Evaluation of damping-off tolerance in spinach cultivars in field soils and in a standardized lab assay with Pythium ultimum

Spinach growers face increasing problems of damping off in the production of fresh market (baby-leaf) spinach due to increasing restrictions on chemical treatments. Damping-off tolerant cultivars are increasingly important, requiring proper evaluation methods. From three locations in the Netherlands with a history of spinach cultivation and from one location in France, potential damping-off pathogens were isolated from the soil, identified to species or genus, and tested for their pathogenicity. Pythium ultimum was the most prevalent pathogen in those fields, causing spinach pre- and post-emergence damping off. Eight spinach cultivars with two or three seed lots each, were evaluated at the same field locations and in a greenhouse with soil sampled from one of the Dutch field sites. Pre-emergence damping off was more discriminating for differences among the cultivars than post-emergence damping off. Variation in levels of infection among trials, replicates, and seed lots of same cultivars, emphasized the need for a more standardized phenotyping assay. For such an assay, a cornmeal/sand-based inoculum with a pathogenic P. ultimum isolate was added to a substrate mixture of sand, perlite, and vermiculite, moistened until 50% water holding capacity, in which spinach seeds were incubated for ten days in a dark climate cabinet at 15°C, including a control treatment without P. ultimum inoculum. The assay showed reproducible results for discriminating differences in pre-emergence damping-off tolerance levels among seed lots. However, cultivar differences in pre-emergence damping-off tolerance levels could not be confirmed due to a large variation among seed lots that needs further investigation.

Physicochemical Characterization of Selected Pomegranate (Punica granatum L.) Cultivars

The physical and chemical characteristics of five pomegranate cultivars (Mridula, Ganesh, White muscut, G-137 and Jalor seedless) were examined in the present investigation. Physical properties of different cultivars were determined such as major diameter (85.05 to 91.62 mm), intermediate diameter (76.85 to 87.83 mm), minor diameter (79.86 to 90.01 mm), sphericity (0.903 to 0.937), fruit weight (294.4 to 404.14 g), fruit volume (289 to 387 mL), number of arils per fruit, weight of 100 arils were evaluated and analysed for the varietal difference. In addition, properties such as peel moisture content (68.72 to 74.15% w.b.), aril moisture content (78.25 to 81.82% w.b.), peel ash content (0.81 to 1.51%), aril ash content (0.29 to 0.53%), juice pH (3.47 to 3.96), total soluble solids (11.60 to 13.00 °Brix), titratable acidity (0.42 to 0.58%), total phenolic content, juice yield per fruit (104 to 186 mL) juice turbidity (142.20 to 364.50 NTU) and textural properties, like fruit compressive strength/firmness of arils (23.09 to 34.54 N), cutting strength of peel (84.33 to 111.35 N) and aril skin puncture force (0.28 to 0.38 N) were also investigated. Overall results suggested that the measured physico-chemical properties were quite different by the cultivar differences.

Light Quality Environment and Photomorphological Responses of Young Olive Trees

Tree densities have increased greatly in olive orchards over the last few decades. In many annual crop species, increased density reduces the horizontal red/far-red (R/FR) and blue/green (B/G) ratios during canopy development even before direct shading occurs, and such changes are known to alter plant morphology. This study with olive trees evaluated: (1) whether the leaf area index (LAI) of neighboring trees modifies the light quality environment prior to a tree being directly shaded and (2) the potential morphological responses of three olive cultivars to changes in light quality. Increasing LAI using different spatial arrangements of potted, three-year-old trees reduced the horizontal R/FR ratio more than that of the B/G ratio. Cultivar-specific responses to low R/FR ratio were observed for individual leaf area and aboveground/belowground biomass ratio using laterally positioned FR mirrors or green fences. No statistically significant responses were detected in response to green vegetation fences that reduced both horizontal R/FR and B/G ratios, but a cluster analysis grouped together the overall morphological responses to both FR mirrors and green fences. These results in olive trees suggest that cultivar differences in response to light quality may be relevant for understanding adaptation to dense orchards and identifying cultivars best suited to them.

Forage production and leaf proportion of lucerne in subtropical environments: cultivar, cutting frequency and canopy effects

In subtropical and humid environments the ‘winter-active’ cultivars of lucerne usually produce more forage with lower leaf proportion (i.e. leaf to stem ratio) than the ‘winter-dormant’ ones. Present research analyze (i) if differences in forage production changes with cutting frequency, and (ii) if differences in leaf proportion are intrinsic (i.e. ‘cultivar differences’) or are due to variations in plant morphology (i.e. ‘aerial biomass and canopy height’). In two subtropical locations a factorial experiment including three alfalfa cultivars (FD4= ‘winter-dormant’, FD6=‘semi-dormant’, FD9=‘winter-active’) and three cutting frequencies (‘high’, ‘intermediate’ and ‘low’) was established. As the cutting frequency decrease (i.e. from ‘high’ to ‘low’) the more winter-active cultivars were more productive than the more winter-dormant ones (FD9>FD6>FD4) due mainly to a higher stem production. However, differences between cultivars disappear (FD9=FD6=FD4) as the cutting frequency increases (i.e. from ‘low’ to ‘high’ cutting frequency). Compared at similar canopy height, differences between cultivars in leaf proportion were practically irrelevant. We confirm that (i) in subtropical and humid environments, the differences in forage production between cultivars contrasting in their winter activity depend of the cutting frequency, and that (ii) the leaf proportion depends mainly of plant morphology, especially canopy height’, being irrelevant the cultivar and the environment. Highlights This paper shows that (i) differences in forage production between cultivars of lucerne depend on the cutting frequency, and that (ii) leaf proportion is governed by plant morphology, especially canopy height. Forage production was similar between cultivars at high cutting frequency but at low cutting frequency winter-active and semi-dormant cultivars (FD6 and FD9) produce more forage than winter dormant (FD4) ones. Lucerne cultivars showing the same leaf proportion when they were compared at similar canopy height suggesting that leaf proportion is not an intrinsic trait Changes in leaf proportion were better explained by changes in canopy height than by changes in thermal time.

Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio

Knowing a tree crop’s seasonal growth and development as a function of heat accumulation can facilitate scheduling of irrigation, pesticide applications, and harvest. Our objective was to compare the goodness of fit of applied models and determine which provides the best description of pistachio nut growth as a function of thermal unit accumulation. Three fruit growth traits of pistachio—pericarp (hull) + endocarp (shell) size, endocarp thickening and hardening, and embryo (kernel) size—exhibited clear nonlinear dependence on heat accumulation. We tested three nonlinear models—Michaelis–Menten, three-parameter logistic, and Gompertz—fitted to fruit development data to create a tool to forecast pest susceptibility and harvest timing. Observation of development began at full bloom and ended at harvest. Data were collected from six pistachio cultivars in one experimental and eight commercial orchards over 3 years. Analyses of residual distribution, parameter standard errors, coefficient of determination (R2) and the Akaike information criterion (AIC) all demonstrated the Gompertz function was the best model. Cultivars differed significantly in all the three parameters (Asym, b, and c) for all three traits with the Gompertz model, demonstrating the Gompertz model can adjust to incorporate cultivar differences. The growth curve of the three traits together provided integrated information on nut biomass accumulation that facilitates predicting the critical timing for multiple orchard management practices.

Biochar Mediated-Alleviation of Chromium Stress and Growth Improvement of Different Maize Cultivars in Tannery Polluted Soils

Soil pollution with heavy metal is a serious problem across the globe and is on the rise due to the current intensification of chemical industry. The leather industry is one of them, discharging chromium (Cr) in huge quantities during the process of leather tanning and polluting the nearby land and water resources, resulting in deterioration of plant growth. In this study, the effects of biochar application at the rate of 3% were studied on four maize cultivars, namely NK-8441, P-1543, NK-8711, and FH-985, grown in two different tannery polluted Kasur (K) and Sialkot (S) soils. Maize plants were harvested at vegetative growth and results showed that Cr toxicity adversely not only affected their growth, physiology, and biochemistry, but also accumulated in their tissues. However, the level of Cr toxicity, accumulation, and its influence on maize cultivars varied greatly in both soils. In this pot experiment, biochar application played a crucial role in lessening the Cr toxicity level, resulting in significant increase in plant height, biomass (fresh and dry), leaf area, chlorophyll pigments, photosynthesis, and relative water content (RWC) over treatment set as a control. However, applied biochar significantly decreased the electrolyte leakage (EL), antioxidant enzymes, lipid peroxidation, proline content, soluble sugars, and available fraction of Cr in soil as well as Cr (VI and III) concentration in root and shoot tissues of maize plant. In addition to this, maize cultivar differences were also found in relation to their tolerance to Cr toxicity and cultivar P-1543 performed better over other cultivars in both soils. In conclusion, biochar application in tannery polluted soils could be an efficient ecofriendly approach to reduce the Cr toxicity and to promote plant health and growth.

Transcriptome and physiological studies reveal key players in wheat nitrogen use efficiency under both high and low N

The effective use of available nitrogen (N) to improve crop grain yields provides an important strategy to reduce environmental N pollution and promote sustainable agriculture. However, little is known about the common genetic basis of N use efficiency (NUE) at varying N availability. Two wheat (Triticum aestivum L.) cultivars were grown in the field with high, moderate and low N supply. Zhoumai 27 outperformed Aikang 58 independent of the N supply and showed improved growth, canopy leaf area index, flag leaf surface area, grain number and yield, and enhanced NUE due to both higher N uptake and utilization efficiency. Further, transcriptome and proteome analyses were performed using flag leaves that provide assimilates for grain growth. Results showed that many genes or proteins that are up- or down-regulated under all N regimes are associated with N and carbon metabolism and transport. This was reinforced by cultivar differences in photosynthesis, assimilate phloem transport, and grain protein/starch yield. Overall, our study supports that improving NUE at both high and low N requires distinct adjustments in leaf metabolism and assimilate partitioning. Identified key genes/proteins may individually or concurrently regulate NUE and are promising targets for maximizing crop NUE irrespective of the N supply.

Source of Metal Ions on Raw Cotton Fibers and their Influence on Dyeing

This work reports on two debated points related to the metal content of cotton fiber and its influence on processing. The first issue is if the metal levels of raw fibers are naturally deposited during fiber development or if the levels are influenced by weathering and harvesting conditions present after boll opening. This was tested by harvesting bolls just as they were opening and after the opened bolls were allowed to field age. The second issue relates to the importance of metal levels on fiber dyeability. Results indicate that the metal levels of newly-opened cotton were not appreciably different from those of aged cotton bolls and that the fiber metal levels after scouring and bleaching had little correlation with dye uptake. Additionally, some metal levels exceeded those previously reported and the environment appeared to have a stronger influence on fiber Ca and Mg levels than did cultivar differences.