Improvement Of Grain Yield Research Articles

Genetic Gains in Grain Yield of a Maize Population Improved through Marker Assisted Recurrent Selection under Stress and Non-stress Conditions in West Africa.

Marker-assisted recurrent selection (MARS) is a breeding method used to accumulate favorable alleles that for example confer tolerance to drought in inbred lines from several genomic regions within a single population. A bi-parental cross formed from two parents that combine resistance to Striga hermonthica with drought tolerance, which was improved through MARS, was used to assess changes in the frequency of favorable alleles and its impact on inbred line improvement. A total of 200 testcrosses of randomly selected S1 lines derived from the original (C0) and advanced selection cycles of this bi-parental population, were evaluated under drought stress (DS) and well-watered (WW) conditions at Ikenne and under artificial Striga infestation at Abuja and Mokwa in Nigeria in 2014 and 2015. Also, 60 randomly selected S1 lines each derived from the four cycles (C0, C1, C2, C3) were genotyped with 233 SNP markers using KASP assay. The results showed that the frequency of favorable alleles increased with MARS in the bi-parental population with none of the markers showing fixation. The gain in grain yield was not significant under DS condition due to the combined effect of DS and armyworm infestation in 2015. Because the parents used for developing the bi-parental cross combined tolerance to drought with resistance to Striga, improvement in grain yield under DS did not result in undesirable changes in resistance to the parasite in the bi-parental maize population improved through MARS. MARS increased the mean number of combinations of favorable alleles in S1 lines from 114 in C0 to 124 in C3. The level of heterozygosity decreased by 15%, while homozygosity increased by 13% due to the loss of some genotypes in the population. This study demonstrated the effectiveness of MARS in increasing the frequency of favorable alleles for tolerance to drought without disrupting the level of resistance to Striga in a bi-parental population targeted as a source of improved maize inbred lines.

Application of natural plant extracts improves the tolerance against combined terminal heat and drought stresses in bread wheat

AbstractDrought and heat are among the main abiotic stresses causing severe damage to the cereal productivity when occur at reproductive stages. In this study, ten wheat cultivars were screened for combined heat and drought tolerance imposed at booting, heading, anthesis and post‐anthesis stages, and role of the foliage applied plant extracts was evaluated in improving the performance of differentially responding wheat cultivars under terminal heat and drought stresses. During both years, wheat crop was raised under ambient temperature and 70% water holding capacity (WHC) till leaf boot stage. The plant extracts (3% each) of sorghum, brassica, sunflower and moringa were foliage applied at booting, anthesis and post‐anthesis stage; and after one week of application of these plant extracts, combined heat and drought was imposed at each respective stage. Heat and drought stresses were imposed at each respective stage by placing pots in glass canopies with temperature of 4 ± 2°C above than the ambient temperature in combination with drought stress (35%WHC) until maturity. Combination of drought and heat stresses significantly reduced the performance of tested wheat cultivars; however, stress at the booting and heading stages was more damaging than the anthesis and post‐anthesis stages. Cultivars Mairaj‐2008 and Chakwal‐50 remained green with extended duration for grain filling, resulting in the maintenance of number of grains per spike and 100‐grain weight under stress conditions and thus had better grain yield and water‐use efficiency. However, in cultivars Fsd‐2008, and Shafaq‐2006, the combined imposition of drought and heat accelerated the grain filling rate with decrease in grain filling duration, grain weight and grain yield. Foliar application of all the plant extracts improved the wheat performance under terminal heat and drought stress; however, brassica extract was the most effective. This improvement in grain yield, water‐use efficiency and transpiration efficiency due to foliage applied plant extracts, under terminal heat and drought stress, was owing to better stay‐green character and accumulation of more soluble phenolics, which imparted stress tolerance as indicated by relatively stable grain weight and grain number. In crux, growing of stay‐green wheat cultivars with better grain filling and foliage application of plant extracts may help improving the performance of bread wheat under combined heat and drought stresses.

ROLE OF ZINC SULPHATE FOR MAIZE (ZEA MAYS L.) AND MUNGBEAN (VIGNA RADIATA L. WILCZEK) YIELD IMPROVEMENT: A REVIEW

Maize is an important cereal crop grown throughout the world for its grain and green fodder. It is used as food for human and feed for animals. Maize is a crop that is most susceptible to Zinc deficiency. The selection of high yielding cultivars and chemical fertilizer use is of high purity under intensive cropping system. Mungbean is being used as food and protein supplements. It is being cooked with vegetables, incorporated with bread and cakes, used as boiled or roasted in syrup. It is also generally used for vegetable dishes and sprout for egg rolls. The present review discussed about the use of zinc sulphate for the improvement of crop yield and quality of maize with mungbean in intercropping system. The present review revealed that plant uses Zinc in many of its vital processes such as protein synthesis, membrane’s structure and functions, expression of genes and tolerance against oxidative stress. The impacts of zinc deficiency cannot be ignored as it has very much serious implication regarding immune system and growth. The use of Zinc for improvement of grain yield of maize and munbean plays an important role. Hence, it should be used as micro nutrient for improving output of maize and mungbean in sole and intercropping growing patterns.

Yield Gains in Extra‐Early Maize Cultivars of Three Breeding Eras under Multiple Environments

Core IdeasThe study determined genetic improvement in grain yield of the cultivars during the breeding eras, investigated trait associations, and identified high‐yielding and stable cultivars across multiple‐stress and non‐stress environments.The study revealed an annual genetic gain of 2.72 and 2.28% for the cultivars under multiple‐stress and non‐stress environments.Cultivars 2004 TZEE‐Y Pop STR C4, TZEE‐W Pop STR QPM C0, TZEE‐W Pop STR BC2 C0 of era 2 and TZEE‐W STR 107 BC1, TZEE‐W Pop STR C5, and 2012 TZEE‐Y DT STR C5 of era 3 were the highest yielding and stable across multiple‐stress environments while 98 Syn EE‐W from era 1, FERKE TZEE‐W STR, TZEE‐W Pop STR C3, TZEE‐Y Pop STR QPM C0 from era 2, and TZEE‐W Pop STR C5, 2009 TZEE‐OR2 STR QPM, 2009 TZEE‐W STR, TZEE‐Y STR 106, TZEE‐W DT C0 STR C5 from era 3 were the most outstanding across non‐stress environments.We conclude that substantial progress has been made in breeding for multiple‐stress tolerant extra‐early maize cultivars in West and central Africa.Availability of extra‐early maize cultivars has facilitated the expansion of maize production into savannas of West and Central Africa (WCA). Fifty‐six extra‐early maize cultivars of three breeding eras;1995 to 2000, 2001 to 2006, and 2007 to 2012 were evaluated for 2 yr under 24 multiple‐stress and 28 non‐stress environments in WCA. Objectives of the study were to determine genetic improvement in grain yield of cultivars developed during the breeding eras, and identify high‐yielding and s multiple‐stress and non‐stress environments. Yield gains from era 1 to era 3 under multiple stresses was associated with increased days to anthesis, reduced stalk lodging, and improved husk cover. Cultivars 2004 TZEE‐Y Pop STR C4, TZEE‐W Pop STR QPM C0, and TZEE‐W Pop STR BC2C0of era 2; and TZEE‐W STR 107 BC1, TZEE‐W Pop STR C5, and 2012 TZEE‐Y DT STR C5of era 3 were high‐yielding and stable across multiple‐stress environments while 98 Syn EE‐W from era 1, FERKE TZEE‐W STR, TZEE‐W Pop STR C3, and TZEE‐Y Pop STR QPM C0from era 2, and TZEE‐W Pop STR C5, 2009 TZEE‐OR2STR QPM, 2009 TZEE‐W STR, TZEE‐Y STR 106, and TZEE‐W DT C0STR C5from era 3 were outstanding across non‐stress environments and should be tested extensively and commercialized. Considerable improvement has been made in breeding for multiple‐stress tolerant extra‐early maize cultivars.

Study on Genotypic Response and Correlation Analysis of the Yield and Yield Attributing Traits of Different Barley (Hordeum Vulgare) Genotypes

Barley, being a tremendous opportunities crop, we are far back regarding study, research and utilization. An experiment was conducted 2014-2015 to evaluate the barley genotypes for their yield attributing traits and correlation and causation. Eleven yield contributing traits viz., days to booting, heading and flowering; peduncle length, spike length, plant height, flag leaf area, flag leaf-1 area, thousand grain weight, biological weight and yield per hectare were recorded. High significant variation among genotypes was found for traits under study. Genotypes SBYT3-13#1115 (1960 kg), 14-SB-NAK-MR#17 (1760 kg) and AM POP#26 (1660 kg) were found to be superior for their per se performance based on grain yield per hectare, yield attributing and other quantitative traits. Thousand grains weight (0.333) had positively highest significant correlation with grain yield per hectare followed by spike length (0.310). Grain yield per hectare showed negative highly significant correlation with days to flowering (-0.796) followed by days to heading (-0.761) and days to booting (-0.663). Peduncle length (0.229), plant height (0.226), biological weight (0.181) and flag leaf area (0.032) were positively correlated with grain yield per hectare while flag leaf-1 area(-0.029) was negatively correlated. Thus, selection for genotypes with higher thousand grain weight and spike length accommodating earlier days to flowering, heading and booting is a prerequisite for attaining improvement in grain yield per hectare.Int J Appl Sci Biotechnol, Vol 4(4): 529-536

Diallel analysis in Barnyard millet (Echinochloa frumentaceae (Roxb.) Link) for quantitative and nutritional characters

With an objective to identify potential parents and crosses for quantitative and nutrient related characters and to understand the gene action for different traits for further improvement, an investigation was carried out in barnyard millet with diallel analysis involving five parents (CO 2, ACM 145, ACM 161, ACM 331 and ACM 332). Five parents and twenty crosses were evaluated for thirteen quantitative and four nutrient traits. The GCA, SCA and RCA variances were significant for almost all the characters suggesting the importance of both additive and non-additive gene action with pre-ponderance of non-additive gene action and significant reciprocal differences indicating the inter action between cytoplasm and the nuclear gene effects. However for single plant yield the gene action was additive as the ratio of GCA to SCA variances was more than one. In the evaluation of parents, taking per se performance and gca effects as criteria the parents in the order ACM 145, ACM 161 and CO 2 were identified as the best general combiners. The crosses ACM 145/CO 2 and ACM 145/ACM 161 were selected as superior over others based on per se performance, sca effects and heterosis percent together and are suggested for utilization in heterosis breeding. Non-significant sca effect was possessed by CO 2/ACM 145 and CO 2/ACM 161 and they could be used for improvement of grain yield by recombination breeding to isolate useful segregants

Expressing Arabidopsis thaliana V-ATPase subunit C in barley (Hordeum vulgare) improves plant performance under saline condition by enabling better osmotic adjustment.

Salinity is a global problem affecting agriculture that results in an estimated US$27 billion loss in revenue per year. Overexpression of vacuolar ATPase subunits has been shown to be beneficial in improving plant performance under saline conditions. Most studies, however, have not shown whether overexpression of genes encoding ATPase subunits results in improvements in grain yield, and have not investigated the physiological mechanisms behind the improvement in plant growth. In this study, we constitutively expressed Arabidopsis Vacuolar ATPase subunit C (AtVHA-C) in barley. Transgenic plants were assessed for agronomical and physiological characteristics, such as fresh and dry biomass, leaf pigment content, stomatal conductance, grain yield, and leaf Na+ and K+ concentration, when grown in either 0 or 300mM NaCl. When compared with non-transformed barley, AtVHA-C expressing barley lines had a smaller reduction in both biomass and grain yield under salinity stress. The transgenic lines accumulated Na+ and K+ in leaves for osmotic adjustment. This in turn saves energy consumed in the synthesis of organic osmolytes that otherwise would be needed for osmotic adjustment.

Potential for Marker-Assisted Simultaneous Improvement of Grain and Biomass Yield in Triticale

Triticale is a promising crop for agricultural biomass production but breeding has until now mainly focused on grain yield. Here, we evaluated the potential of marker-assisted simultaneous improvement of grain yield and biomass yield. To this end, we employed a large triticale doubled haploid population with 647 individuals derived from four families that were phenotyped for grain yield and biomass yield, as well as thousand-kernel weight, tiller density, and plant height in multi-environment field trials. Employing an association mapping approach, we identified quantitative trait loci (QTL) for all the five traits. The phenotypic correlation between grain yield and biomass yield was low, and we detected only one overlapping QTL suggesting different genetic architectures underlying both traits. Our results indicate that a marker-based selection for either grain yield or biomass yield does not adversely affect the other traits. Furthermore, an improvement of the multiplicative yield traits can to some extent also be achieved by selection for QTL identified for the component traits. Taken together, our results suggest that marker-assisted breeding can assist the establishment of dual-purpose triticale cultivars with high grain and biomass yield.

Manganese nutrition improves the productivity and grain biofortification of fine grain aromatic rice in conventional and conservation production systems

Manganese (Mn) deficiency is prevalent in rice-growing regions resulting in poor paddy yield and human health. In this study, role of Mn, applied through various methods, in improving the productivity and grain biofortification of fine grain aromatic rice was evaluated. Manganese was delivered as soil application (SA) (0.5 kg ha−1), foliar spray (FA) (0.02 M Mn), seed priming (SP) (0.1 M Mn) and seed coating (SC) (2 g Mn kg−1 seed) in conventional (puddled transplanted flooded rice) and conservation (direct seeded aerobic rice) production systems at two different sites (Faisalabad, Sheikhupura) in Punjab, Pakistan. Manganese application, through either method, improved the grain yield and grain Mn contents of fine grain aromatic rice grown in both production systems at both sites. However, Mn application as SC and FA was the most beneficial and cost effective in improving the productivity and grain biofortification in this regard. Overall, order of improvement in grain yield was SC (3.85 t ha−1) > FA (3.72 t ha−1) > SP (3.61 t ha−1) > SA (3.36 t ha−1). Maximum net benefits and benefit–cost ratio were obtained through Mn SC in flooded field at Faisalabad, which was followed by Mn SP in direct seeded aerobic rice at the same site. However, maximum marginal rate of return was noted with Mn SC in direct seeded aerobic rice at both sites. In crux, Mn nutrition improved the productivity and grain biofortification of fine grain aromatic rice grown in both conventional and conservation production systems. However, Mn application as seed treatment (SC or SP) was the most cost effective and economical.

Genetic Variability and Associations Between Grain Yield and Related Traits inAmaranthus cruentusandAmaranthus hypochondriacusGrown at Two Locations

AbstractFor plant genetic improvement, it is paramount to determine genetic components for the selection of desirable traits. EighteenAmaranthus cruentusand 11Amaranthus hypochondriacusgenotypes were evaluated at two locations in Nigeria differing in temperature/precipitation to determine the influence of environment on genetic gain. Genotype × environment was significant for all analysed morphological parameters and for grain yield, 1000 seed weight and no. of days to 50% flowering inA. cruentus.InA. hypochondriacusgenotype × environment was significant for plant height, leaf length and width, leaf area, inflorescence length, 1000 seed weight and grain yield. Higher genotypic coefficient of variability, heritability estimates, and genetic advance was observed for the traits at Abeokuta (more wet) than Ibadan (more dry) conditions. Grain yield had positive association with the traits at the two locations except the number of leaves and inflorescence length. Inflorescence length was positively associated with grain yield at Abeokuta and negatively associated at Ibadan. Path analysis indicated simultaneous improvement of grain yield with petiole length and leaf length at Abeokuta but with petiole length and leaf area at Ibadan. In general, the locations had potential for genetic improvement of traits of amaranth grain; therefore, selection criteria for improving grain yield should be considered with respect to environment.

English

Genetic diversity information is a resource for improvement in crop productivity and trait performance, however, there is scanty information on genetic diversity estimates in the maize landraces covering the major geographical regions of Africa. In the current study, the genetic diversity of 35 landraces originating from lowland, midaltitude and highland regions of Africa and held in the IITA Genetic Resource Center, Ibadan, Nigeria, were evaluated using morphological trait evaluation. The landraces were tested in non-stressed environments in Ghana by evaluation of 27 traits. A large within and between genetic variability was identified which increased from highland to lowland populations and was highest in the midaltitude population. Genetic similarity coefficients ranged from 0.00 to 0.80 with mean of 0.26±0.18 across the three populations, and 0.23±0.16, 0.29±0.18, and 0.38±0.25 in the midaltitude, lowland and highland populations, respectively. A total of 21 discriminant traits were identified from the principal components analysis. A UPGMA cluster analysis and PCA biplot produced four main clusters which provide a sound basis for exploitation of heterosis. Nine distant landraces were identified majority of which produced grain yield exceeding 5.0 Mg ha-1. In terms of improvement in grain yield, earliness and drought tolerance, TZm-14, TZm-41, TZm-242, TZm-37, TZm-1360, TZm-1376, TZm-1367, TZm-4, and TZm-270 would be useful. A large genetic diversity resides in the African maize landraces which could be conserved and exploited for maize improvement. Key words: Maize, genetic diversity, African maize landraces, morphological traits, cluster analysis, PCA.

Progress in genetic improvement of grain yield and related physiological traits of Chinese wheat in Henan Province

Wheat is one of the staple food crops worldwide and breeding for high yield wheat is critical to meet the need of increasing world population. To determine the factors that limit wheat yield potential in Henan province, China, 30 wheat cultivars that have been widely grown in Henan province since 1940s were evaluated for grain yield and related physiological traits. The results show that grain yield has been significantly increased since 1940s, with an annual genetic gain of 1.09%, and the increased yield after 1900s was attributed to the introduction of 1BL/1RS translocation. The significant yield increase mainly resulted from a significant increase in grain number per spike (GNPS), thousand kernel weight (TKW) and harvest index (HI), and a significant decrease in plant height due to utilization of semi-dwarfing genes. The genetic improvement of assimilate accumulation and translocation was mainly reflected by the improvement in post-anthesis assimilate accumulation (PoAAA) and post-anthesis transportion rate (PoATR) of pre-anthesis assimilates (PrAA), with genetic gains of 0.63% and 1.89%, respectively. The improvement of the PoAAA was closely related to an increase in net photosynthetic rates (Pn) of flag leaves at anthesis and 20days after anthesis, and leaf area index (LAI) at 20days after anthesis; whereas the improvement of the PoATR of the PrAA was closely associated with the improvement of accumulation and redistribution of the assimilates accumulated in stems and sheaths. As yield increased, the source-sink ratio significantly decreased, reflecting that the source has been gradually becoming a limiting factor to grain yield increase. Therefore, diverse strategies should be adopted to improve biomass (source) in future wheat breeding to meet the need of continuous increasing in wheat yield.

Line × tester analysis for estimating combining ability in F1 hybrids of bread wheat

The present research was conducted so as to estimate the combing ability effects of wheat genotypes for some quantitative traits in a set of line x tester crosses developed from five parents of bread wheat (Triticum aestivum L.), of which two were considered as lines (Anmol91 and Kiran-95) and three as testers (Imadad-05, SKD-1 and Khirman). The characters studied were tillers plant -1 , spike length, spikelets spike -1 , grains spike -1 , grain yield plant -1 and seed index. The experiment was carried out in a randomized complete block design with three replications at Southern Wheat Research Station, A.R.I. Tandojam during the rabi season, 2013-14. Results revealed that variances due to F1 hybrids, lines, testers and line x tester were significant for grain yield and almost for all other characters. Thus, showing these attributes were controlled by both additive and non-additive inheritance. Line ‘Kiran-95’ proved worthy general combiner for spikelets spike -1 , grain yield palnt -1 and seed index. Tester, Imdad-05 was identified as good general combiner for tillers plant -1 , spike length, spikelets spike -1 , grains spike -1 , and seed index, while tester Khirman proved promising for grain yield palnt -1 . The cross Khirman x Imdad-05 was found as potential hybrid for grain yield plant -1 , while other two crosses, namely, Anmol-91 x Khirman and Kiran-95 and Khirman also showed desirable specific combining ability for variety of characters. These parents and cross combinations may be used for varietal improvement through the simple selection in segregating generations to increase yield potential of bread wheat genotypes. This may lead in the fixation of both additive and non-additive components, while making improvement in grain yield and its attributes.

Zinc seed coating improves the growth, grain yield and grain biofortification of bread wheat

This study, comprising three independent experiments, was conducted to optimize the zinc (Zn) application through seed coating for improving the productivity and grain biofortification of wheat. Experiment 1 was conducted in petri plates, while experiment 2 was conducted in sand-filled pots to optimize the Zn seed coating using two sources (ZnSO4, ZnCl2) of Zn. In the first two experiments, seeds of two wheat cultivars Lasani-2008 and Faisalabad-2008 were coated with 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g Zn kg−1 seed using ZnSO4 and ZnCl2 as Zn sources. The results of experiment I revealed that seed coating with 1.25 and 1.50 g Zn kg−1 seed using both sources of Zn improved the seedling emergence. However, seed coated with 1.25 and 1.50 g Zn kg−1 seed using ZnSO4 was better regarding improvement in seedling growth and seedling dry weight. The results of the second experiment indicated that seed coated with 1.25 and 1.50 g Zn kg−1 seed using ZnSO4 improved the seedling emergence and seedling growth of tested wheat cultivars. However, seed coating beyond 1.5 g Zn kg−1 seed using either Zn source suppressed the seedling emergence. Third experiment was carried out in glass house in soil-filled earthen pots. Seeds of both wheat cultivars were coated with pre-optimized treatments (1.25, 1.50 g Zn kg−1 seed) using both Zn sources. Seed coating with all treatments of ZnSO4 and seed coating with 1.25 g Zn kg−1 seed using ZnCl2 improved the seedling emergence and yield-related traits of wheat cultivars. Seed coating with 1.25 g Zn kg−1 seed also improved the chlorophyll a and b contents. Maximum straw Zn contents, before and after anthesis, were recorded from seed coated with 1.5 g Zn kg−1 seed using either Zn source. Increase in grain yield from seed coating followed the sequence 1.25 g Zn kg−1 seed (ZnSO4) >1.25 g Zn kg−1 seed (ZnCl2) >1.5 g Zn kg−1 seed (ZnSO4). However, increase in grain Zn contents from seed coated was 1.5 g Zn kg−1 seed (ZnCl2) >1.25 and 1.5 g Zn kg−1 seed (ZnCl2, ZnSO4) >1.25 g Zn kg−1 seed (ZnSO4). Seed coating with Zn increased the grain Zn contents from 21 to 35 %, while 33–55 % improvement in grain yield was recorded. In conclusion, wheat seeds may be coated with 1.25 g Zn kg−1 seed using either source of Zn for improving the grain yield and grain Zn biofortification.

Progress in improving stem lodging resistance of Chinese wheat cultivars

Lodging is one of the most important factors that reduce wheat grain yields. To improve lodging resistance, increasing the strength of wheat stems has been an important breeding objective. To assess the rate of genetic improvement of the character, 30 wheat accessions, varying from landraces to cultivars that have been widely grown in Henan Province, China during the last 70 years, were tested for several parameters of lodging resistance in a two-year experiment. Stem strength, morphological and anatomical traits, and chemical composition were measured. The results showed that stem strength, both at anthesis and 25 days thereafter, has increased significantly during this period with average annual genetic gains of 1.07 and 0.87 %, respectively. Compared with older wheat cultivars, stem walls of modern cultivars are thicker, and the lignin content is higher. Grain yield has been significantly increased over the last 70 years, and the results of multiple regression analysis indicated that the genetic improvement of grain yield was associated with the increase in stem strength and the decrease in plant height.

De novo balanced complex chromosome rearrangements involving chromosomes 1B and 3B of wheat and 1R of rye.

Complex chromosome rearrangements (CCRs) are defined as structural abnormalities involving more than two chromosome breaks, coupled with exchanges of chromosomal segments. Information on CCRs in plants is limited. In the present study, a plant (26-4) harboring translocation chromosomes 1RS.1BL and 4RS.4DL was selected from a double monosomic (1R and 4R) addition line, which was derived from the hybrid between wheat cultivar MY11 and a Chinese local rye variety. The genome of the plant with double alien translocation chromosomes in the monosomic form showed more instability than that harboring a single translocation. The CCRs involving chromosomes 1RS.1BL and 3B, which were generated de novo in this plant, showed double monosomic translocation chromosomes. A new CCR line with balanced reciprocal translocations 1RS.3BL and 3BS.1BL was developed, which presented normal morphological traits of wheat and underwent rapid growth in the field. A new 1RS.1BL translocation line was also selected from the progeny of plant 26-4. The CCRs and simple 1RS.1BL translocation lines showed significant improvement in grain yield, number of spikes per square meter, kernel number per spike, and resistance to stripe rust and powdery mildew. The CCR line exhibited better agronomic traits and adult plant resistance in the field than its sister line, which harbored a simple 1RS.1BL translocation. The CCRs are remarkable genetic resources for crop improvement.

Grain yield performance and flowering synchrony of CIMMYT’s tropical maize (Zea mays L.) parental inbred lines and single crosses

AbstractMaize production constraints in sub-Saharan Africa (SSA) are being addressed by CIMMYT and partners through an array of projects, focusing on developing and evaluating parental inbred lines and single-crosses as well as formulating, evaluating and releasing high-yielding and stress resilient hybrids adapted to different agro-ecologies. The objectives of the present study were to (1) evaluate the grain yield performance of parental elite inbred lines developed over the years, and single crosses; and (2) ascertain the flowering synchrony among inbred lines and single-cross hybrid parents. Parental inbred lines and single-crosses were evaluated at seven locations in two countries in 2014. Combined analysis of variance revealed differences (P < 0.01) among genotypes for grain yield (GY) and among different years/era of release of the inbred lines. The improvement in GY of inbred lines was estimated to be 1.4 % per year. Under irrigated conditions GY of some single-cross hybrids was over 16 t ha−1. Some single-cross and inbred line parents showed acceptable flowering synchrony, good producibility, and stable performance across testing environments, suggesting that these have high potential for seed production. Further research is needed to determine the physiological and morphological characteristics that contributed to the GY improvement in the parental inbred lines. Information generated from this study will enhance the use of CIMMYT’s tropical mid-altitude parental germplasm by breeders working in both private and public breeding programs for developing and deploying high-yielding maize hybrids for the benefit of small-scale farmers in SSA.

Genotype × Environment Interaction for Plant Density Response in Maize (Zea mays L.)

Increased adaptation to high plant density has been an important factor in improvements in grain yield in maize (Zea mays L.). Despite extensive public literature on variation and improvement in plant density response among maize varieties, much less public information is available on effects of environment and genotype × environment interactions (G × E) on plant density response for grain yield in maize. The present study was conducted to quantify environment effects and G × E effects on plant density response for maize grain yield. A set of 57 synthetic populations, synthetic × inbred line crosses, and synthetic × synthetic population crosses were evaluated across a five year period including 17 individual location–years. The data in this study were an unbalanced combination of multiple experiments that included 370 pedigree‐environment combinations with each containing at least four planting densities and two replications per environment in most cases. G × E accounted for 26% of total genetic variance (genetic variance plus G × E variance) in linear regression coefficients and 39% of variance in quadratic regression coefficients in the regression of grain yield on observed plant density. Variance in G × E for linear and quadratic regression coefficients resulted in variation in optimal densities among varieties being highly specific to individual environments. Average plant density responses varied widely among environments with average optimal plant densities ranging from 5.6 to 9.1 plants m–2.

Physiological, biochemical, and nutritional parameters of wheat treated with a fungicide and foliar fertilizer

Agronomic improvements in grain yield and quality of wheat crops could be obtained through the application of strategies, such as using foliar fungicides with fertilizers, to protect the leaves against pathogens and delay senescence during grain filling. However, few studies have reported the effect of these practices on wheat, although these treatments could represent a new method of increasing wheat production and profits. The objective of this study was to evaluate the effects of foliar fertilizer, applied alone or in combination with a fungicide, on the photochemical, biochemical, and nutritional parameters of wheat plants. The experiment was conducted under greenhouse conditions in a 2 × 3 factorial design (fungicide × foliar fertilizer) with four replications. The fungicide treatment used was azoxystrobin + cyproconazole + mineral oil; the control was left untreated. The foliar fertilizer was used at two different rates, and the control was not treated. Plants were sprayed at the GS29/GS30, GS45, and GS60 growth stages, and the plants were assessed ten days after the last spray. Chlorophyll a fluorescence, the photochemical efficiency of photosystem II (Fv/Fm), and electron transport rate were positively influenced by fertilizer. Fertilizer spraying significantly increased the leaf pigment content (chlorophylls a and b and carotenoids) and the nitrogen, phosphorus, and potassium concentration in flag leaves. When used in mixture, the fertilizer mitigates the stresses generated by the fungicide.

Trianthema portulacastrum and Cyperus rotundus Interference in Maize and Application of Allelopathic Crop Extracts for Their Effective Management1

ABSTRACT Horse purslane (Trianthema portulacastrum) and purple nutsedge (Cyperus rotundus) are two noxious C4 weeds of maize crop causing extensive yield losses. A two years field experiment was performed to estimate interference of T. portulacastrum and C. rotundus and to evaluate the role of allelopathic water extracts for effective weed management in maize. Five plant water extracts in ten binary combinations were foliar applied in triplicated randomized complete block design. Plots treated with commercial herbicide atrazine and weedy check (control), were also maintained for comparison. The highest density of both weed species was observed at 45 days after sowing (DAS) while weed dry biomass was higher at 60 DAS. Binary combination of sorghum-sunflower depicted greater suppression for weed density, dry biomass and persistence index (88-92% for T. portulacastrum and 65-81% for C. rotundus) as compared with weedy check. This treatment combination has also recorded an enhancement of 125% in crop resistance index, 84% in leaf area index and 41% in crop growth rate at 60-75 DAS thus, leading to 51% improvement in grain yield. Binary combination of sunflower-brassica returned maximum marginal net benefit, while sorghum-maize combination anticipated the peak value for marginal rate of return. Along with the effective weed management and higher yield, sorghum-sunflower documented the maximum net economic benefits among different plant extract combinations therefore, suggesting that exogenous application of sorghum-sunflower extract can be effectively used for controlling these weeds in maize field.