Physiological, Morphological Changes and Storage Root Yield of Sweetpotato [Ipomoea batatas (L.) Lam.] under PEG-Induced Water Stress

Sweetpotato is an important tuberous root crop rich in nutrients such as vitamins and carbohydrates, and can grow well in arid regions with less water consuming crop. The aim of this research was to evaluate the storage root yields, physiological, biochemical and morphological traits in sweetpotato cv. ‘Japanese Yellow’ subjected to polyethylene glycol (PEG)-induced water deficit. At harvest (4 months after planting) the number of storage roots per plant and storage root fresh weight in sweetpotato treated with 5% PEG (-0.54 MPa) in nutrient solution of hydroponic culture declined by 20.0% and 47.4% compared to the control without PEG, respectively. Leaf area and leaf dry weight significantly decreased by 85.6% and 95.3%, respectively when exposed to water deficit stress. Sucrose content (114.7 mg g-1 dry weight; DW) in storage roots of sweetpotato grown under PEG-induced water deficit conditions was enriched by 2.2 fold of control (52.5 mg g-1 DW) and was greater than in storage roots derived from soil culture (70.3 mg g-1 DW). Total soluble sugar in the root and storage root tissues was enriched and may play a key role as osmotic adjustment (OA) in PEG-induced water stressed plants. Free proline and sucrose contents were also dominated in the leaf tissues to maintain the leaf osmotic potential in water stressed plants. In addition, chlorophyll degradation, chlorophyll fluorescence diminution and stomatal closure were found in plants grown under PEG-induced water deficit conditions, leading to reduction in net photosynthetic rate (Pn) and subsequently lesser amounts of glucose and fructose contents in the leaf tissues. Sucrose and free proline in the roots of sweetpotato play a key role as major osmotic adjustment when subjected to PEG-induced water deficit condition. Basic knowledge gained from this research will further be investigated the drought defense mechanism in sweetpotato via osmoregulation system

Water-Deficit Tolerance in Sweet Potato [Ipomoea batatas (L.) Lam.] by Foliar Application of Paclobutrazol: Role of Soluble Sugar and Free Proline

The objective of this study was to elevate water deficit tolerance by improving soluble sugar and free proline accumulation, photosynthetic pigment stabilization, photosynthetic abilities, growth performance and storage root yield in sweet potato cv. ‘Tainung 57’ using a foliar application of paclobutrazol (PBZ). The experiment followed a Completely Randomized Block Design with four concentrations of PBZ: 0 (control), 17, 34, and 51 μM before exposure to 47.5% (well irrigation), 32.3% (mild water deficit) or 17.5% (severe water deficit) soil water content. A sweet potato cultivar, ‘Japanese Yellow’, with water deficit tolerance attributes was the positive check in this study. Total soluble sugar content (sucrose, glucose, and fructose) increased by 3.96-folds in ‘Tainung 57’ plants treated with 34 μM PBZ grown under 32.3% soil water content (SWC) compared to the untreated plants, adjusting osmotic potential in the leaves and controlling stomatal closure (represented by stomatal conductance and transpiration rate). In addition, under the same treatment, free proline content (2.15 μmol g-1 FW) increased by 3.84-folds when exposed to 17.5% SWC. PBZ had an improved effect on leaf size, vine length, photosynthetic pigment stability, chlorophyll fluorescence, and net photosynthetic rate; hence, delaying wilting symptoms and maintaining storage root yield (26.93 g plant-1) at the harvesting stage. A positive relationship between photon yield of PSII (ΦPSII) and net photosynthetic rate was demonstrated (r2 = 0.73). The study concludes that soluble sugar and free proline enrichment in PBZ-pretreated plants may play a critical role as major osmoprotectant to control leaf osmotic potential and stomatal closure when plants were subjected to low soil water content, therefore, maintaining the physiological and morphological characters as well as storage root yield

Exogenous Foliar Application of Glycine Betaine to Alleviate Water Deficit Tolerance in Two Indica Rice Genotypes under Greenhouse Conditions

The aim of this investigation was to enhance overall growth, yield attributes as well as physio-biochemical adaptive strategies by exogenous foliar application of glycine betaine (GlyBet) in two rice varieties against water deficit stress under greenhouse conditions. Rice crop cvs. RD43 (low amylose content) and SPR1 (high amylose content) grown in clay pots containing garden soil until booting stage were chosen as the test plant material, sprayed by 0 (control) or 100 mM GlyBet and subsequently subjected to: MWD (mild water deficit by 8 d water withholding; 24.80% SWC; Soil water content) or SWD (severe water deficit by 14 d water withholding; 13.63% SWC) or WW (well-watered conditions or control). Free proline content in cv. RD43 was rapidly increased in relation to the degree of water deficit and suppressed by exogenous GlyBet, while free proline in cv. SPR1 was lower than cv. RD43. Overall growth performances and yield traits in both cultivars under MWD were maintained by exogenous application of GlyBet; however, these parameters declined under SWD even after the GlyBet application. Degradation of photosynthetic pigments and chlorophyll fluorescence in pretreated GlyBet plants under SWD were prevented, resulting in elevated net photosynthetic rate (Pn). Interestingly, Pn was very sensitive parameter that sharply declined under SWD in both RD43 and SPR1 genotypes. Positive relationships between physio-morphological and biochemical changes in rice genotypes were demonstrated with high correlation co-efficiency. Based on the key results, it is concluded that foliar GlyBet application may play an important role in drought-tolerant enhancement in rice crops

Physiological, Morphological Changes and Storage Root Yield of Sweetpotato [Ipomoea batatas (L.) Lam.] under PEG-Induced Water Stress

Sweetpotato is an important tuberous root crop rich in nutrients such as vitamins and carbohydrates, and can grow well in arid regions with less water consuming crop. The aim of this research was to evaluate the storage root yields, physiological, biochemical and morphological traits in sweetpotato cv. ‘Japanese Yellow’ subjected to polyethylene glycol (PEG)-induced water deficit. At harvest (4 months after planting) the number of storage roots per plant and storage root fresh weight in sweetpotato treated with 5% PEG (-0.54 MPa) in nutrient solution of hydroponic culture declined by 20.0% and 47.4% compared to the control without PEG, respectively. Leaf area and leaf dry weight significantly decreased by 85.6% and 95.3%, respectively when exposed to water deficit stress. Sucrose content (114.7 mg g-1 dry weight; DW) in storage roots of sweetpotato grown under PEG-induced water deficit conditions was enriched by 2.2 fold of control (52.5 mg g-1 DW) and was greater than in storage roots derived from soil culture (70.3 mg g-1 DW). Total soluble sugar in the root and storage root tissues was enriched and may play a key role as osmotic adjustment (OA) in PEG-induced water stressed plants. Free proline and sucrose contents were also dominated in the leaf tissues to maintain the leaf osmotic potential in water stressed plants. In addition, chlorophyll degradation, chlorophyll fluorescence diminution and stomatal closure were found in plants grown under PEG-induced water deficit conditions, leading to reduction in net photosynthetic rate (Pn) and subsequently lesser amounts of glucose and fructose contents in the leaf tissues. Sucrose and free proline in the roots of sweetpotato play a key role as major osmotic adjustment when subjected to PEG-induced water deficit condition. Basic knowledge gained from this research will further be investigated the drought defense mechanism in sweetpotato via osmoregulation system

Regulation of anthocyanin accumulation in rice (<i>Oryza sativa</i> L. subsp. <i>indica</i>) using MgSO₄ spraying and low temperature

<p>Pericarp pigmented grains of rice have been reported as anthocyanin enriched source of antioxidants. The aim of this investigation was to regulate anthocyanin accumulation in pericarp pigmented rice cv. ‘Hom Nil’ using 0, 10, 50, and 100 mM MgSO₄ foliar spray. The level of magnesium content in the leaf tissues treated with 100 mM MgSO₄ for 2 d increased 2.6 times over control (0 mM MgSO₄). After growing the treated plants under 16°C for 28 d, photosynthetic abilities were reduced by 17−93%, leading to retarded plant height (39−42% less than control). In addition, grain yield per panicle of the plants grown under 16°C for 28 d was reduced by 26−75% compared to the plants grown under 32°C.Total anthocyanin concentration, cyanidin-3-glucoside and peonidin-3-glucoside in the pericarp of the grains derived from the rice treated with 100 mM MgSO₄ was increased 3.8 times over the control. Peonidin-3-glucoside, a dominant compound was reported for the first time. The study concludes that Mg−enrichment may play a key role as a metalloid in stabilizing anthocyanin, a secondary metabolite in the leaf sheath tissues and pericarp of grains in ‘Hom Nil’ rice cultivar.</p

Data_Sheet_1_Determination of traits responding to iron toxicity stress at different stages and genome-wide association analysis for iron toxicity tolerance in rice (Oryza sativa L.).zip

Rice is the staple food for more than half of the world’s population. Iron toxicity limits rice production in several regions of the world. Breeding Fe-tolerant rice varieties is an excellent approach to address the problem of Fe toxicity. Rice responds differently to Fe toxicity at different stages. Most QTLs associated with Fe toxicity have been identified at the seedling stage, and there are very few studies on Fe toxicity across different stages. In this study, we investigated agro-morphological and physiological traits in response to Fe toxicity in a rice diversity panel at seedling, vegetative, and reproductive stages and applied GWAS to identify QTLs/genes associated with these traits. Among agro-morphological and physiological parameters, leaf bronzing score (LBS) is a key parameter for determining Fe toxicity response at all stages, and SDW could be a promising parameter at the seedling stage. A total of 29 QTLs were identified on ten chromosomes. Among them, three colocalized QTLs were identified on chromosome 5, 6, and 11. Several QTLs identified in this study overlapped with previously identified QTLs from bi-parental QTL mapping and association mapping. Two genes previously reported to be associated with iron homeostasis were identified, i.e., LOC_Os01g72370 (OsIRO2, OsbHLH056) and LOC_Os04g38570 (OsABCB14). In addition, based on gene-based haplotype analysis, LOC_Os05g16670 was identified as a candidate gene for the colocalized QTL on chromosome 5 and LOC_Os11g18320 was identified as a candidate gene for the colocalized QTL on chromosome 11. The QTLs and candidate genes identified in this study could be useful for rice breeding programs for Fe toxicity tolerance.</p