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Zhou R.,Nanjing Agricultural University | Zhou R.,Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in East China | Yu X.,Nanjing Agricultural University | Kjaer K.H.,University of Aarhus | And 4 more authors.
Environmental and Experimental Botany | Year: 2015

Cultivation of tomatoes at high temperatures negatively affects growth and yield. Our aim was to screen tomato genotypes under heat stress for differences in the maximum quantum efficiency of photosystem II (Fv/Fm) and uncover the physiological traits for heat tolerance in a three-step process. Initially, 67 tomato genotypes were ranked according to Fv/Fm. Two genotypes with higher Fv/Fm (heat-tolerant group) and two genotypes with lower Fv/Fm (heat-sensitive group) were selected from the initial screening. Second, the physiological responses of the four genotypes to seven days of heat stress (36/28°C) were analyzed in detail. Third, pollen germination and fruit set of the four genotypes were investigated at high temperature conditions in the field. The results showed that the heat-tolerant group maintained higher leaf pigment content and higher total phenolic content (TPC) than the heat-sensitive group under heat stress. The heat-tolerant group maintained unaltered stomata and pore area and net photosynthesis rate (PN) but increased stomatal conductance (gs) under heat stress compared with the control. Chloroplasts in the heat-tolerant group maintained a normal shape, whereas the chloroplasts in the heat-sensitive group became swollen with decomposed starch grain after heat stress. The heat-tolerant group exhibited a higher pollen germination rate (%), longer pollen tube length and higher fruit set rate compared with the heat-sensitive group at high temperatures in the field. Thus, we concluded that Fv/Fm is an early indicator of heat stress tolerance and that the responses of tomatoes to heat stress were identical in widely different growing conditions. The stay-green trait, improved ability of stomata regulation and higher contents of reactive oxygen species scavengers seemed to be part of the protective mechanisms in heat-tolerant tomatoes. © 2015 Elsevier B.V.

Liu M.,Nanjing Agricultural University | Liu M.,Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in East China | Wu Z.,Nanjing Agricultural University | Wu Z.,Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in East China | And 2 more authors.
Plant Cell, Tissue and Organ Culture | Year: 2015

A stable reference gene is a prerequisite to obtaining reliable quantitative real-time PCR (qPCR) analysis results. Despite the global distribution and nutritional, medicinal and economic value of garlic, reference genes for qPCR have not been reported. Eight garlic housekeeping genes, 18S ribosomal RNA (18S), actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), elongation factor (EF-1α), the α-tubulin (TUA) and β-tubulin (TUB), polyubiquitin (UBQ), and cyclophilin (CYP), were chosen as candidate reference genes. Their stability was evaluated by GeNorm, NormFinder, BestKeeper, the comparative ΔCt method, and RefFinder. The results demonstrated that TUA, GAPDH, UBQ, CYP, and ACT are the most suitable of the eight reference genes for different garlic genotypes, organs, developmental stages, abiotic stresses and media treatments, respectively. To further validate the stability of these reference genes, the expression levels of the superoxide dismutase gene (SOD) were analyzed. The relative quantification of SOD varied according to the stability of the reference gene, thus highlighting the importance of using suitable reference genes in qPCR. Our results also provide a molecular biological basis for studying the mechanisms of development and stress tolerance in garlic. © 2015, Springer Science+Business Media Dordrecht.

Zhou R.,Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in East China | Zhou R.,Nanjing Agricultural University | Wu Z.,Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in East China | Wu Z.,Nanjing Agricultural University | And 3 more authors.
Genetics and Molecular Research | Year: 2015

In order to study genetic variability and develop better strategies for the utilization of 48 tomato cultivars from America, China, the Netherlands, and Portugal, genomic simple sequence repeat (gSSR) and EST-derived SSR (EST-SSR) markers were applied. In all, 15 of 82 gSSR and 18 of 115 EST-SSR markers showed polymorphic loci. There were 995 and 2072 clear fragments amplified by polymorphic gSSR and EST-SSR markers, respectively. The total and average number of alleles detected by EST-SSRs (75, 4.2) was more than gSSRs (54, 3.6) as a result of some multi-locus EST-SSRs. A lower polymorphism information content value was found in gSSRs (0.529) compared to EST-SSRs (0.620). Similarity coefficient matrixes of the 48 tomato cultivars were established based on the gSSRs and EST-SSRs, and UPGMA dendrograms were constructed from the gSSRs and EST-SSRs similarity coefficient matrixes. A high similarity was observed between the gSSRs and EST-SSRs dendrograms. Genetic variability of four tomato populations from different countries showed that the observed number of alleles and Nei’s genetic diversity were highest in the American population, and the effective number of alleles was highest in the Dutch population. The estimated genetic structure showed some tomato cultivars from different countries shared a common genetic background, which might be related to gene flow. It was inferred that both gSSR and EST-SSR markers were effective to assess genetic variability of tomato cultivars, and the combination of both markers could be more effective for genetic diversity analysis in tomato. © FUNPEC-RP.

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