Maize is a sensitive crop to drought and heat stresses, particularly at the reproductive stages of development. The present study investigated the individual and interactive effects of drought (50% field capacity) and heat (38 °C/30 °C) stresses on morpho-physiological growth, yield, nutrient uptake and oxidative metabolism in two maize hybrids i.e., ‘Xida 889’ and ‘Xida 319’. The stress treatments were applied at tasseling stage for 15 days. Drought, heat and drought + heat stress caused oxidative stress by the over-production of ROS (O2−, H2O2, OH−) and enhanced malondialdehyde contents, which led to reduced photosynthetic components, nutrients uptake and yield attributes. The concurrent occurrence of drought and heat was more severe for maize growth than the single stress. However, both stresses induced the metabolites accumulation and enzymatic and non-enzymatic antioxidants to prevent the oxidative damage. The performance of Xida 899 was more prominent than the Xida 319. The greater tolerance of Xida 889 to heat and drought stresses was attributed to strong antioxidant defense system, higher osmolyte accumulation, and maintenance of photosynthetic pigments and nutrient balance compared with Xida 319.

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Interactive effects of drought and heat stresses on morpho-physiological attributes, yield, nutrient uptake and oxidative status in maize hybrids.

Global Warming, Climate Change, and Environmental Pollution: Recipe for a Multifactorial Stress Combination Disaster

Tomato (Solanum lycopersicum L.) belongs to the Solanaceae family and is the second most important fruit or vegetable crop next to potato (Solanum tuberosum L.). It is cultivated for fresh fruit and processed products. Tomatoes contain many health-promoting compounds including vitamins, carotenoids, and phenolic compounds. In addition to its economic and nutritional importance, tomatoes have become the model for the study of fleshy fruit development. Tomato is a climacteric fruit and dramatic metabolic changes occur during its fruit development. In this review, we provide an overview of our current understanding of tomato fruit metabolism. We begin by detailing the genetic and hormonal control of fruit development and ripening, after which we document the primary metabolism of tomato fruits, with a special focus on sugar, organic acid, and amino acid metabolism. Links between primary and secondary metabolic pathways are further highlighted by the importance of pigments, flavonoids, and volatiles for tomato fruit quality. Finally, as tomato plants are sensitive to several abiotic stresses, we briefly summarize the effects of adverse environmental conditions on tomato fruit metabolism and quality.

/pdf/tomato-fruit-development-and-metabolism-1lcfalmbtz.pdf

Tomato Fruit Development and Metabolism

Genetic improvement for drought tolerance in chickpea requires a solid understanding of biochemical processes involved with different physiological mechanisms. The objective of this study is to demonstrate genetic variations in altered metabolic levels in chickpea varieties (tolerant and sensitive) grown under contrasting water regimes through ultrahigh-performance liquid chromatography/high-resolution mass spectrometry-based untargeted metabolomic profiling. Chickpea plants were exposed to drought stress at the 3-leaf stage for 25 days, and the leaves were harvested at 14 and 25 days after the imposition of drought stress. Stress produced significant reduction in chlorophyll content, Fv /Fm , relative water content, and shoot and root dry weight. Twenty known metabolites were identified as most important by 2 different methods including significant analysis of metabolites and partial least squares discriminant analysis. The most pronounced increase in accumulation due to drought stress was demonstrated for allantoin, l-proline, l-arginine, l-histidine, l-isoleucine, and tryptophan. Metabolites that showed a decreased level of accumulation under drought conditions were choline, phenylalanine, gamma-aminobutyric acid, alanine, phenylalanine, tyrosine, glucosamine, guanine, and aspartic acid. Aminoacyl-tRNA and plant secondary metabolite biosynthesis and amino acid metabolism or synthesis pathways were involved in producing genetic variation under drought conditions. Metabolic changes in light of drought conditions highlighted pools of metabolites that affect the metabolic and physiological adjustment in chickpea that reduced drought impacts.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/pce.13195

UPLC-HRMS-based untargeted metabolic profiling reveals changes in chickpea (Cicer arietinum) metabolome following long-term drought stress.

NPR1, nonexpressor of pathogenesis-related gene 1, is a master regulator involved in plant defense response to pathogens, and its regulatory mechanism in the defense pathway has been relatively clear. However, information about the function of NPR1 in plant response to abiotic stress is still limited. Tomato is the fourth most economically crop worldwide and also one of the best-characterized model plants employed in genetic studies. Because of the lack of a stable tomato NPR1 (SlNPR1) mutant, little is known about the function of SlNPR1 in tomato response to biotic and abiotic stresses. Here we isolated SlNPR1 from tomato ‘Ailsa Craig’ and generated slnpr1 mutants using the CRISPR/Cas9 system. Analysis of the cis-acting elements indicated that SlNPR1 might be involved in tomato plant response to drought stress. Expression pattern analysis showed that SlNPR1 was expressed in all plant tissues, and it was strongly induced by drought stress. Thus, we investigated the function of SlNPR1 in tomato-plant drought tolerance. Results showed that slnpr1 mutants exhibited reduced drought tolerance with increased stomatal aperture, higher electrolytic leakage, malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels, and lower activity levels of antioxidant enzymes, compared to wild type (WT) plants. The reduced drought tolerance of slnpr1 mutants was further reflected by the down-regulated expression of drought related key genes, including SlGST, SlDHN, and SlDREB. Collectively, the data suggest that SlNPR1 is involved in regulating tomato plant drought response. These results aid in further understanding the molecular basis underlying SlNPR1 mediation of tomato drought sensitivity.

/pdf/crispr-cas9-mediated-slnpr1-mutagenesis-reduces-tomato-plant-5fec7w6w2z.pdf

CRISPR/Cas9-Mediated SlNPR1 mutagenesis reduces tomato plant drought tolerance.

Abiotic stresses due to environmental factors could adversely affect the growth and development of crops. Among the abiotic stresses, drought and heat stress are two critical threats to crop growth and sustainable agriculture worldwide. Considering global climate change, incidence of combined drought and heat stress is likely to increase. The aim of this study was to shed light on plant growth performance and leaf physiology of three tomatoes cultivars (‘Arvento’, ‘LA1994’ and ‘LA2093’) under control, drought, heat and combined stress. Shoot fresh and dry weight, leaf area and relative water content of all cultivars significantly decreased under drought and combined stress as compared to control. The net photosynthesis and starch content were significantly lower under drought and combined stress than control in the three cultivars. Stomata and pore length of the three cultivars significantly decreased under drought and combined stress as compared to control. The tomato ‘Arvento’ was more affected by heat stress than ‘LA1994’ and ‘LA2093’ due to significant decreases in shoot dry weight, chlorophyll a and carotenoid content, starch content and NPQ (non-photochemical quenching) only in ‘Arvento’ under heat treatment. By comparison, the two heat-tolerant tomatoes were more affected by drought stress compared to ‘Arvento’ as shown by small stomatal and pore area, decreased sucrose content, ΦPSII (quantum yield of photosystem II), ETR (electron transport rate) and qL (fraction of open PSII centers) in ‘LA1994’ and ‘LA2093’. The three cultivars showed similar response when subjected to the combination of drought and heat stress as shown by most physiological parameters, even though only ‘LA1994’ and ‘LA2093’ showed decreased Fv/Fm (maximum potential quantum efficiency of photosystem II), ΦPSII, ETR and qL under combined stress. The cultivars differing in heat sensitivity did not show difference in the combined stress sensitivity, indicating that selection for tomatoes with combined stress tolerance might not be correlated with the single stress tolerance. In this study, drought stress had a predominant effect on tomato over heat stress, which explained why simultaneous application of heat and drought revealed similar physiological responses to the drought stress. These results will uncover the difference and linkage between the physiological response of tomatoes to drought, heat and combined stress and be important for the selection and breeding of tolerant tomato cultivars under single and combine stress.

/pdf/drought-stress-had-a-predominant-effect-over-heat-stress-on-3l0ju7wqot.pdf

Drought stress had a predominant effect over heat stress on three tomato cultivars subjected to combined stress.

Tomato yellow leaf curl virus (TYLCV) has significantly impacted the tomato industry around the world, and the use of insecticides and insect nets have not effectively controlled the spread of this pathogen. The tomato line AVTO1227 is highly resistant to TYLCV. In this study, F2 and BC1 populations derived from AVTO1227 and the susceptible line Money maker were used to assess the genetic mechanism underlying TYLCV resistance. We have identified a recessive TYLCV resistance gene, hereby designated as ty-5, which is linked to SlNACI. Genomic DNA pools from resistant and susceptible groups were constructed, and their genomes were resequenced. The ty-5 gene was identified on an interval encompassing the genomic positions 2.22 Mb to 3.19 Mb on tomato chromosome 4. Genotyping using linkage markers further mapped ty-5 within the interval between markers ty5–25 and ty5–29, where only the pelota gene is located. Consequently, pelota was considered as the candidate gene corresponding to ty-5. Two nucleotide transversions within the promoter region and one transversion in exon region of the pelota gene were detected in the parental lines. However, the relative transcript levels of pelota did not significantly differ among the three tomato lines, regardless of TYLCV infection. This study will facilitate marker-assisted breeding for resistance to TYLCV and lay a foundation for the research of the resistance mechanism of ty-5 in tomato.

/pdf/application-of-whole-genome-resequencing-in-mapping-of-a-13h6b3rm9h.pdf

Application of Whole Genome Resequencing in Mapping of a Tomato Yellow Leaf Curl Virus Resistance Gene.

The study of morphological and molecular diversity and grouping analysis for cultivated inbred tomato lines is very important to help breeders in selecting parental lines for hybrid breeding and developing heterotic groups. In this study, a total of 324 cultivated inbred tomato lines collected from various sources were investigated for the presence of 17 agronomic traits and subsequently genotyped with a 56- (insertion–deletion) InDel assay. The phenotypic coefficient of variation ranged from 5 to 108% with an average of 36%, and the range of phenotypic diversity index was 0.41– 2.06, with an average of 1.59. The outstanding traits in terms of causing phenotypic diversity of the inbred tomato lines are resistance to gray leaf spot, hypocotyl colour, growth habit, fruit shape, plant height, days to 30% first flower, weight per fruit, hardness, brix, acid, number of locules and transverse diameter of fruit by principal component analyses (PCA). The values of Shannon’s information index, polymorphic information content and heterozygosity are 0.61, 0.33 and 0.06 respectively. The PCA and Ward’s method for cluster multivariate analysis based on 17 agronomic traits revealed that there are four major groups with rich genetic diversity within groups. Model-based population structure analysis indicated that the 324 cultivated inbred tomato lines were separated into two main groups that were different from the results of the three main groups and five subgroups by Nei’s (Am Nat 106:283–292, 1973) cluster analysis based on InDel markers. The Mantel test correlation coefficient of the matrices of morphological and InDel distances was 0.229. Overall, this study reveals that 324 cultivated inbred tomato lines are diverse with high homozygosity and a rich genetic background. Nei’s (1973) cluster analysis can serve as an effective approach for assigning germplasm into groups and for providing guidelines for parental selection in hybrid tomato breeding.

Genetic diversity of 324 cultivated tomato germplasm resources using agronomic traits and InDel markers

Anthocyanins are important secondary metabolites with high nutraceutical value. They represent the major red, purple, violet and blue pigments in higher plants but are usually not present in the fruits of domesticated tomatoes. Recently, several genes that regulate anthocyanin accumulation have been identified in wild tomatoes or mutation lines; however, whether there are other new factors involved in the regulation of anthocyanin biosynthesis is still unknown. “Jinling Moyu” (MY) is a novel purple cherry tomato that accumulates considerable anthocyanins in its ripe fruit. A transcriptome comparison analysis of MY fruits with pink and green fruit revealed that several structural genes assigned to the anthocyanin biosynthetic pathway were highly expressed in MY tomato, but all six known regulatory genes of anthocyanin accumulation in tomato fruits were rarely expressed among the samples in this study. However, four other R2R3–MYB and five other bHLH transcription factors were highly correlated with the differentially expressed structural genes in the anthocyanin pathway, indicating that these transcription factors might regulate anthocyanin biosynthesis in MY tomato. Our study will aid in understanding the complex mechanism regulating anthocyanin pigmentation in tomato fruits .

Transcriptome profiles reveal new regulatory factors of anthocyanin accumulation in a novel purple-colored cherry tomato cultivar Jinling Moyu

The invention relates to the technical field of tomato resistance authentication organisms, in particular to a method for quickly, accurately and non-destructively authenticating tomato seedling stageheat resistance. Tomato seeds which need to be authenticated are sown into a plug loaded with a medium, and cultivation is conducted on the condition that the external temperature is not higher than30 DEG C and illumination, moisture, humidity and the like are appropriate. After sowing is conducted for 22 days, seedlings are transplanted into a nutrient pot with the same medium, and the seedlings are watered with a Japanese garden test composition nutrient solution every morning. After sowing is conducted for 25 days, the seedlings are transplanted to an artificial climate tank. After adapting is conducted for 3 days, high temperature treatment is started. Firstly, the seedlings are pretreated for 10 h at 28 DEG C under the dark condition and then are subjected to the high temperature treatment for 12 h at 40 DEG C under the illumination condition; next, a leaf chamber clamp is utilized to clamp the first, the second and the third complete spread leaves of each plant, when dark adapting is conducted for 20 min, Handy PEA is utilized to measure Fv/Fm, and average Fv/Fm of each plant is calculated.

Yu Wengui

Papers

Drought stress had a predominant effect over heat stress on three tomato cultivars subjected to combined stress.

Application of Whole Genome Resequencing in Mapping of a Tomato Yellow Leaf Curl Virus Resistance Gene.

Genetic diversity of 324 cultivated tomato germplasm resources using agronomic traits and InDel markers

Transcriptome profiles reveal new regulatory factors of anthocyanin accumulation in a novel purple-colored cherry tomato cultivar Jinling Moyu

Method for quickly and accurately authenticating tomato seedling stage heat resistance