Salicylic acid confers salt tolerance in potato plants by improving water relations, gaseous exchange, antioxidant activities and osmoregulation

BACKGROUND

Potato is an important vegetable; however, salt stress drastically affects its growth and yield. A pot experiment was therefore conducted to assess salicylic acid efficacy in improving performance of potato cultivars, grown under salt stress (50 mmol L^-1 ). Salicylic acid at 0.5 mmol L^-1 was sprayed on to potato plants after 1 week of salinity application.

RESULTS

Salt stress effects were ameliorated by salicylic acid effectively in both the studied cultivars. N-Y LARA proved more responsive to salicylic acid application than 720-110 NARC, which confirmed genetic variation between cultivars. Salicylic acid scavenged reactive oxygen species by improving antioxidant enzyme activities (superoxide dismutase, catalase, peroxidases) and regulating osmotic adjustment (proline, phenolic contents), which led to enhanced water relation and gaseous exchange attributes, and thereby increased potassium availability and reduced sodium content in potato leaves. Moreover, potato tuber yield showed a positive correlation with potassium content, photosynthesis and antioxidant enzyme activities.

CONCLUSION

Salt tolerance efficacy of salicylic acid is authenticated in improving potato crop performance under salt stress. Salicylic acid effect was more pronounced in N-Y LARA, reflecting greater tolerance than 720-110 NARC, which was confirmed as a susceptible cultivar. Hence salicylic acid at 0.5 mmol L^-1 and cultivation of N-Y LARA may be recommended in saline soil. © 2016 Society of Chemical Industry.

Quantitative trait loci (QTL) mapping for physiological and biochemical attributes in a Pasban90/Frontana recombinant inbred lines (RILs) population of wheat (Triticum aestivum) under salt stress condition

Salt stress causes nutritional imbalance and ion toxicity which affects wheat growth and production. A population of recombinant inbred lines (RILs) were developed by crossing Pasban90 (salt tolerant) and Frontana (salt suceptible) for identification of quantitative trait loci (QTLs) for physiological traits including relative water content, membrane stability index, water potential, osmotic potential, total chlorophyll content, chlorophyll a, chlorophyll b and biochemical traits including proline contents, superoxide dismutase, sodium content, potassium content, chloride content and sodium/potassium ratio by tagging 202 polymorphic simple sequence repeats (SSR) markers. Linkage map of RILs comprised of 21 linkage group covering A, B and D genome for tagging and maped a total of 60 QTLs with major and minor effect. B genome contributed to the highest number of QTLs under salt stress condition. Xgwm70 and Xbarc361 mapped on chromosome 6B was linked with Total chlorophyll, water potential and sodium content. The increasing allele for all these QTLs were advanced from parent Pasban90. Current study showed that Genome B and D had more potentially active genes conferring plant tolerance against salinity stress which may be exploited for marker assisted selection to breed salinity tolerant high yielding wheat varieties.

Effect of Drought Stress on Capsaicin and Antioxidant Contents in Pepper Genotypes at Reproductive Stage

Pepper is one of the most important vegetables and spices in the world. Principal pungency is contributed by secondary metabolites called capsaicinoids, mainly synthesized in the placenta of pepper fruit. Various factors, including drought, limit pepper production. Flowering is one of the most sensitive stages affected by drought stress. The current study was conducted to determine the effect of drought on different pepper genotypes at the flowering and pod formation stages. Hot pepper (Pusajuala and Ghotki) and Bell pepper (Green Wonder and PPE-311) genotypes were subjected to drought (35% field capacity) at two different stages (flowering (DF) and pod formation (DP) stage). In comparison, control plants were maintained at 65% field capacity. The data regarding flowering survival rates, antioxidant protein activity, and proline content, were collected. Results indicated that parameters like flower survival percentage, number of fruits per plant, and fruit weight had significant differences among the genotypes in both treatments. A high proline level was observed in Green Wonder at the pod formation stage compared to other genotypes. Capsaicin contents of hot pepper genotypes were affected at the pod formation stage. Antioxidants like GPX were highly active (190 units) in Ghotki at pod formation. Bell pepper genotypes had a high APX activity, highly observed (100 units) in PPE-311 at pod formation, and significantly differ from hot pepper genotypes. In the catalase case, all the genotypes had the highest values in DP compared to control and DF, but Pusajuala (91 units) and Green Wonder (83 units) performed best compared to other genotypes. Overall, the results indicate that drought stress decreased reproductive growth parameters and pungency of pepper fruit as most of the plant energy was consumed in defense molecules (antioxidants). Therefore, water availability at the flowering and pod formation stage is critical to ensure good yield and pepper quality.

Single nucleotide polymorphism based assessment of genetic diversity in local and exotic onion genotypes

BACKGROUND

Onion is an economically important vegetable cultivated worldwide on a large scale. Liberal exchange of germplasm and frequent selection caused narrow genetic diversity in most crops, including onion. Thus, it is essential to estimate and understand genetic diversity before launching of any breeding program. The current study was conducted to explore genetic diversity among 39 short-day onion genotypes (indigenous and exotic).

METHODS AND RESULTS

All the genotypes were evaluated for various phenotypic traits by using single nucleotide polymorphism (SNP) genotyping based on KASPar assays. Principal component analysis (PCA) was performed to determine the variability among genotypes. The four principal components with eigenvalue greater than 1 accounted for 67.5656% variability for quantitative traits, whereas first five principal components with eigenvalue greater than 0.7 accounted for 86.24% variation among the genotypes for qualitative traits. The principal component analysis identified diverse traits including bulb weight, bulb diameter, plant height, number of survived plants and vitamin C. These traits were further analyzed through ANOVA (Analysis of Variance) following augmented block design to describe genotypic variability for selected traits. Onion genotypes showed significant variation for bulb weight, bulb diameter and Vitamin C. Genotypic clustering based on PCA showed that 15 indigenous genotypes were clustered with exotic genotypes (14) while remaining indigenous genotypes (10) were distant. A total of 30 SNPs were used for assessment of genetic diversity out of these, 24 SNPs were detected with polymorphic loci (0.8%, heterozygosity), while only six markers were with monomorphic sites (0.2% heterozygosity). Subsequently, population structure analysis revealed three different populations indicating significant variability.

CONCLUSION

Conclusively, a significant similarity between exotic and a group of indigenous genotypes indicates direct adoption of exotic genotypes or their sister lines. A further broadening of the genetic base is required and could be done by crossing distant genotypes.

Cucumber grafting on indigenous cucurbit landraces confers salt tolerance and improves fruit yield by enhancing morpho-physio-biochemical and ionic attributes

Pakistan is the 8th most climate-affected country in the globe along with a semi-arid to arid climate, thereby the crops require higher irrigation from underground water. Moreover,  ~ 70% of pumped groundwater in irrigated agriculture is brackish and a major cause of secondary salinization. Cucumber (Cucumis sativus L.) is an important vegetable crop with an annual growth rate of about 3.3% in Pakistan. However, it is a relatively salt-sensitive crop. Therefore, a dire need for an alternate environment-friendly technology like grafting for managing salinity stress in cucumber by utilizing the indigenous cucurbit landraces. In this regard, a non-perforated pot-based study was carried out in a lath house to explore indigenous cucurbit landraces; bottle gourd (Lagenaria siceraria) (cv. Faisalabad Round), pumpkin (Cucurbit pepo. L) (cv. Local Desi Special), sponge gourd (Luffa aegyptiaca) (cv. Local) and ridge gourd (Luffa acutangula) (cv. Desi Special) as rootstocks for inducing salinity tolerance in cucumber (cv. Yahla F1). Four different salts (NaCl) treatments; T0 Control (2.4 dSm-1), T1 (4 dSm-1), T2 (6 dSm-1) and T3 (8 dSm-1) were applied. The grafted cucumber plants were transplanted into the already-induced salinity pots (12-inch). Different morpho-physio-biochemical, antioxidants, ionic, and yield attributes were recorded. The results illustrate that increasing salinity negatively affected the growing cucumber plants. However, grafted cucumber plants showed higher salt tolerance relative to non-grafted ones. Indigenous bottle gourd landrace (cv. Faisalabad Round) exhibited higher salt tolerance compared to non-grafted cucumber plants due to higher up-regulation of morpho-physio-biochemical, ionic, and yield attributes that was also confirmed by principal component analysis (PCA). Shoot and root biomass, chlorophylls contents (a and b), activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) enzymes, antioxidants scavenging activity (ASA), ionic (↑ K and Ca, ↓ Na), and yield-related attributes were found maximum in cucumber plants grafted onto indigenous bottle gourd landrace. Hence, the indigenous bottle gourd landrace 'cv. Faisalabad round' may be utilized as a rootstock for cucumber under a mild pot-based saline environment. However, indigenous bottle gourd landrace 'cv. Faisalabad round' may further be evaluated as rootstocks in moderate saline field conditions for possible developing hybrid rootstock and, subsequently, sustainable cucumber production.

Foliar Application of Salicylic Acid at Different Phenological Stages of Peach Fruit CV. 'Flordaking' Improves Harvest Quality and Reduces Chilling Injury during Low Temperature Storage

Peaches are well-liked amongst the stone fruits in Pakistan. The peach industry faces significant losses, from harvesting to marketing. The objective of this study was to investigate the effectiveness of foliar sprays of salicylic acid (SA) on the fruit quality of peaches (cv. 'Flordaking') at the harvest and postharvest life or stages. Different concentrations of SA (control, 1, 2 and 3 mM) were sprayed on the plants at three growth stages of fruit, i.e., the cell division, cell enlargement and pit-hardening stages. In general, all the SA treatments improved the fruit quality at harvest and maintained higher levels of flesh firmness, titratable acidity and ascorbic acid during storage. However, fruit weight loss, soluble solid contents, membrane leakage, chilling injury, color development, disease and decay incidence and the climacteric peak of ethylene were lowered by SA treatment after six weeks of low-temperature storage. SA at a 3-mM concentration was proven to be the most effective in maintaining the quality for a longer period of time during low-temperature storage. Based on the results, it can be concluded that the application of SA at fruit development stages can improve the harvest quality and storability of 'Flordaking' peaches.

Shattering and yield expression of sesame (Sesamum indicum L) genotypes influenced by paclobutrazol concentration under rainfed conditions of Pothwar

Seed shattering is a critical challenge that significantly reduces sesame production by 50%. These shattering losses can be reduced by selecting shattering resistant genotypes or by incorporating modern agronomic management such as paclobutrazol, which can boost productivity and prevent seed shattering in sesame. Two-years of field trials were conducted to examine the effect of sesame genotypes, environment, and paclobutrazol (PBZ) concentrations. Twelve sesame genotypes were used in a four-way factorial RCBD with three replications and five PBZ concentrations (T₀ = Control; T₁ = 150; T₂ = 300; T₃ = 450; and T₄ = 600 mg L^- 1) under rainfed conditions of Pothwar. The findings revealed significant variations in the major effects of all examined variables (genotypes, locations, years, and PBZ levels). Sesame genotypes PI-154304 and PI-175907 had the highest plant height, number of capsule plant^- 1, seed capsule^- 1, 1000 seed weight, biological yield, and seed yield, while also having the lowest seed losses and shattering percentage. Regarding environments, NARC-Islamabad generated the highest plant height, number of capsule plant^- 1, shattering percentage, and biological yield; however, the URF-Koont produced the highest seed yield with the lowest shattering percentage. Additionally, plant height, capsules plant^- 1, and biological yield were higher in 2021, while seed capsule^- 1, 1000 seed weight, seed losses, shattering percentage, and seed yield were higher in 2020. PBZ concentration affected all measured parameters; plant height and number of seed capsule^- 1 decreased with increasing PBZ concentrations. 450 mg L^- 1 PBZ concentration generated the highest biomass, number of capsules plant^- 1, and seed yield. At the same time, PBZ concentration 600 mg L^- 1 generated the smallest plant, the lowest seed capsules^- 1, the greatest thousand seed weight, and the lowest shattering percentage. The study concluded that paclobutrazol could dramatically reduce shattering percentage and shattering losses while increasing economic returns through better productivity. Based on the findings, the genotypes PI-154304 and PI-175907 with paclobutrazol level 450 mgL^- 1 may be suggested for cultivation in Pothwar farming community under rainfed conditions, as they showed promising shattering resistance as well as enhanced growth and yield.