Stella Lovelli

Effects of salinity on gas exchange, water relations and growth of sunflower (Helianthus annuus)

The aim of this study was to determine the response of sunflower (Helianthus annuus L. cv. Romsum HS90) to salinity in terms of gas exchange, ionic and water relations, and growth. Experiments were carried out in the glasshouse, where sunflower plants were exposed to increasing salinity levels using water with a wide range of electrical conductivity (0.39-20 dS m-1) to provide different degrees of salt stress. The CO2 assimilation rate (A), stomatal conductance and plant aboveground dry weight (DW) significantly decreased as electrical conductivity of the soil increased. The decline in photosynthesis measured in response to salt stress was proportionally greater than the decline in transpiration, resulting in a reduction of water use efficiency, at both the leaf and whole-plant levels. Among the factors inhibiting photosynthetic activity, those of a non-stomatal nature had a greater effect. In particular, an analysis of photosynthetic CO2 assimilation rate vs intercellular CO2 concentration (A vs Ci curves) indicated a reduction in activity of Rubisco (EC 4.1.1.39) as salinity levels increased. Under severe salt-stress conditions, chlorophyll fluorescence showed a slowing of electron transport at the PSII level. Salt accumulation in the rhizosphere caused a reduction in tissue water status that was partly associated with a decline in osmotic potential (Ψπ). Leaf ionic concentration was clearly correlated with values of leaf Ψπ. However, leaf ionic concentration showed discontinuous distribution between younger and older leaves, reflecting a strategy of plants to preserve younger and more metabolically-active leaves from accumulating salt to toxic levels.

Abscisic acid root and leaf concentration in relation to biomass partitioning in salinized tomato plants.

Salinization is one of the most important causes of crop productivity reduction in many areas of the world. Mechanisms that control leaf growth and shoot development under the osmotic phase of salinity are still obscure, and opinions differ regarding the Abscisic acid (ABA) role in regulation of biomass allocation under salt stress. ABA concentration in roots and leaves was analyzed in a genotype of processing tomato under two increasing levels of salinity stress for five weeks: 100 mM NaCl (S10) and 150 mM NaCl (S15), to study the effect of ABA changes on leaf gas exchange and dry matter partitioning of this crop under salinity conditions. In S15, salinization decreased dry matter by 78% and induced significant increases of Na(+) and Cl(-) in both leaves and roots. Dry matter allocated in different parts of plant was significantly different in salt-stressed treatments, as salinization increased root/shoot ratio 2-fold in S15 and 3-fold in S15 compared to the control. Total leaf water potential (Ψ(w)) decreased from an average value of approximately -1.0 MPa, measured on control plants and S10, to -1.17 MPa in S15. In S15, photosynthesis was reduced by 23% and stomatal conductance decreased by 61%. Moreover, salinity induced ABA accumulation both in tomato leaves and roots of the more stressed treatment (S15), where ABA level was higher in roots than in leaves (550 and 312 ng g(-1) fresh weight, respectively). Our results suggest that the dynamics of ABA and ion accumulation in tomato leaves significantly affected both growth and gas exchange-related parameters in tomato. In particular, ABA appeared to be involved in the tomato salinity response and could play an important role in dry matter partitioning between roots and shoots of tomato plants subjected to salt stress.

Innovative Crop Productions for Healthy Food: The Case of Chia (Salvia hispanica L.)

Chia (Salvia hispanica L.) is an ancient crop from Central America which has been recently rediscovered as a source of ω-3 and nutraceuticals in seeds. Besides traditional seed consumption, innovative uses of the plant seeds and leaves have been proposed based on the high protein content and the production of mucilage which lends itself to a range of applications. This chapter reviews research on the plant’s genetics and breeding, quality, and uses. Agronomic studies which have only recently started worldwide are also presented along with results from case studies in Basilicata.

Photosynthetic response to water stress of pigweed (Amaranthus retroflexus) in a Southern-Mediterranean area.

Abstract Pigweed is an increasingly aggressive weed in semiarid environments such as Mediterranean areas, and in general the control of all Amaranthus species is becoming more and more difficult. Increasing pigweed aggressiveness could be a result of its ability to keep a high water use efficiency under drought conditions. An experiment was conducted to study the effect of water stress on the photosynthetic capacity, growth, and leaf water potential of pigweed at the field level and assess if this species, as a model for C4 weeds, is CO2-saturated at the current level of atmospheric CO2 in a Mediterranean area. Pigweed was studied within a naturally occurring weed population in a bell pepper field in southern Italy where a rain-fed treatment (V0) was compared to a fully irrigated one (V100) corresponding to the restoration of 100% of the maximum crop water evapotranspiration. Soil water content was measured periodically, and net assimilation rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration were determined on pigweed leaves. Photosynthetic rates of 37.6 µmol m−2 s−1 in V100 and 13.9 µmol m−2 s−1 in V0 were recorded, with higher transpiration rates in V100; consequently stomatal conductance was significantly lower in rain-fed conditions (0.08 mol m−2 s−1)) compared to the irrigated treatment (0.30 mol m−2 s−1). Photosynthesis in pigweed is not completely CO2-saturated at the current atmospheric CO2 level in the Mediterranean area and this could affect competition and increase of aggressiveness toward crops at the actual CO2 atmospheric concentration in agro-ecosystems. This occurs because unlike other C4 crops already saturated for CO2, weeds that are not CO2-saturated will remain CO2-sensitive to higher ambient CO2 levels. Thus, when they are grown in mixed stands where competition occurs, they can still suppress the slower-growing species. Nomenclature: Redroot pigweed, Amaranthus retroflexus L. AMARE, bell pepper, Capsicum annuum L. ‘Peppone’

Trichoderma harzianum T-22 induces systemic resistance in tomato infected by Cucumber mosaic virus.

Understanding the induction of plant defenses against viruses using biocontrol agents is essential for developing new strategies against these pathogens, given the ineffectiveness of chemical treatments. The ability of Trichoderma harzianum, strain T-22 (T22) to control Cucumber mosaic virus (CMV) in Solanum lycopersicum var. cerasiforme plants and the changes in the physiology of tomato treated/infected with T22/CMV were examined. Plant growth-promoting effects, photosynthetic performance, reactive oxygen species scavenging enzymes, and phytohormones were investigated. T22 improved tomato growth in terms of plant height and improved photosynthesis, total chlorophyll content and plant gas exchange. In contrast, CMV induced a negative effect on dry matter accumulation and inhibited the photosynthetic capacity. The analysis of plant hormones demonstrated that treating with T22 before or simultaneously to CMV infection, led to a systemic resistance by jasmonic acid/ethylene and salicylic acid signaling pathways. Conversely, systemic resistance was abscissic acid-dependent when T22 treatment was administered after the CMV infection. In conclusion, the data reported here indicate that the T22-based strategy may be the most effective measure against CMV.

The role of water availability on weed–crop interactions in processing tomato for southern Italy

Abstract Anthropogenic climate change is projected to increase the occurrence of drought for the Mediterranean region. The aim of this study was to quantify the role of increasing drought on weed-induced crop losses and crop–weed interactions for processing tomato grown in southern Italy. Field experiments were carried out during 2008 and 2009. Two levels of water availability were imposed to compare weed competitive effects under irrigated and rainfed conditions on tomato as a means to quantify weed–crop interactions and associated crop losses when water is limited. In this study, the absolute decline in tomato yields by weed interference was a direct function of water applied (rain + irrigation); however, the relative effect of weed biomass on crop loss appeared to increase under drought when compared to irrigated conditions. Overall, these data indicate that the relative decline in tomato fresh weight from weeds was actually greater under drought, and that the relative crop losses (per unit of weed biomass) actually declined as water availability increased. From a management standpoint, these data suggest that if drought occurrences do increase in the Mediterranean region with climate change, there may be a greater need for complete and thorough weed control for this production system.

USE OF PLANT GROWTH PROMOTING BACTERIA (PGDB) FOR PROMOTING TOMATO GROWTH AND ITS EVALUATION AS BIOLOGICAL CONTROL AGENT

The plant growth promoting effect of some bacteria usable to control plant diseases has a potential for resolving technical problems of plant production. The effects of Burkholderia gladioli pv. agaricicola ICMP11096 on development of tomato seedlings development and control of their infection by Fusarium oxysporum and Sclerotinia sclerotiorum were evaluated in the present study. Bacterized plants showed a higher shoot and root weight and a more extended root system in terms of total length and root density than non-bacterized plants. The bacter- izing treatments gave rise to significant reduction of disease symptoms such as leaf wilting induced by F. oxysporum infection and/or root ne- crosis and leaf yellowing by S. sclerotiorum. The potential use of Burkholderia gladioli pv. agaricicola ICMP11096 in biocontrol of fungal patho- gens and to enhance seedling growth parameters is underlined as a tool to achieve a high commercial quality of nursery tomato plants. Keywords- Plant growth promoting bacteria, Burkholderia gladioli pv. agaricicola, Fusarium oxysporum, Sclerotinia sclerotiorum, tomato, bio- logical control

Evaluation of Native Grasses for Sustainable Turfgrass in the Bioclimatic Mediterranean Region

This study reports the results of a research project (Mi.T.E.A.Med) funded by the Italian Ministry of Agriculture. The research was organised in two phases: the first one involved the screening of the study area (Southern Italy) to find suitable turfgrass species and the second one focused on ex situ cultivation to test the ecotypes with salinity resistance. During the first step of the research, 11 sites from 6 regions of Southern and Central Italy were identified. In these sites, 24 ecotypes of Cynodon dactylon (L.) Pers. were collected and their habitus, phenology, and some biometric parameters have been determined. During the 2 years of research, both botanic and agronomic characterisation of the collected C. dactylon ecotypes was carried out. Some native accessions showed a behaviour similar to commercial cultivars, while an ecotype from the Abruzzo Region showed better results compared to the commercial cultivars for several quality indices. The results of this project showed that Mediterranean-adapted native grass species (e.g. Cynodon dactylon (L.) Pers.) are worth investigating for turfgrass, making for their performance and low resource requirement (especially water). This species can be used as promising alternatives to conventional non-native turfgrasses.

Abscisic Acid and Biomass Partitioning in Tomato Under Salinity

Increasing soil salinization is an enormous cause of crop productivity reduction in many areas of the world. It has a deep backlash on crop yields because it reduces leaf growth and induces leaf senescence, this in turn reduces plant assimilation activity, impairing its capacity for producing further growth or harvestable biomass. Plant has the capacity for adaptation to the environmental conditions likely involving long-distance signals between different organs (e.g., between root and shoot) through phytohormones. Abscisic acid (ABA) between them, surely, has an important action in the whole plant responses to drought and salt stresses. Processes that control leaf growth and shoot development during the osmotic phase of salinity are still not well known and several different opinions exist on cross-talk between other hormones and ABA in the process of biomass allocation under salinity conditions.

Sustainability in Cereal Crop Production in Mediterranean Environments

The continuous increase of the world population (a growth of about one-third is expected by 2050), together with an even larger increase in food demand (especially in emerging countries), will lead in the next 30 years to the necessity to produce 70 % more food. To keep the pace with food demand, global cereal production would need to increase by 40 % overall, or by some 900 million tons between the present and 2050. Single countries can either increase production or increase net imports or a combination of both.