Grain Yield Traits Research Articles

Contribution of morphological traits for grain yield in common bean

Contribution of morphological traits for grain yield in common bean

Phenotypic correlations and path analysis for plant architecture traits and grain production in three generations of cowpea

ABSTRACT The objective of this study was to analyze the phenotypic correlation and path analysis of traits related to plant architecture, earliness and grain yield in F2, BC1 and BC2 generations, from crosses between cowpea cultivars BRS Carijó and BR14 Mulato. Most phenotypic correlations of the examined traits were concordant in statistical significance, with approximate values among the examined generations. For the trait seed weight, significant and positive phenotypic correlations were observed in the three generations only for the trait number of secondary branches. The values of the direct effects were in agreement with the values of the phenotypic correlations, which indicate true association by the phenotypic correlation among the traits of grain yield examined. Path analysis indicated that the selection of productive plants will result in early plants and an increased number of secondary branches. In F2, plants with shorter length of the main branch and shorter length of secondary branches can be obtained. The causal model explained 15 to 30% of the total variation in grain weight in relation to the traits examined. The analyses indicated the possibility of selecting plants with a higher and early grain yield, shorter length of primary branches and lower number of nodes, which are important variables for mechanical or semi-mechanical harvesting.

Putative zeatin O-glucosyltransferase OscZOG1 regulates root and shoot development and formation of agronomic traits in rice.

As a ubiquitous reaction, glucosylation controls the bioactivity of cytokinins in plant growth and development. Here we show that genetic manipulation of zeatin-O-glucosylation regulates the formation of important agronomic traits in rice by manipulating the expression of OscZOG1 gene, encoding a putative zeatin O-glucosyltransferase. We found that OscZOG1 was preferentially expressed in shoot and root meristematic tissues and nascent organs. The growth of lateral roots was stimulated in the overexpression lines, but inhibited in RNA interference lines. In shoots, knockdown of OscZOG1 expression by RNA interference significantly improved tillering, panicle branching, grain number per panicle and seed size, which are important agronomic traits for grain yield. In contrast, constitutive expression of OscZOG1 leads to negative effects on the formation of the grain-yielding traits with a marked increase in the accumulation levels of cis-zeatin O-glucoside (cZOG) in the transgenic rice plants. In this study, our findings demonstrate the feasibility of improving the critical yield-determinant agronomic traits, including tiller number, panicle branches, total grain number per panicle and grain weight by downregulating the expression level of OscZOG1. Our results suggest that modulating the levels of cytokinin glucosylation can function as a fine-tuning switch in regulating the formation of agronomic traits in rice.

SS1 (NAL1)- and SS2-Mediated Genetic Networks Underlying Source-Sink and Yield Traits in Rice (Oryza sativa L.).

Source leaf/sink capacity (SS) traits are important determinants of grain yield (GY) of rice. To understand the genetic basis of the SS relationship in rice, five SS and GY traits of rice were genetically dissected using two reciprocal introgression populations. Seventy-three QTL affecting the SS and GY traits were identified, most of which were detected in one of the parental genetic backgrounds (GBs). Two major QTL at bins 4.7 (SS1) and 3.12 (SS2) were associated consistently with all measured SS and yield traits in both GBs across two contrasting environments. Strong interactions between SS1/SS2 and the detected QTL led us to the discovery of genetic networks affecting the SS and GY traits. The SS1 acted as a regulator controlling two groups of downstream QTL affecting the source leaf width and grain number per panicle (GNP). SS2 functioned as a regulator positively regulating different groups of downstream QTL affecting the source leaf length, GNP, grain weight, and GY. Map-based cloning of SS1 indicates that SS1 is NAL1 involved in polar auxin/IAA transport. Different alleles at NAL1 were apparently able to qualitatively and/or quantitatively control the IAA transport from the apical meristem to different plant tissues and thus regulate those downstream loci/pathways controlling different SS traits of rice. There was a functional allele and a non-functional mutation in the parents at each of the QTL downstream of SS1 or SS2, which were detectable only in the presence of the functional allele of SS1 or SS2. Our results provided direct evidence that SS and yield traits in rice are controlled by complex signaling pathways and suggest further improvement of rice yield potential with enhanced and balanced SS relationships can be achieved by accurately manipulating allelic combinations at loci in the SS1 and SS2 mediated pathways.

Variance components and association between corn hybrids morpho-agronomic characters

The present work aimed at evaluating the canonical correlations between traits of grain yield and morphological traits in maize, in order to verify the associations and interdependence among groups. The experiment was conducted in the agricultural year 2010/2011; consisted of 25 corn hybrids, allocated in five locations of the states of Parana, Santa Catarina e Rio Grande do Sul. Settled two groups of traits, with Group I comprised agronomic characters of grain yield: grain yield plot, the total weight of grains and weight of hundred grains and the group II formed by morphology: stem diameter , leaf angle , tassel length , number of tassel branches , total leaf area , insertion of the ear , plant height in maize. The first, second and third canonical pair proved signifi­cant at the 1% level of probability, using the chi-square test, indicating that the groups are not independent. Hybrids with higher plant height, insertion of ear and leaf angle and fewer branches and tassel length are asso­ciated with the increase in weight of hundred grains in maize. To increase the grain weight, should be consid­ered hybrids with greater insertion of the ear, leaf area and shorter length of the tassel. The increase in leaf area, as well as smaller tassel length is related positively to increase grain yield in maize.

QTL VALIDATION FOR GRAIN YIELD AND NITROGEN USE EFFICIENCY UNDER DIFFERENT NITROGEN LEVELS IN RICE

High yielding rice genotypes with high N use efficiency is very important for agriculture sustainability. The study aimed to validate QTLs linked to grain yield (GY) and Nitrogen Use Efficiency (NUE) related-traits using association analysis and single marker analysis in order to identify marker alleles that are associated with target trait under different nitrogen environments. Fifty five rice genotypes were phenotyped for GY and NUE related traits under four different nitrogen treatments (i.e. 0, 20, 40, and 60 Kg N/Fed, respectively). The fifty five rice genotypes were genotyped using four SSR (RM223, RM246, RM242 and RM72) marker linked to QTLs for GY and NUE. Results showed that different degrees of association between the markers fragments and the different traits under the different N-treatments were found. For RM 223, the obtained two fragments (a1 and a2) showed significant and highly significant association with total dry weight (TDW) and (PL) under all N environments. Regarding RM246 marker, b2 and b3 fragments showed highly significant associations with high R2 values with PNUE, NPR and PL traits under all N-treatments. The b2 fragment showed highly significant association with high R2 values for GY, HI and 1000-GW traits. The RM242 fragments (c1 and c2), showed highly significant association with 1000-G and PL traits with high R2 values across the different N-treatments. Regarding the first fragment (c1), R2 values were ranged between 0.13 and 0.23 for 1000-G trait as well as between 0.13 and 0.18 for PL trait, while with c3 fragment, these values were ranged between 0.108 and 0.19 for 1000-G trait and between 0.26 and 0.36 for PL trait. For RM72 marker d1 fragment showed highly significant associations with 1000-GW, PNUE and NPR traits in the different N-treatments, and the R2 values were ranged between (0.21- 0.31), (0.15- 0.19) and (012-016), respectively. On the other hand there were highly significant association between RM72 d3 fragment and GY, NPR and PL with R2 values were ranged between (0.12-0.18), (0.16-0.19) and (0.15-0.26), respectively. These results will assessed in initiating marker-assisted breeding program for NUE and GY traits under low treatments of nitrogen fertilizers.

DWARF TILLER1, a WUSCHEL-Related Homeobox Transcription Factor, Is Required for Tiller Growth in Rice

Unlike many wild grasses, domesticated rice cultivars have uniform culm height and panicle size among tillers and the main shoot, which is an important trait for grain yield. However, the genetic basis of this trait remains unknown. Here, we report that DWARF TILLER1 (DWT1) controls the developmental uniformity of the main shoot and tillers in rice (Oryza sativa). Most dwt1 mutant plants develop main shoots with normal height and larger panicles, but dwarf tillers bearing smaller panicles compared with those of the wild type. In addition, dwt1 tillers have shorter internodes with fewer and un-elongated cells compared with the wild type, indicating that DWT1 affects cell division and cell elongation. Map-based cloning revealed that DWT1 encodes a WUSCHEL-related homeobox (WOX) transcription factor homologous to the Arabidopsis WOX8 and WOX9. The DWT1 gene is highly expressed in young panicles, but undetectable in the internodes, suggesting that DWT1 expression is spatially or temporally separated from its effect on the internode growth. Transcriptomic analysis revealed altered expression of genes involved in cell division and cell elongation, cytokinin/gibberellin homeostasis and signaling in dwt1 shorter internodes. Moreover, the non-elongating internodes of dwt1 are insensitive to exogenous gibberellin (GA) treatment, and some of the slender rice1 (slr1) dwt1 double mutant exhibits defective internodes similar to the dwt1 single mutant, suggesting that the DWT1 activity in the internode elongation is directly or indirectly associated with GA signaling. This study reveals a genetic pathway synchronizing the development of tillers and the main shoot, and a new function of WOX genes in balancing branch growth in rice.

Evaluation Forage Clipping Stages and Different Levels of Nitrogen on Grain and Forage Yields of TRITICALE (× TRITICOSECALE WITTMACK)

In order to reach suitable forage clipping and estimate nitrogen fertilizer to most economical proficiency, an experiment was carried out at Saatlo Station in 2008-2009 seasons. A factorial experiment was done based on the randomized complete blocks design with 4 replications. The first factor was three levels of clipping stages including non-clipping, clipping at tillering and booting stages. Different levels of nitrogen fertilizer including 0, 40, 80, 120 and 160 kg/ha were arranged at the second factor. Results showed that non-clipping and clipping at booting stage with 610.5 and 203.1 g/m2 had the most and the lowest grain yield, respectively. The highest economical proficiency (3743.06 $/ha) resulted with using 80 kg/ha nitrogen fertilizer and non-clipping. With considering both forage and grain yield, it is necessary that the clipping should be done at tillering stage with using of 120 kg/ha nitrogen fertilizer (3336.56 $/ha). At regression of economical proficiency traits of grain yield, straw and total dry matter remained at the final model. Economical proficiency had the significant positive correlation with spike per square meter (0.87**), grain yield (0.64**), total dry matter (0.65**), plant height (0.52**) and 1000-kernal weight (0.54**).

Evaluation of 14 morphological, yield-related and physiological traits as indicators of drought tolerance in Chinese winter bread wheat revealed by analysis of the membership function value of drought tolerance (MFVD)

Drought is a worldwide problem seriously influencing bread wheat (Triticum aestivum L.) production. The capability of 14 morphological, yield-related and physiological traits as indicators for identifying drought tolerant genotypes in wheat was evaluated among 90 wheat accessions under water-stressed (WS) and well-watered (WW) conditions in this study. The membership function value of drought tolerance (MFVD) of 14 traits was used as a comprehensive index for evaluation and selection of wheat drought tolerance. Ninety wheat genotypes from major wheat production areas of China were used as materials in an experiment by two factors split-plot design with two replications in a rainout shelter. Water treatments were as the main plots and genotypes were as the subplots. The mean values of all 14 traits decreased under water-stressed condition, among the 14 traits, BYPP, DSL, GYPP, SC and TR decreased >25%. This suggested that these 5 traits were more sensitive to water stress. The broad sense heritability of morphological traits (PH, UIL, DSL and SL) was relatively high and that of yield-related traits (BYPP, GYPP, TKW, SN and GNPS) was medium, while the broad sense heritability of physiological traits (PR, TR, CI, SC and SPAD) was low. Five accessions with highly drought tolerance were screened according to MFVD and could be applied for drought tolerance improvement in wheat. Correlation analysis revealed that the wheat drought tolerance was highly significantly and positively correlated with variations of 11 traits under two water treatments (P<0.001). Regression models built based on MFVD indicated that the variation of drought tolerant coefficient of 5 traits of grain yield per plant, transpiration rate, plant height, uppermost internode length and spike length could explain about 91.6% of total variation. Therefore these five traits could be used as a combination to screen wheat germplasm or lines for drought tolerance in wheat breeding program.

Association analysis among morphological and physiological traits of grain yield in wheat and meteorological parameters

In order to identify potential traits determining yield under terminal heat stress during grain filling stages, correlation and path coefficients analyses were conducted to study character associations among 25 morphological and physiological traits in a set of genetically divergent 36 bread wheat genotypes under normal and late sown conditions. Grain yield depicted positive association with grain weight (GW), grains/spike (G/S), biological yield (BY), harvest index (HI) under normal (NS) and late sown (LS) conditions, GGR-3 (grain growth rate at 28 days after anthesis) in LS and negative association with DM (days to maturity) , HU (heat units) and PTU (photothermal unit) in NS and with ChA-1(CHB “a” at anthesis), CHB “a”-1 (total CHB at anthesis) and CHB “a”-2 (total CHB at 28 days after anthesis) in LS. Path coefficient analysis revealed that out of eight characters significantly related to yield under normal sown conditions, PTU, harvest index, biological yield and grains per spike directly affected the grain yield in positive direction. On the basis of strong association with yield and marked direct influence on yield, the numbers of grains are considered to be first order yield components and ought to have top priority in selection under normal sown conditions. Under late sown conditions BY, harvest index (HI), CHB “a”-1 and grain weight had direct positive effect but the grains per spike exhibited negative direct effect despite of the fact that it possessed a positive significant correlation with grain yield. Based on results, it is suggested that high numbers of grains and high grain weight should be given priority for selection of high yielding genotypes in NS and LS, respectively.

Correlated response of morpho-physiological traits of grain yield in durum wheat under normal irrigation and drought stress conditions in greenhouse

In order to evaluate the relationship between different traits of grain yield in durum wheat, 20 durum wheat ( Triticum durum Desf.) landraces selected from the northwest of Iran together with five controls were evaluated under normal and drought stress conditions. Environmental mean squares were significant for all the traits studied except for harvest index which showed that drought stress has significant effect on all the traits. In normal condition, fertile tillers, peduncle length, spike length, number of grain spike and harvest index had the most positive direct effect on yield, while under drought stress condition, biological yield and harvest index had the most positive direct effect on yield. In regression analysis (stepwise method) in normal condition, infertile tillers and 1000 grain weight remained in the final model (R 2 = 0.485), while under stress condition, Fv/Fm, Fm and biological yield remained in the final model (R 2 = 0.667). Factor analysis of the total five factors was used to determine 76.708 and 77.128% of the data changes and adjustments in normal irrigated and drought stress conditions, respectively. The multiple statistical procedures used in this study showed that harvest index and biological yield were the most important yield variables to be considered under drought conditions. So, these traits could be used as selection criteria for increasing yield. Key words : Durum wheat, drought stress, chlorophyll fluorescence, chlorophyll content, multivariate analysis.

Functional dynamics of the nitrogen balance of sorghum: I. N demand of vegetative plant parts

Stay-green, an important trait for grain yield of sorghum grown under water limitation, has been associated with a high leaf nitrogen content at the start of grain filling. This study quantifies the N demand of leaves and stems and explores effects of N stress on the N balance of vegetative plant parts of three sorghum hybrids differing in potential crop height. The hybrids were grown under well-watered conditions at three levels of N supply. Vertical profiles of biomass and N% of leaves and stems, together with leaf size and number, and specific leaf nitrogen (SLN), were measured at regular intervals. The hybrids had similar minimum but different critical and maximum SLN, associated with differences in leaf size and N partitioning, the latter associated with differences in plant height. N demand of expanding new leaves was represented by critical SLN, and structural stem N demand by minimum stem N%. The fraction of N partitioned to leaf blades increased under N stress. A framework for N dynamics of leaves and stems is developed that captures effects of N stress and genotype on N partitioning and on critical and maximum SLN.

Dynamics of Drought Resistance Based on Drought Stress Coefficient Derived from Plant Height in Wheat Development

Plant height is a crucial agronomic trait for grain yield in wheat(Triticum aestivum L.).To detect changes of drought resistance in wheat development,drought stress coefficient(DS|WW) was calculated in five environments(year × experimental site) based on plant heights of 150 doubled haploid(DH) lines derived from Hanxuan 10 × Lumai 14 at five measuring stages using conditional analysis method.The plant heights were measured every 7 d from jointing to flowering(S1–S5) in both rain-fed(drought stress,DS) and well-watered(WW) conditions in five environments including Fenyang,Shanxi in 2001(F01),Haidian,Beijing in 2005(H05) and 2006(H06),Changping,Beijing in 2005(Ch05) and 2006(Ch06).DS|WW is the specific responding of plant height to DS condition relative to WW condition.Unconditional drought stress coefficient(UDS|UWW) represents drought resistance before time t,and conditional drought stress coefficient(CDS|CWW) represents drought resistance within the period from time(t?1) to t.In all five environments,the plant heights were significantly lower under DS than under WW at all five stages(P0.005).The largest plant height difference between DS and WW appeared in F01.The differences among environ-ments for both UDS|UWW and CDS|CWW at each developmental stage were significant at P0.0001.However,the result from multiple comparison analysis showed that part differences between environments in the same experimental site or year after S2 were insignificant,such as UDS3|UWW3 between H06 and Ch06,UDS5|UWW5 between H05 and H06.The significant positive correlations were detected for UDS|UWW between stages except five of ten correlation coefficients in Ch05.Poor correlations were observed for CDS|CWW between stages,however,the correlations between the adjacent stages appeared closer.In all envi-ronments,the significant positive correlations were always detected between UDS|UWW at time t and CDS|CWW before time t in one or more periods,indicating that the drought resistance at time t might partially attribute to that before time t.Path analysis suggested that drought resistance before jointing stage(CDS1|CWW1) and from heading to flowering(CDS5|CWW5) might playimportant roles for plant height at maturity,so,an ample supply of water at these periods are helpful for gaining higher yield.

Caráter stay-green e produtividade de grãos em trigo

O caráter stay-green é um dos fatores que poderá auxiliar o melhorista na obtenção de plantas mais produtivas, devido à permanência verde por um período mais prolongado favorecendo o enchimento de grãos. Desta forma, o objetivo do trabalho foi o de avaliar o desempenho de diferentes constituições genéticas de trigo com e sem a presença do caráter stay-green e verificar se a expressão de alelos que intensificam a coloração verde por um período mais prolongado, os quais auxiliam no incremento da produtividade de grãos. O trabalho foi desenvolvido em campo experimental com delineamento de blocos casualizados com três repetições, em dois anos de cultivo. A presença de constituições genéticas superiores facilita os benefícios expressos pelo caráter stay-green na produtividade de grãos. O caráter stay-green proporciona estabilidade na produtividade de grãos sob efeito de diferentes ambientes.

Selection for Osmoregulation Gene to Improve Grain Yield of Wheat Genotypes under Osmotic Stresses

For identifying osmoreguulation (or) differences in bread wheat genotypes, three experiments by using of randomized complete blocks design with five replications were carried out separately on 6 genotypes (Tabasi, Alvand, Shahi, Sabalan, Sardary and Roshan) under normal, drought and salinity stresses. At earring stage, in order to studying osmotic stress on pollen grains, treatments of 30% PEG (control) and 50% PEG with 10 mM KCl (osmotic stress) were applied. All pollen grains ofgenotypes were been swollen at control treatment, but under osmotic stress except of Roshan pollen grain (due to accumulation of K+ ion) was been shrinkage. Orthogonal analysis of variance showed significant differences for traits of grain yield and its components, soluble sugars, Na+, K+ accumulations. Under stress Roshan genotype had high accumulation of soluble sugars and K+. Increasing of grain yield due to or gene at Roshan than other genotypes under drought and salinity stresses were, respectively 18.14 and 38.80%. So, under drought and salinity stresses, identification of or allele and selection based on it in wheat breeding programs are strongly recommended.

Path analysis and expected response in indirect selection for grain yield in soybean

This study aimed to determine the best auxiliary trait for indirect selection of soybean grain yield, through path analysis and in avoidance of the adverse effects of multicollinearity and expected response. Seventy-nine F5 soybean genotypes from the cross FT-Cometa x Bossier were used. The populations were distributed on the field was the families inserted with replicated controls. Primary and secondary traits of grain yield were evaluated in four phenotypically superior plants per family. The traits number of pods, height and number of nodes were considered as the most important, showing the best combination of direct effect and genotypic correlation. The number of pods achieved the highest expected gain through the estimation method based on the selection differential. On the other hand, plant height, by the method based on selection intensity, was not a good indicator of the most productive plants.