旗叶蜡质含量不同小麦近等基因系的抗旱性

于2013-2014和2014-2015年度,以多蜡质和少蜡质的4个小麦近等基因系为材料,采用田间旱棚方式控制土壤水分,研究了蜡质含量与小麦抗旱性的关系。结果表明,干旱处理后,多蜡质小麦品系旗叶的蜡质含量平均为15.15 mg g?1,较少蜡质小麦品系(8.43 mg g?1)高79.8%;多蜡质小麦品系旗叶的水势较高,干旱处理后下降幅度明显小于少蜡质小麦品系,水分散失率也显著低于少蜡质品系(P< 0.05);多蜡质小麦品系旗叶的光合速率平均下降7.5%,而少蜡质小麦品系下降9.8%;多蜡质小麦品系旗叶PSII最大光化学效率(Fv/Fm)平均下降幅度为3.4%,少蜡质小麦品系下降幅度达到5.8%;多蜡质小麦品系的籽粒产量高于少蜡质品系,平均高3.7%;多蜡质小麦品系的抗旱指数和干旱敏感指数均显著低于少蜡质小麦品系(P< 0.05)。以上结果表明,蜡质能够提高小麦的抗旱性,旗叶蜡质含量可以作为抗旱小麦品种的选择指标。     

Evaluating different bahiagrass cytotypes for heat tolerance and leaf epicuticular wax content

Summary Bahiagrass (Paspalum notatum Flugge) is a polymorphic species indigenous to South America which has become naturalized in the southeastern U.S. The most common form in the United States is Pensacola bahiagrass,P. notatum var.saurae Parodi., which is a valuable forage. Pensacola is a sexual diploid, while most other bahiagrasses are apomictic tetraploids. Pensacola bahiagrass is considered to have greater heat tolerance (based on anin vitro heat tolerance test) than a number of otherPaspalum species, but has less leaf epicuticular wax (a drought avoidance mechanism) than other species. Both heat tolerance and leaf epicuticular wax are desirable characteristics for species grown where periodic drought occurs. We measured both characteristics over two years in a collection of 23 bahiagrass accessions, many of which had been collected in South America near the center of origin of the species. The collection included various ploidy levels. For both years, no accessions ranked statistically lower in damage in the heat tolerance test than Pensacola, although eight had significantly higher damage. Two entries in addition to Pensacola had very low damage in the heat tolerance test. Pensacola was high in leaf wax, with 16 accessions rated significantly lower in wax. The accession having the lowest wax content was a triploid, which also exhibited considerable leaf death in the field in response to drought and heat. The diploid entries tended to be higher in leaf wax than the other ploidy levels. This study has identified additional bahiagrass germplasm which may be of use in a breeding program.     

Evaluation of Paspalum germplasm for variation in leaf wax and heat tolerance

Summary The genus Paspalum contains a number of important forage grasses, including P. dilatatum Poir. (dallisgrass) and P. notatum Flugge (bahiagrass). Even though many Paspalum species are adapted to moist, humid areas, they frequently are subjected to extended periods of drought stress which reduces forage productivity. This study was initiated to determine the range of variation for different indicators of drought tolerance in several Paspalum species. Fifteen species representing a broad cross section of germplasm were grown in a replicated field nursery and sampled for leaf epicuticular wax content on four dates over three years. Wax was extracted with chloroform and quantified by the dichromate oxidation technique. Heat tolerance (solute leakage technique) was also determined by calculating the ratio of the conductivity of the external bathing solution of leaves following a heat treatment to the conductivity of the bathing solution after leaves were boiled. Wax values of the entries ranged from 5.7 to 0.88 mg/dm². Both relative rankings and absolute wax values were very consistent across all sampling dates. The accessions of Paspalum nicorae Parodi and P. quandrifarum Lam. were consistently high in wax content, while the accessions of P. commune Lillo and P. unispicatum (Scribn. et Merr.) Nash were consistently low. The heat tolerance testing demonstrated that the accession of P. notatum var. saurae Parodi was the most heat tolerant of the entries. Results from this investigation demonstrate the wide range of diversity that exists for both epicuticular wax and heat tolerance within the genus Paspalum.     

Effect of terminal water stress on leaf epicuticular wax load,residual transpiration and grain yield in barley

The effect of drought on barley leaf epicuticular wax load (EWL), residual transpiration rates (RTR) and grain yield was examined by subjecting 12 barley genotypes to controlled irrigation and terminal water stress conditions. The mean leaf epicuticular wax load was found to be 9% greater in the plants subjected to terminal water stress than in those provided irrigation, while the mean residual transpiration rate of the irrigated plants was 20% higher than in those subjected to water stress. Under these stress conditions, the correlation between grain yield and the epicuticular wax load was positive (P < 0.01), while that between the grain yield and the residual transpiration rate was negative (P < 0.05). Under the water stress conditions, the breeding lines studied showed a greater mean epicuticular wax load than the commercial varieties, while the residual transpiration rate was greater in these varieties than in the breeding lines. The greater epicuticular wax load of the breeding lines favoured their tolerance of drought, improving their yields over those of the commercial varieties.     

Differences in Ion Accumulation and Salt Tolerance among Glycine Accessions

Salinity reduces crop yield by limiting water uptake and causing ion‐specific stress. Soybean [Glycine max (L.) Merr.] is sensitive to soil salinity. However, there is variability among soybean genotypes and wild relatives for salt tolerance, suggesting that genetic improvement may be possible. The objective of this study was to identify differences in salt tolerance based on ion accumulation in leaves, stems and roots among accessions of four Glycine species. Four NaCl treatments, 0, 50, 75 and 100 mm , were imposed on G. max, G. soja, G. tomentella and G. argyrea accessions with different levels of salinity tolerance. Tolerant genotypes had less leaf scorch and a greater capacity to prevent Na⁺ and Cl^? transport from soil solution to stems and leaves than sensitive genotypes. Magnitude of leaf injury per unit increase in leaf Na⁺ or Cl^? concentrations was lower in tolerant than in susceptible accessions. Also, plant injury was associated more with Na⁺ rather than with Cl^? concentration in leaves. Salt‐tolerant accessions had greater leaf chlorophyll‐meter readings than sensitive genotypes at all NaCl concentrations. Glycine argyrea and G. tomentella accessions possessed higher salt tolerance than G. soja and G. max genotypes.     

Genetic control of in vitro regeneration in alfalfa (Medicago sativa L.)

Summary Cultivars of common wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var. durum) were evaluated for epicuticular wax content and its relationship with spectral reflectance. Epicuticular wax is associated with drought tolerance. Highly significant differences (1.51 to 2.80 mg/dm²) were found in the amount of epicuticular wax (EW) among the cultivars. Water stress significantly enhanced the level of EW. EW content under stress and control conditions were positively correlated (r=0.85, p<0.01) suggesting that selection for this trait could be practised in either environment. Surface reflectance was reduced when the waxy layer from the leaf was removed with chloroform. The reduction for the abaxial surface was twice that for the adaxial surface indicating that the abaxial surface was more waxy than the adaxial one. The mean reduction (both surfaces) termed was positively correlated with the amount of EW (r=0.59, p<0.01).     

Epicuticular wax content and morphology as related to ethylene and storage performance of ‘Navelate’ orange fruit

The effect of ethylene (2 μL L⁻¹) on total and soft epicuticular wax content and wax morphology has been investigated in mature ‘Navelate’ (Citrus sinensis, L. Osbeck) oranges held under non-stressful environmental conditions (22 °C and constant high relative humidity (90–95% RH)). In addition, the objective of the study was to understand whether the ethylene-induced changes in epicuticular wax might participate in the beneficial effect of ethylene reducing non-chilling peel pitting, by modifying peel water, osmotic or turgor potential, or disease incidence caused by Penicillium digitatum (Pers.:Fr.) Sacc. Ethylene increased total and soft epicuticular wax content in ‘Navelate’ fruit and induced structural changes in surface wax that might be related to the formation of new waxes. Changes in epicuticular wax morphology, but not in its content, might be involved in the protective role of ethylene reducing non-chilling peel pitting, although the beneficial effect of the hormone is not related to water stress. Cell water and turgor potentials in freshly harvested fruit and fruit stored in air under non-stressful conditions suggest that water stress is not a limiting factor leading to the development of this physiological disorder. In addition, the results indicated that formation of new waxes in fruit treated with ethylene may partially cover stomata, cracks or areas lacking wax occurring in stored fruit and is likely to improve physical barriers to P. digitatum penetration.     

Effects of moisture stress on leaf appearance,tillering and other aspects of development in Triticum tauschii

Summary A glasshouse study was conducted to describe the dynamics of leaf and tiller appearance of four accessions of T. tauschii (Tt 04, Tt 17, Tt 65 and Tt 74) and to determine the influence of moisture stress (treatments were high and low moisture, imposed seven days after transplanting) on these and other aspects of development in this wild wheat.Under high moisture conditions, accessions differed greatly in flag leaf dimensions, culm length and seed number per spike, the values being lower in Tt 04 than in the other accessions. Low moisture strongly reduced values for these traits, with Tt 04 being least affected, but overall, there was no apparent association between the values obtained for these variables in the high moisture conditions and the effects of moisture stress. For three of the four accessions, final leaf number on the main culm was significantly lower in the low moisture treatment than in the respective control (P<0.05), but the differences between treatments (ca. 0.5 leaves or less) were very small. Maximum tiller number, on the other hand, was strongly reduced by low moisture, and initiation of tillering was inhibited until water was reapplied. There were no apparent after-effects of the moisture regime on the rate of subsequent tiller appearance.The four accessions differed in their leaf appearance rates, giving phyllochron values (117–142° Cd leaf^-1) within the range reported for hexaploid wheat. Low moisture tended to increase phyllochron, but in only one accession was this effect significant. Thus, depending on the accession, low moisture did not affect, or slightly decreased (by ca. 15–20%) the rate of leaf appearance. These effects were similar to those reported for cultivated wheat suggesting that there would be little scope for using these accessions of T. tauschii in breeding for stress tolerance.     

Evaluation of slow rusting resistance components to leaf rust in CIMMYT durum wheats

Information about slow rusting resistance to leaf rust (Puccinia triticina) in durum wheat (Triticum turgidum var. durum) is limited. Three slow rusting components, latent period, receptivity, and uredinium size, were determined at the adult plant stage for seven durums with slow rusting resistance to leaf rust and two susceptible durums in three greenhouse experiments. Additionally, area under the disease progress curve (AUDPC) and final disease severity (FDS) were determined in three field trials under artificial epidemics with the same P. triticina race BBG/BN. Compared to the most susceptible check, the AUDPC and FDS of slow rusting resistant durums were significantly lower and ranged from 13–47 to 22–59%, respectively. The latent period was significantly longer (8.5–10.3 days) and uredinium size significantly smaller (8.1–14.8 × 10⁻² mm²) on slow rusting durums than on the susceptible checks (8.0 days and 17.3–23.8 × 10⁻² mm², respectively). Uredinium size was the most stable slow rusting component across experiments. Correlations between uredinium size versus AUDPC and uredinium size versus FDS for each environment were high (r = 0.86–0.88). Correlations between latent period and field parameters were significant (r = −0.60 to −0.80). Correlations between receptivity and the field parameters were not significant. A multiple regression analysis showed that the variation in AUDPC and FDS was significantly explained only by uredinium size (P < 0.0001). The best slow rusting resistant lines can be used for developing high-yielding durums with more durable resistance to leaf rust.     

Differences between tomato genotypes in stomatal resistance and specific leaf fresh weight in relation to differences in net photosynthesis under low light intensity and low night temperatures

Summary Differences between tomato genotypes (Lycopersicon esculentum Mill.) in stomatal resistance (r_s) and specific leaf fresh weight (SLFW) were observed under low light intensity and low night temperature. No relationship between r_s and previously published rates of net photosynthesis per dm² leaf area (P_A) was discovered. A negative relationship between SLFW and net photosynthesis per gram fresh weight (P_FW) was found but no clear relationship between SLFW and P_A. Genotypes with a low SLFW seem better adapted to a low light intensity.     

Identification and Molecular Phylogenetic Relationships of Δ12-Fatty Acid Desaturase in Arachis

Summary On the basis of the conservative sequence of Δ12-fatty acid desaturase, a cDNA encoding the enzyme was isolated from different genotypes of Arachis. The cDNA consisted of 1140 bp and encoded a polypeptide of 379 amino acid resides with a calculated molecular weight of 42 KD. The predicted amino acid sequence had three histidine conservative regions sharing integral-protease specificity. Hydrophobicity analysis showed that the sequence of the encoded amino acids had two hydrophobic structures sharing the characteristics of membrane-anchored protein, which totally crossed the membrane four times. These analyses revealed that the obtained sequence was Δ12-fatty acid desaturase. Phylogenetic-tree analysis demonstrated that the found Δ12-fatty acid desaturase sequences in Arachis was conservative and was highly homogenous to the Δ12-fatty acid desaturase sequences in other species. The present research provided molecular evidence of phylogenetic relationships among the accessions in Arachis.     

Resistance in Lycopersicon species to black leaf mold caused by Pseudocercospora Fuligena

Over 540 accessions of wild Lycopersicon species or their crosses with L. esculentum were screened for resistance in a series of trials. Forty-six accessions were selected for the final screening trial based on lower disease ratings in previous trials. Of these, L. hirsutum had the greatest number of resistant accessions, followed by L. esculentum and L. peruvianum. Twenty accessions were quantified for their levels of resistance based on leaf area infected, area under disease progress curve (AUDPC), and the degree of sporulation. There was a significant positive correlation between the AUDPC calculated from 20 accessions evaluated under growth room and field conditions. Five L. hirsutum accessions had no sporulation associated with leaf lesions, whereas L. esculentum accessions had an average of 1.6×10⁴ conidia/cm² of leaf tissue. There was significant positive correlation between the AUDPC values and the number of conidia per cm² of leaf tissue.     

Phylogenetic relationships in the genus Arachis based on seed protein profiles

Summary Seed protein profiles of 19 accessions representing seven sections of the genus Arachis were studied using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The general profile showed appreciable homology between these taxa, supporting their classification based on morphology and cross-compatibility relationships. The accessions of section Arachis expressed a high variation confirming inferences from earlier studies. Variation between accessions of a species is limited. Accessions of the section Ambinervosae and Caulorhizae formed one cluster and accessions of sect. Erectoides and Procumbensae formed another. Whereas the representative accessions of sect. Triseminalae and Extranervosae formed two independent clusters. Using the percentage of dissimilarity in electrophoretic bands as a statistical genetic distance between accessions, sect. Arachis (containing the cultivated groundnut, A. hypogaea) is phylogenetically closest to sect. Erectoides followed by Procumbensae, Ambinervosae, Caulorhizae, Triseminalae and Extranervosae, respectively.Submitted as Journal Article No. 1485 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Patancheru, A.P. 502 324, India.     

A proposal for aluminum tolerance selection in white oat under hydroponic conditions

White oat genotypes were subjected to Al stress in hydroponic conditions in order to verify the viability of methods based on minimum nutrient solution (MNS) in comparison to complete nutrient solution (CNS), commonly used in the characterization and selection for Al tolerance in this species. The experimental design was completely randomized blocks with three replicates composed of 10 seedlings each. Six white oat genotypes subjected to different Al levels in minimum (0, 3, 6, and 9 mg L⁻¹) and complete (0, 10, 20, and 30 mg L⁻¹) solutions were evaluated. In this evaluation, the MNS was efficient in identifying aluminum-tolerant, white oat genotypes under hydroponics. The root growth resumption showed to be the most effective trait in the aluminum-tolerant plant selection. At concentrations equal to or higher than 3 mg Al L⁻¹ in minimum and 10 mg Al L⁻¹ in complete solution, severe damage caused by the toxic element on root development was verified. The white oat cultivars UFRGS 14, ALBASUL, and BARBARASUL showed aluminum tolerance in the tested conditions.     

Heterosis and heritability in crosses among Asian and Ethiopian parents of hot pepper genotypes

Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing’s fixed effect model analysis. An open field experiment was conducted in 2004/2005 to investigate heterosis for fourteen traits in 66 F₁ hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H _b²) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h _n²) for most of the important traits like number of fruit per plant (H _b² = 88.3% and h _n² = 46.0%), days to maturity (H _b² = 87.2% and h _n² = 23.1%) and dry fruit yield per plant (H _b² = 72.6% and h _n² = 14.6%). Maximum heterosis over mid-parent and better-parent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (−29.8, −31.5 and −23.6%). These observations suggested a possibility of utilizing dominance genetic potentiality available in diverse genotypes of the crop by heterosis breeding for improving hot pepper to the extent of better economic return compared to the current commercial cultivar under production in the country. Low narrow sense versus very high broad sense heritability for days to maturity and dry fruit yield per plant could be a sign for achievability of earliness and high fruit yield using heterosis in hot pepper. The maximum heterobeltiosis were recorded either from F₁s obtained from Ethiopian and Asian crosses or from within Asian crosses, suggesting the possibility of maximizing heterosis by considering genetically diverse parental genotypes. The manifestation of highest heterosis in hybrids from among Asian lines indicated existence of genetic diversity among Asian genotypes and the potentiality for improvement of hot pepper using genotypes from different regions of the world along with elite inbred lines from local cultivars.     

Evaluation of salt tolerance in rice genotypes by physiological characters

The use of physiological characters as selection criteria in salt tolerance breeding requires the identification of the contribution each individual character makes to salt tolerance. Rice genotypes were evaluated for salt tolerance in terms of grain yield and physiological characters. Plants of twelve genotypes were grown in sand tanks in a greenhouse and irrigated with Yoshida nutrient solution. Sodium chloride and calcium chloride (5:1 molar ratio) were added at two concentrations to give moderate (4.5 dS m^-1) and high (8.3 dS m^-1) salinity treatments. One set of plants was harvested at 635 ^°Cċd (accumulative thermal time) after planting to determine LAI and mineral ion concentrations. Another set of plants was allowed to grow to maturity. High genotypic diversity for LAI and shoot ion contents was observed. LAI contributed the most to the variation of the grain yield under salt stress. Significant correlations between LAI and yield components in both salt-tolerant and-sensitive genotypes further confirmed the significant contribution of LAI to grain yield. K-Na selectivity increased with increasing salinity. Conversely, Na-Ca selectivity decreased with increasing salinity. Significant correlations were identified between grain yield and both Na-Ca and K-Na selectivity. Highly significant (p<0.001) correlations were identified between Na-Ca selectivity and the rankings among genotypes for grain yield. Thus, Na-Ca selectivity could be one salt tolerance component and an useful selection criterion in screening for salt tolerance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in leaf epicuticular wax load and its effect on leaf temperature and physiological traits in wheat cultivars (Triticum aestivum L.) exposed to high temperatures during anthesis

The physiological functions of epicuticular wax (EW) include reflectance of irradiation and the reduction of water loss. When a plant experiences stressful conditions, most notably, high irradiance and temperature, damage to the photosynthetic apparatus can occur and is signalled by a decrease in the F_v/F_max ratio. In this study, we examined the influence of increased EW on physiological function in terms of chlorophyll fluorescence (ChFl), stomatal conductance (g_s), leaf temperature and spectral reflectance indices (SRI) of bread wheat (Triticum aestivum L.) cultivars. The wheat cultivars were subjected to high temperature stress (HT) (38–40°C) under greenhouse conditions when the primary inflorescence was fully emerged to determine its effect on leaf EW deposition. Leaf temperature depression (LTD) was generally lower in control (2.3°C—2012, 0.94°C—2013) compared to HT stress (3.13°C—2012, 4.05°C—2013). Cultivars in control (0.69 to 0.74 F_v/F_max) had significantly higher ChFl compared to HT (0.58 to 0.74 F_v/F_max). HT treatment resulted in higher EW (1.28—2012, 4.59 mg dm^?2—2013) compared to control treatment (1.04—2012 to 4.56 mg dm^?2—2013). Leaves devoid of EW showed significant variation among cultivars at reproductive stages for water index (WI), normalized phaeophytinization index (NPQI) and simple ratio index (SRI). In HT stress conditions, significant correlations were observed between EWL and SRI only at 3DAFE (days after full emergence), suggesting that increased EWL induced by HT and irradiation in early development may provide relief and prevent grain loss. EWL significantly associated with the physiological traits ChFl, g_s, LTD and spike temperature depression (SpTD). These observations suggest that EWL may lessen the effect of high irradiance, thereby, effectively adjusting stomatal conductance, ChFl and leaf temperature, limiting the risk of over excitation of photosystem II.     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

Heat stress in food legumes: evaluation of membrane thermostability methodology and use of infra-red thermometry

Heat tolerance in 45 chickpea, lentil, and faba bean genotypes was investigated during 2007/2008 and 2008/2009 at Alexandria Agriculture Research Station, Alexandria, Egypt, using screening methods employing the membrane thermostability technique. Threshold temperature to be used in screening for heat tolerance at germination was also investigated for each crop. Temperatures, responsible for 50% germination were 40, 33.5, and 29°C for chickpea, faba bean, and lentil, respectively. Germination percent under high temperature varied significantly (P ≤ 0.05) amongst genotypes. Germination percentage ranged from 4.8 to 71.6, 39.2 to 90.0, and 4.8 to 68.6, in chickpea, lentil, and faba bean, respectively. Differences were significant (P ≤ 0.05) among faba bean and chickpea genotypes. Membrane relative injury (RI%) showed significant (P ≤ 0.05) variability among the genotypes and ranged from 10.57 to 58, 5.2 to 61.7, and 15.7 to 52.7 in chickpea, lentil, and faba bean, respectively. Canopy temperature was measured to evaluate heat avoidance in tested genotypes. Infra-red thermometry was used to measure canopy temperature and the gradient of canopy to ambient air temperature (∆T_C-A) in moisture stressed and unstressed treatments. Canopy temperature, leaf water potential (LWP) and leaf water content were affected by the level of soil moisture. Genotypes were able to bring their canopy temperatures to levels lower than ambient air temperatures but the differences were not significant. A heat stress index (HSI) were computed relating the ∆T_C-A in moisture stressed to unstressed treatments. Regression of leaf water potential (LWP) and the heat stress index (HSI) was significant (P ≤ 0.05) in faba bean genotypes in the stressful environment. The results of the present investigation emphasize the efficiency of membrane thermostability technique in selection for heat tolerance in early stages of growth in food legumes.     

QTL-based analysis of genotype-by-environment interaction for grain yield of rice in stress and non-stress environments

Use of DNA-based markers can accelerate cultivar development in variable cultivation environments since, in contrast to phenotype, DNA markers are environment-independent. In an effort to elucidate the genetic basis of genotype-by-environment interaction (G × E) for yield of rice (Oryza sativa L.), the associations between 139 AFLP markers and grain yield were determined for rice grown in fresh water (EC of 0.65 dS m⁻¹) and saline conditions (EC of 4–8 dS m⁻¹) with 0 kg ha⁻¹ or 100 kg ha⁻¹ nitrogen fertilizer in the years 2000 and 2001. A population of recombinant inbred lines of rice, developed from an IR29 × Pokkali cross, was used in the study. Both genotype × salinity and genotype × nitrogen level interactions were significant, with the genotype × salinity interaction being stronger. Through multiple regression analysis using a stepwise procedure for selecting markers, 36 markers were detected for grain yield in the four test conditions and of these 28 were detected in only one test condition implying strong environmental specificity for yield QTL expression. However, the fact that eight QTLs were detected in more than one test condition points to the existence of wide-adaptability genes in this cross. Markers with significant associations with yield explained between 37% and 48% of the yield variation in each test condition. Superior genotypes of rice were identified in all four test conditions based on their marker signatures. Furthermore, across N fertilizer regimes, yield predicted from summed additive effects of QTLs were significantly correlated with observed yield in the same year and across years. Thus marker-assisted selection can help breeders overcome the problem of low selection efficiency encountered during phenotypic selection for yield in stress environments.