Enhancing cotton sustainability: Multi-factorial intercropping, irrigation, and weed effects on productivity, quality and physiology.

Drought stress and weed infestation are significant factors that significantly decrease cotton yield. Increasing the variety of plants within a cotton field ecosystem can strengthen its stability and protect it from susceptibility to both biotic and abiotic pressures. In this two-year experiment (2021 and 2022), the effects of intercropping systems (four growth conditions including mono- and inter-cropped cotton varieties Golestan and Hekmat with Nepeta crispa and dragon's head (Lallemantia iberica)), irrigation (three intervals of 3, 6, and 9 days), and weed competition (weed-free and weedy plots) on the agronomic performance, physiological characteristics, and seed quality of cotton in a semi-arid region of Iran were studied. In 2021, the volume of irrigation water applied was 9873, 6100, and 4650 m3 ha-1 for irrigation intervals of 3, 6, and 9 days, respectively. In 2022, the volumes were 9071, 5605, and 4272 m3 ha-1 for the corresponding irrigation intervals. Over two years, Xanthium strumarium, Amaranthus retroflexus, and Portulaca oleracea were the dominant weed species. Weeds had the most significant impact on total dry weight; weed control increased plant vigor and growth, ranging from 1.4 to 2.3 times, while weed impact on cottonseed yield ranged from 18% to 96% reduction. Increasing irrigation intervals resulted in reductions in various parameters, with decreases of 39%-80% in total dry weight, 34%-57% in cottonseed yield, and 48%-72% in lint yield. The harvest indices for seed cotton, cottonseed, and lint ranged from 35.3% to 56.5%, 18.3%-35.0%, and 15.4%-20.5%, respectively. Weeds were responsible for a 17% decrease in the 1000-seed weight. As the irrigation intervals increased from 3 days to 6 days and 9 days, the number of bolls per plant decreased by 19%-85%. Extending the irrigation interval from 3 days to 6 days and 9 days resulted in a substantial decrease in the photosynthetic rate, ranging from 42% to 92%. Mono-cropped Golestan performed well under unstressed conditions such as 3-day interval irrigation and weed-free conditions. On the other hand, intercropped Hekmat demonstrated better resilience to both moisture and weed stresses. The LER (Land equivalent ratio) indices of both intercropping systems were generally favorable, indicating higher productivity compared to sole cropping. The intercropping systems consistently showed the highest LER indices under weedy conditions, highlighting the significance of intercropping as a valuable method in integrated weed management.

Study the yield and quality of bitter gourd fruit (Momordica charantia) in inoculation with two species of mycorrhizal fungi and phosphorus fertilizer under different irrigation regimes.

Drought is known to be the most important constraint to the growth and yield of agricultural products in the world, and plant symbiosis with arbuscular mycorrhizal fungi (AMF) can be a way to reduce drought stress negative impacts. A two-year experiment to investigate the factorial combination of mycorrhizal fungi (Glomus mosseae, Glomus intraradices, Control) and phosphorus fertilizer (application and non-application of phosphorus) on fruit yield and phenolic acids changes bitter gourd under different irrigation regimes as a split factorial based on a randomized complete block design. Three irrigation regimes, including irrigation after 20%, 50%, and 80% available soil water content depletion (ASWD), were considered in the main plots. The results showed that under water deficit stress, fruit yield and physiological (photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), RWC, total chlorophyll, and root colonization) parameters decreased compared to 20% ASWD, and biochemical (proline, soluble sugar, MDA, CAT, SOD, phenol) parameters and fruit phenolic acids (caffeic acid, coumaric acid, ferulic acid) increased. However, the inoculation of AMF and phosphorus fertilizer in three irrigation regimes decreased MDA content, but physiological and biochemical parameters and fruit phenolic acids were increased. In this study, the factorial combination of AMF and sufficient phosphorus improved the resistance of bitter gourd to water deficit, and this not only improved fruit yield but also increased fruit phenolic acids under 80% ASWD, which can be an innovation in the management of water resources and the production industry of medicinal plants with high antioxidant properties in water deficit areas.

Functional Quality, Antioxidant Capacity and Essential Oil Percentage in Different Mint Species Affected by Salinity Stress.

Saline stress is responsible for significant reductions in the growth of plants, and it globally leads to limitations in the performance of crops, especially in drought-affected areas. However, a better understanding of the mechanisms involved in the resistance of plants to environmental stress can lead to a better plant breeding and selection of cultivars. Mint is one of the most important medicinal plants, and it has important properties for industry, and for the medicinal and pharmacy fields. The effects of salinity on the biochemical and enzymatic properties of 18 ecotypes of mint from six different species, that is, Mentha piperita, Mentha mozafariani, Mentha rotundifolia, Mentha spicata, Mentha pulegium and Mentha longifolia, have been examined in this study. The experimental results showed that salinity increased with increasing in stress integrity influenced the enzymatic properties, proline content, electrolyte leakage, and the hydrogen peroxide, malondialdehyde, and essential oil contents. Cluster analysis and principal component analysis were conducted, and they grouped the studied species on the basis of their biochemical characteristics. According to the obtained biplot results, M. piperita and M. rotundifolia showed better stress tolerance than the other varieties, and M. longifolia was identified as being salt sensitive. Generally, the results showed that H2 O2 and malondialdehyde had a positive connection with each other and showed a reverse relationship with all the enzymatic and non-enzymatic antioxidants. Finally, it was found that the M. spicata, M. rotundifolia and M. piperita ecotypes could be used for future breeding projects to improve the salinity tolerance of other ecotypes.

Saving environment through improving nutrient use efficiency under intensive use of agrochemicals in paddy fields.

Increased environmental and economic costs of chemical fertilizers necessitates serious attention to improve nutrient use efficiency. A 3-year field investigation was conducted to assess the influence of different drainage systems on nitrogen (N), phosphorus (P) and potassium (K) use efficiency of two rice cultivars under alternate wetting and drying (AWD) strategy. The drying of the field was done through a surface drainage system (Control) and four subsurface drainage systems (D0.90L30, D0.65L30, D0.65L15; where D and L represent the drain depth and spacing, respectively, and Bilevel; in which the drains were spaced 15 m apart at depths 0.65 and 0.90 m). During growing seasons, the dry weight (DW) and N, P and K uptake of stem, leaf and panicle was monitored. At harvest, grain yield was also determined. Soil drying through subsurface drainage systems increased the DW of the panicle compared to surface drainage. On average, panicle DW in D0.90L30, Bilevel, D0.65L30, D0.65L15 and Control were 10.7%, 10%, 11.4%, 9.2% and 8.9% of the total DW, respectively. Improving soil aeration in the subsurface drainage systems increased crop production by increasing the share of nutrients in the panicle. The average share of N, P and K in panicle to N, P and K content of the total biomass in the subsurface-drained area was 11.7%, 12.9% and 8.4%, respectively, and in the Control was 9.7%, 10.9% and 7.9%, respectively. On average, the subsurface drainage systems improved rice grain yield and N, P and K use efficiency by 14.2% and 16%, 15% and 16% compared with Control, respectively. According to the results, subsurface drainage may effective for better aeration and increase in nutrient use efficiency in rice production systems.

Investigation of yield, phytochemical composition, and photosynthetic pigments in different mint ecotypes under salinity stress.

Salinity stress is one of the main limiting factors of medicinal plant growth and may affect their characteristics and chemical composition. In order to evaluate the response of different species of Iranian mint to salinity stress, an experiment was designed in greenhouse conditions. In this experiment, six Iranian mint species were cultivated in pots under different salinity stress including 0, 2.5, 5, and 7.5 dS/m. The chlorophyll indices (a, b, total, and a/b ratio), carotenoids, total anthocyanin, total phenolic and flavonoid content, antioxidant activity, dry matter yield, and essential oil content were measured in two different harvest stages. Salinity stress affected various measured traits. The results showed that despite the negative effect of salinity stress on photosynthetic pigments, in some ecotypes and species, photosynthetic pigments were not affected by salinity stress. The amount of total phenolic content, total flavonoid content, and total anthocyanin increased in response to salinity stress. The dry matter decreased under salinity stress, but the content of essential oil increased as a result of salinity stress increment. The results of PCA biplot showed that the E16 and E18 ecotypes were separated by a large distance. Among the various ecotypes, E18 had the most desirable traits which can be recognized as a salt-tolerant ecotype. Also, piperita species was the best among the species in all salinity stress levels.

Identification of a defense response gene involved in signaling pathways against PVA and PVY in potato.

Potato is the most important non-grain food crop in the world. Viruses, particularly potato virus Y (PVY) and potato virus A (PVA), are among the major agricultural pathogens causing severe reduction in potato yield and quality worldwide. Virus infection induces host factors to interfere with its infection cycle. Evaluation of these factors facilitates the development of intrinsic resistance to plant viruses. In this study, a small G-protein as one of the critical signaling factors was evaluated in plant response to PVY and PVA to enhance resistance. For this purpose, the gene expression dataset of G-proteins in potato plant under five biotic (viruses, bacteria, fungi, nematodes, and insects) and four abiotic (cold, heat, salinity, and drought) stress conditions were collected from gene expression databases. We reduced the number of the selected G-proteins to a single protein, StSAR1A, which is possibly involved in virus inhibition. StSAR1A overexpressed transgenic plants were created via the Agrobacterium-mediated method. Real-time PCR and Enzyme-linked immunosorbent assay tests of transgenic plants mechanically inoculated with PVY and PVA indicated that the overexpression of StSAR1A gene enhanced resistance to both viruses. The virus-infected transgenic plants exhibited a greater stem length, a larger leaf size, a higher fresh/dry weight, and a greater node number than those of the wild-type plants. The maximal photochemical efficiency of photosystem II, stomatal conductivity, and net photosynthetic rate in the virus-infected transgenic plants were also obviously higher than those of the control. The present study may help to understand aspects of resistance against viruses.

Effects of water stress and light intensity on chlorophyll fluorescence parameters and pigments of Aloe vera L.

Aloe vera L. is one of the most important medicinal plants in the world. In order to determine the effects of light intensity and water deficit stress on chlorophyll (Chl) fluorescence and pigments of A. vera, a split-plot in time experiment was laid out in a randomized complete block design with four replications in a research greenhouse. The factorial combination of three light intensities (50, 75 and 100% of sunlight) and four irrigation regimes (irrigation after depleting 20, 40, 60 and 80% of soil water content) were considered as main factors. Sampling time was considered as sub factor. The first, second and third samplings were performed 90, 180 and 270 days after imposing the treatments, respectively. The results demonstrated that the highest light intensity and the severe water stress decreased maximum fluorescence (Fm), variable fluorescence (Fv)/Fm, quantum yield of PSII photochemistry (ФPSII), Chl and photochemical quenching (qP) but increased non-photochemical quenching (NPQ), minimum fluorescence (F0) and Anthocyanin (Anth). Additionally, the highest Fm, Fv/Fm, ФPSII and qP and the lowest NPQ and F0 were observed when 50% of sunlight was blocked and irrigation was done after 40% soil water depletion. Irradiance of full sunlight and water deficit stress let to the photoinhibition of photosynthesis, as indicated by a reduced quantum yield of PSII, ФPSII, and qP, as well as higher NPQ. Thus, chlorophyll florescence measurements provide valuable physiological data. Close to half of total solar radiation and irrigation after depleting 40% of soil water content were selected as the most efficient treatments.