Kernel Rows Research Articles

Collection, evaluation and phenotypic diversity assessment of maize (Zea mays) germplasm from North Eastern Himalayan region

Primitive landraces and traditional cultivars of maize (Zea mays L.) are invaluable resources for the humankind. These need to be collected, evaluated, conserved and utilized for increasing agricultural production and quality enhancement. Based on extensive survey, 75 diverse maize accessions were collected from Nagaland and Manipur states of the North Eastern Himalayan region. These collections were evaluated under two different agro-ecological regions, New Delhi and Shillong during kharif 2012 and 2013 using 12 quantitative variables. There was significant morphological variability among the accessions. Trait specific cultivars were identified based on exploration related knowledge and phenotypic valuation. The cluster analysis was performed to assess the variation among genotypes and grouped them into five clusters based on phenotypic traits. The principal component analysis (PCA) was subjected to quantitative datasets to group the accessions and to study contribution of traits for phenotypic variation. The first two principal components explained more than 50% of the phenotypic variation. Plant height, ear height, grain yield, ear width, number of kernel rows and number of kernels per row were major contributing traits towards phenotypic diversity. The different groups obtained can be useful for deriving the inbred lines with diverse features and diversifying the heterotic pools.

Unveiling superior cross combination in maize (Zea mays L.)

An experiment was conducted to find out the heterotic and heterobeliotic in maize during 2013-14 at Agricultural Research Institute, Dera Ismail Khan to get the superior cross combination expressing high hybrid vigour. The crosses were made in 2013 and F1 hybrids along with their parents were studied in 2014. Six maize inbred lines viz; Islamabad-white, Buffa Selection I, Sahiwal-2002, Sadaf, Islamabad Gold and Azam were used and full diallel approach was adopted to get the superior cross combination and to unveil best cross combination. Data were recorded on days to 50% pollen shed, days to 50% silking, plant height, number of ears plant-1 , ear length, number of kernel rows ear-1 , number of kernel row-1, 1000 kernel weight and grain yield kg ha-1. The analysis of variance revealed that means squares due to progenies and their parents were highly significant for all the traits except number of kernels ear-1 and 1000 kernel weight which showed significant differences. Only number of kernels row ear-1 depicted non-significant variation. The analysis of variance (Table 1) showed that mean squares due progenies and parents were highly significant for all the traits. Twenty two crosses had positive heterosis ranged from +0.84% (BS-1 x Sadaf) to 51.3 % (Islamabad-white x Sadaf) for grain yield kg ha-1. For days to 50% pollen shed, heterosis ranged from (-10.8 to +0.6%). The twenty seven hybrids showed negative heterosis, while the two hybrids showed positive heterosis for days to 50% silking. For plant height twenty seven crosses showed positive heterosis ranged from (0.0% to 15.5%). The heterosis and heterobeltiosis for number of ears palnt-1 ranged from (-11.5% to 16.0 %), (-14.6 to +13.8 %) respectively. For ear length heterosis ranged from +0.12% (Islamabad-white x BS-1) to +26 % (BS-1 x Islamabad gold). Heterosis and heterobeltiosis ranged from +2.5 % (BS-1 x Islamabad-white) to 9.1 % (Sahiwal-2002 x Islamabad white) and 4.7 % (BS-1 x Azam) to 7.6 % (Sahiwal-2002 x Islamabad-white) for number of kernel rows ear-1. 1000 kernel weight showed heterosis and heterobeltiosis ranged from +1.5 (BS-1 x Azam) to +19.5 % (Islamabad white x Sadaf) and +0.2 % (Azam x Islamabad white) to 19.2 % (Islamabad white x Sadaf). Hence it is suggested that 3 parents viz; Islamabad Gold, Sahiwal 2002 and Sadaf can give promising yield if included in breeding experiments to unzip genetic configuration. Keyword: Maize; Inbred lines; Heterosis and heterobeltiosis http://dx.doi.org/10.19045/bspab.2017.60071

Hybrid Maturity Influence on Maize Yield and Yield Component Response to Plant Population in Croatia and Nebraska

Maize (Zea mays L.) yield component analysis is limited. Research was conducted in 2012 and 2013 at Zagreb, Croatia and Mead, Nebraska, United States with the objective to determine the influence of environment, hybrid maturity, and plant population (PP) on maize yield and yield components. Three maturity classes of maize hybrids were produced at five PP ranging from 65,000 to 105,000 plants ha−1 under rainfed conditions. Yield, ears m−2, rows ear−1, ear circumference, kernels ear−1, kernels row−1, ear length, and kernel weight were determined. Average yield was 10.7 t ha−1, but was variable for hybrids across PP. The early maturity-hybrids had lesser ear circumference, more kernels ear−1, greater ear length, and fewer rows ear−1 than mid- and late-maturity hybrids. Kernels ear−1 had the highest correlation with yield (r = 0.47; P < 0.01 for early-maturity hybrids; r = 0.55; P < 0.01 for the mid- and late-maturity hybrids). Path analysis indicated that ears m−2, kernels ear−1 and kernel weight had similar direct effects on yield for early-maturity hybrids (R = 0.41 to 0.48) while kernels ear−1 had the largest direct effect (R = 0.58 versus 0.32 to 0.36) for the midand late-maturity hybrids. Rows ear−1 had an indirect effects on yield (R = 0.30 to 0.33) for all hybrids, while kernels row−1 had indirect effect (R = 0.46) on yield for mid- and latematurity hybrids. Yield component compensation was different for early-maturity hybrid than the mid- and late-maturity hybrids, likely due to the proportion of southern dent and northern flint germplasm present in these hybrids.

High Density Linkage Map Construction and Mapping of Yield Trait QTLs in Maize (Zea mays) Using the Genotyping-by-Sequencing (GBS) Technology.

Increasing grain yield is the ultimate goal for maize breeding. High resolution quantitative trait loci (QTL) mapping can help us understand the molecular basis of phenotypic variation of yield and thus facilitate marker assisted breeding. The aim of this study is to use genotyping-by-sequencing (GBS) for large-scale SNP discovery and simultaneous genotyping of all F2 individuals from a cross between two varieties of maize that are in clear contrast in yield and related traits. A set of 199 F2 progeny derived from the cross of varieties SG-5 and SG-7 were generated and genotyped by GBS. A total of 1,046,524,604 reads with an average of 5,258,918 reads per F2 individual were generated. This number of reads represents an approximately 0.36-fold coverage of the maize reference genome Zea_mays.AGPv3.29 for each F2 individual. A total of 68,882 raw SNPs were discovered in the F2 population, which, after stringent filtering, led to a total of 29,927 high quality SNPs. Comparative analysis using these physically mapped marker loci revealed a higher degree of synteny with the reference genome. The SNP genotype data were utilized to construct an intra-specific genetic linkage map of maize consisting of 3,305 bins on 10 linkage groups spanning 2,236.66 cM at an average distance of 0.68 cM between consecutive markers. From this map, we identified 28 QTLs associated with yield traits (100-kernel weight, ear length, ear diameter, cob diameter, kernel row number, corn grains per row, ear weight, and grain weight per plant) using the composite interval mapping (CIM) method and 29 QTLs using the least absolute shrinkage selection operator (LASSO) method. QTLs identified by the CIM method account for 6.4% to 19.7% of the phenotypic variation. Small intervals of three QTLs (qCGR-1, qKW-2, and qGWP-4) contain several genes, including one gene (GRMZM2G139872) encoding the F-box protein, three genes (GRMZM2G180811, GRMZM5G828139, and GRMZM5G873194) encoding the WD40-repeat protein, and one gene (GRMZM2G019183) encoding the UDP-Glycosyltransferase. The work will not only help to understand the mechanisms that control yield traits of maize, but also provide a basis for marker-assisted selection and map-based cloning in further studies.

A fast genomic selection approach for large genomic data.

We propose a novel computational method for genomic selection that combines identical-by-state (IBS)-based Haseman-Elston (HE) regression and best linear prediction (BLP), called HE-BLP. Genomic best linear unbiased prediction (GBLUP) has been widely used in whole-genome prediction for breeding programs. To determine the total genetic variance of a training population, a linear mixed model (LMM) should be solved via restricted maximum likelihood (REML), whose computational complexity is the cube of the sample size. We proposed a novel computational method combining identical-by-state (IBS)-based Haseman-Elston (HE) regression and best linear prediction (BLP), called HE-BLP. With this method, the total genetic variance can be estimated by solving a simple HE linear regression, which has a computational complex of the sample size squared; therefore, it is suitable for large-scale genomic data, except those with which environmental effects need to be estimated simultaneously, because it does not allow for this estimation. In Monte Carlo simulation studies, the estimated heritability based on HE was identical to that based on REML, and the prediction accuracy via HE-BLP and traditional GBLUP was also quite similar when quantitative trait loci (QTLs) were randomly distributed along the genome and their effects followed a normal distribution. In addition, the kernel row number (KRN) trait in a maize IBM population was used to evaluate the performance of the two methods; the results showed similar prediction accuracy of breeding values despite slightly different estimated heritability via HE and REML, probably due to the underlying genetic architecture. HE-BLP can be a future genomic selection method choice for even larger sets of genomic data in certain special cases where environmental effects can be ignored. The software for HE regression and the simulation program is available online in the Genetic Analysis Repository (GEAR; https://github.com/gc5k/GEAR/wiki).

English

Grain yield is a complex quantitative trait that depends on a number of other traits for selection.&nbsp; This study was carried out to reveal the pattern of association with and contribution of traits to grain yield in two maize populations evaluated in three agro-ecological zones of South-Western Nigeria during the 2014 cropping season. The experiment consisted of 10 top-cross and 10 three-way cross maize hybrids, laid out in a randomised complete block design with three replications. Genotypic and phenotypic correlation coefficients and path co-efficient analyses were performed for each hybrid population across the three locations. Results showed significant (p&le;0.05) differences between the two hybrid populations for all the traits mentioned except days to 50% anthesis, ear diameter and 100-grain weight. Field weight in both hybrid populations, number of kernel rows per cob, ear diameter and ear height in top-cross hybrids, as well as ear length and 100-grain weight in the three-way cross hybrids were directly correlated with grain yield. The link between direct and indirect effects on grain yield depends on hybrid population, although some traits showed similar direct effects in both hybrid populations. These traits can be used as the main criteria for grain yield improvement in the respective hybrid populations. Key words: Correlation, path coefficient analysis, hybrid populations, maize (Zea mays L.), grain yield.

Natural diversity of inflorescence architecture traces cryptic domestication genes in barley (Hordeum vulgare L.)

Many-grained mutants occurring spontaneously among their less well-endowed field mates may have appeared to early farmers as fortunate twists of fate foreboding wealth and abundance. In domesticated barley, the number of kernel rows in spike can be tripled by recessive mutant alleles at the Six-rowed spike 1 (vrs1) locus that abolish the suppression of lateral spikelet fertility. In another barley row-type, so called intermedium-spike (int), lateral floret size is often intermediate between six-and two-rowed types. Phenotypic and sequence analyses of our intermedium-spike collection revealed that other genes can increase the size of florets and even stimulate occasional grain setting in lateral spikelets. Here, we show that a complete six-rowed phenotype occurs in a diverse panel of intermedium-spike barley carrying wildtype Vrs1 in the presence of the Int-c.a allele of the intermedium spike-c (int-c) gene, previously considered only as a modifier of lateral spikelet fertility. Int-c.a-type alleles had arisen before domestication and are associated with the enlargement of lateral florets in wild barley, suggesting that natural selection/evolution acts towards reduced lateral floret size. Since Int-c.a cannot overcome the suppression of lateral florets in the genomic background of wild barleys, we infer the existence of other gene loci, at which novel alleles or allelic combinations were selected for after domestication, to increase grain number of barley independently of Vrs1.

AL – NOOR NEW VARIETY OF POPCORN (Zea mays var evarta)

Breeding program was conducted to develop new variety of popcorn (Noor) adapted to Iraqi environment during 2008 -2012 at Al- Latifya Research Station /Agric. Res. Directorate / Minsof Sci&amp; Technology. The aim of this program was to develop new popcorn variety more adapted to Iraqi environment with best traits and high yield and popping expansion. Introduction and hybridization methods applied during at the first stage among local variety AL-Safa and Syrian variety (Halab) and American variety (AMR-2). The Mass selection at later stage for five cycles respectively for new population that produced from hybridization. In fall season 2012 an experiment was conducted to compare new variety (AL- Noor) with exotic and promise genotypes including its parents by using randomized complete block design(RCBD). The rustle showed significant differences at p˃ 0.05 p for all the studied traits except number of leaves and leaf area index and number of ears row. The new variety AL-Noor revealed lowest days a tassling and silking days (60.19 and 62.94) and highest number of ears per plant(1.63), kernels row (42.93), and number of kernels/ plant and highest popping

AL – NOOR NEW VARIETY OF POPCORN (Zea mays var evarta)

Breeding program was conducted to develop new variety of popcorn (Noor) adapted to Iraqi environment during 2008 -2012 at Al- Latifya Research Station /Agric. Res. Directorate / Minsof Sci&amp; Technology. The aim of this program was to develop new popcorn variety more adapted to Iraqi environment with best traits and high yield and popping expansion. Introduction and hybridization methods applied during at the first stage among local variety AL-Safa and Syrian variety (Halab) and American variety (AMR-2). The Mass selection at later stage for five cycles respectively for new population that produced from hybridization. In fall season 2012 an experiment was conducted to compare new variety (AL- Noor) with exotic and promise genotypes including its parents by using randomized complete block design(RCBD). The rustle showed significant differences at p˃ 0.05 p for all the studied traits except number of leaves and leaf area index and number of ears row. The new variety AL-Noor revealed lowest days a tassling and silking days (60.19 and 62.94) and highest number of ears per plant(1.63), kernels row (42.93), and number of kernels/ plant and highest popping&#x0D; expansion (987.50)ml. gm-1.

Why SR52 is such a great maize hybrid? II. Heritability, correlation and path-coefficient analyses

Although exceptional heterosis for yield in the world’s first commercial single cross maize (Zea mays L.) hybrid SR52 has been confirmed, the role of secondary traits hasn’t been established. Objectives of this study were to establish relationship between grain yield and secondary traits, while assessing heritability and genotypic variation in SR52’s segregating populations. Knowledge on associations between yield and secondary traits would be crucial in extracting productive inbred lines from the population. Traits were subjected to correlation and path-coefficient analyses. Path analysis model accounted for over 70% of variation (R2) in all populations. Consistently high positive correlations with grain yield were observed for ear length and number of kernel rows on ear. Ear girth (0.19), and number of kernels per row (0.48) showed high direct effects on yield in the F2 population and the trend was consistent in the backcrosses. Positive indirect effects of most traits on grain yield were negligible with the exception of kernel per row via total number of kernels on ear, which was above 0.40 in the F2 and BCP1. Ear length can be exploited for indirect selection for yield in SR52’s segregating generations. 100-kernel weight and number of kernel rows on ear can, to a lesser extent, be targeted in selecting for grain yield. High to medium phenotypic variability in segregating generations of SR52 for traits such as ear length, number kernel rows on ear and grain yield should give impetus to selection of productive inbred lines from SR52 hybrid because of presence of diversity in the gene pool.

Prediction and validation of double cross hybrids in maize (Zea mays L.)

The experiment comprised of six F1’s, which were selected based on the combinations of low yield × high yield and low ASI × high ASI. The selected six F1’s were crossed in full diallel mating design to synthesise 16 double crosses was estimated and validated on the basis of performance of their constituent single crosses. Out of 16 hybrids, DCH 15 recorded lower tasseling and silking days and hence it can be used further in breeding programme. While, DCH 13 recorded narrow mean for ASI are suggested for use in deriving superior inbred lines with a combination of narrow ASI and higher ear circumference and kernel rows ear-1.The expected yield performance of DCH 5 (125.88), DCH 8 (124.23), DCH 10 (123.96), DCH 15 (123.73), DCH 6 (122.77) and DCH 12 (120.76) out yielded best check, Hema (119.00) for grain yield plant-1respectively. DCH 12 predicted better for most of the characters viz., ASI, ear length, ear circumference, kernel rows-1 and 100 grain weight. While, DCH 15 predicted better for characters viz., days to tasseling, days to silking, plant height (cm), ear height (cm), kernels row-1 and shelling percentage. Therefore, these two crosses may be used as double cross hybrids for breeding programme. In both prediction methods, nearly 14 out of 16 double cross hybrids manifested significant differences between realised and predicted performance suggesting involvement of epistasis in genetic control of grain yield plant-1

UNBRANCHED3 regulates branching by modulating cytokinin biosynthesis and signaling in maize and rice.

UNBRANCHED3 (UB3), a member of the SQUAMOSA promoter binding protein-like (SPL) gene family, regulates kernel row number by negatively modulating the size of the inflorescence meristem in maize. However, the regulatory pathway by which UB3 mediates branching remains unknown. We introduced the UB3 into rice and maize to reveal its effects in the two crop plants, respectively. Furthermore, we performed transcriptome sequencing and protein-DNA binding assay to elucidate the regulatory pathway of UB3. We found that UB3 could bind and regulate the promoters of LONELY GUY1 (LOG1) and Type-A response regulators (ARRs), which participate in cytokinin biosynthesis and signaling. Overexpression of exogenous UB3 in rice (Oryza sativa) dramatically suppressed tillering and panicle branching as a result of a greater decrease in the amount of active cytokinin. By contrast, moderate expression of UB3 suppressed tillering slightly, but promoted panicle branching by cooperating with SPL genes, resulting in a higher grain number per panicle in rice. In maize (Zea mays) ub3 mutant with an increased kernel row number, UB3 showed a low expression but cytokinin biosynthesis-related genes were up-regulated and degradation-related genes were down-regulated. These results suggest that UB3 regulates vegetative and reproductive branching by modulating cytokinin biosynthesis and signaling in maize and rice.

Line &amp;#215; Tester Analysis of Tropical High Land Maize (&amp;lt;i&amp;gt;Zea mays&amp;lt;/i&amp;gt; L.) Inbred Lines Top Crossed with Three East African Maize Populations

Maize breeding efforts to generate high yielding and adaptive cultivars have recently been given emphasis by national maize breeding program. In Ethiopia, the maize production system is mainly dominated by subsistence farmers where their production is below average. The objectives of this study were to determine the combining ability between lines and testers, and to evaluate the performance of crosses (hybrids) and parents for grain yield and yield component traits. Twenty-seven inbred lines were generated by crossing nine female lines (L1-L9) and three male testers (T1-T3) using line × tester mating system at International Maize and Wheat Improvement Center (CIMMYT), East African high land maize improvement program. The inbred lines along with parents were evaluated in randomized complete block design with two replications at three locations (Ambo, Kulumsa and Haramaya). Significant differences were observed among genotypes for all ten traits considered. Eight crosses (L1 × T2, L1 × T3, L3 × T3, L8 × T1, L4 × T2, L9 × T1, L2 × T1, and L2 × T2) had higher yield performance compared to other crosses across environments. Significant mean square differences were found across locations for general combining ability (GCA) due to lines for all traits except for number of kernel rows per ear, whereas GCA due to testers were significant only for grain yield, ear length and 1000-seed weight. Significant mean square due to GCA × Loc (both for lines and testers) was found for days to maturity (38.71*), 1000-seed weight (4582.36**) and grain yield (2756777**), while significant SCA × Loc interaction was found for all traits except number of kernel rows per ear (1.07), ear length (0.79) and ear diameter (0.12), suggesting that the importance of additive and non-additive gene effects in controlling these characters.

Fine Mapping and Genetic Effect Analysis of qKRN5.04 , a Major QTL Associ-ated with Kernel Row Number in Maize

Fine Mapping and Genetic Effect Analysis of <i>qKRN5.04</i> , a Major QTL Associ-ated with Kernel Row Number in Maize

Maize response to time of nitrogen application and planting seasons

Nitrogen (N) response by maize differs due to growing seasons, growth stages, duration and growing domain as N losses is higher due to leaching as well as volatilization. Objective of this study was to know the response of split applications of N and growing seasons on maize under Chitwan environments. Field experiments were conducted for two consecutive years at the research field of NMRP Rampur during the winter, spring, and summer seasons of 2012/013 and 2013/014. Experiments were laid out in factorial randomized complete block design with four replications for all the seasons. Early maturing maize genotype Arun-1 EV was used for the experiments. Five splits of recommended dose of N were tested. Grain yield, days to flowering, plant height, ear height, kernel rows per ear, no. of kernels per row, ear length and thousand grain weight significantly differed due to growing seasons and split applications of N. Significantly higher grain yield (3911 kg ha-1) was obtained with the application of 30 kg N ha-1 each at 30, 45, 60, and 75 days after sowing as compared to control (2801 kg ha-1). Regarding the growing seasons, highest grain yield was obtained in winter (4393 kg ha-1) followed by spring (3791 kg ha-1) and summer (2468 kg ha-1) season, respectively. Results of these studies revealed that four splits of N viz. application of 30 kg N each at 30, 45, 60, and 75 days after sowing respectively, would be more economical to minimize N losses from the soil and efficient use of N at critical growth and development stages of maize.

Estimation of heterosis in yield and yield attributing traits in single cross hybrids of maize

A field experiment was conducted at National Maize Research Program, Rampur, Chitwan, Nepal during winter season from 6th October, 2015 to 5th March 2016 to estimate different heterosis on single cross maize hybrids . Thirteen maize hybrids were tested randomized complete block design with three replications. Hybrid namely RML-98/RL-105 gave the highest standard heterosis (57.5%) for grain yield over CP-666 followed by RML-4/NML-2 (32.6%), RML-95/RL-105 (29%) and RML-5/RL-105 (20.6%). The hybrid RML-98/RL-105 produced the highest standard heterosis (75.1%) for grain yield over Rajkumar followed by RML-4/NML-2(50.2%), RML-95/RL-105(46.6%), RML-5/RL-105 and (35.7%). Mid and better parent heterosis were significantly higher for yield and yield attributes viz. ear length, ear diameter, no of kernel row per ear, no of kernel per row and test weight. The highest positive mid-parent heterosis for grain yield was found in RML-98/RL-105 followed by RML-5/RL-105, RML-95/RL-105, and RML-4/NML-2. For the grain yield the better parent heterosis was the highest in RML-98/RL-105, followed by RML-5/RL-105, RML-95/RL-105, and RML-4/NML-2. These results suggested that maize production can be maximized by cultivating hybrids namely RML-98/RL-105, RML-5/RL-105, RML-95/RL-105, and RML-4/NML-2.

Development of High Tryptophan Maize Near Isogenic Lines Adapted to Temperate Regions through Marker Assisted Selection - Impediments and Benefits.

Breeding program aimed at converting standard maize inbred lines to their quality protein maize (QPM) counterparts for growing in temperate climate is being conducted at Maize Research Institute (MRI). The objective of the research presented herein was to develop QPM versions of two commercial ZP inbreds through marker assisted selection (MAS) with opaque2 specific molecular markers, while maintaining their good agronomic performances and combining abilities. Donor line was a tropical QPM line CML 144. After two backcross and three selfing generations, six near isogenic lines (NILs) with 93% recovery of the recurrent parent genome were created from one cross. Average increments of 30% in tryptophan content and 36% in quality index were obtained, as well as kernels with less than 25% opaque endosperm. Grain yield was increased by 11–31% and combining abilities of the improved lines were on a par with the original line. Correlations between biochemical and agronomic parameters revealed that selection for plant height, ear length and kernel row number together with tryptophan content could be recommended for development of QPM with this material. However, several impediments emerged during selection. Major drawbacks in NIL development were small number of opaque2 recessive homozygotes (4.5% and 7.6% in BC2F2 of two crosses) and poor seed set throughout selection, which led to the loss of one cross. Moreover, in the other cross many plants in different generations had to be omitted from further selection due to the insufficient number of kernels. This phenomenon could be explained by incompatibility between pollen and style, possibly due to the exotic donor germplasm. Overall, it could be expected that the use of NILs, which are adapted to temperate climate and have high percentage of domestic germplasm, would outbalance the noted impediments and increase MAS efficiency in different breeding programs.

Retrotransposon-related genetic distance among inbred lines of sweet corn (Zea mays var. saccharata) and hybrid performance

AbstractHeterosis is a main force underlying the hybrid seed industry in maize. Our experimental approach consists of a correlation study between retrotransposon-related genetic distances between parental inbred lines and hybrid performance. The assumption is that, at least for certain traits, heterosis results from genome rearrangements, largely related to retrotransposon insertions and/or removals. Fifteen maize inbred lines and one F1 hybrid, representative of the genetic diversity among sweet corn and field corn lines were screened for polymorphism by retrotransposon microsatellite amplified polymorphism markers. DNA fingerprints served as row data for estimating genetic diversity of maize inbred lines and its correlation with the heterotic effect in their hybrids. A correlation between phenotypic and molecular distances was evident only at the level of individual inbred lines. Weak correlation between genetic distances and heterosis effect was observed for the average of all inbred lines. Phenotypic distances negatively correlated with heterosis for insertion height, diameter of the ear and number of kernel rows per ear. The relative contribution of each inbred line to heterosis in its derived hybrids was also estimated. Accordingly, we identified inbred lines with increased genetic distances that mostly add to the heterosis effect in their hybrids and that we recommend as prospective to be used in maize breeding programmes.

Application of foliar fertilizer and fungicides on white spot disease control and development of maize

This study aimed to evaluate the effect of forms of application of foliar fertilizers and fungicides to control fungus causing white maize spot, Phaeosphaeria maydis , and the growth and development of hybrids maize. The design had randomized blocks, with the use two sources hybrids maize with different reaction to white maize spot: resistant and susceptive and application with moisture of foliar chemical fungicide + cobalt foliar + molybdenum foliar + manganese and control treatment, without application consisting of four treatments and five replications. In the treatments with application of moisture were done on vegetative maize growth stage V8 (stage that determine that the number of kernel rows), VT (stage that arrives when the last branch of the tassel is completely visible) and reproductive maize growth stage R2 (kernels are white on the outside and resemble a blister). The evaluation of variables of growth of maize plants: grain dry mass, cob dry mass, leaf dry mass, culm dry mass and modificated leaf ear and total plant dry mass. Harvest was carried out when the grains were 20% humidity. The application of fungicides and foliar fertilizers increased the leaves, culm, ear modificated, cobs and shoot dry mass plants maize. The application of fungicides and foliar fertilizers providing returning of 11.409,5 kg ha -1 of shoot dry mass plants with increased of 1.296 kg ha -1 on soil(12,81%). In the susceptive hybrid maize the application of fungicides and foliar fertilizers provide higher dry mass grains and shoot of plants.

Genetic architecture of the maize kernel row number revealed by combining QTL mapping using a high-density genetic map and bulked segregant RNA sequencing.

BackgroundThe maize kernel row number (KRN) is a key component that contributes to grain yield and has high broad-sense heritability (H 2). Quantitative trait locus/loci (QTL) mapping using a high-density genetic map is a powerful approach to detecting loci that are responsible for traits of interest. Bulked segregant ribonucleic acid (RNA) sequencing (BSR-seq) is another rapid and cost-effective strategy to identify QTL. Combining QTL mapping using a high-density genetic map and BSR-seq may dissect comprehensively the genetic architecture underlying the maize KRN.ResultsA panel of 300 F2 individuals derived from inbred lines abe2 and B73 were genotyped using the specific-locus amplified fragment sequencing (SLAF-seq) method. A total of 4,579 high-quality polymorphic SLAF markers were obtained and used to construct a high-density genetic map with a total length of 2,123 centimorgan (cM) and an average distance between adjacent markers of 0.46 cM. Combining the genetic map and KRN of F2 individuals, four QTL (qKRN1, qKRN2, qKRN5, and qKRN8-1) were identified on chromosomes 1, 2, 5, and 8, respectively. The physical intervals of these four QTL ranged from 4.36 Mb for qKRN8-1 to 7.11 Mb for qKRN1 with an average value of 6.08 Mb. Based on high-throughput sequencing of two RNA pools bulked from leaves of plants with extremely high and low KRNs, two QTL were detected on chromosome 8 in the 10–25 Mb (BSR_QTL1) and 60–150 Mb (BSR_QTL2) intervals. According to the physical positions of these QTL, qKRN8-1 was included by BSR_QTL2. In addition, qKRN8-1 was validated using QTL mapping with a recombinant inbred lines population that was derived from inbred lines abe2 and B73.ConclusionsIn this study, we proved that combining QTL mapping using a high-density genetic map and BSR-seq is a powerful and cost-effective approach to comprehensively revealing genetic architecture underlying traits of interest. The QTL for the KRN detected in this study, especially qKRN8-1, can be used for performing fine mapping experiments and marker-assisted selection in maize breeding.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3240-y) contains supplementary material, which is available to authorized users.