Enhancing drought, heat shock, and combined stress tolerance in Myrobalan 29C rootstocks with foliar application of potassium nitrate.

BACKGROUND: Drought and heat stress are significant concerns to food security in arid and semi-arid regions, where global warming is predicted to increase both frequency and severity. To cope with these challenges, the use of drought-tolerant plants or technological interventions are essential. In this study, the effects of foliar potassium nitrate (KNO3) application on the stress tolerance and recovery of Myrobalan 29C rootstocks (Prunus cerasifera Ehrh.) were evaluated. These rootstocks are widely recognized for their adaptability and are extensively used in fruit production. To assess their response, the rootstocks were subjected to drought, heat shock, or a combination of both stressors. Additionally, they were treated with 1.0% KNO3 via foliar application. Throughout the stress and recovery periods, various morphological, physiological, and bio-chemical parameters were measured. RESULTS: Based on our results, KNO3 treatment improved LRWC, Chl stability, SC, and key stress markers like proline, MDA, H2O2, along with antioxidant enzymes CAT, SOD, POD during both stress and recovery phases. Moreover, our results emphasized KNO3's critical role in hormone regulation under stress. KNO3 application significantly altered hormone levels, notably increasing ABA during drought and heat shock stress, essential for stress response and adaptation. In contrast, IAA, GA, and cytokinin's significantly increased during the recovery phase in KNO3-treated plants, indicating improved growth regulation and stress recovery. In addition, KNO3 application improved the recovery process of the rootstocks by restoring their physiological and biochemical functions. CONCLUSION: This study suggests that the application of foliar KNO3 is an effective technique for enhancing the drought and heat tolerance as well as the recovery of Myrobalan 29C rootstocks. These results hold significant value for farmers, policymakers, and researchers, as they offer crucial insights into the development of drought-tolerant crops and the management of climate change's adverse effects on agriculture.

Selection and Molecular Characterization of Promising Plum Rootstocks (Prunus cerasifera L.) among Seedling-Origin Trees.

The plum (Prunus cerasifera Ehrh) has been used worldwide both as a genetic source for breeding new rootstocks and as clonal rootstock for many Prunus species. Considering situations where wild relatives of plums are endangered, in-depth characterization of rootstock traits of genetic diversity of plum germplasm of Turkey with many ecogeographical locations is crucial. In the present study, therefore, three steps were followed for the selection of rootstock candidates among the plum germplasm grown in the Middle Euphrates. This region is characterized by an extremely hot climate with extremely warm summers and very low precipitation in summers. Initially, 79 rootstock candidates were selected based on rootstocks traits, and Myrobalan 29C was also used for the control rootstock in all steps. Hardwood cuttings were taken from each rootstock candidate, and after the rooting process in rootstock candidates, 39 rootstock candidates outperforming other candidates were selected according to root characteristics. Based on rooting ability, forty rootstock candidates with the longest root length below 33.50 mm, root number below 3.00, and rooting cutting number below 30.00% were eliminated. The second step of the study focused on the dwarfing characteristics of 39 rootstock candidates, and 13 and Myrobalan 29C out of 39 rootstock candidates' dwarfing traits showed value higher compared to the other 26 rootstock candidates. Results indicated that the vigor of rootstock candidates was usually found to be strong (26), intermediate (4), and weak (9). Moreover, 13 out of 39 rootstock candidates' dwarfism trait was better than the other 26 rootstock candidates. In Step 3, some morphological, physiological, and molecular evaluations were conducted in 13 rootstock candidates and the Myrobalan 29C clone, and there were significant differences between both rootstock candidates and the parameters evaluated. PCA has also been indicated that the reference rootstock Myrobalan 29C was grouped with 63B62, 63B69, and 63B14. The highest genetic similarity was found between 63B11 and 63B16, as well as between 63B76 and 63B66, while the lowest genetic similarity was observed between 63B72 and 63B61 candidates. Overall, the findings presented here provide valuable information about the level of rootstock candidates that could potentially be superior among previously uncharacterized plum cultivars in this plum-growing region of Turkey.

Remediation of Cadmium Stress in Strawberry Plants Using Humic Acid and Silicon Applications.

(1) Background: Strawberry plants are strongly affected by heavy-metal-contaminated soils, which affects plant growth, yield and fruit quality. The aim of this work was to study the effects of a combination and individual application of silicon (Si) and humic acid (HA) on growth and development of Rubygem strawberries exposed to cadmium (Cd) in greenhouse conditions. (2) Methods: Morphological, physiological and biochemical parameters, including minerals in roots and leaves were determined. (3) Results: Cd stress in strawberry plants decreased plant fresh and dry weight; leaf stomatal conductance; leaf relative water content and chlorophyll content; number of leaves; leaf area; leaf N, P and K levels; and root P, N, Mg, K and Ca contents. Cd increased membrane permeability, leaf temperature, proline levels and lipid peroxidation. Si and HA individual applications to strawberries mitigated the negative effect of Cd stress on biochemical, physiological, morphological and minerals parameters by decreasing membrane permeability, leaf temperature, proline levels and lipid peroxidation. (4) Conclusions: Our findings highlighted that applications of Si, HA and Si + HA were effective in conferring Cd tolerance in strawberry plants by upregulating their many morphological, physiological and biochemical properties and reducing Cd stress.

Exogenous Nitric Oxide and Silicon Applications Alleviate Water Stress in Apricots.

Many plants confront several environmental stresses including heat, water stress, drought, salinity and high-metal concentrations that are crucial in defining plant productivity at different stages of their life cycle. Nitric oxide (NO) and Silicon (Si) are very effective molecules related in most of them and in varied biochemical events that have proven to be protective during cellular injury caused by some stress conditions like water stress. In the current work, we studied the effect of Si and NO alone and NO + Si interactive application on the response of plants exposed to water deficiency and well-watered plants for the Milord apricot variety. Water stress caused a reduce in chlorophyll content, dry and fresh weight, leaf area, stomatal conductivity, leaf relative water content and nutrient elements, while it caused an increase in leaf temperature, leaf proline, leaf malondialdehyde (MDA) content and membrane permeability. Si, NO and Si + NO combination treatments under water stress conditions significantly decreased the adverse effects of water stress on leaf temperature, leaf area, dry and fresh weight, stomata conductivity, relative water content, membrane permeability, L-proline and MDA content. The shoot dry weight, chlorophyll content, stomata conductivity and leaf relative water content in Si + NO treated apricot saplings increased by 59%, 55%, 12% and 8%, respectively. Combined treatment (Si + NO) was detected to be more effective than single applications (Si or NO) on some physiological, biochemical, morphological and nutritional properties of apricot under water stress conditions.

The effect of water stress on some morphological, physiological, and biochemical characteristics and bud success on apple and quince rootstocks.

The effects of different water stress (control, medium, and severe) on some morphological, physiological, and biochemical characteristics and bud success of M9 apple and MA quince rootstocks were determined. The results showed that water stress significantly affected most morphological, physiological, and biochemical characteristics as well as budding success on the both rootstocks. The increasing water stress decreased the relative shoot length, diameter, and plant total fresh and dry weights. Leaf relative water content and chlorophyll index decreased while electrolyte leakage increased with the increase of water stress in both rootstocks. An increase in water stress also resulted in reduction in budding success in Vista Bella/M9 (79.33% and 46.67%) and Santa Maria/MA (70.33% and 15.33%) combinations. However, the water stress in Santa Maria/MA was more prominent. The increase in water stress resulted in higher peroxidase activities as well as phenol contents in both rootstocks. Although catalase activity, anthocyanin, and proline contents increased with the impact of stress, this was not statistically significant. The results suggest that the impact of stress increased with the increase of water stress; therefore, growers should be careful when using M9 and MA rootstocks in both nursery and orchards where water scarcity is present.

Influence of rootstocks on growth, yield, fruit quality and leaf mineral element contents of pear cv. 'Santa Maria' in semi-arid conditions.

BACKGROUND: Rootstocks play an essential role to determining orchard performance of fruit trees. Pyrus communis and Cydonia oblonga are widely used rootstocks for European pear cultivars. The lack of rootstocks adapted to different soil conditions and different grafted cultivars is widely acknowledged in pear culture. Cydonia rootstocks (clonal) and Pyrus rootstocks (seedling or clonal) have their advantages and disadvantages. In each case, site-specific environmental characteristics, specific cultivar response and production objectives must be considered before choosing the best rootstock. In this study, the influence of three Quince (BA 29, Quince A = MA, Quince C = MC) and a local European pear seedling rootstocks on the scion yield, some fruit quality characteristics and leaf macro (N, P, K, Ca and Mg) and micro element (Fe, Zn, Cu, Mn and B) content of 'Santa Maria' pear (Pyrus communis L.) were investigated. RESULTS: Trees on seedling rootstock had the highest annual yield, highest cumulative yield (kg tree(-1)), largest trunk cross-sectional area (TCSA), lowest yield efficiency and lowest cumulative yield (ton ha(-1)) in the 10(th) year after planting. The rootstocks had no significant effect on average fruit weight and fruit volume. Significantly higher fruit firmness was obtained on BA 29 and Quince A. The effect of rootstocks on the mineral element accumulation (N, K, Ca, Mg, Fe, Zn, Cu, Mn and B) was significant. Leaf analysis showed that rootstocks used had different mineral uptake efficiencies throughout the early season. CONCLUSION: The results showed that the rootstocks strongly affected fruit yield, fruit quality and leaf mineral element uptake of 'Santa Maria' pear cultivar. Pear seedling and BA 29 rootstock found to be more prominent in terms of several characteristics for 'Santa Maria' pear cultivar that is grown in highly calcareous soil in semi-arid climate conditions. We determined the highest N, P (although insignificant), K, Ca, Mg, Fe and Cu mineral element concentrations on the pear seedling and BA 29 rootstocks. According to the results, we recommend the seedling rootstock for normal density plantings (400 trees ha(-1)) and BA 29 rootstock for high-density plantings (800 trees ha(-1)) for 'Santa Maria' pear cultivar in semi-arid conditions.

Influence of rootstocks on growth, yield, fruit quality and leaf mineral element contents of pear cv. 'Santa Maria' in semi-arid conditions

BACKGROUND: Rootstocks play an essential role to determining orchard performance of fruit trees. Pyrus communisand Cydonia oblonga are widely used rootstocks for European pear cultivars. The lack of rootstocks adapted to different soil conditions and different grafted cultivars is widely acknowledged in pear culture. Cydonia rootstocks (clonal) and Pyrus rootstocks (seedling or clonal) have their advantages and disadvantages. In each case, site-specific environmental characteristics, specific cultivar response and production objectives must be considered before choosing the best rootstock. In this study, the influence of three Quince (BA 29, Quince A = MA, Quince C = MC) and a local European pear seedling rootstocks on the scion yield, some fruit quality characteristics and leaf macro (N, P, K, Ca and Mg) and micro element (Fe, Zn, Cu, Mn and B) content of 'Santa Maria' pear (Pyrus communis L.) were investigated. RESULTS: Trees on seedling rootstock had the highest annual yield, highest cumulative yield (kg tree(-1)), largest trunk cross-sectional area (TCSA), lowest yield efficiency and lowest cumulative yield (ton ha(-1)) in the 10th year after planting. The rootstocks had no significant effect on average fruit weight and fruit volume. Significantly higher fruit firmness was obtained on BA 29 and Quince A. The effect of rootstocks on the mineral element accumulation (N, K, Ca, Mg, Fe, Zn, Cu, Mn and B) was significant. Leaf analysis showed that rootstocks used had different mineral uptake efficiencies throughout the early season. CONCLUSION: The results showed that the rootstocks strongly affected fruit yield, fruit quality and leaf mineral element uptake of 'Santa Maria' pear cultivar. Pear seedling and BA 29 rootstock found to be more prominent in terms of several characteristics for 'Santa Maria' pear cultivar that is grown in highly calcareous soil in semi-arid climate conditions. We determined the highest N, P (although insignificant), K, Ca, Mg, Fe and Cu mineral element concentrations on the pear seedling and BA 29 rootstocks. According to the results, we recommend the seedling rootstock for normal density plantings (400 trees ha(-1)) and BA 29 rootstock for high-density plantings (800 trees ha(-1)) for 'Santa Maria' pear cultivar in semi-arid conditions.