Response of Retail Lawn Seed Products during Acute Drought and Recovery

Consumers often have multiple choices when purchasing retail lawn products in stores. In this study, we evaluated the acute drought performance of locally available retail lawn seed products (mixtures or blends) at two mowing heights of 2.5 and 3 inches. We hypothesized that the species present in the products and the height-of-cut differentially influence the drought resistance and recovery of the mixtures and blends. In Fall 2016 and 2017, 28 different products consisting of 25 mixtures and 3 blends of turfgrass seeds were established under a fully automated rainout shelter at the St. Paul campus of the University of Minnesota. The drought treatments lasted for 67 days in 2017, and 52 days in 2018; both the 2017 and 2018 treatments were followed by a recovery period. Data were obtained during acute drought treatments and recovery periods for visual turfgrass quality and green turfgrass cover using digital images of the plots. During the first year, several products displayed higher green stability (or the ability to remain green) at the 3-inch height-of-cut compared with the 2.5-inch height-of-cut. Products with tall fescue (Schedonorus arundinaceus) and fine fescue (Festuca sp.) as dominant species generally performed better during the drought treatments, whereas an increasing presence of perennial ryegrass (Lolium perenne) and kentucky bluegrass (Poa pratensis) decreased the visual drought performance of the products. During the recovery period, an effect of the interaction between mowing height and the date of data collection on the percentage of green cover was observed: the lower mowing height improved the early recovery of green cover after acute drought. These findings suggest that consumers in the upper midwestern United States and areas with a climate similar climate to that of St. Paul, MN, who are challenged with multiple choices of lawn seed products should choose products containing a higher tall fescue content and adjust their mowing heights to optimize recovery.

The Effect of Age and Drought on the Recovery of Midday Leaf Hydraulics and Physiological Traits in Oat (Avena nuda)

The leaf hydraulic behavior has a significant role on species survival because plants often encounter drought. The effect of age and drought on the leaf water potential (ѰL), leaf hydraulic conductance (KL), stomatal density (SD) and size (SS), evapotranspiration (E), net photosynthetic rate (Pn) stomatal conductance (gs) and their post drought recovery in naked oat is not understood. This study investigated these facts in two naked oat cultivars, Yanmai (Ym) and Dingyou7 (Dy7). The plants were grown in pots and kept well-watered (WW) for the first ~30 days after sowing (DAS) after that for Experiment 1) the plants were kept in a rainout shelter; in a growth room and kept WW throughout. Experiment 2) the plants were grown at 40% drought to determine the effect of drought on the SD and SS. Experiment 3) the plants were grown in 40% field water capacity (FC) for ~25 days then, they were recovered from drought stress and ѰL, KL, SS, SD, E, Pn, and gs were determined. Under the drought, Ym lost KL whereas; Dy7 could maintain KL and higher midday ѰL and lower SD than Ym. The cultivar Dy7 showed maximum recovery of KL, ѰL, Pn, gs and E than Ym upon re-watering. The loss and recovery of KL, ѰL, Pn, E, gs and SD is controlled genetically in naked oat cultivars in combination with the environmental factors and the cultivar Dy7 has potential to enhance drought resistance in crops plants by genetic crop breeding. © 2021 Friends Science Publishers

Design of Automated Rainout Shelter to Conduct Experiment on Drought Tolerant Maize Genotype

Uneven and low precipitation areas of Nepal are continuously suffering from drought and received low productivity because of unavailability of suitable drought tolerant maize genotype. An attempt has been made first time in Nepal by constructing an automated rainout shelter with soil moisture based automated drip irrigation system at National Maize Research Program in 2018-2019 to conduct an experiment on drought tolerant maize genotype. The rainout shelters automatically covers the cropping area as soon as the rain sensor received a single drop of precipitation and also if the light intensity decreased to value set in the control panel. Likewise, the soil water level in different treatments were maintained on the basis of the treatment controlled with automatic drip irrigation system set to irrigate at threshold value set in the microcontroller. The complete system had found very useful in determining accurate amount of water required to cultivate drought tolerant maize genotype. We have tested drought tolerant variety RampurSo3Fo8 under 10 level of irrigation and it was determined that 495.2 mm of water is maximum level of water to produce highest yield of 3.32 t/ha whereas 445.6 mm to 247.6 mm of water could can be manage to produce competitive yield without any reduction. An experiment under such kind of infrastructure provide useful information on irrigation management practices required for drought variety in the natural environment. The research output also guides farmers and agriculturist in making Nepalese agricultural more sustainable, mechanized and productive.

Rainout Shelter-Induced Water Deficit Negatively Impacts Peanut Yield and Quality in a Sub-Humid Environment

ABSTRACT Water deficit significantly reduces yield potential of peanut (Arachis hypogaea L.) worldwide. Availability of drought tolerant cultivars is essential, but their selection is difficult, in particular in environments where rainfall is unpredictable. This study investigated the response of eleven peanut genotypes to three water regimes and was aimed to determine if use of rainout shelters is a reliable selection method for drought tolerance in a sub-humid environment with unpredictable rainfall pattern. Water regimes were achieved by covering the plots from mid-July to early Sep with the rainout shelters and irrigating the plots to pre-determined levels: well-watered (WW) regime received full irrigation of 40 mm weekly, moderate deficit (MD) 17 mm weekly, and severe deficit (SD) only 40 mm in one “survival” irrigation in late Aug. Results showed that MD and SD reduced yield and grade for all genotypes. Compared with WW, economic value of all genotypes was 24% less under MD and 68% less under SD. Small seeded runner cultivars, ‘Florida 07′ and ‘Georgia 06G', had higher yield and grade than Virginia-type cultivars under deficit irrigation, in particular under SD. Among the Virginia-type, ‘Sugg' had highest yields under SD but was out yielded by ‘Bailey' and ‘Phillips' under MD. ‘Wynne' and ‘Spain' are the largest seeded Virginia-type cultivars; they performed poorest for yield and grade. The relative proportion of oleic fatty acid (C18:1) was less under SD compared to WW; and linoleic fatty acid (C18:2) and total saturated oils were more, but intensities depended on the genotype. Finally, the rainout setting provided comparative results with real farm peanut production in the region; this is important for breeding programs in Virginia and Carolinas, where rainfall unpredictability does not allow for drought screening in an open field setting.

Roots of Lucerne Seedlings are More Resilient to a Water Deficit than Leaves or Stems

Drought is one of the most harmful environmental stresses affecting the physiological, biochemical processes and growth of plants. Lucerne or alfalfa (Medicago sativa L.), one of the most popular pasture species in arid and semi-arid regions, plays a critical role in sustaining agricultural systems in many areas of the world. In order to evaluate the effect of water shortage on water status, biomass distribution and proline content, the relative water content (RWC), biomass and proline concentration in the leaves, stems and roots of lucerne seedlings under three different water regimes were studied in pots under a rainout shelter. The results showed that after water was withheld, the RWC of the different organs decreased significantly; at the same soil water content, the leaf RWC was higher than that of the stem and root. The biomass of the leaves, stems and roots were all reduced by water stress, while the root–shoot ratio increased indicating that the roots were less affected than the leaves and stems. Proline concentration increased with decreasing soil water content with the leaf proline concentration increasing more than that of stems and roots. These results indicate that roots of lucerne seedlings show greater resilience to water deficits than shoots.

Yield potential of upland rice varieties under reproductive-stage drought and optimal water regimes in Nigeria

The goal of most rice improvement programs is the enhancement of farmers’ yield using less land and limited water. This study evaluated 77 upland rice genotypes under optimal upland growing conditions in the field and ranked the genotypes using base indices. Subsequently, eighteen cultivars selected from the field trial were screened under drought in rainout-shelter conditions. The traits evaluated for index selection were yield, days to flowering, plant height, number of panicles and filled grains. Under field conditions, based on the sum of economic weight assigned to five traits used to compute the selection index, IR 68704-145-1-1-B and IR 63380-16 were the best genotypes. In the rainout-shelter experiment, Ofada 2 (508 gm−2) had the highest grain yield under non-stress conditions while ITA 117 (152.38 gm−2) had the highest grain yield under drought stress. The base index was efficient for selecting superior genotypes with the best combination for all the traits considered. Susceptibility to drought stress of the landraces leads to poor grain yield.

Contribution of Root-Knot Nematodes to Aflatoxin Contamination in Peanut (Arachis hypogaea)

ABSTRACT Peanut kernels are susceptible to colonization by some species of Aspergillus which, under conditions of drought and high temperatures, can produce aflatoxins prior to harvest. The objective of this research was to determine the mechanism by which the peanut root-knot nematode (Meloidogyne arenaria) increases aflatoxin contamination in peanut. Research determined 1) the role of nematode infection of roots vs. pods in increased aflatoxin contamination and 2) whether increased aflatoxin production in nematode-infected peanut is due to a greater percentage of small or immature kernels. An additional objective was to determine whether a peanut cultivar with resistance to M. arenaria would reduce the risk of preharvest aflatoxin contamination. In the greenhouse, researchers physically separated root growth from pod set and inoculated each location with M. arenaria or a water control in a 2 × 2 factorial design with 12–15 replications. Of the six trials conducted, data indicated that pod and root infection by M. arenaria was associated with elevated aflatoxin concentrations in one and three trials, respectively. This suggests that root infection by the nematode can increase aflatoxin concentrations in the peanut kernel. Another 2 × 2 factorial experiment was conducted with two peanut genotypes (Tifguard and TifGP-2) and two nematode treatments (with and without M. arenaria) with six replications. The cultivar Tifguard is resistant to M. arenaria and TifGP-2 is susceptible. The experiment was carried out in 24 field microplots equipped with a rainout shelter. The experiment was conducted five times from 2006 to 2010. Infection of TifGP-2 by M. arenaria did not lead to greater percentages of small kernels. In only one year (2007), nematodes appeared to increase the percentage of damaged kernels, though aflatoxin concentrations were not affected by nematodes in that year. In the rainout shelter experiment, 2006 was the only year where nematode infection of peanut increased aflatoxin concentrations. In that year, there were lower aflatoxin concentrations in the nematode-resistant cultivar Tifguard than the susceptible germplasm TifGP-2 (12 vs. 136 ng/g).

POTENCIAL HÍDRICO FOLIAR EM MILHO SUBMETIDO AO DÉFICIT HÍDRICO

O potencial hídrico foliar pode ser considerado como um parâmetro de indicação da condição hídrica das culturas. Este trabalho teve como objetivo estudar o potencial hídrico foliar das plantas de milho sobre déficit hídrico no estágio inicial de desenvolvimento reprodutivo. O experimento foi conduzido no interior de uma cobertura móvel “Rainout shelter”, utilizando o delineamento experimental inteiramente casualizado, com dois tratamentos e quinze repetições. Os tratamentos foram constituídos de dois manejos da água de irrigação: (i) irrigado (as plantas de milho receberam irrigação conforme suas necessidades durante todo o ciclo de desenvolvimento); (ii) déficit hídrico aplicado antes do pendoamento. O déficit hídrico teve uma duração de aproximadamente 50 mm de ETo acumulada. A cobertura móvel foi acionada quando da ocorrência de chuvas, impedindo que esta ocorresse sobre a área experimental. Determinou-se o conteúdo de água disponível nas camadas de 0-10, 10-25, 25-55 e 55-85 cm de profundidade e variação diária do potencial hídrico das folhas de milho. Não foram observadas diferenças entre os tratamentos para o potencial de água na folha. O potencial hídrico foliar em plantas de milho não apresenta variação para déficit hídrico de 50 mm de evapotranspiração de referência acumulada. UNITERMOS: déficit hídrico, potencial hídrico foliar, milho, irrigação. MARTINS, J. D.; CARLESSO. R.; KNIES, A. E.; OLIVEIRA, Z. B.; BROETTO, T.; RODRIGUES, G. J. LEAF WATER POTENTIAL IN MAIZE EXPOSED TO WATER DEFICIT 2 ABSTRACT The leaf water potential can be considered as a parameter for indicating the crops water condition. This work aimed to study the maize leaf water potential on water deficit in the reproductive developmentinitial stage. The experiment was conducted within a mobile coverage "rainout shelter" using a completely randomized design with two treatments and fifteen repetitions. The treatments consisted of two water irrigation management: (i) irrigated (maize was irrigated as needed throughout the development cycle), (ii) water stress applied before tasseling. The drought lasted approximately 50 mm of accumulated reference evapotranspiration (ETo). The mobile coverage was triggered when rainfall occurred, preventing water from falling into the experimental area. Available water was determined in layers of 0-10, 10-25, 25-55 and 55-85 cm depth and daily variation of water potential in maize leaves were also evaluated. There were no differences between treatments for leaf water potential. The maize leaf water potential presented no change to water deficit equivalent to 50 mm of accumulated ETo. KEYWORDS: water deficit, leaf water potential, maize, irrigation.

Genotypic variation for drought stress response traits in soybean. III. Broad-sense heritability of epidermal conductance, osmotic potential, and relative water content

The broad-sense heritability of 3 traits related to leaf survival in severely stressed plants was studied in several hybrid soybean populations. The 3 traits were epidermal conductance (ge), osmotic potential (π), and relative water content (RWC). The populations were generated by hybridising unrelated parental genotypes previously shown to differ in the 3 traits. ge (mm/s) was measured on well watered plants from 10 populations involving all combinations of 5 parental lines, grown in soil-filled beds in the glasshouse. π (MPa) and RWC (%) were measured on severely stressed plants of 3 populations involving all combinations of 3 different parents, growing into a terminal water deficit under a rainout shelter in the field. Broad-sense heritability for ge was significantly different from zero (P < 0.05) in all 10 populations and ranged from 60% to 93%. Heritability estimates for π70 (the tissue osmotic potential at 70% RWC) ranged from 33% to 71%. Only two estimates were statistically significant (P < 0.05) because of large standard errors and the fact that parental differences were smaller than previously observed. Broad-sense heritability for RWC of severely stressed plants ranged from 40% to 74%, and was statistically significant (P < 0.05) for 2 of the 3 populations. For all 3 traits, F2 progeny distributions were consistent with quantitative inheritance with a high degree of additive gene action. It was concluded that capacity exists to breed varieties with low ge, low π70, and high RWC in stressed plants. However, in the case of osmotic potential, genotypes with lower π70 combined with greater precision of measurement would be needed than proved possible in these studies. Further, specific strategies would be needed to select for the critical RWC, the minimal RWC at which leaf tissues die and which provides a measure of tissue dehydration tolerance. More research is also needed to characterise the dynamic relations between ge, π, and RWC in influencing leaf survival in soybean, before they could be confidently used in a breeding program to improve drought tolerance.