Anthesis-silking Interval Research Articles

English

Twenty four inbred lines developed by the Ethiopian National Maize Breeding Program were evaluated at Jimma Agricultural Research Center during the main season of the year 2016 in an 8 X 3 Alpha Lattice (0, 1) design with three replications. The objective was to determine the phenotypic and genotypic association among traits in Ethiopian maize inbred lines and to compare the direct and indirect effects of traits on grain yield. Analysis of variance showed statistically significant (p<0.01) differences among the tested maize inbred lines for most of the traits indicating the existence of sufficient genetic variability which can be exploited in future breeding programs. Grain yield per hectare, thousand kernels weight, ear height, ear diameter, anthesis-silking interval, and plant aspect had higher phenotypic and genotypic coefficients of variation. Grain yield showed positive and highly significant (p<0.01) genotypic association with ear diameter, number of kernels per row, days to 50% silking, number of kernel rows per ear, 1000-kernels weight and leaf width. Grain yield also had positive and highly significant (p<0.01) phenotypic correlation with number of kernels per row and ear diameter. Path coefficient analysis revealed that number of kernels per row, number of kernel rows per ear, plant height, days to maturity, 1000-kernels weight, leaf width and plant aspect had a positive direct genotypic effect on grain yield. Number of kernels per row, number of kernel rows per ear, plant height and 1000-kernels weight exerted high direct effects and also indicated positive and strong association with grain yield indicating that they can be used for indirect selection of inbred lines having higher yield potential per se.   Key words: Character association, inbred lines, morphological traits, path coefficient analysis.

Physiological Basis of Yield Differences in Quality Protein Maize Genotypes of Different Maturity Groups

Yield performance of early maturing maize (Zea mays L.) varieties in the rainforest agroecology of southwest Nigeria, is lower than that of intermediate varieties and that there was no yield advantage in the late varieties over the intermediate maturing varieties. However, the physiological basis of yield differences is yet to be fully investigated. This study was carried out to investigate the physiological basis underlying yield differences in quality protein maize genotypes of different maturity groups. Field experiment was conducted as randomized complete block design (RCBD) with three replicates at Institute of Agricultural Research and Training, Obafemi Awolowo University, Moor Plantation, Ibadan during 2013 and 2014 cropping seasons. The results indicated that season influenced days to 50% Anthesis (DTA), days to 50% silking (DTS), anthesis silking interval (ASI), plant height (PLHT), ear height (EHT), ear per plant (EPP), ear aspect (EASP), kernel width (KWDT) and grain yield (GYD). Maturity groups also influenced DTA, DTS, PASP, PLHT, EHT, and with no effect on GYD. The overall mean grain yields across seasons were 4.44, 4.16, 3.64 and 3.36 t/ha for season 1, 2, 3 and 4, respectively. It was concluded from this study that all the maturity groups used had similar grain yield.

Mapping quantitative trait loci associated with southern leaf blight resistance in maize (Zea mays L.)

AbstractSouthern leaf blight (SLB) caused by the fungus Cochliobolus heterostrophus (Drechs.) Drechs. is a major foliar disease of maize worldwide. Our objectives were to identify quantitative trait loci (QTL) for resistance to SLB and flowering traits in recombinant inbred line (RIL) population derived from the cross of inbred lines LM5 (resistant) and CM140 (susceptible). A set of 207 RILs were phenotyped for resistance to SLB at three time intervals for two consecutive years. Four putative QTL for SLB resistance were detected on chromosomes 3, 8 and 9 that accounted for 54% of the total phenotypic variation. Days to silking and anthesis–silking interval (ASI) QTL were located on chromosomes 6, 7 and 9. A comparison of the obtained results with the published SLB resistance QTL studies suggested that the detected bins 9.03/02 and 8.03/8.02 are the hot spots for SLB resistance whereas novel QTL were identified in bins 3.08 and 8.01/8.04. The linked markers are being utilized for marker‐assisted mobilization of QTL conferring resistance to SLB in elite maize backgrounds. Fine mapping of identified QTL will facilitate identification of candidate genes underlying SLB resistance.

Genetic Variability and Inter-relatedness of Agronomic Traits of Single Cross Hybrid Maize in Contrasting Soil Nitrogen-nutritional Conditions

Background: Lowering the nitrogen demand is the most cost effective and sustainable option to increase grain yield of maize in poor fertility soil.
 Aim: This study was conducted to estimate the variability and inter-traits’ association of white and yellow hybrid maize in soil nitrogen-nutritional stress and optimal conditions.
 Materials and Methods: 150 white and 66 yellow single cross hybrid maize were evaluated in contrasting soil (stress and optimal) N conditions in Ibadan in 2014 and 2015. The trial for the white maize was laid out in 19 × 8 lattice design while the yellow maize was experimented in randomized complete block design. Each trial was replicated three times. Data were collected on days to anthesis (DTA), days to silking (DTS), plant height (PH), ear height (EH), anthesis-silking-interval (ASI) and grain yield (GY) were estimated while leaf senescence (LS), plant aspect (PASP) and ear aspect (EASP) were scored. Data collected were subjected to analysis of variance while variances and broad sense heritability were calculated and rated.
 Results: Greater variability existed among white maize than the yellow maize for the traits. Inheritance of the traits can be predicted in optimal N than stress condition. Additive genes action was responsible for inheritance of DTA and DTS while both additive and non-additive control the GY, PH, EH and LS of the white maize in both N conditions. For yellow maize, the DTA and DTS were controlled by additive genes action in both N conditions. The GY, ASI, PH, EH and LS were governed by both additive and non-additive genes actions in N stress condition. Additive genes action is responsible for inheritance of PH and EH while both additive and non-additive actions govern inheritance of GY, ASI and LS in optimal condition. The GY had positive relationship with the DTA, DTS and LS in both N conditions for the white maize while the GY positively correlated with PH, EH and LS in N stress, but with ASI only in optimal condition for the yellow maize.
 Conclusion: Grain yield, flowering, height and leaf senescence can be used in selecting maize for nitrogen-use-efficiency.

Diallel analysis of maize inbred lines for agronomic traits in nitrogen stress and optimal conditions

Increasing demand, soil cultivation pressure and adverse climate change effects necessitated maize production in nitrogen stress soils. This study examined the general combining ability (GCA) of 12 maize inbreds and specific combining ability of their crosses for agronomic traits under varied nitrogen conditions. GCA accounted for 53% of the variation for grain yield (GY) under stress and 40% under optimal condition. GCA contributed over 59% for days to anthesis (DTA) and days to silking (DTS), anthesis-silking-interval (ASI) and ear aspect (EASP) under both conditions. BD74-165 and BD74-161 had positive significant GCA for GY under stress with TZEI12 under optimal and BD74-222 under both conditions. TZEI13 and TZEI16 had positive significant GCA for DTA and ASI under stress, and TZEI12, TZEI11 and BD74-161 under optimal. Additive genes control DTA, DTS and PH; non-additive genes were responsible for ASI, PASP and EASP while both additive and non-additive genes governed inheritance of GY, EH and leaf-senescence (SEN) under stress. Inheritance of GY, ASI, PH, PASP and EASP were due to non-additive genes; DTA and DTS to additive genes while additive and non-additive genes control EH and SEN under opti­mal condition. Inbreds with significant GCA can be parents for GY improvement under respective conditions. Keywords: Combining ability; diallel; low nitrogen; maize lines; stress tolerance

DIVERSIDAD GENOTIPICA DE 291 LÍNEAS DE MAÍZ DE CIMMYT Y CARACTERIZACIÓN FENOTÍPICA EN EL SUR DE CÓRDOBA, ARGENTINA

CIMMYT maize inbred lines (CMLs) are freely distributed to breeding programs around the world. Better information on phenotypic and genotypic diversity may provide guidance to breeders on how to use more efficiently the CMLs in their breeding programs. In this study a group of 291 CIMMYT maize inbred lines, was phenotyped by nine agro-morphological traits in south Córdoba, Argentina and genotyped using 18,082 SNPs. Based on the geographic information and the environmental adaptation, 291 CMLs were classified into eight subgroups. Anthesis-silking interval (IAE) was the trait with higher phenotypic diversity. A 40% of maize inbred lines, with IAE less than five days, show a good adaptation to growing conditions in south Córdoba, Argentina. The low phenotypic variation explained by environmental adaptation subgroups indicates that population structure is only a minor factor contributing to phenotypic diversity in this panel. Principal component analysis (ACP) allowed us to obtain phenotypic and genotypic orderings. Generalized procrustes analysis (APG) indicated a 60% consensus between both data type from the total panel of maize lines. In each environmental adaptation subgroup, the APG consensus was higher. This result, which might indicate linkage disequilibrium between SNPs markers and the genes controlling these agro-morphological traits, is promising and could be used as an initial tool in the identification of Quantitative Trait Loci (QTL). Information on genetic diversity, population structure and phenotypic diversity in local environments will help maize breeders to better understand how to use the current CIMMYT maize inbred lines group. Key words: broad-sense heritability, multivariate analysis, SNPs, agro-morphological traits.

Genetical studies of corn crop to exploit heterosis, proportional contribution and gene action at diverse water regimes

The study is based on mating fashion of line × tester and its relative analysis to exploit the heterosis, proportional contribution of diverse lines, testers, their interaction and gene action in cross combinations of different corn genotypes under different water regimes. Total 12 parents comprised of eight lines and four testers; crossed to produce 32F1 hybrids. Parents including their hybrids were evaluated in CRD with three water treatments under controlled conditions with three replications in two seasons. Heterosis, percent contribution of lines, testers and line × tester interaction and gene action were studied for the traits i.e. ear leaf area, number of kernel rows per ear, 100 grain weight, biological yield, vegetative dry matter and anthesis-silking interval. Variable heterosis both in magnitude and direction was observed. Both additive and non-additive gene effects have role in the control of anthesis-silking interval; whereas non-additive gene effects were observed for ear leaf area, number of kernel rows per ear, 100 grain weight, biological yield and vegetative dry matter. However100 seed weight was mainly affected by dominance effects under this study that helped for the selection of parents to be used for the development of synthetics and hybrids durable for different water regimes. Keywords: Additive; Hybrid; Line × tester; Susceptible; Water stress http://dx.doi.org/10.19045/bspab.2019.80077

Phenotypic plasticity of maize grain yield and related secondary traits: Differences between inbreds and hybrids in response to contrasting water and nitrogen regimes

Correct characterization of heritability and phenotypic plasticity (PP) is critical for breeding purposes. The latter refers to the variation range of a trait in response to changes in the environment and has been assessed as the difference between percentiles 10th (P10) and 90th (P90) of each trait, which does not reflect below the median (P50) variations to the same extent as the above the median ones. This inconsistency may affect the classification of stable (low PP) or plastic (high PP) given to traits, as well as their relative ranking and PP relationship with heritability. The objectives of current research were to evaluate corrected PP (PPC) variation in grain yield (GY) and related secondary traits among contrasting maize genotypic groups (inbreds and hybrids) grown under contrasting water regimes (WR) and nitrogen (N) availabilities. The relationship between PPC and broad-sense heritability (H2) was also assessed. Field experiments were conducted during three (N) or seven (WR) growing seasons at two mid-latitude environments of Argentina. Measured traits were days and thermal time to 50% anthesis (A50 and TTA) and to 50% silking (S50 and TTS), the anthesis-silking interval in days (ASID) and in TT (ASITT), plant height (Ph), prolificacy (Pr), GY, kernel numbers (KN), and kernel weight (KW). Values for percentiles 10th (P10), 50th (P50) and 90th (P90) of each trait were identified for each treatment combination. P50 was set to 1, and values obtained for P10 and P90 were expressed as ratios with P50. P10 was corrected (P10C= P50 – P50/P10) to reflect the below P50 variations to the same extent as those above P50. Corrected PP was estimated as PPC= P90 - P10C. P90 values of all traits corresponded to non-stressed plots whereas P10C values corresponded to stressed plots, except for ASIs (opposite trend). A large plasticity (PPC>mean PPC) was usually verified for ASIs, GY and KN. Mean inbreds PPC had a larger variation than mean hybrids PPC (+19% for WR and +29% for N), except for GY under contrasting WR (hybrids > inbreds). A common trend across all evaluated traits was the markedly larger effect on PPC of P10C than of P90, in agreement with the predominant representation of stressful conditions by the former and in contrast to previous studies where no correction was performed on P10. Our results demonstrated the lack of relationship between H2 and PP and improved current knowledge about the importance of environment modulation on PP of most expansion-related and production traits, highlighting the relevance of the evaluated resource (water or N) as well as of the genotypic group (hybrids or inbreds) on final phenotype expression.

English

Inbred line development requires information on the nature and magnitude of genetic variability and transmissibility of desired trait in source populations. In this study, the level of genetic variability, heritability and genetic advance of thirteen agronomic and fresh yield traits among twelve shrunken-2 super-sweet corn populations were evaluated. Field experiments were conducted for two years in Ibadan, Nigeria using a randomised complete block design with three replicates. Estimates of genetic variability components, broad-sense heritability and genetic advance were computed for each trait. All the traits exhibited significant genotypic differences. Genotypic variance was significant for number of marketable cobs, yield of cobs, number of cobs, number of kernel rows, husk cover, ear height and days to anthesis, while environmental variance was significant for all the traits. Phenotypic coefficients of variation were higher than the corresponding genotypic coefficients of variation for all traits. Broad-sense heritability ranged from 22.2% for anthesis-silking interval to 85.1% for husk cover. The genetic advance was high (32.7%) for husk cover, medium (12.0%) for yield of cobs and low for other traits. Genetic variability was present among the shrunken-2 super-sweet corn populations. Opportunities abound for further improvement of the populations and extraction of lines for hybrid seed production. Key words: Broad-sense heritability, genotypic coefficient of variation, husk cover score, sweet corn, yield of marketable cobs. &nbsp

Evaluating Maize Genotype Performance under Low Nitrogen Conditions Using RGB UAV Phenotyping Techniques.

Maize is the most cultivated cereal in Africa in terms of land area and production, but low soil nitrogen availability often constrains yields. Developing new maize varieties with high and reliable yields using traditional crop breeding techniques in field conditions can be slow and costly. Remote sensing has become an important tool in the modernization of field-based high-throughput plant phenotyping (HTPP), providing faster gains towards the improvement of yield potential and adaptation to abiotic and biotic limiting conditions. We evaluated the performance of a set of remote sensing indices derived from red–green–blue (RGB) images along with field-based multispectral normalized difference vegetation index (NDVI) and leaf chlorophyll content (SPAD values) as phenotypic traits for assessing maize performance under managed low-nitrogen conditions. HTPP measurements were conducted from the ground and from an unmanned aerial vehicle (UAV). For the ground-level RGB indices, the strongest correlations to yield were observed with hue, greener green area (GGA), and a newly developed RGB HTPP index, NDLab (normalized difference Commission Internationale de I´Edairage (CIE)Lab index), while GGA and crop senescence index (CSI) correlated better with grain yield from the UAV. Regarding ground sensors, SPAD exhibited the closest correlation with grain yield, notably increasing in its correlation when measured in the vegetative stage. Additionally, we evaluated how different HTPP indices contributed to the explanation of yield in combination with agronomic data, such as anthesis silking interval (ASI), anthesis date (AD), and plant height (PH). Multivariate regression models, including RGB indices (R2 > 0.60), outperformed other models using only agronomic parameters or field sensors (R2 > 0.50), reinforcing RGB HTPP’s potential to improve yield assessments. Finally, we compared the low-N results to the same panel of 64 maize genotypes grown under optimal conditions, noting that only 11% of the total genotypes appeared in the highest yield producing quartile for both trials. Furthermore, we calculated the grain yield loss index (GYLI) for each genotype, which showed a large range of variability, suggesting that low-N performance is not necessarily exclusive of high productivity in optimal conditions.

Gains in grain yield of released maize (Zea mays L.) cultivars under drought and well-watered conditions

AbstractMaize (Zea mays L.) grain yield is severely constrained by drought and this study was conducted to assess gains in grain yield and other traits of released maize cultivars. Twenty-three maize cultivars plus a check were evaluated under drought and well-watered conditions at Zaria and Kadawa during 2015/2016 and 2016/2017 dry seasons. The 24 cultivars were evaluated using 6 x 4 lattice design with three replications. Genotypes differed significantly for all measured traits except anthesis-silking interval (ASI), husk cover, and number of ears per plant under drought, and ASI, husk cover, and ear aspect under well-watered conditions. Under drought, grain yield ranged from 2251 kg ha−1 for SAMMAZ 31 to 4938 kg ha−1 for SAMMAZ 19, with a genetic gain of 1.93% yr−1. Under well-watered conditions, grain yield varied from 3082 kg ha−1 for SAMMAZ 37 to 5689 kg ha−1 for SAMMAZ 51, with the same genetic gain found under drought conditions. Grain yield reduction as a result of drought was 28.4% and performance under drought predicted performance under well-watered conditions better than vice versa with regression coefficient value of 0.8. Grain yield had significant correlations with all measured traits under both water conditions, except for husk cover, plant and ear heights under drought. Our data revealed that substantial genetic gains have been made in breeding for high grain yield cultivars under drought and well-watered conditions over a period of 16 years in Nigeria.

Changes in heterosis of maize (Zea mays L.) varietal cross hybrids after four cycles of reciprocal recurrent selection

Two improved tropical maize composites, TZL COMP3 and TZL COMP4; representing complementary heterotic pools have been subjected to four cycles of reciprocal recurrent selection (RRS) for two decades to enhance varietal cross performance. The objectives of this study were to evaluate the effect of selection on genetic gain in heterosis for grain yield and other agronomic traits of these composites. Ten parental populations representing the C0 to C4 of each composite and their crosses plus a varietal check were evaluated in a trial at eight environments in Nigeria. Grain yield of the varietal crosses increased with selection by 3.1% cycle–1. Mean grain yields of the C4 × C4 varietal cross exceeded that of a popular improved reference variety by 23%. Selection also reduced anthesis-silking interval, improved ear characteristics, phenotypic appeal and resistance to foliar diseases. Mid-parent heterosis (MPH) increased from 4% at C0 × C0 to 24% at C4 × C4. The average rate of genetic gain in heterosis for grain yield in population crosses was 3.1% possibly because of presence of non-additive gene effects. The results of our study present the potential usefulness of the advanced selection cycle as sources of diverse inbred lines with improved combining ability as well as improved varietal crosses that can be multiplied and deployed in areas with limited market access.

Heritability and Correlations for Agronomic and Physiologic Traits of Maize under Deficit Irrigation at Two Growth Stages

Strong associations between agronomic and physiologic traits and drought tolerance, high heritability and high genetic advance for such traits would allow plant breeder to use such traits as selection criteria for selecting drought tolerant genotypes. The objectives of the present investigation were: (i) to explain the relationships between the drought tolerance index (DTI) and 14 agronomic and physiologic traits of 22 maize genotypes and (ii) to estimate the broad-sense heritability (h2b) and genetic advance (GA) from selection for such traits, in order to determine the selection criteria for DTI. A two-year experiment was carried out using a split plot experiment with three replications. The main plots were devoted to irrigation regimes, i.e. well watering (WW), water stress at flowering (WSF) and at grain filling (WSG), and sub plots to maize genotypes. It is evident from results that the best selection criteria for drought tolerance in our study were: 100-kernel weight (100KW) and chlorophyll concentration index (CCI) under WSF and WSG, anthesis-silking interval (ASI), upper stem diameter (SDU) and lower stem diameter (SDL) under WSF and kernels/row (KPR) and ear leaf area (ELA) under WSG, since they show high correlation (r) values with grain yield/plant (GYPP), high h2b and high GA estimates under the respective environments. Under well watering conditions, KPR, 100KW, CCI, and SDL traits showed high (r) values, high h2b and high GA estimates and therefore could be considered selection criteria for GYPP under non-stressed environment. The results concluded that predicted selection gain would be higher if selection was practiced under WW for lower values of days to silking and higher values of ears/plant, rows/ear, KPR, 100KW, SDU and SDL, under WSF for lower values of ASI and higher values of GYPP and under WSG for lower values of plant height, ear height, and barren stalks, and higher values of CCI and ELA.

On the dynamic determinants of reproductive failure under drought in maize

Reproductive failure under drought in maize (Zea mays) is a major cause of instability in global food systems. While there has been extensive research on maize reproductive physiology, it has not been formalized in mathematical form to enable the study and prediction of emergent phenotypes, physiological epistasis and pleiotropy. We developed a quantitative synthesis organized as a dynamical model for cohorting of reproductive structures along the ear while accounting for carbon and water supply and demand balances. The model can simulate the dynamics of silk initiation, elongation, fertilization and kernel growth, and can generate well-known emergent phenotypes such as the relationship between plant growth, anthesis-silking interval, kernel number and yield, as well as ear phenotypes under drought (e.g. tip kernel abortion). Simulation of field experiments with controlled drought conditions showed that predictions tracked well the observed response of yield and yield components to timing of water deficit. This framework represents a significant improvement from previous approaches to simulate reproductive physiology in maize. We envisage opportunities for this predictive capacity to advance our understanding of maize reproductive biology by informing experimentation, supporting breeding and increasing productivity in maize.

Gene action and combining analysis for kernel yield and its attributing traits in maize [zea mays (l.)

Eight maize (Zea mays L.) genotypes were crossed in a half diallel mating design.The analysis of variance for combining ability revealed that mean sum of squares due to general combining ability were found significant for all the traits except cob girth, whereas, the specific combining ability effects were found highly significant for all the characters except anthesis-silking interval. The low ratio (<1.0) of GCA to SCA variance for sixteen traits indicated that non-additive type of gene action was predominant in the expression of yield and component traits. Based on estimates of general combining ability effects revealed that four parents BLD-11 (5.19), CML-338 (4.28), VL-1032 (1.68) and VL-109178 (1.25) were found good general combiners because they registered significant and positive gca effects. The estimates of sca effects revealed that 23 hybrids were exhibited significant positive sca effects. The spectrum of differences in sca effects for this trait ranged from -2.70 (CBE-98 × CML-338) to 27.57 (CBE-98 × MRCN-3) and the top most three hybrids for kernel yield per plant on the basis of specific combining ability effects were CBE-98 × MRCN-3 (27.57), CBE-98 × BLD-11 (23.16) and CBE-26 × BLD-11 (21.20).

Flowering dynamics, pollen, and pistil contribution to grain yield in response to high temperature during maize flowering

High temperature (HT) stress during flowering severely threatens crop grain yield, however, little is known about the underlying mechanisms in maize. A HT sensitive maize hybrid was subjected to 32/22 ℃ (maximum/minimum temperature, control), 36/26 ℃, and 40/30 ℃ for 14 consecutive days bracketing flowering (trial 1) and for seven days prior to flowering (trial 2). Maize grain yield did not decrease in the 36/26 ℃ treatment during trial 1 compared to the control treatment, but reduced by 73.6% in the 40/30 ℃ treatment as a result of reduced kernel number rather than kernel weight. High temperature stress advanced tasseling and pollen shedding, extended the anthesis-silking interval, and reduced the number and viability of pollen shed, but had no effects on silking. The shortened duration of pollen shedding was a result of the accelerated flowering speed of the tassel inflorescence. Leaf assimilate can be transferred to the tassel, but cannot be converted into starch in the HT stressed pollen. The damaged pollen morphology and the interrupted sugar to starch physiological process explained the reduced pollen viability. Starch granule number and size in the pollen decreased with the increased temperature. Thus, male organ growth is more sensitive to HT than female organs. Understanding the underlying mechanisms has implications for selecting or breeding HT tolerant maize.

Influence of nitrogen application on dry biomass allocation and translocation in two maize varieties under short pre-anthesis and prolonged bracketing flowering periods of drought

ABSTRACTPlants have evolved different mechanisms to survive under stress conditions. This field study was conducted to evaluate the influence of nitrogen (N) application on dry biomass allocation and translocation in two maize varieties under short pre-anthesis and prolonged bracketing flowering period of drought. Two maize varieties, ‘Pioneer 30B80ʹ and ‘Suwan 4452ʹ receiving N at 0 (control), 160 (optimal) and 320 (supra-optimal) kg ha−1 were subjected to short pre-anthesis and prolonged bracketing flowering periods of drought. Prolonged bracketing flowering period of drought had more suppressive effect on anthesis-silking interval, dry matter allocation and translocation, leaf greenness, contribution of current assimilates to grain (CCAG), kernel number, kernel weight and kernel yield of two maize varieties than a short pre-anthesis drought. Nitrogen application at optimal level was the best for all traits, except CCAG. The maize variety ‘Pioneer 30B80ʹ performed better under both drought types due to more root xylem vessels of large size and more accumulation of dry matter in leaves and roots than the variety ‘Suwan 4452ʹ. Therefore, the variety ‘Pioneer 30B80ʹ may be planted in drought prone environments and may be used in breeding program aimed at developing drought-tolerant cultivars.

Effect of water-deficit on tassel development in maize

Maize often exhibits asynchronous pollination under abiotic and biotic stress conditions; however, the molecular basis of this developmental deficiency has not been elucidated. Tassel development is a key process affecting the anthesis-silking interval (ASI) in maize. In this study, we showed that pollen shedding was delayed and ASI was significantly increased in B73 and Chang7-2 inbred lines under water deficit conditions, which resulted in longer barren tip length and decreased yields under both controlled and field conditions. Comparative transcriptome analysis performed on immature tassels derived from plants grown under well-watered and water deficit conditions identified 1931 and 1713 differentially expressed genes (DEGs) in B73 and Chang7-2, respectively. Further, 28 differentially co-expressed transcription factors were identified across both lines. Collectively, we demonstrated that the molecular regulation of tassel development is associated with water deficit stress at early vegetative stage in maize. This finding extends our understanding of the molecular basis of maize tassel development during abiotic stress.

PERTUMBUHAN DAN PRODUKSI BEBERAPA GENOTYPE JAGUNG (Zea mays L.) CALON HIBRIDA UMUR GENJAH DAN VARIETAS PEMBANDING BIMA 7 PADA JARAK TANAM YANG BERBEDA

This research was conducted with the aim of: 1) To observe growth and production of maize genotypes hybrid candidate early age, 2) Determine optimal spacing that will result in maximal production of genotype hybrid candidate early maturing and 3) To know interaction between maize genotypes hybrid candidate of early maturing and plant spacing. Research was conducted on dry land located in Bajeng, Gowa, South Sulawesi. Research was conducted from April to July 2017 using Split Plot Design method. As the main plot is the maize genotype consisting of 3 genotypes: ST201328, ST201359, ST201312 and varieties comparison Bima 7 while for sub plot is treatment the various spacing between two levels are: 60 cm x 20 cm and 50 cm x 20 cm. Treatment combination was repeated three times as a block to obtain 24 experimental units. The results of this research show that: 1) Maize genotype ST201328 is maize early maturing hibrid has appearance shortest plant, fastest flowering male age as well flowering female, smallest Anthesis Silking Interval (ASI), fastest harvest age and longer cob. Genotype ST201312 has appearance highest plant, greatest Anthesis Silking Interval, greatest Leaf Area Index and longest cob. 2) Plant spacing 50 cm x 20 cm obtained high Leaf Area Index and highest location cob. Average highest production dry seeds on plant spacing 50 cm x 20 cm for all maize genotypes tested. 3) Interaction that happaned between maize genotype ST201312`on plant spacing 60 cm x 20 cm obtained longest cob is 18,07 cm and differs markedly with varieties comparison Bima 7. Maize genotype ST201312 on plant spacing 50 cm x 20 cm obtained yield dry cheeks is amount 10,58 ton ha–1.

English

Experiments were conducted at Sokoine University of Agriculture in Morogoro, Tanzania to assess the growth performance and grain yield of ten maize cultivars under well-watered and water stressed conditions. The ten cultivars (CML 444, CML395, CML539, WE 4107, WE 2112, WE 3102, WE 4112 and WE 4116) obtained from Water Efficiency Maize for Africa (WEMA) project and two local market cultivars (&lsquo;STAHA&rsquo; and &lsquo;TMV1&rsquo;) were grown in a Randomized Complete Block design with a 10&times;3 factorial treatment arrangement and three replications. The three drought stress treatments were 50, 75 or 100% of field capacity with 10 kpa (equivalent to field capacity) and 30 kpa (drought) using tensiometers. Drought stress was initiated at vegetative stage (three weeks after emergence) for thirty days and flowering stage (one week before to two weeks after flowering). Plant height, stem diameter, leaf length, leaf width and chlorophyll content were measured at weekly intervals from two weeks after planting to maturity. Days to anthesis and silking were used to calculate Anthesis-Silking Interval (ASI) and kernel dry mass were recorded at harvest. Vegetative growth responses were not affected by water stress, but plant height and leaf chlorophyll content tended to decrease, while ASI ranging from 5.2 to 11.1 days and kernel dry mass decreased with increased drought stress. Dry kernel weight was significantly greater among five of the cultivars designated drought tolerant and the lowest in the two drought susceptible cultivars. Drought tolerant genes were expressed at different levels and only a few cultivars expressed all three genes at the vegetative and flowering stages. Thus, vegetative response of maize to drought stress varied based on cultivars. However, it appears that drought stress exerted more impacts on reproductive processes compared to vegetative. Key words: Cultivars, drought, genotypes, grain yield, growth performance, hybrids. &nbsp