly reduced seedling dry weight, specific leaf area (SLA), and transpiration efficiency (TE) in both chickpea types, relative to the well-watered controls, but their responses varied, with relatively fewer reductions in desi genotypes, Bakhar-2011 and Bitall-2016, and kabuli genotypes, K-70005 and Noor-2013. These four genotypes were used in experiment 2, which was similar to the first but conducted in a climate chamber and the drought was imposed at planting. Drought stress reduced stand establishment, growth, photosynthesis, water relations, α-amylase activity, sugar metabolism, proline, phenolic accumulation, nitrogen and potassium to varying degrees in the four tested genotypes. The reductions were greater in kabuli genotypes than desi genotypes. Under drought stress, desi genotypes germinated better, and had higher trehalose, total and reducing sugars, sucrose, α-amylase activity, photosynthesis, growth, and mineral concentrations than kabuli genotypes. The desi genotype Bakhar-2011 performed better under drought than the desi genotype Bitall-2016 due to better germination metabolism and accumulation of free proline, total phenolics, and trehalose, which maintained carbon assimilation and prevented oxidative damage. In conclusion, desi chickpea types tolerate drought stress better than kabuli types due to better germination metabolism and trehalose accumulation, which prevented oxidative damage, helped with efficient water use, and sustained plant growth.

Farooq M ，Ullah A ，Lee DJ ，Alghamdi SS ，Siddique KHM ... -  《-》

Dynamics of the antioxidant system during seed osmopriming, post-priming germination, and seedling establishment in Spinach (Spinacia oleracea).

Osmopriming is a pre-sowing treatment that improves seed germination performance and stress tolerance. To understand osmopriming physiology, and its association with post-priming stress tolerance, we investigated the antioxidant system dynamics during three stages: during osmopriming, post-priming germination, and seedling establishment. Spinach seeds (Spinacia oleracea L. cv. Bloomsdale) were primed with -0.6 MPa PEG at 15°C for 8 d, and dried at room temperature for 2 d. Unprimed and primed germinating seeds/seedlings were subjected to a chilling and desiccation stresses. Seed/seedling samples were collected for antioxidant assays and germination performance and stress tolerance were evaluated. Our data indicate that: (1) during osmopriming the transition of seeds from dry to germinating state represses the antioxidant pathways (residing in dry seeds) that involve CAT and SOD enzymes but stimulates another pathway (only detectable in imbibed seeds) involving APX; (2) a renewal of antioxidant system, possibly required by seedling establishment, occurs after roughly 5 d of germination; (3) osmopriming strengthens the antioxidant system and increases seed germination potential, resulting in an increased stress tolerance in germinating seeds. Osmopriming-mediated promotive effect on stress tolerance, however, may diminish in relatively older (e.g. ~5-week) seedlings.

Chen K ，Arora R 《-》

Seed Priming with Melatonin Improves the Seed Germination of Waxy Maize under Chilling Stress via Promoting the Antioxidant System and Starch Metabolism.

Cao Q ，Li G ，Cui Z ，Yang F ，Jiang X ，Diallo L ，Kong F ... -  《-》

Drought priming induces chilling tolerance and improves reproductive functioning in chickpea (Cicer arietinum L.).

Priming alleviates membrane damage, chlorophyll degradation along with cryoprotectants accumulation during chilling stress that leads to improved reproductive functioning and increased seed yield. Chilling temperatures below 15 °C have severe implications on the reproductive growth and development of chickpea. The abnormal reproductive development and subsequent reproductive failure lead to substantial yield loss. We exposed five chickpea cultivars (PBG1, GPF2, PDG3, PDG4, and PBG5) to drought stress (Priming) during the vegetative stage and analyzed for chilling tolerance during the reproductive stage. These varieties were raised in the fields in two sets: one set of plants were subjected to drought stress at the vegetative stage for 30 days (priming) and the second set of plants were irrigated regularly (non-primed). The leaf samples were harvested at the flowering, podding, and seed filling stage and analyzed for membrane damage, water status, chlorophyll content, cellular respiration, and certain cryoprotective solutes. The reproductive development was analyzed by accessing pollen viability, in vivo and in vitro germination, pollen load, and in vivo pollen tube growth. Principal component analysis (PCA) revealed that priming improved membrane damage, chlorophyll b degradation, and accumulation of cryoprotectants in GPF2, PDG3, and PBG5 at the flowering stage (< 15 °C). Pearson's correlation analysis showed a negative correlation with the accumulation of proline and carbohydrates with flower, pod, and seed abortion. Only, PBG5 responded best to priming while PBG1 was worst. In PBG5, priming resulted in reduced membrane damage and lipid peroxidation, improved water content, reduced chlorophyll degradation, and enhanced cryoprotective solutes accumulation, which led to increased reproductive functioning and finally improved seed yield and harvest index. Lastly, the priming response is variable and cultivar-specific but overall improve plant tolerance.

Saini R ，Das R ，Adhikary A ，Kumar R ，Singh I ，Nayyar H ，Kumar S ... -  《-》