Identification of tomato accessions as source of new genes for improving heat tolerance: from controlled experiments to field

Background: Due to global warming, the search for new sources for heat tolerance and the identification of genes involved in this process has become an important challenge as of today. The main objective of the current research was to verify whether the heat tolerance determined in controlled greenhouse experiments could be a good predictor of the agronomic performance in field cultivation under climatic high temperature stress. Results: Tomato accessions were grown in greenhouse under three temperature regimes: control (T1), moderate (T2) and extreme heat stress (T3). Reproductive traits (flower and fruit number and fruit set) were used to define heat tolerance. In a first screening, heat tolerance was evaluated in 219 tomato accessions. A total of 51 accessions were identified as being potentially heat tolerant. Among those, 28 accessions, together with 10 accessions from Italy (7) and Bulgaria (3), selected for their heat tolerance in the field in parallel experiments, were re-evaluated at three temperature treatments. Sixteen tomato accessions showed a significant heat tolerance at T3, including five wild species, two traditional cultivars and four commercial varieties, one accession from Bulgaria and four from Italy. The 15 most promising accessions for heat tolerance were assayed in field trials in Italy and Bulgaria, confirming the good performance of most of them at high temperatures. Finally, a differential gene expression analysis in pre-anthesis (ovary) and post-anthesis (developing fruit) under heat stress among pairs of contrasting genotypes (tolerant and sensitive from traditional and modern groups) showed that the major differential responses were produced in post-anthesis fruit. The response of the sensitive genotypes included the induction of HSP genes, whereas the tolerant genotype response included the induction of genes involved in the regulation of hormones or enzymes such as abscisic acid and transferases. Conclusions: The high temperature tolerance of fifteen tomato accessions observed in controlled greenhouse experiments were confirmed in agronomic field experiments providing new sources of heat tolerance that could be incorporated into breeding programs. A DEG analysis showed the complex response of tomato to heat and deciphered the different mechanisms activated in sensitive and tolerant tomato accessions under heat stress

Identification of tomato accessions as source of new genes for improving heat tolerance: from controlled experiments to field

Background: Due to global warming, the search for new sources for heat tolerance and the identification of genes involved in this process has become an important challenge as of today. The main objective of the current research was to verify whether the heat tolerance determined in controlled greenhouse experiments could be a good predictor of the agronomic performance in field cultivation under climatic high temperature stress. Results: Tomato accessions were grown in greenhouse under three temperature regimes: control (T1), moderate (T2) and extreme heat stress (T3). Reproductive traits (flower and fruit number and fruit set) were used to define heat tolerance. In a first screening, heat tolerance was evaluated in 219 tomato accessions. A total of 51 accessions were identified as being potentially heat tolerant. Among those, 28 accessions, together with 10 accessions from Italy (7) and Bulgaria (3), selected for their heat tolerance in the field in parallel experiments, were re-evaluated at three temperature treatments. Sixteen tomato accessions showed a significant heat tolerance at T3, including five wild species, two traditional cultivars and four commercial varieties, one accession from Bulgaria and four from Italy. The 15 most promising accessions for heat tolerance were assayed in field trials in Italy and Bulgaria, confirming the good performance of most of them at high temperatures. Finally, a differential gene expression analysis in pre-anthesis (ovary) and post-anthesis (developing fruit) under heat stress among pairs of contrasting genotypes (tolerant and sensitive from traditional and modern groups) showed that the major differential responses were produced in post-anthesis fruit. The response of the sensitive genotypes included the induction of HSP genes, whereas the tolerant genotype response included the induction of genes involved in the regulation of hormones or enzymes such as abscisic acid and transferases. Conclusions: The high temperature tolerance of fifteen tomato accessions observed in controlled greenhouse experiments were confirmed in agronomic field experiments providing new sources of heat tolerance that could be incorporated into breeding programs. A DEG analysis showed the complex response of tomato to heat and deciphered the different mechanisms activated in sensitive and tolerant tomato accessions under heat stress

Wpływ wermikompostu na wzrost, zawartość azotu, wymianę gazową liści i plonowanie papryki

The purpose of this study was to investigate the effect of the vermicompost Lumbrical, produced by the Californian earthworm Lumbricus rubellus, on growth, nitrogen content, leaf gas exchange and productivity of pepper plants (cv. Gorogled 6). The experiments were carried out in 2007-2009, on experimental field of the Agroecological Centre of the Agricultural University of Plovdiv (Bulgaria). Immediately before planting, two levels of the vermicompost were applied: 50 and 100 cm3 per plant. Thirty days after planting, some of the plants fertilized with 50 cm3 Lumbrical (the third variant) were additionally fed with a solution of vermicompost (200 cm3 per plant). Prior to the experiment, chemical and microbiological analyses were performed on both the soil and vermicompost. During plant vegetation, some biometrical indices characterizing the plant growth were measured. The nitrogen concentration and nitrate reductase activity in leaves of pepper plants were determined. The leaf gas exchange was taken into account. The pepper yield and quality parameters of fruits were analyzed. The results of the present study showed that by feeding the pepper with the vermicompost Lumbrical it was possible to increase the plants’ vegetative mass improve the development of their generative organs. Incorporation of the vermicompost into the soil increased the content of N in the root area. It also considerably raised the nitrogen content in leaves of pepper plants. A positive correlation between the content N in leaves and the activity of the enzyme called nitrate reductase was observed. The positive effect of the vermicompost was reflected by improved leaf gas exchange parameters and productivity of plants

INFLUENCE OF REDUCED IRRIGATION ON PHENOLOGICAL AND MORPHOLOGICAL CHARACTERS OF DIFFERENT TOMATO GENOTYPES

Cultivated plants are often exposed to different types of environmental stress which has a negative effect on the vegetative and reproductive development. In the current study the influence of water deficit on phenological and morphological characters of different tomato genotypes was investigated. The experiment was conducted at the Maritsa Vegetable Crops Research Institute in two consecutive years (2016-2017) with 11indeterminate and 13 determinate tomato accessions grown under optimum and 50% reduced irrigation. The results showed that the plants of indeterminate and determinate tomato types answered the water deficit with a decrease of the fruit number (53.0% and 32.2% respectively), fruit weight (42.9% and 19.2%), plant fresh weight (36.0% and 37.5%), flower number (19.1% and 11.5%), pericarp thickness (19.1% and 10.6%), fruit length (17.9% and 13.5%) and fruit width (15.9% and 8.1%). In the predominant part of the accessions grown in the reduced watering regime the total soluble solids were higher than these of the accessions grown in the optimal one. Strong to very strong positive correlations of plant height, flower number, fruit number and fruit weight in optimal irrigation with the same characters in reduced irrigation were found

EVALUATION OF PRODUCTIVITY AND PRODUCTIVITY COMPOUNDS IN TOMATO ACCESSIONS GROWN UNDER ELEVATED TEMPERATURE AND REDUCED IRRIGATION

The aim of this experimental work was to evaluate the productivity and productivity compounds in tomato accessions grown under elevated temperature and reduced irrigation. The experiment was conducted at the Maritsa Vegetable Crops Research Institute with 25 tomato accessions (14 determinate and 11 indeterminate) in the period of 2016 and 2017. Two watering regimes were applied - optimum and 50% reduced. Productivity per plant, number of fruits per plant and average fruit weigh were measured. Environmental descriptors air temperature, air humidity, rainfalls and soil moisture at 15 and 30 cm depth were recorded by weather station Caipos Wave. As a result of reduced irrigation and high temperatures a decrease of the productivity per plant formed on the base of number and average fruit weight was observed. The studied indeterminate tomato accessions showed low heat tolerance compared to the determinate ones. Decrease of the productivity per plant with 25.2% close to the positive control was established in accession BG 985 from the determinate tomato for processing and with 35.5% in accession Spectar belonging to the determinate tomato for fresh consumption. A decrease of the productivity less than 50% was observed only in indeterminate tomato accession BG 21β (47.3%). The reduced irrigation and the high temperatures had a weaker negative effect on the fruit number (13.3-57.1%) and average fruit weight per plant (5.0-57.8%) compared to the productivity. Three-way analysis of variance showed that watering regime influenced mainly the productivity per plant in the three studied tomato groups, fruit number and average fruit weight per plant in determinate tomato for fresh consumption. Differences in number and average fruit weight per plant in determinate tomato for processing and indeterminate ones were determined by genotype. As a result of this study perspective tomato accessions suitable for breeding of drought stress were selected

IMPACT OF WATER DEFICIT ON SENSORY PROFILE OF TOMATO (SOLANUM LYCOPERSICON L.) GROWN UNDER HOT SUMMER CONDITIONS IN BULGARIA

The effect of water deficit on sensory characteristics of tomato (Solanum lycopersicon L.) was investigated. A field experiment was carried out during 2016-2017 period under the hot summer conditions in Bulgaria. Twenty four Bulgarian tomato accessions representing three types - indeterminate, determinate for processing and determinate for fresh consumption - were harvested. Optimum and 50% reduced watering regimes were applied using a drip irrigation system. Temperatures over 35ºС during the vegetation were recorded in 26% of the days of the first experimental year and 40% of the days of the second one. The sensory analysis of the tomato fruits was performed by trained panelists on the traits: appearance, shape, external colour, internal colour, aroma, peel tenderness, visible fibre, sourness, sweetness, texture and overall taste. Negative effects of the deficit irrigation were observed on the appearance, shape and total sensory evaluation of tomato fruits regardless of the tomato type. Negative effects were also recorded on the texture of determinate tomato for processing and peel tenderness of determinate tomato for fresh consumption. The sweetness was better expressed in tomatoes grown under water deficit in all studied genotypes. Reduced irrigation did not result in aroma, external colour and visible fibre. Two-way analysis of variance revealed a significant influence of genotype on the sensory traits in the range of 39.56-74.79% in indeterminate tomato accessions, 33.49 - 56.05% in determinate tomato for processing, 14.96 - 62.93% in determinate tomato for fresh consumption. Slight influence of the applied watering regime was established except for appearance, shape and sweetness. Indeterminate tomato accessions Rozovo sartse and BG 21 β, determinate accession for processing BG 2086 and determinate accession for fresh consumption Marti and BG 252 demonstrated the best sensory profile in both treatments of irrigation