Understanding the Impact of Drought in Coffea Genotypes: Transcriptomic Analysis Supports a Common High Resilience to Moderate Water Deficit but a Genotype Dependent Sensitivity to Severe Water Deficit

Water scarcity is the most significant factor limiting coffee production, although some cultivars can still have important drought tolerance. This study analyzed leaf transcriptomes of two coffee cultivars with contrasting physiological responses, Coffea canephora cv. CL153 and Coffea. arabica cv. Icatu, subjected to moderate (MWD) or severe water deficits (SWD). We found that MWD had a low impact compared with SWD, where 10% of all genes in Icatu and 17% in CL153 reacted to drought, being mainly down-regulated upon stress. Drought triggered a genotype-specific response involving the up-regulation of reticuline oxidase genes in CL153 and heat shock proteins in Icatu. Responsiveness to drought also included desiccation protectant genes, but primarily, aspartic proteases, especially in CL153. A total of 83 Transcription Factors were found engaged in response to drought, mainly up-regulated, especially under SWD. Together with the enrollment of 49 phosphatases and 272 protein kinases, results suggest the involvement of ABA-signaling processes in drought acclimation. The integration of these findings with complementing physiological and biochemical studies reveals that both genotypes are more resilient to moderate drought than previously thought and suggests the existence of post-transcriptional mechanisms modulating the response to drought.

Detection of Epistasis for Seed and Some Phytochemical Traits in Coriander under Different Irrigation Regimes

Coriander (Coriander sativum L.) is an annual herb mainly cultivated for its seed characteristics. Drought stress is a major problem which affects coriander behaviour through biochemical responses. This study aimed to determine the nature and magnitude of epistasis in inheritance of seed yield (SY), percent of dehulled seed (PODS), percent of seed hulls (POSH), essential oil content (EOC), essential oil yield (EOY), dehulled seed fatty acid content (DSFAC), hull fatty acid content (HFAC), fatty acid content (FAC), and fatty acid yield (FAY), and to estimate additive and dominance variance for the traits not influenced by epistasic effects. Three testers, TN-59-158 (highly drought-susceptible), TN-58-230 (highly drought-tolerant, but low-yielding), and their F1 hybrid were each crossed for six genotypes. The experiment was performed under different levels of water deficit: control (C), moderate water deficit (MWD), and severe water deficit (SWD) conditions. Epistasis affected the expression of SY, EOC, EOY, FAC, and FAY in all water conditions, PODS in C, POSH in SWD, HFAC in MWD, and DSFAC in both C and MWD conditions. Total epistasic effects were partitioned, showing that both [i] and [j + l] type interactions were significant, with a prevalent influence of [i] type interactions on these traits except for POSH and FAC in the SWD condition, which exhibited a higher value of the [j + l] type. Both additive and non-additive gene actions were significant for those traits not significantly affected by epistasis in C, MWD, or SWD conditions. An additive type of gene action was preponderant for PODS in MWD and SWD, POSH in MWD, DSFAC in SWD, and HFAC in C and SWD conditions.

Funneliformis mosseae inoculation under water deficit stress improves the yield and phytochemical characteristics of thyme in intercropping with soybean

Intercropping of medicinal plants/legumes along with bio-fertilizer application is a relatively new sustainable practice for improving the yield and secondary metabolites production. Here, a 2-years field experiment was performed to evaluate the effects of water deficit stress and arbuscular mycorrhizal fungi (AMF) application (as bio-fertilizer) on nutrients concentration, dry matter yield, essential oil quantity and quality of thyme in intercropping with soybean. Three irrigation levels, including (i) irrigation after depletion of 20% (I20) as non-stressed, 50% (I50) as moderate water deficit and 80% (I80) available water as severe water deficit were applied as the main factor. The sub-factor was represented by different cropping patterns including thyme sole culture, replacement intercrop ratio of 50:50 and 66:34 (soybean: thyme) and the third factor was non-usage (control) and usage of AMF. According to our results, the thyme dry yield under moderate and severe water deficit stress decreased by 35 and 44% in the first year, and by 27 and 40% in the second year compared with non-stressed (I20) plants, respectively. Also, the macro- and micro-nutrients of thyme leaves increased significantly in intercropping patterns after application of AMF. The maximum essential oil percentage of thyme was achieved in 50:50 intercropping ratio treated with AMF. Under moderate and severe water deficits, the major constituents of thyme essential oil including thymol, p-cymene and γ-terpinene were increased in intercropping patterns treated with AMF. Generally, AMF application in intercropping ratio of 50:50 may be proposed to farmers as an eco-friendly approach to achieve desirable essential oil quality and quantity in thyme under water deficit stress conditions.

Grain and Oil Yields of Safflower (Carthamus Tinctorius L.) Affected By Water Deficit and Growth Regulators

In order to evaluate the effects of growth regulators on yield parameters and oil content of safflower (Carthamus tinctorius L.), a field experiment was conducted under different irrigation intervals in 2019. All plots were irrigated regularly until the seedling establishment and thereafter irrigation intervals were applied after 70, 100, 130, and 160 mm evaporation from class A pan, as normal irrigation and mild, moderate, and severe water deficits, respectively. Foliar sprays of water (control), putrescine (60 µg/L), and 24-epibrassinolide (25 µg/L) at a rate of 1,000 L/ha were applied slightly before flowering. The results revealed that means of plant biomass, grains per capitol, grains per plant, grain yield, harvest index, oil percentage, and yield were decreased under limited irrigations, but 1,000-seeds weight was only reduced under severe water deficit. However, fo-liar sprays of growth regulators, particularly putrescine, increased grains per plant, grain yield, and harvest index, leading to an improvement in oil yield per unit area under different levels of water supply. These results suggest that foliar application of putrescine is a superior treatment for improving the productivity of safflower plants under normal and stressful conditions.

Screening of Iranian Tarragon Accessions Based on Physiological and Phytochemical Responses Under Water Deficit: Applications for Development and Breeding

In this study, screening of tarragon accessions based on physiological and phytochemical traits was investigated under water deficit. The compounding impacts of water deficit * accessions significantly altered the chlorophyll and carotenoid contetnt, malondialdehyde, electrolyte leakage, superoxide dismutase, catalase and ascorbate peroxidase. The HPLC analyse revealed the presence of chlorogenic, syringic, ferulic, vanilic, chicoric and p-coumaric acids as major phenolic acids, while quercetin and herniarin were detected as the predominant flavonoid and coumarin compounds in the extracts. The quality and quantity of tarragon secondary metabolites were impacted by water deficit, suggesting that drought stress either increased the amounts of some common compounds or introduced some new compounds that were not present under normal conditions. In some genotypes, the content of some secondary metabolites in tarragon had the highest values under severe water deficit stress. The results indicated that Hamadan, Varamin and Estahbanat accessions could be introduced as tolerant accessions. Due to the very different response of tarragon accessions to water deficit and the existence of diversity between these accessions, the findings of the present study could be an effective step in identifying and achieving homogeneous, drought-tolerant and high-yield potential accessions, and may help tarragon breeding programs and development of cultivation.

Funneliformis Mosseae Application Under Water Deficit Stress Improves The Drug Yield And Phytochemical Characteristics of Thyme (Thymus vulgaris L.) in Intercropping With Soybean (Glycine Max L.)

Todays, there is a considerable demand in the global herbal market for thyme (Thymus vulgaris L.) and its related products such as extracts and essential oil (EO). In order to comply with this objective, an improvement of its cultivation area under water scarcity conditions is required. On this basis, a 2-year field experiment was performed with 18 treatments and three replications. Three irrigation levels, including i) irrigation after depletion of 20% (I20), 50% (I50) and 80 (I80) available water were applied as the first factor. The Second factor was different cropping patterns including thyme sole culture (Ts), soybean–thyme intercropping (in proportion of 50:50 and 66:34) and the third factor was non-usage (control) and usage of arbuscular mycorrhizal fungi (AMF) as bio-fertilizer. According to our results, the thyme dry yield under moderate (I50) and severe water deficit stress (I80) decreased by 35 and 44% in the first year, and by 27 and 40% in the second year compared with non-stressed (I20) plants, respectively. Also, the macro- and micro-nutrients of thyme leaves increased significantly in intercropping patterns after application of AMF. The maximum EO percentage of thyme was achieved in 50:50 intercropping ratio and moderate water deficit (I50). The major constituents of thyme EO were thymol, γ-terpinene, p-cymene, camphene, 1,8-cineole, camphor, (E)-caryophyllene, carvacrol and myrcene. Interestingly, as the water deficit stress was intensified the content of thymol, γ-terpinene and p-cymene increased significantly. Generally, AMF application in intercropping ratio of 50:50 (soybean: thyme) may be proposed to farmers as an eco-friendly approach to achieve desirable EO quality and quantity in thyme under water deficit stress conditions.

Improving Resistance of Foeniculum Vulgare to Water Deficit Stress by Natural Regulators

This research was conducted as a combined analysis with four replications in two years (2018 ‒ 2019). Treatments were irrigation up to 90%, 50%, and 20% field capacity (as normal irrigation, moderate and severe water deficit stresses, respectively) and foliar application of natural regulators (untreated as control, salicylic acid, spermidine, and methanol). Increasing water deficit stress was led to a significant increase in essential oil percentage and proline content and a significant decrease in yield parameters and seed yield. Most of the traits (except the percentage of essential oil) were affected by natural growth regulators. The highest seed yield (1,127.59 kg/ha), plant biomass (5,426.92 kg/ha), essential oil yield (22.67 kg/ha), and proline content (29.34 μmol/g fresh weight) were obtained in methanol treated plants under normal irrigation. However, the highest amount of these traits under moderate and severe water deficit was recorded for salicylic acid-treated plants. Therefore, foliar spray of methanol was a useful treatment for non-stress conditions, but, application of salicylic acid was the superior treatment for reducing the negative effects of water deficit stress on Foeniculum vulgare.

Growth and organic solutes accumulation in seedlings of Caatinga tree species in response of water deficit and potassium

Drought stress negatively influences a variety of essential physiological process for plant growth and biomass production, and potassium contributes to the absorption of water and maintaining cell turgor, being crucial to understand the seedlings water stress responses. This research aimed to verify the effects to water deficiency and potassium on the growth and accumulation of organic solutes in Myracrodruon urundeuva, Libidibia ferrea, and Mimosa tenuiflora. The treatments were distributed in a 3 x 3 factorial scheme, with three water levels (100%pc - control, 50%pc - moderate water deficit, and 25%pc - severe water deficit) and three doses of potassium (0, 97.5 and 195 mg dm-3 K). The plants were sown in black plastic bags, containing 5 kg of soil. Were evaluated plant height, stem diameter, and leaf concentrations of total soluble sugars, total free amino acids, and proteins. The water deficit caused a reduction in the growth of M. urundeuva and M. tenuiflora plants, regardless of the added potassium. The plants of M. urundeuva and M. tenuiflora were not demanding in potassium, while potassium fertilization with 97.5 mg dm-3 K favored L. ferrea plants, especially when kept under moderate water deficit. The moderate water deficit promoted accumulation of total free amino acids and soluble proteins in M. urundeuva, while in L. ferrea there was accumulation of total free amino acids under severe water deficit. Increase in the potassium promoted reduction in the concentrations of total soluble sugars and soluble proteins.

Arbuscular Mycorrhizas and Phosphorus Fertilizer Affect Photosynthetic Capacity and Antioxidant Enzyme Activity in Peppermint Under Different Water Conditions

In order to investigate the effect of arbuscular mycorrhizas and phosphorus levels on photosynthetic capacity and enzyme activity in peppermint under different water conditions, an experiment was conducted during the 2017–2018 growing seasons. The experimental treatments comprised water deficiency at three levels (a1: irrigation after 70 mm evaporation from pan of Class A, a2: irrigation after 110 mm evaporation from pan of Class A, and a3: irrigation after 150 mm evaporation from pan of Class A), phosphorus fertilizer at three levels (without phosphorus fertilization, 25% recommended phosphorus amount, and 50% recommended phosphorus amount), and different mycorrhiza species (nonmycorrhizal inoculation, <em>Rhizophagus intraradices</em>, <em>Funneliformis mosseae</em>, <em>Glomus hoi</em>, and mixture of all three species). Results showed that water stress significantly reduced chlorophyll <em>a</em>, chlorophyll <em>b</em>, total chlorophyll, and essential oil yield, but increased the stomatal resistance of peppermint. The essential oil yield of peppermint was significantly reduced by severe water deficit (a3). However, inoculation with <em>R. intraradices</em>, <em>G. hoi</em>, and a mixture of all three species under severe water deficit, increased the essential oil percentage of peppermint by 21%, 21%, and 31.5%, respectively. Application of 50% recommended phosphorus fertilizer increased the yield of essential oil by 18.9%. In addition, menthol increased by 24.1% (highest) under a3 irrigation, using 25% of the optimal dosage of phosphate fertilizer and nonmycorrhizal inoculation. The maximum catalase and peroxidase activity was obtained in the treatment of <em>G. hoi </em>mycorrhizal fertilizer, after application of 25% recommended dose of phosphorus fertilizer and a2 and a3 irrigation.