Polyethylene glycol-induced drought stress screening of selected Philippine high-yielding sugarcane varieties

به‌منظور بررسی تأثیر محلول‌پاشی متانول بر ویژگی‌های کمی، هدایت روزنه‌ای و محتوای پرولین سویا در شرایط تنش خشکی، آزمایشی به‌صورت کرت‌های خرد شده در قالب بلوک‌های کامل تصادفی با سه تکرار در مزرعه پژوهشی دانشکده کشاورزی مغان در سال 1390 اجرا گردید. تنش خشکی در سه سطح شامل: آبیاری پس از 40 (شاهد)، 55 و 70 درصد تخلیه رطوبت قابل دسترس به‌عنوان عامل اصلی و محلول‌پاشی متانول در چهار سطح شامل: عدم محلول‌پاشی، محلول‌پاشی با 7، 21 و 35 درصد حجمی متانول به‌عنوان عامل فرعی لحاظ شدند. نتایح نشان داد که تأثیر تنش خشکی و محلول‌پاشی متانول بر ارتفاع بوته، تعداد برگ در بوته، سطح برگ، تعداد غلاف و دانه در بوته، وزن هزاردانه، عملکرد بیولوژیک و دانه، هدایت روزنه‌ای و محتوای پرولین برگ معنی‌دار شد. افزایش تنش خشکی موجب افزایش محتوای پرولین برگ و کاهش سایر ویژگی‌ها گردید، به‌طوری‌که تیمار آبیاری پس از 70 درصد تخلیه رطوبتی قابل دسترس در مقایسه با تیمار شاهد موجب کاهش 51/2 درصد عملکرد دانه شد. با محلول‌پاشی متانول تا 21 درصد حجمی تمام ویژگی‌های مورد بررسی به‌جز محتوای پرولین افزایش و افزایش درصد حجمی متانول بیشتر از آن سبب کاهش آنها گردید. محلول‌پاشی متانول با 21 درصد حجمی بیشترین تأثیر را بر ویژگی‌های کمی و هدایت روزنه‌ای داشت، به‌طوری‌که موجب افزایش 25/6 درصد عملکرد دانه گردید.

Drought is one of the main factors limiting rice (Oryza sativa L.) productivity and has become an increasingly severe problem in many regions worldwide. Establishing breeding programs to develop new drought-tolerant varieties requires an understanding of the effect of drought on rice plants and the mechanisms of drought tolerance in rice. We conducted a pot experiment to explore growth characteristics, root plasticity, and stomatal conductance in six rice varieties (DA8, Malagkit Pirurutong, Thierno Bande, Pate Blanc MN1, Kinandang Patong, and Moroberekan) in response to different drought stress and re-watering conditions. Drought stress significantly depressed plant growth, root size, and stomatal conductance in all experimental varieties. These negative effects depended on both the variety and the severity of the drought stress treatment. Under moderate drought stress (10 days after drought treatment), growth was less influenced in roots than in shoots. In contrast, there was an opposite trend under severe drought stress (15 days after drought treatment), with growth being more severely affected in roots than in shoots. Rice plants recovered from drought stress in terms of dry matter accumulation, root size, and stomatal conductance after re-watering; however, the recovery pattern differed among varieties. DA8 exhibited the highest dry weight accumulation and root size (root length, root surface area, root volume, fine root length, and thick root length) under well-watered, drought stress, and re-watering conditions. Kinandang Patong showed the highest recovery ability in dry matter accumulation, root length, root surface area, and stomatal conductance after re-watering. Malagkit Pirurutong expressed the poorest recovery ability in dry matter accumulation after re-watering. These three varieties might be selected for further experiments focusing on the mechanisms of drought tolerance and recovery ability in rice.

Drought imposes a significant challenge for crop production. However, little is known about the impact of drought priming and nitrogen (N) application and their interactive effects on drought resilience, yield, and grain quality in wheat. Spring wheat (cv. Stettler) was grown in plastic pots (25 cm diameter) with high, moderate, and low soil water levels and received N (added N) or without N (no N added), and subjected to acute drought for 10 days, then rewatering at the tillering stage. Canopy temperature, maximum efficiency of photosystem II, and normalized difference vegetation index were measured at 3-day intervals during drought-recovery periods to quantify drought resistance and resilience. Above-ground dry matter, straw dry matter, seed dry matter, harvest index, and grain N, phosphorus (P), and zinc (Zn) concentrations were determined. Both moderate- and low-water-grown plants had higher drought resistance than high-water-grown plants. The addition of N alleviated acute drought stress in high- and moderate-water-grown plants but exacerbated drought stress in low-water-grown plants. Both high and moderate water resulted in higher grain yields, but had a lower harvest index than low water. The highest and lowest grain N were observed in the low- and high-water-grown plants, respectively. The addition of N increased N and N:P in grains but decreased grain Zn:N. This study showed that moderate drought priming along with N application can improve drought resistance, yield, and grain quality. The results also indicated that canopy thermal imaging is a useful tool for high-throughput quantification of the drought resistance of wheat.

Estimation of drought effects on different bread wheat genotypes using morpho-physiological traits

In light of anticipated climate change, we assessed the possibility to use an airborne platform to measure canopy temperature (CT) and the normalized differential vegetation index (NDVI) as well as the suitability of both traits for their use in breeding for tolerance to heat stress. We evaluated 71 subtropical maize (Zea mays L.) hybrids under heat stress and combined heat and drought stress in an environment with average temperatures of 29.8°C during the growing season and 31.2°C during the flowering period. Grain yield (GY) ranged from 0.33 to 4.19 Mg ha−1 under heat stress and from 0 to 1.37 Mg ha−1 under combined heat and drought stress, going along with increases in CT from 42.5°C to 49.5°C and decreases in NDVI from 0.54 to 0.48. The NDVI explained differences between and within treatments, while CT explained differences in GY among treatments and genotypes within the heat and drought stress treatment, as indicated by genetic correlations with GY. A principal component analysis was used to identify combinations of physiological characteristics associated with genotypic variation in GY. Results showed that selection gains for GY could be improved by 0.486 Mg ha−1 and 0.015 Mg ha−1 under heat and combined heat and drought stress, respectively, if selection is simultaneously carried out for GY, NDVI, and lower CT and shorter anthesis silking interval. We postulate that the use of selection indices, including CT and NDVI in conjunction with GY, will improve selection gains and increase cost efficiency of breeding programs.

In two growing seasons of wheat (2015-2017), we conducted a field trial with Taishan 28 in Tai'an Academy of Agricultural Science Feicheng experimental base, Tai'an City, Shandong Province. There were four irrigation levels of 150 (A1), 300 (A2), 450 (A3), and 600 (A4) m3·hm-2, and four nitrogen application levels of 90 (B1), 135 (B2), 180 (B3), and 225 (B4) kg·hm-2. We examined the effects of the combination effects of irrigation and nitrogen on dry matter accumulation and transport, nitrogen accumulation and transport, water consumption and utilization, photosynthetic characteristics, wheat grain yield and yield components of wheat. The results showed that dry matter accumulation, nitrogen accumulation, vegetative organs production, storage and the transportation volume to grains of the dry matter and nitrogen, and dry matter and nitrogen accumulation of grain in the mature stage of wheat all reached the maximum in A3B3 treatment, which were significantly different from other treatments. Under all the nitrogen treatments, soil water consumption in the 60-200 cm soil layer was A3>A4>A2>A1. Water use efficiency and nitrogen use efficiency in A3B3 treatment were higher than that under A3B4, A4B3 and A4B4. The net photosynthetic rate, stomatal conductance and transpiration rate of flag leaves from 7 to 28 days after flowe-ring were all significantly higher in A3B3 treatment, which was conducive to the photosynthetic synthesis of carbohydrates in wheat. The interaction effect of water and nitrogen addition significantly affected grain yield and yield components. Wheat yield was the highest in A3B3 treatment which reached at 9400 kg·hm-2. In conclusion, the treatment with irrigation of 450 m3·hm-2 and nitrogen of 180 kg·hm-2 could significantly improve dry matter and nitrogen accumulation, and promote transportation volume of the dry matter and nitrogen to grain. Compared with the high water and nitrogen treatment, it could effectively increase water use efficiency and nitrogen use efficiency, enhance photosynthetic capacity of flag leaf, produce more carbohydrate, and increase grain yield.

Biochar and Arbuscular mycorrhizal fungi mediated enhanced drought tolerance in Okra (Abelmoschus esculentus) plant growth, root morphological traits and physiological properties

Water deficit and phosphorus (P) deficiency in soil have become the main limiting factors for the production of maize (<i>Zea mays</i> L.), but it still remains unclear how water and P regulate maize root morphology and P uptake. Through an experiment of potted soil culture, this study has set 4 water gradients [35% (W1), 55% (W2), 75% (W3) and 100% (W4)] of field capacity, and two P levels [high P: 205 mg (P)∙kg^-1; low P: 11 mg (P)∙kg^-1] to investigate the coupling effects of water and P on root growth and P uptake in maize seedlings. The results have shown that: (1) Regardless of soil P supply, the shoot dry weight, root dry weight, total root length, and root surface area of maize seedlings shows a trend of increasing first and then decreasing with increasing water supply intensity; the soil available P content also shows similar trend; the root mass ratio and mean root diameter shows a downward trend with the increase of water supply intensity; furthermore, the P content and P accumulation of plants shows a steady increase with the increase of water supply intensity; (2) Water deficit (W1) and excess water supply (W4) is not conducive to root growth and dry matter accumulation in maize. Water deficit (W1) inhibits the acquisition of soil P by maize, while excess water supply (W4) causes extravagant absorption of soil P (W4). Mild water stress (W2) can promote the growth and dry matter accumulation of maize roots and reduce the extravagant absorption of soil P, and adequate water supply (W3) can promote root growth, dry matter accumulation and the absorption of soil P; (3) Phosphorus supply significantly increases the dry weight, root dry weight (except W4), total root length, root surface area, plant P content (except W4) and P accumulation of maize seedlings, but reduces the root mass ratio of maize. It is thus evident that water is a key factor controlling the morphology and accumulation of dry matter in maize roots, and P is a key factor controlling P uptake and soil available P content in corn field. The better coupling between water and P can promote maize root growth and dry matter accumulation, as well as reduce the extravagant absorption of soil P.

UAV based soil salinity assessment of cropland

Standing water is an important contributor for yield formations and physiological activities at flowering stage of the rice crop. It may help to maintain tissue temperature below the critical level by transpiration cooling. Drought and heat stress arising from late planting may affect on transpiration cooling, resulting in high canopy temperature. Canopy temperature can be used as a selection criteria for drought tolerant variety screening. Thus, it is important to study the importance of canopy temperature related traits and trait diversity on heat and drought stress. This field trial was conducted at the Field Crops Research and Development Institute, Mahailluppallama, to investigate the changes of pattern and distribution of morphological traits across eight rice varieties under four management conditions (i.e., early planting flood, late planting flood, early planting drought and late planting drought), to identify the transpiration cooling related traits. Morphological traits were subjected to factor analysis across the management conditions. Factor coefficients of each selected trait were used as an explanatory variable for regression on canopy temperature. Factor one highly correlated with plant height and panicle length. Tiller angle and number of tillers were highly correlated with Factor two. Pollen fertility was highly correlated with Factor three. Factor one negatively and Factor two positively correlated with canopy temperature across flooded, drought stress and heat stress conditions. Thus, canopy angle, pollen fertility index, plant height and tiller angle are important characters in variety selection for drought and heat stress. The variety Bg 366, Pachchaperumal and Kaluheenati have high transpiration cooling ability among the tested varieties.

Effects of different water stresses under subsurface infiltration irrigation on eggplant growth and water productivity

High temperature is one of the major environmental factors limiting soybean growth and development. Investigating the effects of high temperature at different growth stages on dry matter accumulation and sugar metabolism can help elucidate the physiological mechanisms underlying heat-induced yield loss, thereby providing a theoretical foundation for breeding heat- tolerant soybean varieties. In this study, two soybean varieties—Liaodou 24 (heat-insensitive) and SN22-15 (heat-sensitive)—were grown under pot conditions and subjected to high-temperature treatments at different developmental stages. Dry matter accumulation, photosynthetic parameters, and sugar content were measured. Under high-temperature conditions, Liaodou 24 exhibited significantly higher leaf color index, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, transpiration rate, and dry matter weight of stems, leaves, petioles, and pods compared to SN22-15. High-temperature stress during the R1 and R3 stages, Liaodou 24 also showed significantly higher levels of soluble sugar content, sucrose content, and starch content in various plant parts than SN22-15. High-temperature stress during the V4, R1, and R3 stages, Liaodou 24 produced more pods per plant, more grains per plant, and greater seed weight per plant than SN22-15. Notably, high-temperature stress during the R3 stage caused a marked yield reduction in SN22-15. Excessive heat impaired photosynthesis in soybean leaves, inhibited the synthesis of photosynthetic products, reduced dry matter and sugar accumulation, and ultimately led to yield decline. Liaodou 24, being relatively heat-tolerant, showed moderate reductions in dry matter accumulation, sugar metabolism, and yield under high temperatures, only during the R3 stage. In contrast, SN22-15, as a heat-sensitive variety, experienced significant reductions in these traits across all growth stages, with the most severe impact occurring during the R3 stage. These findings suggested that in soybean breeding programs, developing varieties with appropriate maturity periods could help avoid yield loss due to high temperatures during the early podding stage.

Accurate, rapid, and nondestructive estimates of turfgrass leaf water status are important for site-specific irrigation and drought stress management. The objective of this study was to identify changes and correlations among the canopy reflectance, canopy temperature, and leaf relative water content (RWC) of perennial ryegrass ( Lolium perenne L.) under water deficit conditions. Six cultivars of perennial ryegrass were subjected to dry-downs in the field from May to Aug. 2007 and from June to Aug. 2008. Turf quality was positively correlated with soil moisture (SM), RWC, and normalized difference vegetation index (NDVI), but negatively correlated with canopy and ambient temperature differentials (ΔT). ΔT was well correlated with RWC ( r = –0.77 to –0.78) and SM ( r = –0.66 to –0.74), whereas SM was correlated with RWC ( r = 0.64 to 0.74) across seasons in both years. When a wide range of stress symptoms occurred in July and Aug., RWCs became highly correlated with ΔT ( r = –0.80 to –0.89) and NDVI ( r = 0.77 to 0.81), whereas ΔT was correlated with NDVI ( r = –0.70 to –0.80) in both years. SM was well correlated with RWC ( r = 0.71 to 0.80), NDVI ( r = 0.70 to 0.73), and ΔT ( r = –0.76 to –0.78) in July and August in both years. These results suggest that changes in ΔT can be used to predict well the leaf water and soil moisture content of perennial ryegrass under water deficit conditions. Combined with NDVI, the correlations can be used for direct mapping of the variability in grass water status, thus improving irrigation management.

Drought and heat stress can result in aflatoxin contamination of peanuts especially when this occurs during the last three to six wk of the growing season. Identifying drought-tolerant genotypes may aid in development of peanuts that are less susceptible to aflatoxin contamination. Research was conducted to phenotype seven peanut genotypes based on their response to drought stress. Six peanut genotypes that have exhibited lower aflatoxin and/or drought tolerance in previous researches (Tifguard, Tifrunner, Florida-07, PI 158839, NC 3033, C76-16) were compared to an aflatoxin-susceptible genotype, A72. The phenotyping methods included visual ratings, chlorophyll fluorescence (PI_ABS, φ_EO, and F_v/F_m), SPAD chlorophyll meter reading (SCMR), normalized difference vegetation index (NDVI), canopy temperature (CT), canopy temperature depression (CTD), and pod yield. Based on these traits, Tifguard and Tifrunner exhibited greater drought tolerance mechanisms than the other genotypes and may be good candidates to be incorporated in future drought tolerance studies. After the aflatoxin content of the different genotypes was measured, aflatoxin contamination showed high correlations with visual ratings (0.85), CTD (0.81), NDVI (0.79), and CT (0.73), and moderate correlations with F_v/F_m (0.62) and SCMR (0.57) (P ≥ 0.05). These easily measurable, rapid and cost-effective phenotyping methods may be used as alternative to more tedious and costly methods of identifying genotypes that are less susceptible to aflatoxin contamination. Using a combination of these methods is beneficial but not always practical. The combined use of visual ratings, CTD and NDVI is advised for initial evaluation of drought tolerance in peanut genotypes.

ABSTRACTDrought and heat stress can result in aflatoxin contamination of peanuts especially when this occurs during the last three to six wk of the growing season. Identifying drought-tolerant genotypes may aid in development of peanuts that are less susceptible to aflatoxin contamination. Research was conducted to phenotype seven peanut genotypes based on their response to drought stress. Six peanut genotypes that have exhibited lower aflatoxin and/or drought tolerance in previous researches (Tifguard, Tifrunner, Florida-07, PI 158839, NC 3033, C76-16) were compared to an aflatoxin-susceptible genotype, A72. The phenotyping methods included visual ratings, chlorophyll fluorescence (PIABS, ϕEO, and Fv/Fm), SPAD chlorophyll meter reading (SCMR), normalized difference vegetation index (NDVI), canopy temperature (CT), canopy temperature depression (CTD), and pod yield. Based on these traits, Tifguard and Tifrunner exhibited greater drought tolerance mechanisms than the other genotypes and may be good candidates to be incorporated in future drought tolerance studies. After the aflatoxin content of the different genotypes was measured, aflatoxin contamination showed high correlations with visual ratings (0.85), CTD (0.81), NDVI (0.79), and CT (0.73), and moderate correlations with Fv/Fm (0.62) and SCMR (0.57) (P ≥ 0.05). These easily measurable, rapid and cost-effective phenotyping methods may be used as alternative to more tedious and costly methods of identifying genotypes that are less susceptible to aflatoxin contamination. Using a combination of these methods is beneficial but not always practical. The combined use of visual ratings, CTD and NDVI is advised for initial evaluation of drought tolerance in peanut genotypes.