Alleviating heat stress during early-season establishment of containerized strawberry transplants

BACKGROUND: Earlier planting under subtropical climatic conditions has been proposed as a means of increasing strawberry (Fragaria×ananassa Duch.) profitability but exposes transplants to heat stress. OBJECTIVE: Therefore, physical and chemical methods of ameliorating heat stress on the establishment, growth, and yield of containerized strawberry transplants were evaluated. METHODS: We used a split-plot design with white-on-black (white) mulch and black mulch as main plot treatments; and a factorial arrangement of transplant type and stress-prevention application was randomly assigned to the subplots. ‘Florida Radiance’ Jiffy plug and tray plug transplants were treated either with s-abscisic acid or with kaolin. RESULTS: White mulch resulted in greater plant vigor and vegetative growth than black mulch. Kaolin plus white mulch provided protection against heat stress as indicated by increased photosynthesis rates. At 4 weeks after transplanting, plant vigor and shoot growth were higher and flowering occurred earlier with Jiffy plug transplants than with tray plug transplants. Early marketable yields were higher with white mulch than with black mulch in three of the four site years. CONCLUSIONS: A combination of white mulch, Jiffy plug transplants, and kaolin application appears to have the best potential for alleviating heat stress during early-season strawberry establishment under subtropical conditions.

Light Spectra and Root Stocks Affect Response of Greenhouse Tomatoes to Long Photoperiod of Supplemental Lighting

Plant biomass and yield are largely dictated by the total amount of light intercepted by the plant (daily light integral (DLI)—intensity × photoperiod). It is more economical to supply the desired DLI with a long photoperiod of low-intensity light because it uses fewer light fixtures, reducing capital costs. Furthermore, heat released by the light fixtures under a long photoperiod extended well into the night helps to meet the heating requirement during the night. However, extending the photoperiod beyond a critical length (>17 h) may be detrimental to production and lead to leaf chlorosis and a reduction in leaf growth and plant vigor in greenhouse tomato production. It is known that red light can increase leaf growth and plant vigor, as can certain rootstocks, which could compensate for the loss in plant vigor and leaf growth from long photoperiods. Therefore, this study investigated the response of tomatoes grafted onto different rootstocks to a long photoperiod of lighting under red and other light spectra. Tomato plants ‘Trovanzo’ grafted onto ‘Emperator’ or ‘Kaiser’ were subjected to two spectral compositions—100% red or a mix of red (75%), blue (20%), and green (5%) light for 17 h or 23 h. The four treatments supplied similar DLI. Leaf chlorosis appeared in all plants under 23 h lighting regardless of spectral compositions between 20 and 54 days into the treatment. The yield for 23 h mixed lighting treatment was lower than both 17 h lighting treatments. However, the 23 h red lighting treatment resulted in less leaf chlorosis and the plants grafted onto ‘Emperator’ produced a similar yield as both 17 h lighting treatments. Therefore, both spectral compositions and rootstocks affected the response of greenhouse tomatoes to long photoperiods of lighting. With red light and proper rootstock, the negative yield impact from long photoperiod lighting can be eliminated.

Genetic Analyses and Genomic Predictions of Root Rot Resistance in Common Bean Across Trials and Populations

Root rot in common bean is a disease that causes serious damage to grain production, particularly in the upland areas of Eastern and Central Africa where significant losses occur in susceptible bean varieties. Pythium spp. and Fusarium spp. are among the soil pathogens causing the disease. In this study, a panel of 228 lines, named RR for root rot disease, was developed and evaluated in the greenhouse for Pythium myriotylum and in a root rot naturally infected field trial for plant vigor, number of plants germinated, and seed weight. The results showed positive and significant correlations between greenhouse and field evaluations, as well as high heritability (0.71–0.94) of evaluated traits. In GWAS analysis no consistent significant marker trait associations for root rot disease traits were observed, indicating the absence of major resistance genes. However, genomic prediction accuracy was found to be high for Pythium, plant vigor and related traits. In addition, good predictions of field phenotypes were obtained using the greenhouse derived data as a training population and vice versa. Genomic predictions were evaluated across and within further published data sets on root rots in other panels. Pythium and Fusarium evaluations carried out in Uganda on the Andean Diversity Panel showed good predictive ability for the root rot response in the RR panel. Genomic prediction is shown to be a promising method to estimate tolerance to Pythium, Fusarium and root rot related traits, indicating a quantitative resistance mechanism. Quantitative analyses could be applied to other disease-related traits to capture more genetic diversity with genetic models.

Assessing the impact of soil erosion on plant vigor (NDVI) and the spatial patterns of soil-bound Cu, Zn and B micro- and N, P macronutrients in a sloping vineyard (Tokaj, Hungary)

<p>Soil erosion in sloping vineyards greatly influence the spatial distribution of soil nutrient contents and can affect plant nutrition and vigor. The study aimed to evaluate possible links between the grapevine (Vitis Vinifera) vigor and the erosion-impacted macro- and micronutrient contents in the topsoil. Our study combined field observations, laboratory measurements and remote sensing data.</p><p>The field experiment was performed in a 1.8 ha vineyard plot in Tokaj (NE Hungary) with a mean slope of 8° and a slope length of 270 m. The main soil type in the vineyard is Regosol developed on loess. The stock unearthing method was applied for estimating soil loss/sedimentation in the vineyard. The study plot is separated by pathways perpendicular to the south-facing main slope into four equal areas with decreasing slope steepness. A total of 42 soil samples (0-10 cm) were collected (10-12 in each area) to measure organic matter content, plant-available nitrite+nitrate-N, P<sub>2</sub>O<sub>5</sub>-P, and total contents of Cu, Zn and B micronutrients. Additionally, five subsoil samples were taken at 2 m depth for determining micronutrient accumulation in the topsoil due to vine treatments. The spatial variability of topsoil nutrient contents was assessed by interpolating the measured parameters using the inverse distance weighting method. The effects of soil erosion and spatial distribution of the nutrient contents on plant vigor were analyzed using the Normalized Difference Vegetation Index (NDVI). Sentinel-2 images with 10 m resolution were acquired on three dates in June and July 2020. In the study area, a median Cu enrichment factor (EF=topsoil/subsoil) of 2.7 can be attributed to a prevailing anthropogenic origin of the topsoil-bound Cu content. The vineyard is an organic farm, therefore Cu use (in a dose of 4 kg/ha/year) is an obvious way to protect grapevines against fungal infections. We also observed a moderate degree of Zn and B enrichment in the topsoil (EF<sub>Zn</sub>: 1.2, EF<sub>B</sub>: 1.4) due to vine treatments with foliar fertilizers. The element distribution maps show a fairly similar spatial pattern of Cu, available P<sub>2</sub>O<sub>5</sub>-P, and organic matter contents. Their accumulation in the footslope area with the lowest steepness can be seen. Compared with the soil loss/sedimentation map based on stock unearthing data, the Cu, P<sub>2</sub>O<sub>5</sub>-P and organic matter contents of the topsoil are lower in areas subject to more intense erosion, which may even affect the development of vines. The latter is to be examined in the light of vegetation indices (NDVI). Changes in vegetation indices along the main slope can be observed with clearly increasing NDVI values in the footslope area. Spatial changes in B, Zn and nitrite-nitrate-N contents do not show a clear relationship with the topographic patterns of the area and the resulting soil erosion losses. Besides the nutrient contents, the presumably higher soil moisture content in the footslope area may also explain the higher NDVI values.</p><p><sub>I. B. is grateful for the support of the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences. The research received funds from the OTKA 1K 116981.</sub></p>

Assessing water doses, water use efficiency and tomato quality under greenhouse conditions in Natabuela-Ecuador

<p>In Ecuador, tomato (Solanum lycopersicum L.) is a main crop which production has been increase in the latest decade. The crop is grown throughout the country, although it is in the Sierra region where locate the greenhouse production areas. Tomato manufacturers face the water scarcity problems and in addition, the small and medium producers have little knowledge regarding the amount of water they should apply to the crop, and how they should manage. Considering this framework, this study first is aimed at determining the optimal water doses for tomato crop cultivated under greenhouse conditions in the Sierra region and second, it is aimed at establishing the best irrigation frequency. The experimental study was carried out from June to December 2020, in a metallic greenhouse with plastic cover, located in the Natabuela’s parish which belong to the city of Antonio Ante in the Imbabura province. The variables studied were:  two water doses (100% and 120% of the of the evapotraspiration, ET) and four irrigation frequencies (two irrigations and one irrigation a day, one irrigation every other day and one irrigation every two days). In total, eight treatments were evaluated in an 2 x 4 factorial design, under a completely random block distribution, with four repetitions. The results show that the 120% ET irrigation dose produces the highest plant vigor and total and commercial production, while the 100% ET irrigation dose presents a higher citric acid percentage and total soluble solids content. Likewise, both doses do not showed significant differences in their water use efficiency and pH. Therefore, if the increase in production is searching then, it would be advisable to apply the 120% ET dose, although if the search is for the production quality it would be better to apply 100% ET. Regarding the irrigation frequency, one or two irrigations a day produced higher plant vigor as well as higher production and water use efficiency. None of the irrigation frequencies studied had significant differences in plant height and fruit quality variables.</p><p> </p>

Tolerance in Maize Landraces to Diabrotica speciosa (Coleoptera: Chrysomelidae) Larvae and Its Relationship to Plant Pigments, Compatible Osmolytes, and Vigor

The rootworm Diabrotica speciosa (Germar) is native to South America and causes severe economic losses to several crops due to root feeding and disease spread. In maize (Zea mays L.), losses in production come from larval rootworm attack on plant roots resulting in plant health problems, including stalk lodging. More options for controlling this pest are needed to create well balanced, integrated pest management programs for farmers in this region. Natural sources of tolerance in maize genotypes are important for maize breeding programs, and this study investigated the expression of tolerance in several Brazilian maize landraces to D. speciosa. Plant vigor and compounds associated with plant health, including chlorophylls, carotenoids, glycine betaine, and proline were assessed for each landrace. Five landraces and one maize cultivar were selected based on their levels of antibiosis-resistance to D. speciosa that were determined in a prior screening. The percent reduction in plant growth was used as the measure of tolerance. The landrace Azteca was classified as tolerant to D. speciosa larval feeding, displaying less reduction in plant matter despite having lower plant vigor. This landrace also had higher amounts of chlorophyl and carotenoid pigments, suggesting a positive correlation between tolerance to D. speciosa and higher contents of these photosynthetic pigments. The compatible osmolytes glycine betaine and proline do not seem to be associated with tolerance in maize landraces to D. speciosa larvae. Landrace Azteca seems promising for plant breeding, and repeated field studies are needed to confirm its suitability in maize integrated pest management.