Phytochemical analysis and allelopathic potential of essential oil of yarrow (Achillea spp.) ecotypes against redroot pigweed (Amaranthus retroflexus L.).

This study will contribute to the knowledge of plant allelopathy and its application in weed management, as well as to the valuation of medicinal and neglected plant species. An allelopathy experiment was conducted to introduce Achillea spp. as an effective species on the red root pigweed (Amaranthus retroflexus L.). The allelopathic effect of dry material from the flower, leaf and stem of Tanacetum polycephalum L. and 9 Achillea spp. (Achillea santolina L., A. millefolium L., A. nobilis L., A. conferta DC., A. vermicularis Trin., A. beibersteinii Afan., A. talagonica Boiss., A. tenuifolia Lam., A. aleppica DC.) applied to the soil on the growth of redroot pigweed seedling was tested. Five different ratios of aerial dry material of different species as residues (at 0, 10, 20, 40, and 50 g kg-1 dry weight) were used in the pots. Achillea residual had a significant effect on the growth of redroot pigweed. Achillea vermicolaris and A. aleppica were the most effective species at stopping the growth of redroot pigweed, reducing its dry matter by 90% at 0.07 and 0.02 g kg-1 dry weight, respectively. Based on the results of GC/MS analyses, 152 different compounds were found in the essential oil of Achillea spp. The possible relationship between allelochemicals and seedling investigation by partial least squares regression between effective doses for controlling redroot pigweed and allelochemical compounds of Achillea species. Result showed that cis-Menth-2-en-1-ol, α-Terpinyl, propionate and Bornyl acetate had the most effect on inhibiting the growth of redroot pigweed. Our research revealed that the Achillea genus has a lot of potential as a bioherbicide. This means that its leftovers or mulch could be used as a good cover crop to control redroot pigweed.

Canola as a potential forage.

The nutritive quality of four cultivars of canola forage (Brassica napus L.), Orient, Midas, Global, and Hybrid (Cobra × Regent), which were harvested in the early-spring period, were compared with green-winter barley (GWB) in terms of their yields, chemical composition, in vitro gas production variables, in situ crude protein (CP) degradation, and predicted dry matter intake (PDMI). Data were statistically analyzed using a completely randomized design with four replications and three samples per replication. The study was based on a randomized complete block design, and data were analyzed using SAS, general linear model procedure for normal distribution. The canola dry matter (DM) yield was highest in Orient cultivar and lowest in Midas (P < 0.05). Organic matter (OM), CP, neutral detergent fiber (NDF), and lignin(sa) concentration of the four cultivars ranged from 862 to 865, 218 to 247, 295 to 340, and 35 to 53 g/kg DM, respectively. The estimated OM disappearance (OMD), effective degradability of CP, effective rumen degradable protein (ERDP), digestible undegradable protein, and metabolizable protein (MP) of the forages were from 636 to 671 g/kg, 878 to 910, 172 to 193, 1.9 to 3.4, and 112 to 126 g/kg DM, respectively. Compared to Global and Hybrid cultivars, Orient and Midas contained higher CP, OMD, ERDP, MP concentration, and PDMI, but lower NDF, acid detergent fiber (ADF), and lignin(sa) concentrations (P < 0.05). The level of glucosinolates in the forages ranged from 0.38 to 1.51 µmol/g DM, which is below the detrimental level for ruminants. Compared to winter canola cultivars, GWB had higher DM yield (P < 0.003), NDF, lignin(sa), PDMI (P < 0.01), and digestible undegradable protein (P < 0.04), but had lower OMD (P < 0.03), ERDP (P = 0.01), and MP (P < 0.009). Based on the obtained results, the variation in the nutritive quality among the canola cultivars is relatively small, and the Orient cultivar, which is most comparable to GWB, was judged to be nutritionally the best among the cultivars.

Effects of precipitation and temperature on crop production variability in northeast Iran.

Climate variability adversely impacts crop production and imposes a major constraint on farming planning, mostly under rainfed conditions, across the world. Considering the recent advances in climate science, many studies are trying to provide a reliable basis for climate, and subsequently agricultural production, forecasts. The El Niño-Southern Oscillation phenomenon (ENSO) is one of the principle sources of interannual climatic variability. In Iran, primarily in the northeast, rainfed cereal yield shows a high annual variability. This study investigated the role played by precipitation, temperature and three climate indices [Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and NINO 3.4] in historically observed rainfed crop yields (1983-2005) of both barley and wheat in the northeast of Iran. The results revealed differences in the association between crop yield and climatic factors at different locations. The south of the study area is a very hot location, and the maximum temperature proved to be the limiting and determining factor for crop yields; temperature variability resulted in crop yield variability. For the north of the study area, NINO 3.4 exhibited a clear association trend with crop yields. In central locations, NAO provided a solid basis for the relationship between crop yields and climate factors.

The potential of tebuconazole for mitigating oxidative stress caused by limited irrigation and improving sugar yield and root quality traits in sugar beet.

Water deficit is the main reason for sugar yield losses in semi-arid areas. Triazole derivatives may mitigate the harmful impacts of water stress. Therefore, this study aimed to assess the effect of tebuconazole (TEB) application on antioxidants, root quality traits, and sugar yield under drought stress conditions. The treatments included three levels of irrigation set according to crop evapotranspiration (ETC): 100%, 75%, and 50% ETC, as well as three levels of TEB (0, 25, and 50 mg L-1). While significantly increasing antioxidant and alpha-amino-nitrogen (α-amino-N) contents, limited irrigation decreased total chlorophyll content, net photosynthesis rate, leaf relative water content, the weight of roots, and sugar yield. In contrast, TEB treatment resulted in a marked rise in all biological and physiological traits as well as enzymatic antioxidants. Our findings indicated that the decline in α-amino-N content might be linked to increased NR activity in response to the TEB application. Our results also showed that the stress-ameliorating role of TEB cannot be associated with the increase of flavonols (quercetin and rutin). Overall, the results demonstrated that TEB has a high potential for ameliorating the negative impacts of limited irrigation.

Growth, yield and quality of two guar (Cyamopsis tetragonoloba L.) ecotypes affected by sowing date and planting density in a semi-arid area.

The growth period, phenology, grain yield and gum content of two different guar ecotypes were studied in response to different sowing dates and plant densities. A two-year field experiment was conducted as a split-factorial in a randomized complete block design (RCBD) with three replicates in the research field of Tarbiat Modares University during 2016 and 2017 growing season. Main plots consisted of four sowing dates (May 21, June 4, June 21 and July 5 in 2016 and May 10, May 26, June 10 and June 26 in 2017), and subplots including three plant densities (13, 20 and 40 plants m-2) and two ecotypes (Pakistani and Indian). Based on findings, the phenological traits, plant height, grain yield and harvest index were significantly affected by plant density. The effect of ecotypes was statistically significant (p<0.05) on all traits except harvest index in the first year. Furthermore, the seed sowings on May 21 and May 26 with 13 plants m-2 led to highest grain yield (3004.8 and 2826.10 kg.ha-1 for two consecutive years). The high gum content (33.68 and 33.78% for two consecutive years) was also recorded for Pakistani ecotype while for gravity, Indian ecotype showed higher value in both crop years. By and large, the Pakistani ecotype showed better response compared to the Indian one in both years, especially in 1st and 2nd sowing dates.

Nodulation and root traits in four grasspea (Lathyrus sativus) ecotypes under root-zone temperatures.

In order to study the effect of four Root-Zone Temperatures (RZT) (5, 10, 15 and 25 degrees C) on nodulation and nitrogen percent of four grasspea ecotypes (ardabil, zanjan, mashhad and sharkord), an experiment was conducted in a controlled-environmental chamber in 2005. There were differences (p < 0.01) among ecotypes, RZT and ecotypes *RZT for root length, forage dry matter, root dry matter, nodule dry weight, nodule number, nodule cluster number, nodule cluster diameter, nodule diameter, nodule distribution (root length that has nodule) and plant nitrogen percent. Mashad and ardabil ecotypes produced the most and least nodule number at 25 and 5 degrees C, respectively. The maximum and minimum nodule cluster number were observed in ardabil ecotype under 25 and 5 degrees C RZT, respectively. Root distribution was the most and the least in mashhad and ardabil ecotypes under 25 and 5 degrees C RZT, respectively. Ardabil produced the highest dry nodule weight at 25 degrees C RZT. The least dry nodule weight was belonged to ardabil ecotype under 5 degrees C RZT. Plant nitrogen percent was the highest in ardabile ecotype at 15 degrees C RZT and the lowest in mashhad ecotype under 5 degrees C RZT. This experiment showed that at low RZT (i.e., 5 and 10 degrees C) none of ecotypes had preferred on other ecotypes in point of view measured traits except nodule diameter. Ardabile and mashhad ecotypes were better than other ecotypes at 15 and 25 degrees C RZT respectively for most traits.