Blossom-end Rot Research Articles

Hydroxycinnamic Acid Oligomers-Based Biostimulant Nurspray® Enhances Tomato Yield, Fruit Quality, and Reduces Blossom-End Rot

Tomato production faces challenges such as high input costs, pests, diseases, and climate change. Biostimulants like Nurspray®, based on hydroxycinnamic acid oligomers, offer a promising solution. This study evaluated the impact of different application timings of Nurspray® on tomato yield and fruit quality under open-field conditions. Four treatments were tested: T1 (control), T2 (Nurspray® at BBCH 19–51), T3 (Nurspray® at BBCH 19–51–61), and T4 (Nurspray® at BBCH 19–23–51). The results showed significant improvements in root development, canopy cover, and flowering for T3 and T4, with root systems increasing by up to 103% in T4 compared to the control. Fruit yield and quality were enhanced, with a reduction in blossom-end rot (BER) incidence to 0% in T3 and T4, compared to 5% in the control. Additionally, T4 produced the highest dry matter content in fruits. The optimal application strategy was three doses of Nurspray® at BBCH 19–23–51, enhancing both yield and fruit quality. This study highlights the potential of Nurspray® as an organic biostimulant in sustainable tomato farming.

Comparative Effects of Calcium, Boron, and Zinc Inhibiting Physiological Disorders, Improving Yield and Quality of Solanum lycopersicum.

Localized calcium deficiency at the tomato flower end causes a physiological disorder called blossom end rot, resulting in yield losses of up to 50 percent. Fruit cracking is another physiological disorder of tomatoes that most often occurs when the movement of water and solutes to the tomato is protracted or rapid, but the underlying cause of fruit cracking is, again, calcium deficiency. Therefore, the present field experiment was conducted with the aim of increasing yield and reducing physiological disorders in tomatoes with a foliar application of calcium and micronutrients (zinc and boron). Four levels of calcium (0, 0.3, 0.6, and 0.9%), three levels of boron (0, 0.25, and 0.5%), and three levels of Zinc (0, 0.25, and 0.5%) were applied foliarly three times (starting at flowering, the 2nd application was repeated when the fruits set, and the 3rd after a period of 15 days from the fruits set). An addition of 0.6% calcium increased yield and associated traits with a decreased flower drop. Likewise, a 0.9% calcium addition increased fruit Ca content and decreased blossom end rot, fruit cracking, and Zn content. Foliar spraying with 0.25% boron (compound B) improved flowering and production while reducing flower drop and tomato fruit cracking. Similarly, an application of 0.5% B significantly increased Ca and B content with minimal blossom end rot and Zn content. Likewise, a 0.5% Zn application resulted in yield and yield-related traits with increased fruit B and Zn contents while blossom end rot, fruit cracking, and fruit Ca content were lower when 0.5% of foliar Zn was applied. Therefore, it is concluded that a foliar application of Ca, B, and Zn can be used alone or in combination to minimize the physiological disorders, increase production, and improve tomato fruit quality.

Evaluation of Impact of Biofertilizer and Mulch Types on Growth and Production of Tomato Cultivar Gustavi F1 in Lowland Areas

Tomato plants are expected to have an ideal growing environment to optimize their growth and production. Therefore, this study aimed to investigate the effect of various concentrations of biofertilizer, mulch types, and their interactions on growth and production of the Gustavi F1 tomato cultivar. A randomized group design (RGD) arranged factorially was used for the analysis, with the first factor consisting of no mulch (M0), straw mulch (M1), and plastic mulch (M2). The second factor was five biofertilizer concentrations, including 0 ml.l-1 (L0), 5 ml.l-1 (L1), 10 ml.l-1 (L2) 15 ml.l-1 (L3), and 20 ml.l-1 (L4). Data were analyzed using the F test (analysis of variance), and in cases of significant differences, the analysis proceeded with Duncan Multiple Range Test (DMRT) at an α level of 5%. Growth parameters observed in the experiments included plant height at 1 and 3 weeks after planting, while production parameters comprised fruit diameter, the number of fruits per plant, the percentage of fruits experiencing Blossom End-Rot (BER), and fruit weight per plot. The results showed that the use of plastic mulch significantly increased the number of fruits per plant, while the 0 ml.l-1 biofertilizer concentration showed the most effective reduction in the percentage of fruits experiencing BER. Moreover, an interaction between mulch and biofertilizer treatments was observed, particularly in relation to plant height 1 week after planting, the number of fruits per plant, and the percentage of fruits experiencing BER.

Understanding the Regular Biological Mechanism of Susceptibility of Tomato Plants to Low Incidences of Blossom-End Rot

Blossom-end rot (BER) is a physiological disorder caused by calcium deficiency, often paired with moisture stress and irregular traditional watering practices. To understand the biological mechanism affecting the incidence of BER, different tomato genotypes were cultivated in sandy soil and were traditionally irrigated. Nine tomato genotypes were investigated to assess their susceptibility to BER, and the incidence rate varied from 7.1% in “Voskhod” to 57.6% in “Majnat” genotypes. This study also comprehensively analyzed various physiological and biochemical parameters to elucidate their correlation with BER incidence in tomato plants. Our findings revealed a range of parameters positively correlated with BER incidence, including the relative water content of roots, the number of fruits per plant, vitamin C content, and potassium content. Parameters related to fruit quality, such as titratable acidity, peroxidase content, and firmness degree, also showed positive correlations with BER incidence. Conversely, parameters such as total yield per hectare, chlorophyll content, average plant height, and calcium content demonstrated strong negative correlations with BER incidence, suggesting potential protective effects against this disorder. This study highlights that genotypes with higher marketable yields, such as ‘Voskhod’ (65 tons/ha), showed lower BER incidence, underscoring the importance of selecting the appropriate genotype in improving yield and reducing blossom-end rot in tomato fields. Conversely, cultivars with high BER sensitivity, such as ‘Chelnok’ (26.3 tons/ha), require specially designed cultivation management to avoid production declines.

Grafting onto Tomato Rootstocks Improves Outcomes for Dry-farmed Tomato

Vegetable grafting can mitigate the negative effects of drought on crop production. Dry farming, which is the production of crops without irrigation during a dry growing season, can result in lower yields, smaller fruit, and a higher incidence of blossom-end rot (BER), which is a physiological disorder associated with drought stress. To determine the effects of grafting on yield and fruit quality of dry-farmed tomato (Solanum lycopersicum), three years of trials were conducted using different scion–rootstock combinations and ungrafted controls. In 2020, grafting onto rootstocks ‘DRO141TX’ and ‘Fortamino’ resulted in greater total yield and average fruit weight and a lower BER incidence for dry-farmed tomato than grafting onto the rootstock ‘Shincheonggang’ or using ungrafted plants. In 2021, grafting onto the rootstock ‘DRO141TX’ again increased yields and average fruit weight and decreased BER incidence when compared with ungrafted plants (‘Fortamino’ was not tested). Interactions were detected between different scion–rootstock combinations in terms of the degree of reduction of necrotic BER (BER resulting in a large, sunken, grey or black spot, making the fruit unmarketable) when grafted onto ‘DRO141TX’, with the scion ‘Azoychka’ having a 69% reduction in necrotic BER and the scion ‘Astrakhanskie’ having a 93% reduction in necrotic BER. In 2022, an interaction was detected between the rootstocks and scions in terms of their effect on large fruit (>0.33 lb) yield, with ‘BHN 871’ grafted onto ‘Fortamino’ producing the highest yields of large fruit and ‘Big Beef’ grafted onto ‘Fortamino’ producing the lowest yields. Overall, grafting onto the rootstocks ‘DRO141TX’ or ‘Fortamino’ improved diverse dry-farmed tomato outcomes in the Willamette Valley of Oregon, USA.

Improved Tomato Disease Detection with YOLOv5 and YOLOv8

This study delves into the application of deep learning for precise tomato disease detection, focusing on four crucial categories: healthy, blossom end rot, splitting rotation, and sun-scaled rotation. The performance of two lightweight object detection models, namely YOLOv5l and YOLOv8l, was compared on a custom tomato disease dataset. Initially, both models were trained without data augmentation to establish a baseline. Subsequently, diverse data augmentation techniques were obtained from Roboflow to significantly expand and enrich the dataset content. These techniques aimed to enhance the models' robustness to variations in lighting, pose, and background conditions. Following data augmentation, the YOLOv5l and YOLOv8l models were re-trained and their performance across all disease categories was meticulously analyzed. After data augmentation, a significant improvement in accuracy was observed for both models, highlighting its effectiveness in bolstering the models' ability to accurately detect tomato diseases. YOLOv8l consistently achieved slightly higher accuracy compared to YOLOv5l, particularly when excluding background images from the evaluation.

Physiological and transcriptomic analyses of healthy and blossom-end-rot (BER)-defected fruit of chili pepper (Capsicum annuum. L.)

Physiological and transcriptomic analyses of healthy and blossom-end-rot (BER)-defected fruit of chili pepper (Capsicum annuum. L.)

Exogenous application of gibberellic acid reduces antioxidant capacity of leaves, resulting in increased Tipburn damages in Lisianthus cultivars

Tipburn (calcium (Ca) deficiency disorder of new leaf tips) is a severe problem in horticultural crop production. Studies have focused on the fact that tipburn commonly occurs during bolting and shown that plants exhibited greater tipburn damage than the control when bolting was induced using exogenous gibberellic acid (GA). However, why exogenous GA application enhances tipburn damage and why tipburn occurs during bolting remains unclear. To address this knowledge gap, we investigated the occurrence of tipburn, Ca concentrations in each organ, antioxidant capacity (superoxide dismutase (SOD) and catalase activity), and gene expression in three lisianthus cultivars (‘Umihonoka’ (UH), ‘Reina White’ (RW), and ‘Voyage Peach’ (VP)), where bolting was induced through exogenous active GA application (GA treatment) and discussed the cause of tipburn occurring during bolting. The incidence and severity of tipburn in the GA treatment were significantly higher than those in the control group in all cultivars. The Ca concentrations in the top leaves of the GA treatment were similar to or higher than those in the control treatment for all cultivars. In contrast, SOD activity in VP was significantly lower in GA treatment than that in the control, which was consistent with the results of SOD-CuZn expression. Additionally, significantly lower catalase activity at GA treatment were detected in the UH and RW than at the control. Recent studies have reported that reactive oxygen species and antioxidants significantly affect the appearance of blossom-end rot. Therefore, exogenous GA application decreased the antioxidant capacity of the upper leaves, resulting in increased tipburn damage. In addition, it is known that a decrease in antioxidant capacity and an increase in H2O2 concentration in leaves of Arabidopsis is a trigger for the initiation of bolting. Our findings provide important insight into the causes and ecological implications of tipburn during bolting.

Mulching and drip irrigation to mitigate soil salinity on tomato (Lycoperscon esculentum L.) production in coastal area

Bangladesh’s coastal regions are rich in saline water resources. The majority of these resources are still not being used to their full potential. In the southern Bangladeshi region of Patuakhali, research was conducted to investigate the effects of mulching and drip irrigation on tomato yield, quality, and blossom-end rot (BER) at different soil salinity thresholds. There were four distinct treatments applied: T1= drip irrigation with polythene mulch, T2 = drip irrigation with straw mulch, T3 = drip irrigation without mulch, and T4 = standard procedure. While soil salinity was much greater in treatment T3 (1.19–8.42 dS/m) fallowed by T4 (1.23–8.63 dS/m), T1 treatments had the lowest level of salinity and the highest moisture retention during every development stage of the crops, ranging from 1.28–4.29 dS/m. Treatment T3 exhibited the highest soil salinity levels (ranging from 1.19 to 8.42 dS/m), followed by T4 with a range of 1.23 to 8.63 dS/m. In contrast, T1 treatments consistently maintained the lowest salinity levels (ranging from 1.28 to 4.29 dS/m) and the highest moisture retention throughout all stages of crop development. In terms of yield, drip irrigation with no mulch treatment (T3) provided the lowest output (13.37 t/ha), whereas polyethylene mulching treatment (T1) produced the maximum yield (46.04 t/ha). According to the study, conserving moisture in tomato fields and reducing soil salinity may both be achieved with drip irrigation combined with polythene mulch. The research suggests that employing drip irrigation in conjunction with polythene mulch could effectively preserve moisture in tomato fields and concurrently decrease soil salinity.

Effect of Salicylic Acid and Calcium on Growth, Yield, and Fruit Quality of Pepper (Capsicum annuum L.) Grown Hydroponically

The aim of this study was to investigate the effects of spraying plants with 0.03% salicylic acid (SA), 0.7% calcium nitrate (Ca), and 0.03% salicylic acid together with 0.7% calcium nitrate (SA + Ca) on plant growth, yield, and fruit quality of peppers grown in a mineral wool substrate. The control plants were sprayed with water (C). Two red-fruited sweet pepper cultivars were used in the study: ‘Aifos’, and ‘Palermo’, which produce fruits characterized by different shapes. Biometric measurements of the plants showed a higher growth rate of pepper plants when SA and Ca were applied foliarly compared to the control. Plants treated simultaneously with SA and Ca were characterized by the highest steady-state fluorescence yield [Fs]. The relative chlorophyll content of pepper leaves was also higher in plants sprayed with SA, Ca, and SA + Ca than in plants in the control. The analysis of pepper yield showed in both cultivars the effect of foliar treatment of plants with SA and Ca and SA + Ca on increasing pepper resistance to the occurrence of Ca deficiency on pepper fruit (Blossom end rot). Pepper fruits harvested from plants treated with SA, Ca, and SA + Ca had more juicy flesh.

PRANAM-Ca: An Eggshell Derived Calcium Fertilizer and Its Impact on Blossom end Rot in Tomato Cultivation

Eggshells, amounting to a staggering 76.7 million tons annually, are often inadequately disposed of in landfills, leading to significant nutrient loss for both plants and humans, while contributing to environmental pollution and emitting unpleasant odors. In response to these challenges, recent research has been dedicated to repurposing eggshells, exploring their applications in diverse fields such as biochemistry, biomedicine, environmental technology, and agriculture. Recognized as an exceptional source of calcium, eggshells offer notable benefits for calcium-demanding crops, including tomatoes, chilli and cotton. In a comprehensive study conducted, we investigated the application of organic foliar calcium derived from eggshells on tomato plants. The results demonstrated substantial improvements in addressing physiological disorders, promoting overall growth, and enhancing yield, signifies the importance of calcium fertilizer for growing healthy crop. With this background, Multiplex R&D team has made an effort to develop an in-house technology to derive the calcium from waste eggshell. Afterwards, how to scale-up and commercialise it as a sprayable form of Organic calcium fertilizer, PRANAM-CA. Present paper aims to describe the technique to derive calcium from eggshell and its impact on managing the blossom end rot in Tomato cultivation under protected glass-house condition.

Foliar application of natural zeolites affects the growth and productivity of processing tomato

The foliar application of zeolites has been proven to positively affect plant physiology suggesting that it could improve plant growth, however, this topic has been little studied. Two field trials were carried out (in 2021 and 2022) to study the potential beneficial effect of natural zeolite particle films on processing tomato crops. Natural zeolites i) clinoptinolite + and mordenite (CubZeo) and ii) micronized clinoptinolite (BigZeo) were sprayed onto the plants six times in the central crop cycles. In both trials, BigZeo promoted leaf and fruit dry mass (DM) accumulation, and leaf area from the early crop stage compared to the water-sprayed plants (Control). The final aerial DM of BigZeo plants enhanced more in the year with favourable (+39.2%) (2022) than in that with more stressing thermal conditions (2021) (+12.1%). Concurrently, the marketable yield was improved by + 36% in both years with positive effects also on fruit total soluble solids. Under heat stress, the CubZeo crop showed even lower aerial DM than the Control, however, the marketable yield remained similar due to higher fruit DM and higher incidence of blossom-end-rot (BER) in untreated plants. In 2022, CubZeo promoted DM accumulation, leaf expansion and yield even if to a lesser extent than the BigZeo treatment. In the fruits the concentrations of K, Ca, and Mg rose in zeolite-treated plants. The improved Ca level in the fruits can explain the lower occurrence of BER in the zeolite-treated plants, particularly with CubZeo. Si was observed at the highest level in fruits and stems of BigZeo-treated plants, followed by CubZeo and Control ones. The accumulation of Si could explain the best crop responses elicited by BigZeo, whereas the observed responses did not appear to involve changes in the photosynthetic machinery. However, further and comprehensive investigations are needed to define the zeolite film particle characteristics and the related physiological and nutritional changes in the plants.

Using Date Palm Waste as an Alternative for Rockwool: Sweet Pepper Performance under Both Soilless Culture Substrates.

The degradation of soil quality due to environmental conditions and improper management practices has caused a shrinkage in land areas suitable for crop cultivation. This necessitates a transition towards soilless culture systems, which offer desirable conditions for crop growth and development and increase resource use efficiency. One of the growth-limiting factors in soilless culture systems is the type of growing substrate. The use of more sustainable resources and environmentally friendly growing substrates is a challenge that affects the soilless culture industry. This work evaluates the efficacy of date palm waste (DPW) and rockwool as growing substrates for sweet pepper (Capsicum annuum L.) under greenhouse conditions. The plant height, stem diameter, average total leaf area, φPSII, and Fm' of leaf fluorescence show significant increases when plants are grown in rockwool. No differences are found in terms of the total yield or the number of marketable fruits and fruit quality between the two substrates. However, the DPW substrate shows a significant decrease in the number of unmarketable fruits and number of Blossom End Rot (BER) fruits. Plants grown in both growing substrates consume equal water amounts for the optimal fruit production, while the water use efficiency of rockwool is better than that of DPW. Our results highlight DPW's role in soilless production and as a key solution for resource-saving production systems.

Site Factors Related to Dry Farm Vegetable Productivity and Quality in the Willamette Valley of Oregon

Dry farming has been defined as rainfed crop production in a climate with more than 20 inches of annual precipitation, but where most precipitation falls outside the growing season. Dry farming is garnering interest in the western United States because it allows farmers to produce crops despite a lack of access to irrigation or water rights or to eliminate the infrastructure, labor, and energy costs of irrigation systems. Sites have differing suitability for dry farming, and some sites that can be farmed with irrigation will perform poorly when dry-farmed. To determine site factors associated with dry farm yield and fruit quality, trials of ‘Early Girl’ tomato (Solanum lycopersicum) and ‘North Georgia Candy Roaster’ winter squash (Cucurbita maxima) were conducted at 17 participant farms in the Willamette Valley in Oregon, USA, in 2018 and 2019. The mean blossom-end rot (BER) incidence was higher in the Willamette Valley than in coastal California; this was probably because of the Willamette Valley’s hotter and drier climate. Increasing the available water-holding capacity of soil, total available water (available water-holding capacity of the soil plus in-season rainfall), native productivity rating, soil pH (0–6 inches and 24–36 inches), soil nutrient concentrations (0–6 inches and 24–36 inches), and in-season rainfall were positively associated with at least one measure of tomato or winter squash yield, fruit number, or average fruit weight. An earlier planting date was positively associated with winter squash total yield and total fruit number in 2019. The water-limited yield potential (the total yield potential if water was the only limiting factor) for 20-ft2/plant plots was estimated to be 2.2 tons/acre per inch for tomato and 2.8 tons/acre per inch for winter squash. In 2019, high-density plantings (20 ft2/plant) had higher tomato and winter squash mean total yields, mean total fruit numbers, and mean tomato unblemished yield than low-density plantings (40 ft2/plant). In 2019, planting tomato at 20 ft2/plant decreased the mean BER incidence by 15.6% when compared with planting tomato at 40 ft2/plant.

Responses of yield, fruit quality and water relations of sweet pepper in Mediterranean greenhouses to increasing salinity

Increasing salinization of groundwater used for irrigation is a current and growing problem for vegetable production in greenhouses in the Mediterranean Basin. Vegetable growers in this system require clear information of crop response to salinity, particularly of threshold values. For sweet pepper in Mediterranean greenhouses, this work (i) evaluated the effect of increasing salinity on various parameters of crop yield, fruit quality and plant water relations, and (ii) determined threshold and slope values for the Maas and Hoffman (M&H) model. Sweet pepper was grown with nutrient solutions (ns) with electrical conductivities (EC) of 2.5 (T1), 3.5 (T2), 4.5 (T3), 5.5 (T4), 6.5 (T5) and 7.5 (T6) dS m−1. There were substantial and statistically significant reductions in total and marketable yield, dry matter production (DMP) and average fruit weight, with increasing salinity. In treatment T4 (ns of 5.5 dS m−1), the respective reductions for these parameters, compared to T1 (ns of 2.5 dS m−1), were 37%, 37%, 47%, 52% and 30%. Applying the M&H model, soil solution EC threshold (ECsst) values for total and marketable yield were 4.8 and 5.0 dS m−1. The respective slope values were − 8.0 and − 12.0%/dS m−1. The more rapid decline in marketable yield was influenced by a large increase in the incidence of blossom end rot (BER) with increasing salinity. In treatment T1, 25% of discarded fruit had BER which increased to 70% in T6. Average fruit size was affected by salinity, but fruit number was not. Most fruit quality parameters were unaffected by increasing salinity. However, fruits were more red and more yellow. Leaf water potential (ΨW), leaf osmotic potential (ΨO), stomatal conductance (gS) and leaf turgor potential (ΨP) followed the Maas and Hoffman model, with ΨW, ΨO and gS declining and ΨP increasing after the EC threshold value. The ECsst value for ΨW was 5.0 dS m−1, and for ΨO, gS and ΨP was 5.6–5.8 dS m−1. Considering all data, an ECsst value of 5.0 dS m−1 is suggested for sweet pepper grown in Mediterranean greenhouses.

Fungicide Sensitivity in the European Canker Fungus, Neonectria ditissima

Neonectria ditissima is one of the most serious pathogens of apple trees in temperate climatic zones, causing bark canker as well as pre- and post-harvest fruit rots. Control of fruit rots in particular is hampered by uncertainty about the sensitivity to, and efficacy of, available fungicides. Using 43 N. ditissima isolates from Germany and South Tyrol, the effective concentrations causing a 50% inhibition of germ-tube growth (EC50) were determined for fludioxonil (0.009–0.046 ppm), trifloxystrobin (0.018–0.43 ppm), thiophanate-methyl (2.05–15.9 ppm), dodine (0.61–6.33 ppm), cyprodinil (5.04–83.7 ppm), pyrimethanil (22.0–500 ppm), fluopyram (1.35–140 ppm) and boscalid (> 500 ppm). In a detached-fruit assay based on artificial wound inoculation of apples previously dipped in fungicides at commercial dosages, fludioxonil and, to a lesser extent, fluopyram and dodine significantly reduced the fruit rot lesion size, whereas trifloxystrobin, cyprodinil and boscalid did not. Lesion size was also directly correlated to the amount of conidial inoculum, whereby wounds inoculated with 5000 conidia gave rise to larger lesions than those with 500 or 50 conidia. In a field trial of apple trees artificially inoculated with N. ditissima conidia at flowering, fludioxonil gave good control of blossom-end rot, and trifloxystrobin gave limited control, whereas cyprodinil was ineffective. Therefore, the efficacies of different fungicides were broadly in line with the EC50 values determined under laboratory conditions.

Constraints faced under open and protected cultivation of vegetables- A case studyof tomatoes and capsicum in Karnataka

The present study aimed to analyze the constraints faced by farmers in the production and marketing oftomatoes and capsicum under open and protected cultivation practices in Karnataka. The study was conducted in majortwo vegetable producing districts of Karnataka. Kolar from South Karnataka and Belagavi from North Karnataka were thetwo districts selected for the study. Rank Based Quotient (RBQ) was adopted for the analysis. The results indicated thatheavy incidence of pests and diseases (RBQ value 69.44) and severe incidence of blossom end rot due to calcium deficiency(RBQ value 85.19) were the major production constraints under open and protected cultivation practices, respectively.Lack of quality planting material and requirement of intensive management practices were the other serious productionproblems under open field cultivation of tomatoes. While, incidence of fruit borer and requirement of high cost forestablishment were the production problems faced by the farmers under protected cultivation of tomatoes. Heavy drop ofimmature fruits under open cultivation and high cost of establishment under protected cultivation were the other seriousproblems faced by farmers in production of capsicum. Lower market price during peak harvesting season and high fluctuationin prices for capsicum were the serious marketing problems. Use of disease-free quality planting material, self-raising ofseedlings, utilization of calcium fertilizers and adoption of cost-effective management practices and proper portfolio managementwere the measures suggested to the farmers to overcome these problems. These findings will be helpful to the policy makersand farmers for developing policy framework and relevant guidance for promoting vegetable production in the state.

Uncovering tomato candidate genes associated with drought tolerance using Solanum pennellii introgression lines.

Tomato plants are sensitive to drought stress throughout their growth cycle. To be considered drought-tolerant, a cultivar should display tolerance at all developmental stages. This study aimed to evaluate whether Solanum pennellii introgression lines (ILs) previously selected as drought-tolerant during germination/seedling growth maintained this tolerance in the vegetative/reproductive stage. We then investigated these ILs to uncover candidate genes. The plants were subjected to two different environmental conditions: well-watered and drought-stressed (water withheld for ≤ 20 d after flowering). Phenotyping for morphological, physiological, fruit quality, and yield-related traits was performed, and the data was analyzed using a mixed-model approach. Using a multi-trait index that relies on factor analysis and genotype-ideotype distance (FAI-BLUP index), the genotypes were ordered based on how far they were from the drought-tolerant ideotype. Afterward, the tomato IL population map furnished by the SOL Genomics Network was utilized to identify introgressed segments of significance for the identification of candidate genes. Significant genotypic differences were found in the yield, water content, mean weight, length, and width of the fruit, the percentage of fruits displaying blossom-end rot, and titratable acidity. The drought-tolerance ideotype was built considering the maximum values for the fruit water content, number of fruits, mean fruit weight, and yield, minimum values for blossom-end rot, and mean values for titratable acidity. IL 1-4-18, IL 7-4-1, IL 7-1, IL 7-5-5, and IL 1-2 were ranked above M-82 and therefore considered drought-tolerant during the vegetative/reproductive stage. IL 1-4-18 and IL1-2 sustained drought tolerance displayed during germination/seedling growth into the vegetative/reproductive stage. The following candidate genes associated with drought tolerance were identified: AHG2, At1g55840, PRXIIF, SAP5, REF4-RELATED 1, PRXQ, CFS1, LCD, CCD1, and SCS. Because they are already associated with genetic markers, they can be transferred to elite tomato cultivars through marker-assisted technology after validation.

Starch deficiency in tomato causes transcriptional reprogramming that modulates fruit development, metabolism and stress responses.

Tomato fruit (Solanum lycopersicum) store carbon as starch during early development and mobilize it at the onset of ripening. Starch accumulation has been suggested to buffer fluctuations in carbon supply to the fruit under abiotic stress, and contribute to sugar levels in ripe fruit. However, the role of starch accumulation and metabolism during fruit development is still unclear. Here we show that the tomato mutant adpressa (adp) harbors a mutation in a gene encoding the small subunit of ADP-glucose pyrophosphorylase (AGPase), which abolishes starch synthesis. The disruption of starch biosynthesis causes major transcriptional and metabolic remodeling in adp fruit but only minor effects on fruit size and ripening. Changes in gene expression and metabolite profiles indicate that the lack of carbon flow into starch increases levels of soluble sugars during fruit growth, triggers a readjustment of central carbohydrate and lipid metabolism, and activates growth and stress protection pathways. Accordingly, adp fruits are remarkably resistant to blossom-end rot, a common physiological disorder induced by environmental stress. Our results provide insights into the effects of perturbations of carbohydrate metabolism on tomato fruit development, with potential implications for the enhancement of protective mechanisms against abiotic stress in fleshy fruit.

Effects of Ca Sprays on Fruit Ca Content and Yield of Tomato Variety Susceptible to Blossom-End Rot.

Several factors are involved in the incidence of blossom-end rot (BER) in tomato fruit, but the main one is insufficient Ca uptake and transport through the plant, resulting in Ca deficiency in the fruit. Sprays of Ca-containing products are considered to be a possible measure to overcome the local Ca deficiency in tomato fruit. Therefore, the main objective was to evaluate the effectiveness of additional Ca supply to tomato fruits for increasing Ca content and reducing fruit damage. Sprays of five different commercial preparations containing (Brexil Duo, Calmax Zero N, Ca(NO3)2, CaCl2) or promoting (Greenstim) Ca uptake were tested using BER-sensitive large-fruit variety 'Beorange'. The experiment was conducted in the commercial greenhouse 'Getlini EKO', Latvia, during the autumn-spring season of 2020/2021 under controlled conditions, eliminating the adverse impact of external factors. The results revealed that none of the preparations were effective in increasing Ca content, preventing BER, and did not promote the tomato yield. As good agricultural practices were followed in the greenhouse to manage BER, we concluded that a non-marketable yield of around 15% should be expected for 'Beorange' when grown under artificial light, possibly due to the impact of abiotic stresses and genetically determined susceptibility.