Rejuvenating potato growth and yield in challenging semiarid and saline sandy Cholistan: harnessing PGPB-coated N and P application strategies

BACKGROUND

Potato serves as a major non-cereal food crop and income source for small-scale growers in Punjab, Pakistan. Unfortunately, improper fertilization practices have led to low crop yields, worsened by challenging environmental conditions and poor groundwater quality in the Cholistan region. To address this, we conducted an experiment to assess the impact of two fertilizer application approaches on potato cv. Barna using plant growth-promoting bacteria (PGPB) coated biofertilizers. The first approach, termed conventional fertilizer application (CFA), involved four split applications of PGPB-coated fertilizers at a rate of 100:75 kg acre-1 (N and P). The second, modified fertilizer application (MFA), employed nine split applications at a rate of 80:40 kg acre-1.

RESULTS

The MFA approach significantly improved various plant attributes compared to the CFA. This included increased plant height (28%), stem number (45%), leaf count (46%), leaf area index (36%), leaf thickness (three-folds), chlorophyll content (53%), quantum yield of photosystem II (45%), photosynthetically active radiations (56%), electrochromic shift (5.6%), proton flux (24.6%), proton conductivity (71%), linear electron flow (72%), photosynthetic rate (35%), water use efficiency (76%), and substomatal CO2 (two-folds), and lowered non-photochemical quenching (56%), non-regulatory energy dissipation (33%), transpiration rate (59%), and stomatal conductance (70%). Additionally, the MFA approach resulted in higher tuber production per plant (21%), average tuber weight (21.9%), tuber diameter (24.5%), total tuber yield (29.1%), marketable yield (22.7%), seed-grade yield (9%), specific gravity (9.6%), and soluble solids (7.1%). It also reduced undesirable factors like goli and downgrade yields by 57.6% and 98.8%, respectively. Furthermore, plants under the MFA approach exhibited enhanced nitrogen (27.8%) and phosphorus uptake (40.6%), with improved N (26.1%) and P uptake efficiency (43.7%) compared to the CFA approach.

CONCLUSION

The use of PGPB-coated N and P fertilizers with a higher number of splits at a lower rate significantly boosts potato production in the alkaline sandy soils of Cholistan.

Layer by layer application of chitosan and carboxymethyl cellulose coatings delays ripening of mango fruit by suppressing cell wall polysaccharides disassembly

Mango is a climacteric fruit that ripens quickly after harvest due to its climacteric nature. Edible coatings have been reported to delay the ripening of various harvested fruit. The efficacy of the applied edible coatings could be improved by using in combination as a layer-by-layer (LBL) approach. So, the influence of LBL application of chitosan (CH) and carboxymethyl cellulose (CMC) was studied on mangoes during postharvest storage at 15 °C for 20 days. Mangoes were coated with monolayers of CH (1 % w/v) and CMC (1 % w/v) as well as LBL application of CH and CMC and were compared with control. The treatment of mangoes with CH and CMC-based LBL treatment resulted in lower decay percentage and weight loss along with higher total chlorophyll pigments and suppressed total carotenoid accumulation. The LBL application of CH and CMC showed lower activity of chlorophyll degrading such as chlorophyllase (CPS), pheophytinase (Phe), Mg-dechalatase (MGD) and chlorophyll degrading peroxidase (Chl-POD) enzymes as well as reduced changes in b*, a* and L* along with a suppressed increase in ethylene (EP) and CO2 production (CPR) rates having higher antioxidant such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) enzymes activity. In addition, mangoes coated with LBL treatment of CH and CMC exhibited lower water-soluble pectin (WSP) and higher protopectin (PP) having higher concentrations of chelate soluble (CSP) and sodium carbonate-soluble pectin (SCP). Similarly, LBL-coated mangoes showed significantly higher hemicellulose (HCLS) and cellulose (CLS) contents in contrast with control. It was observed that mangoes coated with CH and CMC-based LBL coating exhibited higher flesh firmness and showed suppressed cellulase (CS), pectin methylesterase (PME), polygalacturonase (PG) and β-galactosidase (β-Gal) enzymes activity. The concentrations of total soluble solids and ripening index were markedly lower and titratable acidity was higher in the LBL-based coating treatment in comparison with control. In conclusion, LBL treatment based on CH and CMC coatings could be used for the delay of ripening and softening of harvested mangoes.

Combined application of hot water treatment and eucalyptus leaf extract postpones seneṣcence in harvested green chilies by conserving their antioxidants: a sustainable approach

BACKGROUND

Green chili is the predominant vegetable in tropical and subtropical regions with high economic value. However, after harvest, it exhibits vigorous metabolic activities due to the high moisture level, leading to a reduction in bioactive compounds and hence reduced shelf life and nutritional quality. Low temperature storage results in the onset of chilling injury symptoms. Therefore, developing techniques to increase the shelf life of green chilies and safeguard their nutritional value has become a serious concern for researchers. In this regard, an experiment was conducted to evaluate the impact of the alone or combined application of hot water treatment (HWT) (45 °C for 15 min) and eucalyptus leaf extract (ELE) (30%) on 'Golden Hot' chilies in comparison to the control. After treatment, chilies were stored at 20 ± 1.5 °C for 20 days.

RESULTS

HWT + ELE-treated chilies had a significant reduction in fruit weight loss (14.6%), fungal decay index (35%), red chili percentage (41.2%), soluble solid content (42.9%), ripening index (48.9%), and reactive oxygen species production like H2O2 (55.1%) and O-2 (46.5%) during shelf in comparison to control, followed by the alone application of HWT and ELE. Furthermore, the combined use of HWT and ELE effectively improved the antioxidative properties of stored chilies including DPPH radical scavenging activities (54.6%), ascorbic acid content (28.4%), phenolic content (31.8%), as well as the enzyme activities of POD (103%), CAT (128%), SOD (26.5%), and APX (43.8%) in comparison to the control. Additionally, the green chilies underwent HWT + ELE treatment also exhibited higher chlorophyll levels (100%) and general appearance (79.6%) with reduced anthocyanin content (40.8%) and wrinkling (43%), leading to a higher marketable fruit (41.3%) than the control.

CONCLUSION

The pre-storage application of HWT and ELE could be used as an antimicrobial, non-chemical, non-toxic, and eco-friendly treatment for preserving the postharvest quality of green chilies at ambient temperature (20 ± 1.5 °C).

Postharvest starch and sugars adjustment in potato tubers of wide-ranging dormancy genotypes subjected to various sprout forcing techniques

The development of an efficient, safe, and environment-friendly technique to terminate tuber dormancy in potatoes (Solanum tuberosum L.) is of great concern due to the immense scope of multiple cropping all over the globe. The breakage of tuber dormancy has been associated with numerous physiological changes, including a decline in the level of starch and an increase in the levels of sugars during storage of freshly harvested seed potatoes, although their consistency across genotypes and various dormancy-breaking techniques have not yet been fully elucidated. The purpose of the present research is to assess the efficacy of four different dormancy-breaking techniques, such as soaking in 90, 60, or 30 mg L-1 solutions of benzyl amino purine (BAP) and 30, 20, or 10 mg L-1 gibberellic acid (GA3) alone and in the combination of optimized concentrations; cold pre-treatment at 6, 4, or 2 °C; electric shock at 80, 60, 40, or 20 Vs; and irradiation at 3.5, 3, 2.5, 2, 1.5, or 1 kGy on the tuber dormancy period and sprout length of six genotypes. Furthermore, the changes that occurred in tuber weight and endogenous starch, sucrose, fructose, and glucose contents in experimental genotypes following the application of these techniques were also examined. Overall, the most effective technique to terminate tuber dormancy and hasten spout growth was the combined application of BAP and GA3, which reduced the length of dormancy by 9.6 days compared to the untreated control, following 6.7 days of electric current, 4.4 days of cold pre-treatment, and finally irradiation (3.3 days). The 60 mg L-1 solution of BAP greatly reduced the dormancy period in all genotypes but did not affect the sprout length at all. The genotypes showed a weak negative correlation (r =  - 0.4) (P < 0.05) of endogenous starch contents with dormancy breakage and weight loss or a moderate (r =  - 0.5) correlation with sprout length, but a strong positive correlation (r = 0.8) of tuber glucose, fructose, and sucrose contents with dormancy breakage and weight loss. During 3 weeks of storage, sprouting commencement and significant weight loss occurred as tuber dormancy advanced towards breakage due to a reduction in starch and an increase in the sucrose, fructose, and glucose contents of the tubers. These findings could be advantageous for postponing or accelerating seed potato storage as well as investigating related physiological research in the future.

The combined application of Arabic gum coating and γ-aminobutyric acid mitigates chilling injury and maintains eating quality of 'Kinnow' mandarin fruits

Low temperature storage of citrus generally extends the storage potential but leads to chilling injury appearance on the rind of fruits. The said physiological disorder has been found associated with changes in the metabolism of cell walls and other attributes. In this work, the influence of Arabic gum [AG (10 %)] and γ-amminobutyric acid [GABA (10 mmol L^-1)] either alone or in combined form was studied on fruits of 'Kinnow' mandarin during storage at 5 ± 1 °C for 60 days. The results exhibited that the combined AG + GABA treatment significantly suppressed weight loss (5.13 %), chilling injury (CI) symptoms (2.41 score), incidence of disease (13.33 %), respiration rate [(4.81 μmol kg^-1 h^-1) RPR] and ethylene production [(0.86 nmol kg^-1 h^-1) EPR]. In addition, AG + GABA application reduced relative electrolyte (37.89 %) leakage (REL), malondialdehyde [(25.99 nmol kg^-1) MDA], superoxide anion [(15.23 nmol min^-1 kg^-1) O₂^•-] and hydrogen peroxide [(27.08 nmol kg^-1) H₂O₂] along with lower lipoxygenase [(23.81 U mg^-1 protein) LOX] and phospholipase D [(14.07 U mg^-1 protein) PLD] enzyme activities compared with control. The AG + GABA treated 'Kinnow' group showed higher glutamate decarboxylase [(43.18 U mg^-1 protein) GAD] and lower GABA transaminase [(15.93 U mg^-1 protein) GABA-T] activity having higher endogenous GABA (42.02 mg kg^-1) content. The fruits treated with AG + GABA exhibited higher cell walls (CW) components such as Na₂CO₃-soluble pectin [(6.55 g kg^-1) NCSP], chelate-soluble pectin [(7.13 g kg^-1) CSP] and protopectin [(11.03 g kg^-1) PRP] concentrations along with lower water-soluble pectin [(10.64 g kg^-1) WSP] compared to control. In addition, 'Kinnow' fruits treated with AG + GABA showed higher firmness (8.63 N) and lower activities of CW degrading such as cellulase [(11.23 U mg^-1 protein) CX], polygalacturonase [(22.59 U mg^-1 protein) PG], pectin methylesterase [(15.61 U mg^-1 protein) PME] and β-galactosidase [(20.64 U mg^-1 protein) β-Gal] enzymes. The activity of catalase [(41.56 U mg^-1 protein) CAT], ascorbate peroxidase [(55.57 U mg^-1 protein) APX], superoxide dismutase [(52.93 U mg^-1 protein) SOD] and peroxidase [(31.02 U mg^-1 protein) POD] was also higher in combined treatment. In addition, AG + GABA treated fruits showed better biochemical and sensory attributes than the control. So, combined AG + GABA could be used for CI mitigation and storage life prolongation of 'Kinnow' fruits.

Postharvest dormancy-related changes of endogenous hormones in relation to different dormancy-breaking methods of potato (Solanum tuberosum L.) tubers

Development of an efficient and eco-friendly technique to break tuber dormancy in potato (Solanum tuberosum L.) is highly demanded due to the production of two or more crops annually. Several physiological and hormonal changes have been found to be related to the breaking of tuber dormancy; however, their consistency with genotypes and different protocols have not been well clarified. This study aims to evaluate the effectiveness of four dormancy-breaking methods, that is, plant growth regulator (PGR) dipping in 30, 60, or 90 mgL^-1 benzyl amino purine (BAP) and 10, 20, or 30 mgL^-1 gibberellic acids (GA3) alone and in the combination of optimized concentrations; electric current application at 20, 40, 60, or 80 Vs; cold pre-treatment at 2, 4, or 6 °C; irradiation at 1, 1.5, 2, 2.5, 3, or 3.5 kGy. In addition, changes in endogenous levels of abscisic acid (ABA), zeatin (ZT), and gibberellin A₁ (GA₁) in six potato genotypes after subjecting to these methods were investigated. Overall, the highest effective method for dormancy duration was the PGR application which shortened the duration by 18 days, followed by electric current (13 days), cold pre-treatment (9 days), and then irradiation (7 days). The solution of 60 mgL^-1 BAP significantly reduced the dormancy duration in all genotypes but did not have a significant effect on the sprout length. While 20 mgL^-1 GA₃ produced maximum sprout length with a non-significant effect on dormancy duration. The genotype × PGR interaction for dormancy duration was more pronounced in short- and medium-term dormancy genotypes than in long-term dormancy genotypes. The genotypes displayed a significant positive correlation between dormancy duration and ABA levels but exhibited a negative correlation between dormancy duration and ZT as well as GA₁ levels. From the first to the third week of storage, ABA was decreased in tubers while, however, ZT and GA₁ were increased. The obtained results could be useful for the postharvest storage of potato tuber and the related field of physiological investigation in future.