Calidad de fruto y aceite de olivos maduros en condiciones de cultivo de secado parcial de la zona radical

This study was conducted to evaluate the quantitative and qualitative effects of partial rootzone drying (PRD) irrigation on olive trees and their fruit and oil quality. Olive trees of the Moroccan Picholine variety were grown under arid conditions in Marrakech, and exposed to four irrigation treatments: Control (irrigated with 100 % of the crop evapotranspiration, on the two sides of the root system), PRD1 (irrigated with 50 % of the control, on one side of the root system, switching every two weeks), PRD2 (irrigated with 50 % of the control, on one side of the root system, switching every four weeks) and PRD3 (irrigated with the same amount of water as the control applied on one side of the root system, switching every two weeks). The individual fruit weight, dimensions and oil contents were generally greater under PRD than the control. Whereas, the fruit water content was lower under PRD1 and PRD2 than the control and PRD3. Oil acidity was not affected by irrigation, while the total polyphenol content, which affects the oxidative stability and sensory characteristics of the oil, increased in response to the PRD irrigation, especially under PRD1 (246.0 ppm) and PRD2 (278.5 ppm) treatments, against 148.4 ppm and 101.8 ppm for PRD3 and the control respectively. This increase could explain the oil bitterness observed under PRD1 and PRD2. The fatty acid composition was not affected by PRD1 and PRD2. The oil quality based on UV absorption coefficients (K232 and K270) decreased significantly under PRD2. Chlorophyll content and maturity index were antagonistic, and olive ripeness was found to be precocious under PRD irrigation treatments compared to the control.Este estudio fue realizado para evaluar los efectos cuantitativos y cualitativos de la irrigación de olivos por secado parcial de la zona radical (PRD) sobre la calidad de su fruto y de su aceite. Los olivos de la variedad marroquí Picholine fueron cultivados en condiciones áridas en Marrakech, y expuestos a cuatro tratamientos de irrigación: Control (irrigado con el 100 % de la evapotranspiración de la cosecha, en los dos lados del sistema radical), PRD1 (irrigado con el 50 % del control, en sólo un lado del sistema radical, cambiando cada dos semanas), PRD2 (irrigado con el 50 % del control, en un lado del sistema radical, cambiando cada cuatro semanas) y PRD3 (irrigado con la misma cantidad del agua que el control aplicado en un lado del sistema radical, cambiando cada dos semanas). El peso individual del fruto, sus dimensiones y el contenido en aceite fueron generalmente mayores bajo PRD que en el control. Mientras que, el contenido de agua de la aceituna fue inferior en PRD1 y PRD2 que en el control y en PRD3. La acidez del aceite no se afectó por el régimen de irrigación, mientras que el contenido total de polifenoles, que afecta a la estabilidad oxidativa y a las características sensoriales del aceite, aumentó en respuesta a la irrigación mediante PRD, sobre todo con los tratamientos PRD1 (246.0 ppm) y PRD2 (278.5 ppm), frente a los 148.4 ppm y 101.8 ppm de PRD3 y el control, respectivamente. Este aumento podría explicar el amargor del aceite obtenida con PRD1 y PRD2. La composición de ácidos grasos no fue afectada por PRD1 Y PRD2. La calidad del aceite basada en los coeficientes de absorción UV (K232 y K270) disminuyó considerablemente con PRD2. El contenido de clorofila resultó antagonista del índice de madurez, y éste último se desarrolló más precozmente en los tratamientos de irrigación PRD que en el control

Screening sorghum germplasm for tolerance to soil salinity

Sorghum (Sorghum bicolor) is known to be relat ively more tolerant to sal ini ty than other crops, such as maize (Zea mays) or legumes and thus has the potent ial to replace maize in saline soils ( Igar tua et al . 1994). The existence of large interspeci f ic (Yang et al . 1990) and int ra-speci f ic (Maas 1985, Azhar and McNe i l l y 1988, De La Rosa-Ibarra and Mai t i 1995) var iat ion for sal ini ty tolerance of fers a scope for integrat ing these tolerant crop genotypes wi th appropriate management practices to better exploi t the saline soils

Selective Phenotyping Traits Related to Multiple Stress and Drought Response in Dry Bean

Abiotic stress tolerance in dry bean (Phaseolus vulgaris L.) is complex. Increased population sizes are contributing to finding QTL conditioning stress response but phenotyping has not kept pace with high throughput genotyping for such studies. Our objectives were to determine effectiveness of 20 most tolerant and 20 most susceptible lines representing phenotypic extremes from a RIL population (‘Buster’ x \u27Roza’ [BR]) to facilitate examination of 19 traits for relevance to stress response and to validate existing QTL conditioning stress response. Using phenotypic extremes tested across multiple trials, eight of the 19 traits were clearly associated with drought stress. Pod wall ratio (PW), plant biomass by weight or a visual rating, and greenness index (NDVI) were most associated with seed yield (SY) under stress followed by phenology traits. The phenotypic extreme lines were also useful for validating QTL previously identified in the whole RIL population conditioning SY, seed weight (SW) and days to flower (DF), harvest maturity (HM), and seed fill (DSF). New QTL were identified for biomass, PW, and NDVI which co-segregated with major QTL for seed yield SY1.1BR and SY2.1BR. The preliminary finding of NDVI 1.1BR supports aerial imaging in larger genetic populations geared toward QTL analysis of stress response. In summary, phenotypic extremes helped sort through traits relevant to stress response in the Buster x Roza RIL population and verified the effect of two major QTL in response to terminal drought

Variation in Transpiration Efficiency and Related Traits in a Groundnut Mapping Population.

Transpiration efficiency (TE) was evaluated in groundnut genotypes JUG 26, ICGS 76, CSMG 84-1, ICGS 44, ICGV 86031, TAG 24 and ICG 2773 using the dry-down method. Pot-grown plants were irrigated to 90% field capacity then subjected to drought stress (i.e. irrigating plants with 70% of the water lost the day before the onset of drought stress) at 28 days after sowing (DAS). Significant variation among the genotypes for TE was evident, with TAG 24 and ICGV 86031 showing the lowest and highest values of TE, respectively. The soil water content where transpiration began to decline relative to the control varied among the genotypes, and these threshold values were negatively correlated to TE. In another dry-down experiment, 318 F8 recombinant inbred lines (RILs) obtained from a cross between ICGV 86031 and TAG 24 were also characterized, along with their parents, for TE. Substantial variation was observed among the RILs for transpiration, TE and specific leaf area (SLA) before and after the imposition of drought stress, and for SPAD chlorophyll meter readings (SCMR) before, during and at the end of drought stress. ICGV 86031 recorded greater TE and SCMA, and lower SLA than TAG 24. The analysis of TE values for the RILs revealed that the trait segregated transgressively and was governed by polygenes. The heritability value was highest for SLA, followed by SCMR. The heritability values were low for TE and transpiration. SLA and SCMR can be useful as alternative indices when the direct biomass-based evaluation of TE is not possible

Variation in root traits of chickpea (Cicer arietinum L.) grown under terminal drought

Deep and prolific root systems have been associated with enhanced avoidance of terminal drought stress in chickpea. This research evaluated the root traits of 257 recombinant inbred lines (RILs) derived from a cross between a breeding line with a large root system (ICC 4958) and an agronomically preferred variety (Annigeri) to assess the potential for identifying QTL for desirable root traits and to investigate the relationship between root traits, plant growth and seed yield under terminal drought stress. The root traits of field-grown chickpea RILs were measured using the monolith method during the 2001-2002 cropping season, while their shoot biomass and seed yield were evaluated during both 2000-2001 and 2001-2002 seasons. Significant genetic variation was observed amongst the RIL population for root length density, root dry weight and shoot dry weight at 35 days after sowing and for shoot biomass and seed yield at maturity. A linear relationship was observed between root dry weight and shoot dry weight at 35 days after sowing. The overall distribution of root length density and root dry weight among the RILs indicated that these traits are likely to be under polygenic control. The heritability of root dry weight was 0.27 and root length density was 0.23, compared to 0.49 for shoot dry weight at the same stage. The RILs exhibited a range of combinations of root size and seed yield, with a few RILs showing large root systems and high seed yield. However, there was no general correlation between seed yield and root size. High shoot biomass and harvest index contributed to high seed yield of the RILs. The implications for the molecular breeding of drought-avoidance root traits in chickpea are discussed

Screening sorghum genotypes for salinity tolerant biomass production

Genetic improvement of salt tolerance is of high importance due to the extent and the constant increase in salt affected areas. Sorghum [Sorghum bicolor (L.) Moench] has been considered relatively more salt tolerant than maize and has the potential as a grain and fodder crop for salt affected areas. One hundred sorghum genotypes were screened for salinity tolerance in pots containing Alfisol and initially irrigated with a 250-mM NaCl solution in a randomized block design with three replications. Subsequently 46 selected genotypes were assessed in a second trial to confirm their responses to salinity. Substantial variation in shoot biomass ratio was identified among the genotypes. The performance of genotypes was consistent across experiments. Seven salinity tolerant and ten salinity sensitive genotypes are reported. Relative shoot lengths of seedlings were genetically correlated to the shoot biomass ratios at all stages of sampling though the relationships were not close enough to use the trait as a selection criterion. In general, the whole-plant tolerance to salinity resulted in reduced shoot Na+ concentration. The K+/Na+ and Ca2+/Na+ ratios were also positively related to tolerance but with a lesser r 2. Therefore, it is concluded that genotypic diversity exists for salt tolerance biomass production and that Na+ exclusion from the shoot may be a major mechanism involved in that tolerance

Management of drought in ICRISAT cereal and legume mandate crops improvement

This chapter reviews the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)'s research achievements in the domain of crop drought tolerance and presents future perspectives in the genetic enhancement of crop water use and drought adaptation in the semiarid tropics (Patancheru, Andhra Pradesh, India). Exploration of crop genetic variability and genotype-environment interactions has contributed significantly to developing suitable screening methods for specific drought-tolerant traits. Genetic sources of drought tolerance were also identified at ICRISAT for all mandate crops (viz., pearl millet (Pennisetum glaucum), sorghum (Sorghum bicolor), chickpea (Cicer arietinum), groundnut and pigeon pea), and some of the associated traits have been well characterized. A large spectrum of genotype duration is now available, from long to short and extra-short duration, and matching genotype duration with likely period of soil water availability is the first strategy used against terminal-drought stress. Identification and genetic mapping of quantitative trait loci for specific drought-tolerant traits using molecular markers are currently receiving greater research focus. This approach provides a powerful tool for dissecting the genetic basis of drought tolerance. If validated with accurate phenotyping and properly integrated in marker-assisted breeding programmes, this approach will accelerate the development of drought-tolerant genotypes. Overall, the progress made at ICRISAT during the last three decades proves that it is realistic to develop varieties that have increased yield under drought-prone conditions. Further multidisciplinary research integrating plant breeding, simulation modelling, physiology and molecular genetics will realize the potential of these approaches and increase the efficiency of crop improvement in drought-prone environments

Variation in transpiration efficiency and its related traits in a groundnut (Arachis hypogaea L.) mapping population

Transpiration efficiency (TE) has been recognized as an important source of yield variation under drought stress in groundnut. Here the variation for TE is evaluated in a set of 318 recombinant inbred lines (RILs) of groundnut at F8 generation, derived from a cross between a high TE (ICGV 86031) and a low TE (TAG 24) parent, and the value of specific leaf area (SLA), SPAD chlorophyll meter readings (SCMR) and carbon isotope discrimination (Δ13C) as surrogates of TE are measured. Transpiration efficiency was measured gravimetrically in the 318 RILs and parents under progressive soil drying in a pot culture in two post-rainy seasons. Large and consistent variation for TE existed among the RILs across years. The overall distribution of TE among the RILs indicated that TE was governed by dominant and additive genes. Surrogates SLA and SCMR, were measured prior, during and after completion of the drought period, whereas Δ13C was measured on the dried tissue after harvest. Transpiration efficiency was negatively associated with SLA after the completion of stress treatment (r2=0.15) and Δ13C in leaves (r2=0.13) and positively associated with SCMR during stress (r2=0.17). These associations, all fairly weak, were significant only in 2004. None of these relationships was found in 2005. Although the heritability of SCMR during 2005 was relatively higher than that of TE, and although SCMR has previously been used to identify contrasting germplasm for TE, the stress-dependence of the relationship with TE, and the poor regression coefficients (r2) with that RIL population, do not confer that these surrogates are adequately robust enough in that population. Though more time consuming, a direct gravimetric evaluation for TE appeared to be more reliable

Relationships Between Transpiration Efficiency and Its Surrogate Traits in the rd29A:DREB1A Transgenic Lines of Groundnut

Transpiration efficiency (TE) contributes to crop performance under water-limited conditions, but is difficult to measure. Herein, we assess the relationships between TE and surrogate traits and how these interact with water regimes, using isogenic materials: five transgenic events of groundnut and their wild-type (WT) parent JL 24, among which large variation in TE was previously reported. These five events came from the insertion of transcription factor DREB1A from Arabidopsis thaliana, driven by stress responsive promoter rd29. The events were in T3 generation and had been selected from a preliminary trial for having a large range of variation in the time needed to deplete soil moisture upon exposure to soil drying. Two experiments were conducted, in each case with plants exposed to well-watered (WW) and water-stressed (WS) conditions. Significant correlations were found between TE and soil plant analysis development chlorophyll meter readings (SCMR), TE and specific leaf area (SLA), and SLA and SCMR in both experiments. Nevertheless, these significant relationships were confined to the drought stress (DS) treatment. No correlation between TE and Δ13C (carbon isotope discrimination) was found in the present study, regardless of the water regime, and in none of the two experiments. A significant negative correlation was established between TE and the fraction of transpirable soil water (FTSW) threshold values where transpiration declined upon soil drying, in both experiments. The mean vapour pressure deficit in the two different seasons (1.47 kPa and 0.73 kPa) did not affect the ranking of genotypes for TE. It is concluded that surrogates for TE, when used, need careful consideration of the drought stress status of plants at the time of measurement, and that differences in TE might be closely related to how plants respond to soil drying, with high TE genotypes maintaining gas exchange until the soil is dryer than low TE genotypes

Identification of orthologous regions associated with tissue growth under water-limited conditions

Plant recovery from early season drought is related to the amount of biomass retained during stress and biomass production after the end of stress. Reduction in leaf expansion is one of the first responses to water deficit. It is assumed that the control of tissue development under water deficit contributes to traits such as early vigor, as well as maintenance of growth of reproductive organs. To dissect the underlying mechanisms controlling tissue expansion under water-limited conditions, we used a multilevel approach combining quantitative genetics and genomics. To identify orthologous genetic regions controlling tissue growth under water-limited conditions a series of QTL mapping and microarray gene expression studies were conducted in rice and maize. Results of differentially expressed genes from microarray experiments, QTLs and candidate genes related to growth in the different species are compared on consensus maps (within species) and then on synteny maps (between species), to identify common genetic regions between rice and maize