Componentes de produção como indicadores de tolerância à seca em cana-de-açúcar

A deficiência de água é um dos principais fatores que limitam a produção da cana-de-açúcar (Saccharum officinarum L.). Estudar os efeitos do estresse hídrico sobre os componentes de produção e sua relação com a produtividade pode ajudar os programas de melhoramento a selecionar genótipos produtivos sob essa condição. O objetivo deste estudo foi investigar as relações entre os caracteres número de colmos, altura de colmos, diâmetro de colmos e massa de colmos com a produtividade de cana-de-açúcar cultivada em uma área, sob deficiência moderada de água, durante o período de maior desenvolvimento, a fim de prover informações que auxiliem melhoristas na adoção de características para selecionar variedades tolerantes à seca. Foram cultivados 78 genótipos e dois padrões, um tolerante e outro sensível ao estresse hídrico, sob deficiência moderada de água em campo e durante o ano agrícola 2005/2006 em Weslaco, Texas, Estados Unidos. Produtividade e os componentes de produção foram avaliados. Sob estresse, o padrão tolerante (TCP93-4245) apresentou maior produtividade, número de colmos, altura de colmos e massa de colmos do que o padrão sensível (TCP87-3388). Entretanto, o padrão sensível apresentou maior diâmetro de colmos. Associação linear foi encontrada entre produtividade e seus componentes, mas diâmetro de colmos foi bastante instável entre os genótipos. Altura de colmos apresentou correlação positiva com número, diâmetro e massa de colmos. Diâmetro de colmos também apresentou correlação positiva com massa de colmos. Portanto, durante o processo de seleção, quando um desses componentes é melhorado para tolerância à seca, o componente correlacionado deverá também ser melhorado, tornando-se possível selecionar genótipos com elevada produtividade e número, altura e massa de colmos sob deficiência hídrica.Water deficit is one of the major factors limiting the production of sugarcane (Saccharum officinarum L.). A study of the effects of limited water condition on yield components and their relationship with productivity can aid breeding programs in selecting for high yielding genotypes under this condition. The objective of this study was to investigate the relationships among the parameters stalk number, stalk height, stalk diameter, and stalk weight with cane yield in sugarcane growing in a field under moderate water stress during its grand growth period, in order to provide information to help breeders in adopting traits for selecting drought tolerant varieties. Seventy-eight genotypes plus two controls, one drought-tolerant and one drought-susceptible, were grown under a moderate water deficit condition in the field in 2005/2006 at Weslaco, TX. Productivity and yield components were measured. Under stress, the tolerant control (TCP93-4245) showed higher productivity, stalk number, stalk height and stalk weight than the susceptible one (TCP87-3388). However, the susceptible control showed higher stalk diameter. Linear association was found between productivity and its yield components, but stalk diameter showed to be fairly unstable among genotypes. Stalk height showed significant correlation with stalk number, stalk diameter and stalk weight. Stalk diameter also showed positive correlation with stalk weight. Therefore, during the selection procedure, when one of these traits is enhanced by drought tolerance, the correlated trait should also increase, making it feasible to select genotypes with high productivity, stalk number, stalk height, and stalk weight under water deficit

Responses of Jatropha curcas

Two greenhouse experiments were conducted to quantify growth responses of Jatropha curcas to a range of salt and drought stresses. Typical symptoms of salinity stress such as leaf edge yellowing were observed in all elevated salinity treatments and the degree of the foliar salt damage increased with the salinity of irrigation water. Total dry weight (DW) of Jatropha plants was reduced by 30%, 30%, and 50%, respectively, when irrigated with saline solutions at electrical conductivity of 3.0, 6.0, and 9.0 dS m−1 compared to that in the control. Leaf Na+ concentration was much higher than that observed in most glycophytes. Leaf Cl− concentrations were also high. In the drought stress experiment, plants were irrigated daily with nutrient solution at 100%, 70%, 50%, or 30% daily water use (DWU). Deficit irrigation reduced plant growth and leaf development. The DW of leaves, roots, and total were reduced in the 70%, 50%, and 30% DWU compared to the 100% DWU control treatment. In summary, salinity stress and deficit irrigation significantly reduced the growth and leaf development of greenhouse-grown Jatropha plants

Provitamin A biofortification of cassava enhances shelf life but reduces dry matter content of storage roots due to altered carbon partitioning into starch

Storage roots of cassava (Manihot esculenta Crantz), a major subsistence crop of sub-Saharan Africa, are calorie rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots were enhanced by coexpression of transgenes for deoxy-d-xylulose-5-phosphate synthase (DXS) and bacterial phytoene synthase (crtB), mediated by the patatin-type 1 promoter. Storage roots harvested from field-grown plants accumulated carotenoids to ≤50 lg/g DW, 15- to 20-fold increases relative to roots from nontransgenic plants. Approximately 85%–90% of these carotenoids accumulated as all-trans-β-carotene, the most nutritionally efficacious carotenoid. β-Carotene-accumulating storage roots displayed delayed onset of postharvest physiological deterioration, a major constraint limiting utilization of cassava products. Large metabolite changes were detected in β-carotene-enhanced storage roots. Most significantly, an inverse correlation was observed between β-carotene and dry matter content, with reductions of 50%–60% of dry matter content in the highest carotenoid-accumulating storage roots of different cultivars. Further analysis confirmed a concomitant reduction in starch content and increased levels of total fatty acids, triacylglycerols, soluble sugars and abscisic acid. Potato engineered to co-express DXS and crtB displayed a similar correlation between β-carotene accumulation, reduced dry matter and starch content and elevated oil and soluble sugars in tubers. Transcriptome analyses revealed a reduced expression of genes involved in starch biosynthesis including ADP-glucose pyrophosphorylase genes in transgenic, carotene-accumulating cassava roots relative to nontransgenic roots. These findings highlight unintended metabolic consequences of provitamin A biofortification of starch-rich organs and point to strategies for redirecting metabolic flux to restore starch production

Macronutrient Removal by Muskmelons Grown on Calcareous Soils

Advances in understanding plant physiology and nutrient requirements now allow growers to supply crops with sufficient nutrients to optimize growth and yield. However, for certain high value horticultural crops, fertilizer requirements for optimum yields often differ from the requirements for quality traits such as taste, flavor, texture and shelf‐life. Timing of fertilizer application, as well as soil and plant factors, are also critical in quality considerations. Currently, there are no nutrient management guidelines for optimizing produce quality even though certain nutrient elements such as potassium (K) are known to influence quality development. Information on nutrient uptake and removal amounts is useful in developing fertility recommendations for crops with different nutrient requirements and quality standards. In this study, leaf, stem and fruit tissues of muskmelons (Cucumis melo L. var ‘Cruiser’) were sampled from fields differing in soil type and analyzed to calculate nutrient removal amounts. There were little differences in the concentration of major nutrients (N, P, K) in plant tissues (leaves, stems) during vegetative development. However after fruit set, the concentration of these nutrients was significantly reduced as developing fruits became sinks for these nutrient. Differences were also observed in tissue nutrient concentrations among the sampling sites and this was coincident with soil type; tissues sampled from sites with heavy soils tended to have higher nutrient concentrations than those from sites with light textured soils. Fruit yields ranged from 9‐13 t∙acre‐1 and was greater in the heavy textured sites. Estimates of nutrient removal amounts ranged from 18‐38 lbs N/acre, 3‐6 lbs P/acre, and 35‐80 lbs K/acre and varied significantly among sites. Exceptionally dry weather conditions during the 2009 growing season potentially affected the uptake and accumulation patterns of these nutrients since fruit yields were also generally lower than average. Data collected over multiple years under different weather conditions, soil types and yield scenarios will be needed to establish realistic nutrient removal values that can be used to develop fertilizer application guidelines aimed at improving fruit quality

Economics of Lignocellulosic Ethanol Production From Energy Cane

A probabilistic financial model was developed to assess the economic feasibility of energy-cane-based hydrolysis ethanol production. At an expected price of $1.97/gallon and no tax credit, the chances of a positive NPV were 70%. By slightly increasing feedstock and ethanol yields by 5 units, the chances rose to 95%

Partial least squares-discriminant analysis (PLS-DA).

<p>Correlations between permissive and non-permissive hosts of <i>Candidatus</i> Liberibacter asiaticus (<i>C</i>Las) and their free amino acid content as explanatory variables (X). The ellipse represents the Hotelling T² with 95% confidence interval (R²X_cum = 0.58, R²Y_cum = 0.99, Q²_cum = 0.79 for all hosts tested (A); R²X_cum = 0.64, R²Y_cum = 1, Q²_cum = 0.89 for <i>C</i>Las-permissive and non-permissive plants only (B). Q²_cum = cumulative fraction of the total variation of X’s that can be predicted by the extracted components; R²X_cum and R²Y_cum represent the fraction of the sum of squares of all X’s and Y’s explained by the current components, respectively. P = <i>C</i>Las-permissive and NP = <i>C</i>Las-non-permissive hosts defined as: OJY = young orange jasmine, OJM = mature orange jasmine, CLY = young curry leaf, CLM = mature curry leaf, WSY = young white sapote, WSM = mature white sapote, GFY = young grapefruit, GFM = mature grapefruit, SOY = young sweet orange, SOM = mature sweet orange, LEY = young lemon, LEM = mature lemon, PW = periwinkle plant, ACPAd = <i>D</i>. <i>citri</i> adults, and ACPNy = <i>D</i>. <i>citri</i> nymphs. The amino acids are defined as: AAAA, α-amino adipic acid; AABA, α-aminobutyric acid; Ala, alanine; Arg, arginine; Asn, asparagine; Asp, aspartate; BABA, β-aminobutyric acid; BALA, β-alanine; Carno, carnosine, Cit, citrulline; Cys, cystine; Cysta, cystathionine; Eth, ethanolamine; GABA, γ-aminobutyric acid; Gln, glutamine; Glu, glutamate; Gly, glycine; His, histidine; Hom, homocysteine; Hpro, hydroxyproline; Hydlys, hydroxyl-lysine; Ile, isoleucine; Leu, leucine; Lys, lysine; Meh, 1-methyl histidine; Met, methionine; Orn, ornithine; Phe, phenylalanine; PHOS, phosphoethanolamine; Orn, ornithine, Pro, proline; Sar, sarcosine; SEP, phosphoserine; Ser, serine; Tau, taurine; Thr, threonine; Trp, Tryptophan; Tyr, tyrosine; Val, valine.</p

Contrasting amino acid profiles among permissive and non-permissive hosts of <i>Candidatus</i> Liberibacter asiaticus, putative causal agent of Huanglongbing

<div><p>Huanglongbing is a devastating disease of citrus. In this study, a comprehensive profile of phloem sap amino acids (AA) in four permissive host plants of <i>Candidatus</i> Liberibacter asiaticus (<i>C</i>Las) and three non-permissive Rutaceae plants was conducted to gain a better understanding of host factors that may promote or suppress the bacterium. The AA profiles of <i>Diaphorina citri</i> nymphs and adults were similarly analyzed. A total of 38 unique AAs were detected in phloem sap of the various plants and <i>D</i>. <i>citri</i> samples, with phloem sap of young shoots containing more AAs and at higher concentrations than their mature counterparts. All AAs detected in phloem sap of non-permissive plants were also present in <i>C</i>Las -permissive hosts plus additional AAs in the latter class of plants. However, the relative composition of 18 commonly shared AAs varied between <i>C</i>Las -permissive hosts and non-permissive plants. Multivariate analysis with a partial least square discriminant methodology revealed a total of 12 AAs as major factors affecting <i>C</i>Las host status, of which seven were positively related to <i>C</i>Las tolerance/resistance and five positively associated with <i>C</i>Las susceptibility. Most of the AAs positively associated with <i>C</i>Las susceptibility were predominantly of the glutamate family, notably stressed-induced AAs such as arginine, GABA and proline. In contrast, AAs positively correlated with <i>C</i>Las tolerance/resistance were mainly of the serine family. Further analysis revealed that whereas the relative proportions of AAs positively associated with <i>C</i>Las susceptibility did not vary with host developmental stages, those associated with <i>C</i>Las tolerance/resistance increased with flush shoot maturity. Significantly, the proline-to-glycine ratio was determined to be an important discriminating factor for <i>C</i>Las permissivity with higher values characteristic of <i>C</i>Las -permissive hosts. This ratio could be exploited as a biomarker in HLB-resistance breeding programs.</p></div

Cluster heatmap describing the relative concentrations of free amino acids in phloem sap of permissive hosts of <i>Candidatus</i> Liberibacter asiaticus, non-permissive plants and whole <i>Diaphorina citri</i> nymphs and adults (OJY = young orange jasmine, OJM = mature orange jasmine, CLY = young curry leaf, CLM = mature curry leaf, WSY = young white sapote, WSM = mature white sapote, GFY = young grapefruit, GFM = mature grapefruit, SOY = young sweet orange, SOM = mature sweet orange, LEY = young lemon, LEM = mature lemon, PW = periwinkle plant, ACPAd = <i>D</i>. <i>citri</i> adults, and ACPNy = <i>D</i>. <i>citri</i> nymphs).

<p>Cluster heatmap describing the relative concentrations of free amino acids in phloem sap of permissive hosts of <i>Candidatus</i> Liberibacter asiaticus, non-permissive plants and whole <i>Diaphorina citri</i> nymphs and adults (OJY = young orange jasmine, OJM = mature orange jasmine, CLY = young curry leaf, CLM = mature curry leaf, WSY = young white sapote, WSM = mature white sapote, GFY = young grapefruit, GFM = mature grapefruit, SOY = young sweet orange, SOM = mature sweet orange, LEY = young lemon, LEM = mature lemon, PW = periwinkle plant, ACPAd = <i>D</i>. <i>citri</i> adults, and ACPNy = <i>D</i>. <i>citri</i> nymphs).</p