Terminal Growth Stages Research Articles

Genotype x Environment Interaction and Stability Analysis for Seed Yield in Desi Chickpea (Cicer arietinum L.) under Irrigated Condition

Background: Chickpea is mainly grown on marginal lands and encounter the problem of erratic rainfall that causes lack of water availability especially at terminal growth stages. Exploration of yield stability and defining the adaptation domains of advance genotypes in different ecosystem is highly imperative for crop genetic improvement programs. Development of variety with high yield potential and stable under irrigated condition is one of the major objectives of chickpea improvement programme, which can be achieved by improving selection efficiency with estimating stability parameters. Ten chickpea genotypes as advance breeding lines and popular varieties were evaluated to assess seed yield stability under irrigated condition during rabi 2021-22. Methods: Experiments were conducted in randomized block design with three replications at five different locations of Karnataka i.e. Bidar, Kalaburagi, Bheemarayanagudi, Raichur and Hagari. The interaction analysis (AMMI ANOVA) indicates large variations for seed yield due to highly significant (p less than 0.01) environment (65.42%) and significant (p less than 0.05) genotype (10.03%), thus the genotypes were diverse with large sum of squares for seed yield and environment. Result: The differential response of chickpea genotypes for seed yield across the environments was observed. IPCA1 and IPCA2 together captured 12.97 per cent of the interaction mean squares RG-2016-134 and KCD-2019-05 showed higher mean yields and adaptable to favourable environments. Based on AMMI bi-plot analysis, genotypes (KCD-2019-05 and Super Annigeri-1) were stable and (DC-17-1111 and RG-2016-134) were unstable. Similarly, best performer genotypes and three mega environments were noticed through the analysis. Three environments i.e., (Bidar, Kalaburagi and Raichur) were found with most selective for seed yield estimation. The genotypes (RGV-203, KCD-2019-02 and Super Annigeri-1) were the best among all the ten tested genotypes in terms of seed yield stability.

Warmer nights predominantly alter yield and biomass in wheat experiencing heat waves at the terminal growth stage

Warmer nights predominantly alter yield and biomass in wheat experiencing heat waves at the terminal growth stage

The Roles of Net Photosynthetic Rate and Transpiration Efficiency on Economic Yield of Jerusalem artichoke (Helianthus tuberosus L.) Genotypes under Different Drought Durations during the Terminal Growth Stages

Knowledge of the influence of different drought durations during the terminal growth stages on net photosynthetic rate (Pn), transpiration rate (Tr), transpiration efficiency (TE), and tuber fresh weight (economic yield) is relatively limited in Jerusalem artichoke. Our aim was to examine the effect of different drought durations during the terminal growth stages on Pn, Tr, TE, and economic yield in Jerusalem artichoke genotypes with different ranges of drought tolerance. A two-year field experiment was established in the northeast of Thailand. A split-plot design replicated four times was used. Three water treatments, optimal conditions (SD0), short-drought (SD1), and long-drought (SD2) durations during the terminal growth stages, were arranged as main plots. Six genotypes (HEL256, JA37, HEL253, JA4, JA60, and JA125) are subplots. Different durations of drought in SD1 and SD2 reduced Pn, Tr, and economic yield, while drought stress during the terminal growth stages increased TE in whole genotypes over SD0 treatments. Drought-tolerant genotypes JA125 and JA4 exhibited high Pn, medium TE, and low economic yield reduction under SD2. Utilization of these superior parents in breeding could lead to the generation of new progenies with high economic yield productivity and drought tolerance during the long drought duration during the terminal growth stage. In addition, high SPAD chlorophyll meter readings (SCMR) in SD1 and SD2 and low specific leaf area (SLA) in SD1 could be used as indirect selection traits to survey high Pn genotypes in Jerusalem artichoke. Consequently, these indirect selection traits may allow for speedy breeding programs in Jerusalem artichokes.

Physiomorphic and molecular-based evaluation of wheat germplasm under drought and heat stress.

Drought and heat stress are potential problems that can reduce wheat yield, particularly during the terminal growth stages in arid and semiarid regions of the world. The current study intended to examine the impact of individual and combined drought and heat stress on the biochemical contents (antioxidant enzymes, proline, soluble proteins, and soluble sugars), physiological parameters (chlorophyll content, cell membrane stability, photosynthesis, stomatal conductance, and transpiration), plant-water relations (relative water content, water potential, osmotic potential, and pressure potential), agronomic traits (flag leaf area, plant height, number of tillers per plant, spike length, grains per spike, and thousand-grain weight), and gene expression (TaHSF1a, TaWRKY-33, TaNAC2L, and TaGASR1) in four different thermostable and drought-tolerant wheat genotypes (i.e., Gold-16, HS-240, Suntop, and Hemai-13) collected from different countries. The tri-replicate experiment was conducted using two factorial arrangements in a randomized complete block design (RCBD). All measured traits, except total soluble sugars, proline, and cell membrane stability index, showed significant reduction under both combined and individual treatments. Furthermore, correlation analysis revealed a significant association between biochemical and physiological characteristics and crop agronomic productivity. Furthermore, principal component analysis (PCA) and heatmap analysis demonstrated significant levels of variation in traits according to the type of stress and nature of wheat genotype. The spectrographs and micrographs generated by scanning electron microscopy for the selected high- and low- tolerance samples revealed clear differences in mineral distribution and starch granulation. All studied genes showed comparatively high levels of relative expression under combined treatments of drought and heat stress in all wheat genotypes, but this expression was the highest in 'Gold-16' followed by 'HS-240', 'Suntop', and 'Hemai-13'. Overall, this study concluded that plants are proactive entities and they respond to stresses at all levels; however, the tolerant plants tend to retain the integrity of their biochemical, physiological, and molecular equilibrium.

AMMI and GGE biplot analysis of yield under terminal heat tolerance in wheat.

Wheat is an important cereal crop that helps to meet the food grain needs of people all over the world. Heat stress is one of the most significant abiotic stresses that wheat crops face during terminal growth stages in the wheat growing regions like India. It is very important to identify heat tolerant genotypes to be used as donors for breeding tolerant varieties. Thirty-six wheat genotypes were evaluated under different sowing dates viz., Timely sown (TS), Late sown (LS) and very late sown (VLS), and the fourth was sown in the Temperature controlled phenotyping facility (TCPF) across two years. Genotypes were planted following lattice square design with two replications. Data was recorded for yield and yield contributing traits and analysed using selection indices as well AMMI and GGE biplot stability models. Heat stress affected all the traits under different heat environments which ranged from 1.6% (Spikelet number) to 37.2% (grain yield). Regression analysis indicated that the thousand grains weight (R2 = 0.50) contributed significantly towards grain yield under heat stress. Stress susceptibility index (SSI) found genotypes GW322, RAJ3765, Raj4037and MACS6145 as heat tolerant whereas, Stress Tolerance Index (STI) identified C306, HD2967, WH1080, WH730, DBW90, HD2932, DBW17, RAJ3765 as heat tolerant and high yielding. AMMI biplot analysis indicated stable genotypes DBW90, WH730, RAJ4083, CBW38, HD2932, NI5439, WR544, whereas GGE biplot analysis revealed stable genotypes NIAW34, NI5439, RAJ4083, DBW90, PBW590, Raj3765, HUW 510, WH730, HD2967 and UP2382. Heat stress affects significantly all yield contributing traits. Thousand grain weight was the most important trait that can be used as a selection criterion for selecting tolerant lines. Based on selection indices and both AMMI and GGE analysis, genotype RAJ3765 was identified to be highly heat tolerant with good grain yield.

Multiple-Temporal Scale Variations in Nighttime Sap Flow Response to Environmental Factors in Ficus concinna over a Subtropical Megacity, Southern China

With ongoing climate change and rapid urbanization, the influence of extreme weather conditions on long-term nocturnal sap flow (Qn) dynamics in subtropical urban tree species is poorly understood despite the importance of Qn for the water budgets and development plantation. We continuously measured nighttime sap flow in Ficus concinna over multiple years (2014–2020) in a subtropical megacity, Shenzhen, to explore the environmental controls on Qn and dynamics in plant water consumption at different timescales. Nocturnally, Qn was shown to be positively driven by the air temperature (Ta), vapor pressure deficit (VPD), and canopy conductance (expressed as a ratio of transpiration to VPD), yet negatively regulated by relative humidity (RH). Seasonally, variations in Qn were determined by VPD in fast growth, Ta, T/VPD, and meteoric water input to soils in middle growth, and RH in the terminal growth stages of the trees. Annual mean Qn varied from 2.87 to 6.30 kg d−1 with an interannual mean of 4.39 ± 1.43 kg d−1 (± standard deviation). Interannually, the key regulatory parameters of Qn were found to be Ta, T/VPD, and precipitation (P)-induced-soil moisture content (SMC), which individually explained 69, 63, 83, and 76% of the variation, respectively. The proportion of the nocturnal to the total 24-h sap flow (i.e., Qn/Q24-h × 100) ranged from 0.18 to 17.39%, with an interannual mean of 8.87%. It is suggested that high temperatures could increase transpirational demand and, hence, water losses during the night. Our findings can potentially assist in sustainable water management in subtropical areas and urban planning under increasing urban heat islands expected with future climate change.

Transcriptome Analysis of Pennisetum glaucum (L.) R. Br. Provides Insight Into Heat Stress Responses.

Pennisetum glaucum (L.) R. Br., being widely grown in dry and hot weather, frequently encounters heat stress at various stages of growth. The crop, due to its inherent capacity, efficiently overcomes such stress during vegetative stages. However, the same is not always the case with the terminal (flowering through grain filling) stages of growth, where recovery from stress is more challenging. However, certain pearl millet genotypes such as 841-B are known to overcome heat stress even at the terminal growth stages. Therefore, we performed RNA sequencing of two contrasting genotypes of pearl millet (841-B and PPMI-69) subjected to heat stress (42°C for 6 h) at flowering stages. Over 274 million high quality reads with an average length of 150 nt were generated, which were assembled into 47,310 unigenes having an average length of 1,254 nucleotides, N50 length of 1853 nucleotides, and GC content of 53.11%. Blastx resulted in the annotation of 35,628 unigenes, and functional classification showed 15,950 unigenes designated to 51 Gene Ontology terms. A total of 13,786 unigenes were allocated to 23 Clusters of Orthologous Groups, and 4,255 unigenes were distributed to 132 functional Kyoto Encyclopedia of Genes and Genomes database pathways. A total of 12,976 simple sequence repeats and 305,759 SNPs were identified in the transcriptome data. Out of 2,301 differentially expressed genes, 10 potential candidate genes were selected based on log2 fold change and adjusted p value parameters for their differential gene expression by qRT-PCR. We were able to identify differentially expressed genes unique to either of the two genotypes, and also, some DEGs common to both the genotypes were enriched. The differential expression patterns suggested that 841-B 6 h has better ability to maintain homeostasis during heat stress as compared to PPMI-69 6 h. The sequencing data generated in this study, like the SSRs and SNPs, shall serve as an important resource for the development of genetic markers, and the differentially expressed heat responsive genes shall be used for the development of transgenic crops.

English

Salinity stress is one of the leading abiotic stresses seriously affecting the crop productivity across the world. Early growth stages are more affected by salinity stress than terminal growth stages. Therefore, maize genotypes were evaluated for their performance in three different studies (Experiment-1: irrigation of seeds with salt solutions (distilled water, 4 dS/m, 6 dS/m and 10 dS/m) for 5 days, Experiment-2: application of different salinity treatments (distilled water, 4 dS/m, 6 dS/m and 10 dS/m) for 20 days from sowing to seedling emergence stage, Experiment-3: application of salinity stresses in hydroponic culture under four above mentioned different salinity treatments. Time to start germination (TSG), time to 50% germination (TFG) and final germination percentage (FGP) of the maize genotypes was reduced by salinity stress. Radicle length, plumule length, root and shoot length and fresh weight and chlorophyll contents were also linearly reduced in maize genotypes by increasing salinity levels. Moreover, sodium (Na+) concentration was increased in seeds and seedlings of maize genotypes whereas; potassium (K+) concentration was reduced with gradual rise in salinity levels. Principal Component Analysis (PCA) biplots facilitated the efficient assortment of susceptible, moderately susceptible, moderately tolerant and tolerant maize genotypes for each of the three studies separately. Genotype „YS-2008‟ was susceptible for seed treatment and hydroponic studies whereas, genotype „T267-5‟ was susceptible for early seedling and hydroponic studies. Genotype „C864-284‟ was tolerant in early seedling and hydroponic studies. The GGE biplot analysis indicated that „YS-2008‟ genotype was susceptible for salinity stress. Under hydroponic conditions, genotypes could effectively be discriminated by the imposition of severe salt stress (10 dS/m); however, under seed treatments and early seedling growth stages, mild stress treatments (4 dS/m) were sufficient enough to discriminate the maize genotypes. Hydroponic evaluation of genotypes is suitable and preferable under high stress conditions at early growth stages. Identified tolerant and susceptible genotypes could be effectively used in different breeding programs to develop salt tolerant new cultivars for commercial purposes. © 2021 Friends Science Publishers

Temporal Vegetation Indices and Plant Height from Remotely Sensed Imagery Can Predict Grain Yield and Flowering Time Breeding Value in Maize via Machine Learning Regression

Unoccupied aerial system (UAS; i.e., drone equipped with sensors) field-based high-throughput phenotyping (HTP) platforms are used to collect high quality images of plant nurseries to screen genetic materials (e.g., hybrids and inbreds) throughout plant growth at relatively low cost. In this study, a set of 100 advanced breeding maize (Zea mays L.) hybrids were planted at optimal (OHOT trial) and delayed planting dates (DHOT trial). Twelve UAS surveys were conducted over the trials throughout the growing season. Fifteen vegetative indices (VIs) and the 99th percentile canopy height measurement (CHMs) were extracted from processed UAS imagery (orthomosaics and point clouds) which were used to predict plot-level grain yield, days to anthesis (DTA), and silking (DTS). A novel statistical approach utilizing a nested design was fit to predict temporal best linear unbiased predictors (TBLUP) for the combined temporal UAS data. Our results demonstrated machine learning-based regressions (ridge, lasso, and elastic net) had from 4- to 9-fold increases in the prediction accuracies and from 13- to 73-fold reductions in root mean squared error (RMSE) compared to classical linear regression in prediction of grain yield or flowering time. Ridge regression performed best in predicting grain yield (prediction accuracy = ~0.6), while lasso and elastic net regressions performed best in predicting DTA and DTS (prediction accuracy = ~0.8) consistently in both trials. We demonstrated that predictor variable importance descended towards the terminal stages of growth, signifying the importance of phenotype collection beyond classical terminal growth stages. This study is among the first to demonstrate an ability to predict yield in elite hybrid maize breeding trials using temporal UAS image-based phenotypes and supports the potential benefit of phenomic selection approaches in estimating breeding values before harvest.

Selection and screening of drought tolerant high yielding chickpea genotypes based on physio-biochemical indices and multi-environmental yield trials

BackgroundChickpea is one of the major legume crops being cultivated in the arid and semi-arid regions of Pakistan. It is mainly grown on the marginal areas where, terminal drought stress is one of the serious threats to its productivity. For defining the appropriate selection criteria for screening drought tolerant chickpea genotypes, present study was conducted. Distinct chickpea germplasm was collected from different pulses breeding institutes of Pakistan and evaluated for drought tolerance at germination and early seedling stages, furthermore, at late vegetative growth stages physiochemical traits and multi-environment yield performance were also tested.ResultsChickpea genotypes under different environments, were significantly varied for different seedling traits, physio-chemical attributes and seed yield. Genotypes showing drought tolerance by performing better at an early seedling stages were not correspondingly high yielding. Screening for drought tolerance on seed yield basis is the most appropriate trait to develop the drought tolerant as well as high yielding chickpea genotypes. Results confirmed that traits of early growth stages were not reflecting the drought tolerance at terminal growth stages and also did not confer high yielding. NIAB-rain fed environment proved ideal in nature to screen the chickpea genotypes whereas, NIAB-lysimeter and Kalur Kot was least effective for selecting genotypes with high seed yield. Genotypes D0091–10, K010–10, D0085–10, K005–10, D0078–10, 08AG016, 08AG004, D0080–10, 09AG002, K002–10 and D0099–10 were high yielding and drought tolerant based on their performance across multiple hotspot environments.ConclusionsThe selected genotypes are intended for further evaluation for varietal approval to recommend for general cultivation on farmer fields in drought hit areas of Pakistan. Among physio-biochemical traits, higher proline, glycine betain, RWC and CMS were reflecting the higher capability to tolerate the drought stress in chickpea. Drought sensitive genotypes (K0037–10, 2204, K0052–10, 09AG015, K0042–10, CM709/06, K0068–10, K004–10, K0026–10 and K0063–10) were also identified in present study which were resourceful asset for using as contrasting parents in hybridization programs. To our knowledge, this is first report using an integrated approach involving, physio-biochemical indices, and multi-environmental yield trials, for comparison, screening and selection of chickpea genotypes for drought tolerance.

Impact of Sowing Dates on Terminal Heat Tolerance of Different Wheat (Triticum aestivum L.) Cultivars

Terminal heat stress leads to significant yield reduction in wheat. Adaptation strategies to combat this could be either growing heat-tolerant cultivars or adjustments in sowing date. A study was conducted for 2 years to understand the impact of terminal heat stress on wheat using three different wheat cultivars (HD 2932, WR 544 and HD 2967) and three sowing date, viz. D1 (second week of November), D2 (first week of December) and D3 (last week of December) at Indian Agricultural Research Institute (IARI), New Delhi, India. Results revealed that timely sown crop (D1) showed significantly higher number of tillers m−2 (450), plant height (93.5 cm), 1000-grain weight (38 g), grain yield (6.3 t ha−1) and harvest index (0.44) compared with D2 and D3. Yield loss occurred by 70, 29 and 77 kg ha−1 per day due to delay in sowing beyond D1 in varieties, viz. ‘HD 2932,’ ‘WR 544’ and ‘HD 2967,’ respectively. The late-sown crop resulted lower yield, which encountered higher temperature in its terminal growth stages. Among three varieties used, ‘WR 544’ had lesser decline in growth and yield than other two varieties due to late sowing. It implied that ‘WR 544’ had thermo-tolerant characteristics. Higher yield in wheat requires both heat-tolerant cultivars and better agronomic strategy under terminal heat stress condition. This study concluded that varietal selection and adjustment in sowing date could be the appropriate adaptation strategies under changing climate especially the terminal heat stress.

Identification of microsatellite markers associated with grain protein content in durum wheat grown under drought stress at terminal growth stages

Grain protein content (GPC) in durum wheat is a crucial determinant of pasta quality and as such is an important economic factor. This study was carried out to determine the microsatellite markers (SSRs) as associated with GPC in durum wheat grown under normal and moisture stress conditions. F3 and F4 population derived from 151 F2 individuals developed from a cross between Oste-Gata (drought tolerant) and Massara-1 (drought susceptible) genotypes, were used. The population was evaluated under four environmental conditions (two irrigation regimes in two growing seasons). The results of single marker regression analysis (SMA) revealed that 2, 4 and 10 markers to be associated with GPC, test weight (TW) and 1000 grain weight (TGW), respectively. These markers explained between 4.4 and 21.8% of the phenotypic variation in either environmental condition. The most significant marker observed for GPC was located on 5B chromosome near Xgwm408 under normal conditions and the other marker was observed on 1A, explaining about 15% of phenotypic variance. However, it was not recognized any marker related to GPC under drought stress conditions. Xgwm408 marker was coincident with the markers identified for TW, TGW and components of grain yield under drought stress conditions. In spite of 5B, the other chromosomes such as 2B and 3B were related to quantitative traits like TW and TGW. Composite interval mapping (CIM) identified 4 and 5 putative minor and major QTL for TW and TGW, respectively. Two QTL near Xbarc101 and Xbarc124 markers on 3B and 2B chromosome, explained up to 45.2 and 6% of phenotypic variations of TGW and TW, respectively.

Effects of kernel weight and source-limitation on wheat grain yield under heat stress

High temperature in terminal growth stages is a major stress of wheat productivity in South-west Iran, as well as in other Mediterranean environments and the long-term spring temperatures trend to increase. Determination of affecting factors or traits helps to improve the yield potential of wheat. The effects of heat stress during and post anthesis for physiologic, phenologic and agronomic traits was evaluated in ten bread wheat genotypes. The research was conducted under field condition in two different dates under less and more heated environments (two different sowing times). Also, source levels were manipulated through 50% spikelet removal at anthesis to evaluate cultivar source/sink limitations to kernel growth. The results depicted that grain yield, kernel number per spike and 1000 kernel weight were reduced by 24.1%, 9.2% and 23.7% in warmer environment, respectively. Hence, kernel weight was more suited for heat stress screening than other traits evaluated in this study. Thus, wheat genotypes that are able to maintain high individual kernel weight despite heat stress may possess a high level of heat tolerance. Furthermore, results indicated that the poor grain filling could mainly be attributed not to sink-limited conditions, but to source-limited conditions. Key words : Heat, stress intensity, tolerance, sink-source limitation.

Assimilate Supply as a Yield Determination Factor in Spring Wheat under High Temperature Conditions in the Mediterranean Zone of South-East Turkey

Wheat in the Mediterranean zone often encounters high temperatures during the terminal growth stage. This study investigated whether assimilate supply by source-function plays a dominant role in determining grain production in spring wheat exposed to high terminaltemperatures in the Mediterranean zone of south-east Turkey. The spring wheat cultivar Adana99 was grown under irrigated conditions sowing according to the current schedule (CS plants) and late-sowing (LS plants) for two years. Grain yield of CS plants, which were subjected to relatively lower temperatures during the terminal growth stage, was higher than that of LS plants, which were subjected to relatively higher temperatures. A high temperature in the post-anthesis period accelerated leaf senescence and reduced radiation-use efficiency. Halving the plant density at anthesis, which increases assimilate supply to grains, significantly increased the grain dry weight (GDW) and whole plant dry weight (WPDW) in the post-anthesis period. Grain filling percentage (F%, observed/final GDW) in thinned plants, which was regarded as potential F%, showed a single logistic equation based on cumulative temperature after anthesis, regardless of post-anthesis temperatures. In the LS plants, the daily increase in WPDM ( Δwpdw) decreased, but the peak of an increase rate of potential GDW estimated from F% was shifted to earlier-filling stage, resulting in reduced GDW at harvest. The final GDW in both years closely correlated with the estimated Δwpdw in the grain-filling period. These results suggest that source-function for assimilate supply in the post-anthesis period is one of the important yield-determining processes in spring wheat subjected to high temperatures.

Size distribution of the Late Devonian ammonoid Prolobites: indication for possible mass spawning events

Worldwide, the ammonoid genus Prolobites is only known from a few localities, and from these fossil beds almost all of the specimens are adults as shown by the presence of a terminal growth stage. This is in marked contrast to the co-occurring ammonoid genera such as Sporadoceras, Prionoceras, and Platyclymenia. Size distribution of specimens of Prolobites from three studied localities show that, unlike in the co-occurring ammonoid species, most of the material belongs to adult individuals. The morphometric analysis of Prolobites delphinus (Sandberger & Sandberger 1851) demonstrates the intraspecific variability including variants with elliptical coiling and that dimorphism is not detectable. The Prolobites material shows close resemblance to spawning populations of Recent coleoids such as the squid Todarodes filippovae Adam 1975. Possible mass spawning events are discussed in the context of the size distribution and limited geographic range of Prolobites. Finally, the potential fecundity and brooding behaviour of Prolobites is hypothesized using the examples of post spawning egg care in Recent coleoids.

Identification of microsatellite markers linked with yield components under drought stress at terminal growth stages in durum wheat

Grain yield and yield components are the main important traits involved in durum wheat (Triticum turgidum L.) improvement programs. The purpose of this research was to identify quantitative trait loci (QTL) associated with yield components such as 1000 grain weight (TGW), grain weight per spike (GWS), number of grains per spike (GNS), spike number per m2 (SN), spike weight (SW), spike harvest index (SHI) and harvest index (HI) using microsatellite markers. Populations of F3 and F4 lines derived from 151 F2 individuals developed from a cross between Oste-Gata, a drought tolerant, and Massara-1, a drought susceptible durum wheat genotypes, were used. The populations were evaluated under four environmental conditions including two irrigation regimes of drought stress at terminal growth stages and normal field conditions in two growing seasons. Two hundred microsatellite markers reported for A and B genomes of bread wheat were used for parental polymorphism analysis and 30 polymorphic markers were applied to genotype 151 F2:3 families. QTL analysis was performed using genome-wide single marker regression analysis (SMA) and composite interval mapping (CIM). The results of SMA revealed that about 20% of the phenotypic variation of harvest index and TGW could be explained by Xcfd22-7B and Xcfa2114-6A markers in different environmental conditions. Similarly, Xgwm181-3B, Xwmc405-7B and Xgwm148-3B and marker Xwmc166-7B were found to be associated with SHI and GWS, respectively. A total of 20 minor and major QTL were detected; five for TGW, two for GWS, two for GNS, three for SN, five for HI, two for SHI and one for SW. The mapped QTL associated with ten markers. Moreover, some of these QTL were prominent and stable under drought stress and non drought stress environments and explained up to 49.5% of the phenotypic variation.

Root contribution to stay-green in rice (Oryza sativa L.) subjected to desiccated soils in the post-anthesis period

The stay-green trait as a maintenance capacity of green leaves assimilating under des- iccated soils in the post-anthesis period is known in several crop plants. Our objectives were to clarify if the capacity to stay green in the terminal growth stage is related to root performance in Vietnam rain-fed rice cultivars. Three Vietnam cultivars were grown under flood conditions in 130-L volume pots. Irrigation was withheld from half of the pots at the anthesis period, while the flood condition was maintained in the remaining pots. The SPAD value as an indicator of green color, green leaf area (GLA) and leaf conductance (CL) decreased after heading, but trends of the decrease by soil desicca- tion differed among cultivars. The cultivar, which showed higher maintenance of the SPAD value, GLA and CL under desiccated soils, had significantly denser roots in the surface soil layer at harvest. The water absorption rate per soil volume and per root length of almost all soil layers in the cultivar was maintained longer and higher in desiccated soils. The SPAD value and GLA of detached leaves in the cultivar incubated under dark and humid conditions were maintained significantly longer. This showed that the leaf properties contribute to the maintenance of green leaves. These results suggest that in stay-green rice cultivars the properties that keep the leaves green contribute to a delay in the suppression of assimilate processes and maintain the water absorption function of the roots by maintaining the assimilate supply to roots.

Patch reef development in the florigemma-Bank Member (Oxfordian) from the Deister Mts (NW Germany): a type example for Late Jurassic coral thrombolite thickets

Small reefal bioconstructions that developed in lagoonal settings are widespread in a few horizons of the Late Jurassic (Oxfordian) succession of the Korallenoolith Formation, exposed southwest of Hannover, Northwest Germany. Especially the florigemma-Bank Member, “sandwiched” between oolite shoal deposits, exposes a high variety of build-ups, ranging from coral thrombolite patch reefs, to biostromes and to coral meadows. The reefs show a distribution with gradual facies variations along an outcrop belt that extends about 30 km from the Wesergebirge in the NW to the Osterwald Mts in the SE. The patch reefs from the Deister Mts locality at the “Speckhals” are developed as coral-chaetetid-solenoporid-microbialite reefs and represent a reef type that was hitherto unknown so far north of its Tethyan counterparts. They are mainly built up by coral thickets that are preserved in situ up to 1.5 m in height and a few metres in diameter. They contain up to 20 coral species of different morphotypes but are chiefly composed of phaceloid Stylosmilia corallina and Goniocora socialis subordinately. The tightly branched Stylosmilia colonies are stabilized by their anastomosing growth. The coral branches are coated with microbial crusts and micro-encrusters reinforcing the coral framework. Encrusters and other biota within the thicket show a typical community replacement sequence: Lithocodium aggregatum, Koskinobullina socialis and Iberopora bodeuri are pioneer organisms, whereas the occurrence of non-rigid sponges represents the terminal growth stage. The latter are preserved in situ and seem to be characteristic so far poorly known constituents of the Late Jurassic cryptobiont reef dweller community. The distance and overall arrangement of branches seems to be the crucial factor for the manifestation of a (cryptic) habitat promoting such community replacement sequences. Widely spaced branches often lack any encrusting and/or other reef dwelling organisms, whereas tightly branched corals, as is St. corallina, stimulate such biota. Hence, such reefs are well suited for research on coelobites and community sequences of encrusting and cavity dwelling organisms.

GROWTH AND SHELL VARIATION IN THE TROPICAL EASTERN PACIFIC INTERTIDAL GASTROPOD GENUSPURPURA:ECOLOGICAL AND EVOLUTIONARY IMPLICATIONS

In this study we investigate variation in shell morphology among Purpura pansa Gould, 1853 and P. columellaris Lamarck, 1822; high intertidal predatory gastropods found in the eastern tropical Pacific. Field observations on the high frequency of shells intermediate in apertural characteristics, the occurrence of cross-copulations between distinct morph types, coupled with morphometric analyses and examination of sectioned shells lead us to conclude that these two forms are the same species. Hence, we propose P. pansa as a junior synonym of P. columellaris.Growth studies reveal that the thicker shelled columellaris morph is much slower growing and represents a terminal growth stage of the pansa morph. Unlike some other thaidid species, starvation experiments failed to induce thickening of the apertural lip and apertural tooth formation. The stimulus that cues thickening is unknown.Field experiments indicated that thick-toothed morphs are relatively more resistant to predation and are most common in wave protected, high predation risk environments. Absence of thick-shelled morphs in populations ofthe geminate congener, P. patula in the Caribbean suggests that predation is probably less severe in this region.