Leaf Fresh Mass Research Articles

Effect of Nitrogen and Shade on Photosynthetic Gas Exchange and Productivity of Wheat Under Elevated Atmospheric CO2 Concentration

Sufficient nitrogen and shade may benefit photosynthetic down-regulation at elevated CO2 concentrations. Two levels of atmospheric CO2 400 and 760 μmol mol−1 were simulated using controlled environment open-top chambers, wheat (Triticum aestivum L) was grown at two N application rates (0 and 200 mg N kg−1 soil), and two photosynthetic photon fluxes (PPF, 100 and 60 % of solar irradiance). The increasing leaf N concentration, shade and N application extended the wheat developmental period and increased flag leaf fresh mass, water content, plant height and spike length by 11 d, 125, 126, 29 and 43 %, respectively. However, with sufficient N and elevated CO2, shade decreased dry mass, kilo-grain weight, instantaneous water use efficiency, grain water use efficiency and photosynthetic N use efficiency was increased by 30, 12, 2, 36 and 44 %, as compared with the unshaded treatment. Higher N application and shade increased N and chlorophyll concentration in flag leaves by 135 and 35 %, resulting in extended growth stage and increased plant and leaf water content, caused significant increments of plant height, grain number per spike and grain weight per spike under elevated CO2 as compared to N-deprived (0 mg N kg−1 soil) and unshaded treatment. Shade significantly increased leaf and plant water content, but did not affect wheat water and nitrogen use efficiency, which indicated that the decline of water content in flag leaves was a response of wheat to elevated CO2. The increment of leaf water status may extend the growth period to relieve photosynthesis acclimation at elevated CO2.

Evaluation of Lettuce Genotypes for Salinity Tolerance

Lettuce is one of the most commonly used salad vegetables and considered to be a relatively salt-sensitive crop. Salinity is a major constraint to crop production in all important lettuce growing regions of the United States, and the water quality problem is exacerbated by climate change. To identify salt-tolerant lettuce genotypes, 178 cultivars and germplasm accessions (56 butterhead, 39 crisphead, 35 romaine, 33 leaf, and 15 wild types) were selected from a preliminary screening of more than 3800 genotypes, and tested for salinity tolerance in sand cultures under greenhouse conditions. Plants were grown in Hoagland nutrient solution, either with or without 30/15 mm NaCl/CaCl2, and leaf fresh and dry mass (FM and DM), chlorophyll index, and maximal photochemical efficiency (Fv/Fm) were measured 4 weeks after plants were transplanted. Generally, salinity decreased lettuce shoot FM and DM, increased DM/FM ratio and chlorophyll index, and had no effect on Fv/Fm. Some lettuce varieties showed salt tolerance (less than 15% reduction in FM), such as PI 342515, PI 358020c, ‘Morgana’, ‘Amerika’ (butterhead), ‘Laura’ (crisphead), PI 289023, PI 273577, PI 278066, PI 177425 (romaine), PI 171676a, PI 177423, PI 342477, and PI 358018b (leaf). The results indicate that lettuce genotypes differ greatly in their salt sensitivity, which could be useful for growers to choose cultivars and for breeders to improve lettuce adaptation to salinity stress.

Synchrotron-Based Techniques Shed Light on Mechanisms of Plant Sensitivity and Tolerance to High Manganese in the Root Environment.

Plant species differ in response to high available manganese (Mn), but the mechanisms of sensitivity and tolerance are poorly understood. In solution culture, greater than or equal to 30 µm Mn decreased the growth of soybean (Glycine max), but white lupin (Lupinus albus), narrow-leafed lupin (Lupin angustifolius), and sunflower (Helianthus annuus) grew well at 100 µm Mn. Differences in species' tolerance to high Mn could not be explained simply by differences in root, stem, or leaf Mn status, being 8.6, 17.1, 6.8, and 9.5 mmol kg(-1) leaf fresh mass at 100 µm Mn. Furthermore, x-ray absorption near edge structure analyses identified the predominance of Mn(II), bound mostly to malate or citrate, in roots and stems of all four species. Rather, differences in tolerance were due to variations in Mn distribution and speciation within leaves. In Mn-sensitive soybean, in situ analysis of fresh leaves using x-ray fluorescence microscopy combined with x-ray absorption near edge structure showed high Mn in the veins, and manganite [Mn(III)] accumulated in necrotic lesions apparently through low Mn sequestration in vacuoles or other vesicles. In the two lupin species, most Mn accumulated in vacuoles as either soluble Mn(II) malate or citrate. In sunflower, Mn was sequestered as manganite at the base of nonglandular trichomes. Hence, tolerance to high Mn was ascribed to effective sinks for Mn in leaves, as Mn(II) within vacuoles or through oxidation of Mn(II) to Mn(III) in trichomes. These two mechanisms prevented Mn accumulation in the cytoplasm and apoplast, thereby ensuring tolerance to high Mn in the root environment.

ADUBAÇÃO N-K NO ABACAXIZEIRO ‘BRS IMPERIAL’ - I - EFEITO NO DESENVOLVIMENTO E NA FLORAÇÃO DA PLANTA

RESUMO O abacaxizeiro ‘BRS Imperial’ é cultivar resistente à fusariose, com folhas sem espinhos, e que carece de informações técnicas específicas para o seu manejo. Este trabalho teve como objetivo avaliar o efeito de doses de N e K2O no desenvolvimento vegetativo, na floração e nos atributos de desenvolvimento da folha ‘D’ do ‘BRS Imperial’, buscando estabelecer parâmetros da planta para a indução artificial do florescimento. Em delineamento em blocos ao acaso e cinco repetições, testaram-se quatro doses de N (0; 160; 320; 550 kg ha-1) e quatro doses de K2O (0; 240; 480 e 600 kg ha-1), em esquema fatorial completo 4 x 4. A adubação potássica influenciou de forma positiva na massa fresca e no comprimento da planta, bem como no número de mudas por planta após a colheita dos frutos, enquanto a aplicação de N influenciou na emissão de folhas e na massa fresca de mudas. A adubação nitrogenada diminuiu o percentual de florescimento induzido artificialmente, enquanto a potássica aumentou esse parâmetro. A massa máxima estimada da folha ‘D’ foi de 56 g na dose de 364 kg ha-1 de N e na maior dose de K2O (600 kg ha-1). A massa da folha ‘D’ apresentou a melhor correlação com a massa do fruto, sendo estimada a massa mínima de 44 g para obtenção de frutos de 900 g, massa mínima exigida pelo mercado para comercialização.

Reliability of leaf relative water content (RWC) measurements after storage: consequences for in situ measurements

Relative water content (RWC) is widely used to describe plant water status, and is commonly measured gravimetrically. The ephemeral nature of leaf fresh mass poses severe constraints for such measurements in field-grown plants. These constraints can be overcome by transporting the leaves in waterproof containers into the lab. However, even then, leaves lose water, and other changes may happen. The effects of a delay on the measurement of RWC have not been quantified so far. In this study, the influence of duration of storage up to 96 h and storage temperature on RWC and its components was investigated for four species. Alnus incana subsp. rugosa (Du Roi) R.T. Clausen, Impatiens capensis Meerb., and Scirpus microcarpus J.Presl & C.Presl leaves were stored in plastic bags, whereas those of Comptonia peregrina (L.) J.M.Coult. were stored in plastic vials. RWC remained within 5% of the initial value during 24 h cool storage, but after that, larger changes were observed. The effects of storage were species specific, being most pronounced in species poorly protected against desiccation, and under warm conditions. The effects of storage were not only limited to water loss, but also included cellular degradation. In general, storage at 10 °C for 24 h enables measurement of RWC for field-grown plants with accuracy of a few percent, but care has to be taken with species vulnerable to desiccation, possibly requiring faster measurement and a cooler storage temperature.

Changes in chloroplast ultrastructure in leaves of drought-stressed maize inbred lines

Chloroplasts are commonly the site of the earliest abiotic injury visible in plant ultrastructure. In this study, six inbred lines of maize (Zea mays L.) were used to analyze changes in the ultrastructure of chloroplasts and related physiological parameters under conditions of drought stress simulated by 20% polyethylene glycol 6000 (−0.6 MPa) for two days. Chloroplasts of three maize lines proved to be more sensitive. They showed changes in the ultrastructure in response to drought, including damage of thylakoid membranes, an increase in the number and size of plastoglobuli, swelling of thylakoid membranes both stromal and granal, disorganization of the thylakoid membrane system, an obvious increase in the intrathylakoid space, and a decrease in the length-to-width ratio and area of chloroplasts. In addition, the contents of malondialdehyde increased markedly in the sensitive lines. Contrary to the sensitive lines, stable structures and shapes of chloroplasts were observed in the drought-resistant lines; it could be considered as an advantage contributing to drought tolerance in the plants. In addition, the drought index of leaf fresh mass (LMDI) in the drought-sensitive lines was ≤ 0.5, which was also associated with a lower content of leaf chlorophyll. In contrast, drought tolerance coincided with lesser growth reduction, and higher LMDI and leaf chlorophyll content.

Change in growth and physiological parameters in soybean seedlings in response to toxic action of copper

Soybean (Glycine max l., cv. Alina) seedlings grown for 5 days on medium containing 1.5–50 μm CuSO4 displayed inhibition of their growth and shoot and root system biomass accumulation, and this effect correlated with copper ions’ concentration. The content of chlorophyll in leaves remained unchanged, while the total content of soluble carbohydrates per 1 g fresh leaf and root mass increased. The inhibition of root growth appeared to be marked at a lower concentration of copper ions in the medium as compared to that intensified the entering into root cells of Evans blue, the known indicator of cell viability. Copper ion excess in the medium did not prevent the process of lateral root initiation and their exit on the primary root surface but significantly suppressed their subsequent growth. It was shown that the Cu-stress resulted in changes in filament actin (F-actin) content in the root cells of the seedlings. F-actin amount increased after 20 h growth of the plants on the medium with 10 μM CuSO4, whereas on the medium containing 50 μM CuSO4 F-actin content in root tip cells dropped considerably as compared to the control. The content of F-actin in the root apex became equal to that in the basal part of the root that completed growth. These results allowed us to suggest that fast Cu-stress-induced retardation of soybean seedling growth is likely to be associated with disturbance of organization and functioning of the actin cytoskeleton (AC) leading to inhibition of cell and organs growth and changes in architecture of the root system due to damage of the mechanism of auxin transport and distribution.

Label-free nanoUPLC-MSE based quantification of antimicrobial peptides from the leaf apoplast of Nicotiana attenuata.

BackgroundOverexpressing novel antimicrobial peptides (AMPs) in plants is a promising approach for crop disease resistance engineering. However, the in planta stability and subcellular localization of each AMP should be validated for the respective plant species, which can be challenging due to the small sizes and extreme pI ranges of AMPs which limits the utility of standard proteomic gel-based methods. Despite recent advances in quantitative shotgun proteomics, its potential for AMP analysis has not been utilized and high throughput methods are still lacking.ResultsWe created transgenic Nicotiana attenuata plants that independently express 10 different AMPs under a constitutive 35S promoter and compared the extracellular accumulation of each AMP using a universal and versatile protein quantification method. We coupled a rapid apoplastic peptide extraction with label-free protein quantification by nanoUPLC-MSE analysis using Hi3 method and identified/quantified 7 of 10 expressed AMPs in the transgenic plants ranging from 37 to 91 amino acids in length. The quantitative comparison among the transgenic plant lines showed that three particular peptides, belonging to the defensin, knottin and lipid-transfer protein families, attained the highest concentrations of 91 to 254 pmol per g leaf fresh mass, which identified them as best suited for ectopic expression in N. attenuata. The chosen mass spectrometric approach proved to be highly sensitive in the detection of different AMP types and exhibited the high level of analytical reproducibility required for label-free quantitative measurements along with a simple protocol required for the sample preparation.ConclusionsHeterologous expression of AMPs in plants can result in highly variable and non-predictable peptide amounts and we present a universal quantitative method to confirm peptide stability and extracellular deposition. The method allows for the rapid quantification of apoplastic peptides without cumbersome and time-consuming purification or chromatographic steps and can be easily adapted to other plant species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0398-9) contains supplementary material, which is available to authorized users.

Influence of irrigation regime on the leaf area and leaf area index of French bean (Phaseolus vulgaris L.)

In field experiments the influence of irrigation regime on leaf area and leaf area index in bean plants are investigated. Cultivar “Strike was used, which is a highly yield, with cylindrical pods and is intended mainly for the canning industry. Experiments were conducted according to the block method, in four replications and size of experimental plots 17.5 m 2 , and crop plots - 10 m 2 and planting pattern of 50 x 5 cm. The variants are the following: 1. Without irrigation; 2. Optimum irrigation by the maintenance of “pre-irrigation soil moisture” over 80% of the Field Capacity (FC); 3. Irrigation with variant 2, but with 30% reduction of irrigation norm; 4. Irrigation with variant 2, but with 70% reduction of irrigation norm. A close relationship betwee n the irrigation norms and leaf area index (LAI) for the conditions of the experiment is established. This relationship is subject to the equation Y=1-0.609(1-x) 1,5 , where R 2 = 0.981. Relationship has been found between LAI and yield, which is expressed best by the quadratic equation: Y=547.8 x-31.9x 2 -746.6, at R 2 = 0.91. The relationship between the mass of leaves (x) and LA is linear, as in terms of dry mass, it is expressed by the equation LA= 81.95x, with R 2 =0.843. In terms of fresh leaf mass equation is: LA=35.073x at R 2 =0.912.

Effects of Grafting on Alkali Stress in Tomato Plants: Datura Rootstock Improve Alkalinity Tolerance of Tomato Plants

Plant growth, nutritional status, and proline content were investigated in non-grafted and grafted greenhouse tomato plants onto five rootstocks of eggplant, datura, orange nightshade, local Iranian tobacco, and field tomato, exposed to 0, 5, and 10 mM sodium bicarbonate (NaHCO3) to determine whether grafting could improve alkalinity tolerance of tomato. The leaf fresh mass of ungrafted and grafted tomato plants decreased significantly as NaHCO3 levels increased. Despite other rootstocks and ungrafted plants, alkalinity had no significant effect on stem and root fresh mass and shoot phosphorus (P), potassium (K) and magnesium (Mg) concentrations of datura grafted plants. The lowest solution pH and electrical conductivity (EC) values and the highest leaf proline content were observed in the plants grafted onto datura rootstock. Moreover, sodium (Na) concentration in shoots was lower in plants grafted onto datura rootstock than in other plants especially under high NaHCO3 levels. Overall, using datura rootstock improved alkalinity tolerance of tomato plants under NaHCO3 stress.

Growth and Mineral Constituents’ Variations in Halophytic Species under Salinity

The present investigation was made to study the effect of different concentrations of sodium chloride on the growth and mineral constituents in different parts of Clerodendron inerme. The plant and could survive a wide range of 100-1000 mM of NaCl. The upper limit for the survival of Clerodendron inerme was 500 mM NaCl. However, favourable growth response by seedlings was confined to 200 mM NaCl. The morphological parameters such as shoot and length, number of leaves, total leaf area, fresh and dry mass and mineral constituents such as sodium, potassium and calcium were assessed.

Growth and Mineral Constituents’ Variations in Halophytic Species under Salinity

The present investigation was made to study the effect of different concentrations of sodium chloride on the growth and mineral constituents in different parts of Clerodendron inerme. The plant and could survive a wide range of 100-1000 mM of NaCl. The upper limit for the survival of Clerodendron inerme was 500 mM NaCl. However, favourable growth response by seedlings was confined to 200 mM NaCl. The morphological parameters such as shoot and length, number of leaves, total leaf area, fresh and dry mass and mineral constituents such as sodium, potassium and calcium were assessed.

Influence of nutrient and water additions on functional traits of Salsola nitraria in desert grassland

Aims Our objective was to better understand the response of plant functional traits of Salsola nitraria to environmental change, such as global climate change and nutrient addition, in desert grassland. Methods We conducted field experiments of moisture and nutrient additions for three years(2009–2011) in a desert grassland of northwest Xinjiang in China. We investigated plant functional traits of S. nitraria and in the fourth year(2012) measured plant height, stem fresh mass, stem dry mass, leaf fresh mass, leaf dry mass, etc. under different treatments of nutrient and water additions. Important findings The combination of fertilizer and moisture had a significant influence on stem fresh mass, leaf fresh mass, leaf area, specific leaf area, leaf saturated water content, and leaf dry matter content(two-way ANOVA, p 0.05), while the effect of either fertilizer or moisture alone was not significant. None of the treatment effects on plant height were significant. The maximum values of plant height, stem fresh weight, stem dry weight, leaf saturated fresh weight, leaf dry weight, leaf area, and specific leaf area appeared in the snow and fertilizer additions(N1 W2), and the second highest was in the control(N0 W0). Maximum leaf saturated water content was observed in the control(N0 W0), and the second highest appeared in the snow and fertilizer additions(N1 W2). The fertilizer addition(N1 W0) could significantly decrease the level of leaf saturated water content. In all of the treatments, leaf dry matter content was higher than that under the control, and among them, the rain addition(N0 W2) significantly increased leaf dry matter content. In the control, there were many significant negative correlations between leaf dry matter content and other functional traits and many significant positive correlations between different functional traits. After the fertilizer and/or moisture addition, the correlation coefficient was reduced. In desert grassland of the Junggar Basin, the different performance of S. nitraria under different treatments was the result of plant adaptations to environmental changes.

Changes in chlorophyll content and fluorescence and fruit yield contributing traits in different genotypes of strawberry (Fragaria x ananassa DUCH.)

Analysis of changes in chlorophyll fluorescence parameters in strawberry leaves was based on a field experiment performed in the years 2009–2010. Ten genotypes including 5 cultivars: ‘Kent’, ‘Teresa’, ‘Senga Sengana’, ‘Chandler’ and the breeding clone 1387 as well as their inbred progeny, were the object of the study. During the experiment the following indicators were evaluated: chlorophyll a and b content in fresh leaf mass as well as fluorescence parameters: minimum (F0) and maximum fluorescence yield (Fm), photochemical efficiency of PS II (Fv/Fm), actual quantum yield of PSII photochemistry (Y), minimum (F0’) and maximum efficiency of fluorescence (Fm’) in the light, coefficient of photochemical (qP) and non-photo- chemical (qN) fluorescence quenching. In this work, we also examined the effect of repeated inbreeding on strawberry fruit yield and yield components. The analysis of changes of these parameters showed that inbreeding caused a reaction in all tested cultivars. In all inbred progeny, chlorophyll a and b content decreased compared to the cultivars. Generally, the photoche- mical efficiency of photosystem II (Fv/Fm) and the parameter ΔF/ Fm’ were not affected by strong inbreeding. In analyzing the values of the coefficients qP and qN, it has been observed that changes in their values depend on the sensitivity of the examined genotypes to self-pollination. The functioning of PS II is the most sensitive indicator of the effect of various factors on plants and is useful, among others, in breeding to select plants with a required genotype. The yield – determining features such as: fruit yield per plant, weight of single fruit, number of fruit per plant and weight of leaves per plant in S3 generation, were lower as compared with parental forms.

High-plant density planting of basil (Ocimum basilicum) during summer/fall growth season improves yield in a closed hydroponic system

The objective of this study was to determine the combined effect of plant densities and leaf harvesting method on yield of hydroponically grown basil. The experiment was carried out during the spring/summer (September–December 2012) and during summer/fall (January–April 2013) seasons. Basil plantlets were transplanted 30 days after seeding, utilising a gravel-film technique hydroponic system under a 40% black-and-white shadenet structure. Plants were subjected to five plant densities, i.e. 10, 16, 20, 25 and 40 plants/m2, with two harvesting methods, i.e. tipping and cutting. Experimental layout was a randomised complete block design with four replicates. During the spring/summer season, the results showed no significant differences in plant growth and total yield per unit area at plant densities of 20, 25 or 40 plants/m2. Results during the summer/fall season showed the highest leaf fresh mass, leaf area and total plant fresh mass at the highest plant density of 40 plants/m2. Harvesting method did not have a significant effect on yield or on the total fresh and dry mass of basil. Results demonstrate that a plant density of 40 plants/m2 can improve growth and yield of basil significantly during the summer/fall season. However, during the spring/summer season, a plant density of 20 and 25 plants/m2 will be more cost effective with no significant effect on yield. Plant density recommendations are, therefore, 40 plants/m2 during the summer/fall season and 20 or 25 plants/m2 during spring/summer season.

Estabelecimento inicial de plântulas de Myracrodruon urundeuva Allemão em diferentes substrato

Objetivou-se com este trabalho avaliar o crescimento inicial de plântulas de M. urundeuva estabelecidas em diferentes substratos. O trabalho foi realizado no Laboratório de Sementes e no Viveiro de Mudas da Universidade Estadual da Bahia (UNEB), Barreiras, BA. As sementes foram coletadas de árvores daquela universidade. Foi utilizado o delineamento inteiramente casualizado com seis tratamentos e quatro repetições, sendo os tratamentos T1: solo; T2: areia; T3: solo + areia + esterco; T4: casca de madeira; T5: bagaço de cana-de-açúcar + esterco; e T6: bagaço de cana-de-açúcar + esterco + cinzas. A semeadura foi realizada em bandejas plásticas, com diferentes substratos, utilizando-se 20 sementes, colocadas a uma profundidade de 1,0 cm. Foram avaliados o índice de velocidade de emergência (%), a altura da parte aérea e da radícula, o comprimento das plântulas e das folhas, o número de folhas e as massas verde e seca da parte aérea e da radícula. Plântulas estabelecidas utilizando casca de madeira como substratos obtiveram melhores resultados quanto ao número e comprimento das folhas, altura da parte aérea e massa verde e seca da parte aérea. Em contraste, os percentuais de índice de velocidade de emergência obtiveram os piores resultados em plântulas estabelecidas em substratos com casca de madeira. Os resultados de radículas não diferiram entre as plântulas estabelecidas com os diferentes substratos. Os substratos contendo composto de casca de madeira ou bagaço de cana + esterco forneceram as melhores condições para o crescimento inicial de plântulas de M. urundeuva.

Effect of plant spacing and harvesting frequency on the yield of Swiss chard cultivars (Beta vulgaris L.) in a closed hydroponic system

The objective of this study was to determine the combined effect of plant densities and leaf harvesting frequencies on yield of two hydroponically grown Swiss chard cultivars. Swiss chard plantlets were transplanted 28 days after seeding, utilizing a gravel-film technique hydroponic system. Thirty treatment combinations were used, namely two Swiss chard cultivars (‘Ford Hook Giant’ and ‘Star 1801’), five plant densities (10, 16, 25, 40 and 50 plants/m2), combined with three leaf harvesting frequencies (after every 7, 14 and 21 days). The first harvest with measurement of leaf area, fresh and dry mass, and number of leaves was done 30 days after transplanting. The results demonstrate that the Swiss chard cultivars responded differently to harvesting frequencies and plant densities. The highest yield was obtained with cultivar ‘Ford Hook Giant’, at a plant density of 40 plants/m2, when plants were harvested on a biweekly basis. With cultivar Star 1801, harvesting frequency had no significant effect on yield. Plant density of 40 plants/m2 combined with harvesting frequency of 14 days are therefore recommended to improve yield of ‘Ford Hook Giant’. Key words: Leaf fresh mass, leaf area, leaf dry mass, plant density.

Uso de diferentes doses de manipueira na cultura da alface em substituição à adubação mineral

Objetivou-se, neste trabalho, verificar o efeito ocasionado pelo uso de diferentes doses de manipueira nas características agronômicas da alface em substituição à adubação mineral. O referido estudo foi desenvolvido em uma área pertencente ao Departamento de Tecnologia Rural da Universidade Federal Rural de Pernambuco, Recife, PE, no período de maio a agosto de 2010. O experimento foi conduzido em ambiente protegido em delineamento inteiramente casualizado, com seis tratamentos compostos das seguintes doses: 0, 5, 15, 25, 45, 65 m³ ha-1 e cinco repetições. Utilizou-se a cultivar de alface Regina 2000, dispondo-se uma planta por vaso de 4 L. Foram avaliadas, em função das doses aplicadas, as seguintes características agronômicas da alface: área foliar, altura de planta, número de folhas, matéria fresca e matéria seca da alface. Ao final do experimento constatou-se que a dose de 45 m³ ha-1 foi a que propiciou maior ganho de altura de planta, área foliar e, consequentemente, também maior produção de matéria fresca e seca. Assim sendo, o uso da manipueira serviu como fonte de adubação para a cultura da alface, dependendo da dose aplicada.

QTL for fibre-related traits in grain × sweet sorghum as a tool for the enhancement of sorghum as a biomass crop

Compared to maize and temperate grasses, sorghum has received less attention in terms of improving cell wall components. The objectives of this study were to identify quantitative trait loci (QTL) with main effects, epistatic and pleiotropic effects along with QTL×environment (QE) interactions controlling fibre-related traits in sorghum. Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), cellulose, hemicellulose, fresh leaf mass, stripped stalk mass, dry stalk mass, fresh biomass and dry biomass were analysed from a population of 188 grain×sweet sorghum recombinant inbred lines. A genetic map consisting of 157 DNA markers was constructed, and QTL were detected using composite interval mapping (CIM). CIM detected more than 5 additive QTL per trait explaining 7.1-24.7% of the phenotypic variation. Abundant co-localization of these QTL was observed across all chromosomes, and the highest cluster was identified on chromosome 6. Searching for candidate genes using the confidence interval of our QTL clusters reveals that these clusters might comprise a set of genes that are tightly linked. Some QTL showed multiple effects; however, the allele for each trait was favouring the parent with the increasing effect. QE interactions were observed for QTL showing multiple effects. Additive×additive interaction was observed for 7 out of 10 traits, indicating the importance of epistatic analysis. However, the phenotypic variation explained by digenic interactions was lower compared to the individual QTL. Our results indicate that various genetic components contribute to fibre-related traits and should be considered during the enhancement of sorghum for lignocellulosic biomass.

NaCl tolerance in Lycopersicon pennellii introgression lines: QTL related to physiological responses

The growth and ion content of salt sensitive Lycopersicon esculentum Mill. cv. M82 and salt tolerant L. pennellii Correll accession LA716 were examined under both control and stress conditions (150 mM NaCl). L. esculentum grew more vigorously than L. pennellii under optimal conditions, however, L. pennellii was able to maintain its growth better than cultivated tomato when the plants were exposed to salinity. Sodium content of both L. esculentum and L. pennellii increased as a result of NaCl stress. In addition, both species showed reduced potassium and calcium content due to salinity. The physiological traits were also measured in a population of 52 L. pennellii introgression lines grown under both normal and stress conditions. A total of 311 quantitative trait loci (QTL) were identified for the studied traits: plant height, stem diameter, leaf number, leaf and root fresh and dry mass, and sodium, potassium and calcium contents. Some of the loci (124) were identified under both control and stress conditions while 86 QTL were identified only under non-stress conditions and 101 loci were identified only under NaCl stress.