Development of rapid and inexpensive screening tools for heat and drought stress tolerance is needed and will be helpful in cotton breeding programs and selecting cultivars for a niche environment. ...In this study, several pollen-based traits at optimum and high temperatures and physiological parameters measured during the boll-filling period were used to evaluate variability among the cultivars for heat and drought stresses. Principal component analysis and drought stress response index methods were used to categorize cotton cultivars into three heat and drought tolerant clusters. Based on the combined analysis, PX532211WRF has been identified as heat- and drought-tolerant, and would be expected to perform better under both heat- and drought-stressed environments. A poor correlation between reproductive and physiological indices indicates that screening breeders have to use different traits to screen cultivars for reproductive and vegetative tolerance. Identified traits could serve as valuable screening tools in cotton breeding programs aimed at developing genotypes to a changing climate. Moreover, cultivar-dependent relative scores will aid in the identification of cultivars best suited to niche environments to alleviate the influences of abiotic stresses at both vegetative and reproductive stages.
Elevated CO
2
along with drought is a serious global threat to crop productivity. Therefore, understanding the molecular mechanisms plants use to protect these stresses is the key for plant growth ...and development. In this study, we mimicked natural stress conditions under a controlled Soil-Plant-Atmosphere-Research (SPAR) system and provided the evidence for how miRNAs regulate target genes under elevated CO
2
and drought conditions. Significant physiological and biomass data supported the effective utilization of source-sink (leaf to root) under elevated CO
2
. Additionally, elevated CO
2
partially rescued the effect of drought on total biomass. We identified both known and novel miRNAs differentially expressed during drought, CO
2
, and combined stress, along with putative targets. A total of 32 conserved miRNAs belonged to 23 miRNA families, and 25 novel miRNAs were identified by deep sequencing. Using the existing sweet potato genome database and stringent analyses, a total of 42 and 22 potential target genes were predicted for the conserved and novel miRNAs, respectively. These target genes are involved in drought response, hormone signaling, photosynthesis, carbon fixation, sucrose and starch metabolism, etc. Gene ontology and KEGG ontology functional enrichment revealed that these miRNAs might target transcription factors (MYB, TCP, NAC), hormone signaling regulators (ARF, AP2/ERF), cold and drought factors (corA), carbon metabolism (ATP synthase, fructose-1,6-bisphosphate), and photosynthesis (photosystem I and II complex units). Our study is the first report identifying targets of miRNAs under elevated CO
2
levels and could support the molecular mechanisms under elevated CO
2
in sweet potato and other crops in the future.
Temperature impacts several growth and developmental processes in sweetpotato Ipomoea batatas L. (Lam) including storage root (SR) initiation. To quantify early season growth and developmental ...responses of sweetpotato, an experiment was conducted using sunlit growth chambers at a wide range of day/night temperatures, 20/12, 25/17, 30/22, 35/27, and 40/32°C, from transplanting to 59 d using cultivar Beauregard. Growth and developmental rates were estimated from plants harvested at regular intervals. Total and SR numbers recorded at each harvest were analyzed by fitting sigmoidal curves to estimate SR initiation rates. With increasing temperature, SR conversion efficiency increased quadratically with an optimum at 23.9°C. Adventitous and SR developmental rates were increased linearly and quadratically, respectively, with increasing temperature, and maximum rate of SR initiation was reached at 29.5°C in 16.7 d. Vine and leaf area growth rates showed quadratic trends with temperature with maximum rates at 29 and 33°C, respectively. While quadratic functions best described temperature responses of total, stem, and SR biomass, the optimum temperatures varied among them at 29.2, 30.1, and 26.5°C, respectively. Leaf biomass, conversely, increased linearly with temperature. Fraction of biomass partitioned to roots declined linearly and at high temperature it declined by 75%, compared to the fraction at SR optimum temperature. The SR production efficiency declined from 0.43 to 0.08 g SR kg−1 total weight, and dropped by 81% at high temperature relative to optimum. Quantified growth and developmental responses derived from the developed temperature‐dependent functional algorithms will be useful to develop sweetpotato crop models and management decisions.
Temperature affects reproductive potential, aesthetic, and commercial value of ornamental peppers (Capsicum annuum L.). Limited information is available on cultivar tolerance to temperature stress. ...An experiment was conducted using pollen and physiological parameters to assess high and low temperature tolerance in ornamental peppers. In vitro pollen germination (PG) and pollen tube length (PTL) of 12 morphologically diverse ornamental pepper cultivars were measured at a range of temperatures, 10 to 45 degrees C with 5 degrees C increments. Cell membrane thermostability (CMT), chlorophyll stability index (CSI), canopy temperature depression (CTD), and pollen viability (PV) were measured during flowering. From the modified bilinear temperature-PG and PTL response functions, cardinal temperatures (Tmin, Topt, and Tmax) for PG and PTL and maximum PG (PGmax) and PTL (PTLmax) were estimated. Cultivars varied significantly for PG, PTL, cardinal temperatures for PG and PTL, and all three physiological parameters. Cumulative temperature response index (CTRI) of each cultivar, calculated as the sum of 12 individual temperature responses derived from PV, PGmax, PTLmax, Tmin, Topt, and Tmax for PG and PTL, CMT, CTD, and CSI were used to distinguish differences among the cultivars and classify for high (heat) and low (cold) temperature tolerance. Based on CTRI-heat, cultivars were classified as heat-sensitive ('Black Pearl', 'Red Missile', and 'Salsa Yellow'), intermediate ('Calico', 'Purple Flash', 'Sangria', and 'Variegata'), and heat-tolerant ('Chilly Chili', 'Medusa', 'Thai Hot', 'Explosive Ember', and 'Treasures Red'). Similarly, cultivars were classified for cold tolerance as cold-sensitive, moderately cold-sensitive, moderately cold-tolerant, and cold-tolerant based on CTRI-cold. 'Red Missile' and 'Salsa Yellow' were classified as cold-tolerant. Cultivar screening using pollen parameters will be ideal for reproductive temperature tolerance, whereas physiological parameters will be suitable for screening vegetative temperature tolerance. The identified heat- and cold-tolerant cultivars are potential candidates in breeding programs to develop new ornamental and vegetable pepper genotypes for high and low temperature tolerance.
Upland cotton (
L.) growth and development during the pre-and post-flowering stages are susceptible to high temperature and drought. We report the field-based characterization of multiple ...morpho-physiological and reproductive stress resilience traits in 11 interspecific chromosome substitution (CS) lines isogenic to each other and the inbred
line TM-1. Significant genetic variability was detected (
< 0.001) in multiple traits in CS lines carrying chromosomes and chromosome segments from CS-B (
) and CS-T (
). Line CS-T15sh had a positive effect on photosynthesis (13%), stomatal conductance (33%), and transpiration (24%), and a canopy 6.8 °C cooler than TM-1. The average pollen germination was approximately 8% greater among the CS-B than CS-T lines. Based on the stress response index, three CS lines are identified as heat- and drought-tolerant (CS-T07, CS-B15sh, and CS-B18). The three lines demonstrated enhanced photosynthesis (14%), stomatal conductance (29%), transpiration (13%), and pollen germination (23.6%) compared to TM-1 under field conditions, i.e., traits that would expectedly enhance performance in stressful environments. The generated phenotypic data and stress-tolerance indices on novel CS lines, along with phenotypic methods, would help in developing new cultivars with improved resilience to the effects of global warming.
Soil moisture‐dependent, quantitative information on sweetpotato Ipomoea batatas L. (Lam) plant processes is vital for crop management and modeling because of the projected shrinking and uneven ...distributions of rainfall and irrigation water supply due to climate change. This study was conducted to quantify the growth, physiology, biomass, and storage root yield responses of sweetpotato under four evapotranspiration‐based irrigation treatments (100, 60, 40, and 20% ET) in sunlit growth chambers. Irrigation treatments were imposed from 41 to 97 d after transplanting. Midday leaf water potentials (LWP) and soil moisture contents were measured throughout the experiment. Gas exchange and other physiological measurements were recorded during last 3 wk of the experiment. Plant growth and developmental parameters were measured at 97 d after transplanting. The midday LWP was strongly and linearly correlated with soil moisture content showing the interplay between these two processes. Net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) declined while photosynthetic water‐use efficiency (Pn/Tr) increased with decreasing LWP. Both total chlorophyll content and cell membrane thermostability (CMT) declined linearly with decreasing LWP. Vine length, leaf area, and node number per plant decreased linearly, by 3.2 cm, 96.6 cm2, and 0.39 no. plant−1, respectively, per unit change in ET‐based irrigation. The optimum soil moisture for total plant and storage root dry weights were obtained under the irrigation treatments of 100 and 72% ET, respectively. Biomass partitioning to storage roots declined linearly and leaf and stem portioning increased with increased irrigation. Outcomes of this research will help producers schedule irrigation to maximize yield and researchers to develop sweetpotato crop models.
•Significant variability in physiological, biophysical, and pollen germination traits were determined.•Pollen germination and pollen tube length of roses were reduced by high-temperature stress.•A ...weak correlation between the pollen viability and tube length was observed under high-temperature stress.•Cultivars sharing heat- and drought-adaptive traits are identified using cluster analysis.
Rose plants growing under natural conditions are exposed to unfavorable environmental conditions such as high temperature and drought, particularly around the blooming stage. This can reduce the reproductive potential and aesthetic value of commercial rose cultivars, which are often more sensitive to harsh conditions. Plants adjust to adverse environments by regulating several morpho-physiological and biochemical processes, which are the key to tolerance mechanisms. Thus, to examine genetic potential of 22 roses, we characterized 18 traits: gas exchange, leaf biophysical, pigments, and pollen germination characteristics using field-grown roses at the blooming stage. A broad genetic variability (P < 0.001) in all measured traits suggests that roses comprise heat- and drought-adaptive traits. A weak correlation between the pollen viability or germination and the pollen tube length at 38 °C signifying the complexity of reproductive processes. However, three rose cultivars, Moje Hammarberg, Carefree Spirit, and Lavender Meidiland had better pollen germination-related traits (25 %) along with high photosynthetic capacity (24 %) and pigment traits (22 %) compared with sensitive cultivars. The generated phenotypic data, along with reliable phenotyping methods and identified candidate cultivars, would help develop roses with enhanced resilience to stress for dry and hotter climates.
Biochar has widely been utilized as an agricultural soil amendment owing to its enhanced surface properties and cost-effectiveness. In the present work, the influence of tea waste biochar (TWBC) upon ...acid modification on Allium cepa L. (red onion) growth has been studied. Its effect as a soil amendment has also been studied by assessing the nutrient retention, microbial population growth and immobilization of potentially toxic metal ions. A greenhouse experiment was carried out by applying different biochar (BC) ratios (2% and 5% w/w) to soil as the growth media for onion plants. A 2.4 times (2.4 × ) reduction of phosphate from leaching was observed upon BC application at a ratio of 2% than that of 5%. Moreover, red onion plants that grew in the BC-fertilizer amended soil at a 2% ratio showed higher growth compared to that of 5%. A ∼1.3 × and ∼1.2 × increment of total dry weight was observed upon amendment of soil fertilizer system with nitric and sulfuric acid-modified TWBC, respectively. An analysis of the potentially toxic metal ion uptake by the respective plant parts showed that lead uptake by the roots of red onion was ∼8.3 × less in BC amended soil compared to that in contaminated soil. Thus, acid-modified TWBC can be considered a potential soil amendment for an enhanced red onion growth. Employing TWBC as a soil amendment in tropical countries, where tea-waste is in abundance, will boost sustainable agriculture.
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•Effect of acid modified tea waste biochar on Allium cepa L. growth was evaluated.•Application ratio of 2% biochar exhibited the highest plant growth characteristics.•Reduced nutrient leaching upon incorporation of modified biochar.•Toxic metal ion uptake by plants was reduced upon biochar application.
•Growth and physiological responses of two sweet potato cultivars were quantified against five levels of soil moisture.•Shoot growth of sweetpotato cultivar Evangeline decreased more rapidly than ...Beauregard with shrinking soil moisture.•With decreasing soil moisture, shoot biomass declined more rapidly than root biomass in both cultivars.•Maintaining soil moisture closure to field capacity during early season is beneficial for early crop development.
Soil moisture deficit at early season is detrimental for sweetpotato growth and development affecting final yield. This study investigated the effects of different soil moisture regimes on early season growth, developmental, and physiological responses of two sweetpotato cultivars, ‘Beauregard’ and ‘Evangeline’, grown in a greenhouse environment. Five levels of soil moisture treatments, 0.256, 0.216, 0.164, 0.107, and 0.058m3m−3 of VWC, were maintained through sensor-based soil moisture monitoring, and semi-automated programmed irrigation. Midday leaf water potential (LWP), gas exchange, and fluorescence were measured weekly from 30 to 50 days after transplanting (DAT). Growth and development of plants were evaluated through harvesting four plants at 5-day intervals from 14 to 50 DAT. Leaf pigments and cell and chlorophyll stability indices were also determined. Midday LWP of sweetpotato declined linearly with decreasing soil moisture levels. The photosynthetic rate also declined linearly in Beauregard and quadratically in Evangeline with decreasing soil moisture. Both cultivars had a close association between photosynthetic rate and stomatal conductance over the soil moisture treatments, suggesting that stomatal closure is a key limitation for the drop in photosynthesis. Chlorophyll concentration was significantly lower at extreme soil moisture deficit conditions. Significant difference was found in water use efficiency between cultivars and among soil moisture treatments. Rates of vine elongation and leaf formation of Evangeline decreased more rapidly than Beauregard with declining soil moisture levels. Also with decreasing soil moisture, the shoot biomass declined more rapidly than root biomass. The results showed that maintaining soil moisture closer to field capacity (0.256m3m−3 of VWC) during early season is beneficial for early development of both root and shoot system and thus better crop performance. The data and the inferences derived from the functional algorithms developed in this study will be useful for crop modelling, field-level irrigation scheduling, and planting decisions.
ABSTRACT
At present climate changes and extreme weather events which are significantly affects the productivity of coconut in the major coconut growing areas in the country and ultimately it will ...threaten the livelihood of coconut cultivating community. The present study was undertaken to determine the coconut growers’ knowledge and perceptions about climate change and adaptation strategies. The study was conducted in Puttalam district which is more vulnerable to climate change impacts. The study sample comprised of 140 coconut growers. The study findings emphasized that notable fraction of growers have fairly high knowledge and perceptions about climate change and various impacts. Further, age, education and farming experience were found to be positively related and gender, land holding, family size, land ownership were negatively related with growers’ knowledge and perceptions. Additionally, age, family size and education were found to be significantly related with growers’ knowledge and only the family size and education were found to be significantly related with growers’ perceptions. Moreover, growers’ knowledge was positively and significantly related with their perceptions and adaptation measures as well as perceptions also positively and significantly related with adaptation measures. Also, findings showed that significant importance to create extension and awareness campaigns to educate the coconut growers about climate change related risks and uncertainties and suitable adaptation strategies. Therefore, agriculture policy makers should more focus on mitigating impacts of climate change to enhance the sustainable coconut cultivation in the country with providing more information, financial supports and subsidies to growers to adopt suitable adaptation measures.
Keywords: adaptation strategies, climate change, coconut growers’ knowledge, perceptions
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