Aplicación de índices de tolerancia a la salinidad en plántulas de maíz

Los objetivos de este trabajo fueron: estudiar la aplicación de diferentes índices de tolerancia en caracteres de plántulas de maíz y evaluar su posible utilidad en la identificación de genotipos tolerantes a la salinidad. Se probaron 68 accesiones en dos ambientes (0 y 100m MClNa). Se midieron: largo de raíz, vástago y 3ª hoja y peso seco de raíz y de parte aérea. Se incluyeron 6 índices de tolerancia: índice de susceptibilidad al estrés (SSI), índice de tolerancia al estrés (STI), tolerancia al estrés (TOL), media geométrica de la productividad (GMP), productividad media (MP) e índice de estabilidad del rendimiento (YSI). Debido a la variación espacial relacionada con la concentración de sal en ambientes salinos, sería importante identificar genotipos estables frente a una gama amplia de suelos salinos. El biplot agrupó las accesiones, caracteres medidos en ambientes con y sin estrés e índices de tolerancia a sal, y demostró que los índices GMP, MP y STI fueron los que permitieron identificar los accesiones estables que se caracterizan por tener una alta expresión de estos caracteres en ambos ambientes. La aplicación del método de Componentes Principales (CP) identificó a los caracteres peso seco aéreo y largo de raíz como los de mayor contribución y ambos estuvieron asociados con dichos indices de tolerancia a salinidad. De esta manera, en este estudio las accesiones 1, 7, 30, 33, 43 y 45 fueron los más estables para los caracteres peso seco aéreo y largo de raíz. Entre ellos las accesiones 30 y 33 fueron superiores (pertenecientes a genotipos del Grupo A) porque mostraron los escores más altos sobre el eje CP1 pero sus aportes al CP2 fueron bastantes pequeños, para la mayoría de las variables.The aims of this research were: to study the application of different tolerance Indices in traits measured in maize seedlings and to assess their possible use in the identification of genotypes tolerant to salinity. Sixty eight accessions were tested in two environments (0 and 100mM NaCl). We recorded length for radicle, shoot and third leaf and dry weight for root and shoot. Six stress tolerance indices were included: stress susceptibility (SSI), stress tolerance index (STI), stress tolerance (TOL), geometric mean productivity (GMP), mean productivity (MP) and yield stability index (YSI. Saline environments show a great spatial variation in relation to the salt concentration, for this reason it would be important to identify genotypes with stable behavior in a variety of saline soils. The biplot method allowed clustering accessions, traits measured in stress and non stress environment and salt tolerance Indexes in a same graphic, and showed that GMP, MP and STI indexes were the ones who helped identify the high yielding (group A genotype) and stable accessions, characterized by a high expression of these characters in both environments. Principal Component method showed that shoot dry weight and root length had the highest contribution and both were associated with these above indices in salinity. Therefore, in this study the accessions: 1, 7, 30, 33, 43 and 45 had stable values for the traits root length and shoot dry weight. Within this group the 30 and 33 entries were superior (bellowing to Group A genotypes) because they had the highest PC1 scores but its PC2 scores were rather small for the most of the variables.Fil: Collado, Mónica B.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Aulicino, Mónica Beatriz. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arturi, Miguel Jacinto. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; ArgentinaFil: Molina, María del Carmen. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Instituto Fitotécnico de "Santa Catalina"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

An integrated molecular and conventional breeding scheme for enhancing genetic gain in maize in Africa

Open Access Journal; Published online: 06 Nov 2019Maize production in West and Central Africa (WCA) is constrained by a wide range of interacting stresses that keep productivity below potential yields. Among the many problems afflicting maize production in WCA, drought, foliar diseases, and parasitic weeds are the most critical. Several decades of efforts devoted to the genetic improvement of maize have resulted in remarkable genetic gain, leading to increased yields of maize on farmers’ fields. The revolution unfolding in the areas of genomics, bioinformatics, and phenomics is generating innovative tools, resources, and technologies for transforming crop breeding programs. It is envisaged that such tools will be integrated within maize breeding programs, thereby advancing these programs and addressing current and future challenges. Accordingly, the maize improvement program within International Institute of Tropical Agriculture (IITA) is undergoing a process of modernization through the introduction of innovative tools and new schemes that are expected to enhance genetic gains and impact on smallholder farmers in the region. Genomic tools enable genetic dissections of complex traits and promote an understanding of the physiological basis of key agronomic and nutritional quality traits. Marker-aided selection and genome-wide selection schemes are being implemented to accelerate genetic gain relating to yield, resilience, and nutritional quality. Therefore, strategies that effectively combine genotypic information with data from field phenotyping and laboratory-based analysis are currently being optimized. Molecular breeding, guided by methodically defined product profiles tailored to different agroecological zones and conditions of climate change, supported by state-of-the-art decision-making tools, is pivotal for the advancement of modern, genomics-aided maize improvement programs. Accelerated genetic gain, in turn, catalyzes a faster variety replacement rate. It is critical to forge and strengthen partnerships for enhancing the impacts of breeding products on farmers’ livelihood. IITA has well-established channels for delivering its research products/technologies to partner organizations for further testing, multiplication, and dissemination across various countries within the subregion. Capacity building of national agricultural research system (NARS) will facilitate the smooth transfer of technologies and best practices from IITA and its partners

Variability for growth and yield traits in single cross hybrids of maize (Zea mays L.)

Saabunud / Received 29.09.2021 ; Aktsepteeritud / Accepted 18.11.2021 ; Avaldatud veebis / Published online 18.11.2021 ; Vastutav autor / Corresponding author: Jiban Shrestha [email protected] single-cross hybrids of maize were evaluated in a randomized complete block design with three replications to investigate genetic variability and correlation among growth and yield traits at Khumaltar, Lalitpur, Nepal from March 13 to September 05, 2021. The hybrids were grouped into four clusters using Euclidean Average Linkage method. The cluster analysis showed the presence of genetic variability in the evaluated hybrids. The maximum distance between cluster centroids (194.28) was found between cluster 2 and cluster 4, indicating genetic dissimilarity. Grain yield had the maximum values of phenotypic coefficient of variation (PCV) (35.02%), followed by ear height (17.82%) and plant height (12.22%). Similarly, grain yield had the maximum values of genotypic coefficient of variation (GCV) (26.24%) followed by the number of kernel rows/cob (8.77%) and days to 50% silking (8.72%). Days to 50% silking and days to 50% tasseling had the highest values of heritability (86%) followed by cob diameter (84%) and no. of kernel rows in cob (68%). The leaf area per plant had the maximum values of genetic advance (GA) (74.87 cm2), followed by plant height (27.80 cm) and days to 50% silking (9.66 days). Similarly, the maximum values of genetic advance as percent of the mean (GAM) was found for grain yield (40.50%) followed by days to 50% silking (16.70%) and days to 50% tasseling (16.17%). The hybrids namely KWM-91 × KWM-93 produced the maximum values of grain yield (9.99 t ha–1) followed by KWM-93 × KWM-91 (9.63 t ha–1) and KWM-92 × KWM-93 (9.40 t ha–1). Grain yield showed positive and significant phenotypic correlation with days to 50% silking (r = 0.41), days to 50% tasseling (r = 0.39), plant height (r = 0.37), cob diameter (r = 0.49) and the number of kernel rows in cob (r = 0.38). Therefore, utilization of present genetic variability along with indirect selection for traits having significant association with grain yield, high heritability and GAM could aid in the improvement of maize productivity

Comparative performance of top cross and population cross hybrids in white Maize using a common tester

Improved maize populations and cross hybrids can be beneficial alternatives for commercial single-cross hybrids and good elite sources for diverse inbred lines. A set of 22 genotypes comprised 10 population crosses, 10 top crosses, and two check cultivars were evaluated at Cereal Crop Research Institute, Pirsabak-Nowshera, in a randomized complete block design with three replicates in 2014. This research's major aims were to determine the magnitude of heterosis and the degree of character association between yield and its attributes to select superior genotypes from the breeding material. Data were recorded on maturity, and yield associated traits, where significant genetic variability was observed among the genotypes for all the studied traits except days to silking. Mean values for the studied traits ranged from 44 to 52 days for tasseling, 48 to 54 days for anthesis, 49 to 54 days for silking, -1.33 to 2.33 for the anthesis-silking interval, 2.53 to 8.47 kg for fresh ear weight, 12 to 16 rows for kernel rows cob-1, 27.15 to 37.49 g for 100-kernel weight and 2830 to 7649 kg ha-1 for grain yield. Days to silking, anthesis silking interval, and kernel rows cob-1 showed low broad sense heritability (12.08%, 24.84%, 27.59%), days to tasseling, days to anthesis revealed moderate heritability (40.53%, 36.62%), while fresh ear, 100-kernel weight, and grain yield exhibited high broad-sense heritability (94.89%, 82.33%, 90%). Negative and significant heterotic values were observed for maturity traits, while heterotic values were positive and significant for yield-associated traits. Correlation analysis revealed that characters like fresh ear weight (r = 0.93) and 100-kernel weight (r = 0.50) manifested a strong positive and significant association with grain yield. Based on mean performance and grain yield, promising hybrids were 3008F3 x 2007-WC and 3008F3 x 2010.

Genomic insights into maize: Advanced techniques for analysing diversity and enhancing crop traits

Maize is the third important staple food crop grown globally. The demand for maize production has increased significantly due to its multiple uses, including food, feed and various industrial applications. As a result, the area under maize cultivation is expanding, driven by its lucrative market price. Being a highly adaptive crop, the development of high-yielding hybrids better suited to climate change will help bridge the gap between demand and supply. Maize is an allogamous crop, exhibiting greater genetic diversity compared to autogamous crops. Therefore, intensified exploration of maize genetic diversity and effective utilization of germplasm will enhance the maize breeding programs. However, the domestication of maize has led to a decline in genetic diversity and the loss of valuable alleles. Human selection has significantly altered the morphology of maize from its wild ancestor. CIMMYT currently maintains around 28000 maize accessions, including landraces and wild relatives. Genetic diversity can be analysed using D2 statistics and clustering methods, employing morphological, molecular, quantitative and qualitative data. Careful consideration is needed when selecting appropriate methods and software for such analyses based on available data. In recent years, SSR markers and SNPs have gained popularity for diversity analysis. Studying genetic diversity in maize is crucial for identifying novel traits and the introgression of these traits into new hybrids using advanced technology requires further attention

Evaluation of early maturing maize (zea mays L.) hybrids for multiple-stress tolerance.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Maize (Zea mays L.) is the most important cereal in Africa, but a number of constraints including biotic, abiotic and socio-economic factors affect its production. The abiotic factors such as drought, low nitrogen (N) and heat contribute to the low grain yield production, which creates a challenge that needs to be addressed by researchers. Thus, development and use of early maturing maize hybrids could help in stabilizing maize production. Early maturing maize hybrids help in reducing the growing period to escape some of the abiotic stresses that contains variability for high yield potential and adaptive traits. This study, therefore, was aimed at breeding and identifying early maturing maize hybrids cultivars that are tolerant to drought and low N stresses. Fifty early maturing maize hybrids including six commercial checks were evaluated under stress and non-stress environments during the 2016/17 maize growing season in South Africa. The objectives were (i) to estimate variance components, correlation and path coefficients among grain yield and secondary traits in early maturing maize hybrids across stress and non-stress environments and (ii) to evaluate genotype by environment interaction effects and stability for grain yield performance in early maturing maize hybrids across stress and non-stress environments. To estimate the variance components, correlation and path coefficients among grain yield and secondary traits in early maturing maize hybrids across stress and non-stress environments, quantitative traits data including grain yield and its secondary components were recorded. Statistical analyses revealed that the effect of genotype, environment and genotype by environment interaction were significant (P<0.01) for all the traits. Hybrids CZH16084, CZH16064 and CZH16095 under managed drought, low N and optimum environments, respectively, were identified as the outstanding genotypes for grain yield and recommended for further testing, release and registration. High magnitude of phenotypic and genotypic coefficient of variation as well as high heritability were recorded for each single environment for anthesis days, silking days, ear height and plant height, suggesting that those traits interacted with the environment. Grain yield was positively correlated with anthesis days and ear height, field weight, grain moisture at Potchefstroom while at Lutzville and Cedara had negative correlation with those traits, suggesting that the genotypes differed significantly for most of the phenotypic traits. Path coefficient analyses revealed that anthesis days and anthesis-silking interval had positive direct effects while silking days, plant height and ear per plant had a negative direct effect on grain yield in all the environments. These traits are recommended for effective selection to the improvement of maize grain yield. To evaluate genotype by environment interaction effects and stability for grain yield performance in early maturing maize hybrids across stress and non-stress environments, data collected from all environments which were Lutzville (managed drought), Potchefstroom (optimum), Cedara (optimum) and Cedara (low nitrogen) during the 2016/17 summer planting season, were subjected to ANOVA and GGE biplot analyses. Analysis of variance for individual environments showed that the genotype mean squares were significant at P<0.01. The ANOVA across environments showed that the genotype, environment and genotype by environment interaction mean squares were significant at P<0.01 for grain yield. From the GGE biplot analysis, the two principal components (PC1 and PC2) contributed 64.8% of the total variability due to genotypes plus genotype by environment interaction, with PC1 and PC2 accounting for 35.97% and 28.83%, respectively. The use of GGE biplot analyses provided a clear basis for determining the stability and performance of the 50 early maize hybrids and ranked them according to order. The best performing genotypes were G13 (CZH15448), G46 (CZH15574), G15 (local check 2), G33 (CZH16094), G7 (CZH16083), G20 (CZH16090) and G4 (CZH16089). The following hybrids were adapted to specific environments as follows: G26 (CZH16070), G34 (CZH16074), G9 (CZH15499) and G18(CZH16071) at Cedara (optimum) conditions; G46 (CZH15574), G40 (CZH16069) and G12 (CZH16080) excluding the checks G23 (local check 1) and G14 (SC301) at Potchefstroom (optimum); G22 (CZH16093), G6 (CZH15575), G49 (CZH16068) and G17 (CZH15600) excluding the check G15 (local check 2) at Cedara (low N) and G33 (CZH16094), G37 (CZH15184), G41 (CZH16082), G28 (CZH16076) and G8 (CZH16065) at Lutzville (managed drought). The GGE biplot analysis also identified nine stable and high yielding genotypes, which included G6 (CZH15575), G46 (CZH15574), G22 (CZH16093), G49 (CZH16068), G12 (CZH16080), G17 (CZH15600), G28 (CZH16076), G47 (CZH15452), and G8 (CZH16065). These genotypes will contribute to high maize yields and stable grain production in specific and across environments and are therefore, recommended for further testing and release

Estimation of Yield traits & Correlation in Zea Mays

Seven Zea mays genotypes were planted at two sites Aleppo and Edleb which are research centres belongs to the General Commission of Scientific Agricultural research GCSAR northern Syria. Yield traits (ear diameter, ear length, row number per ear-1, grain number per ear-1, thousand grain weight) were studied in order to estimate the variation between genotypes and to between sites and to select the best genotypes concerning studied yield&nbsp; traits to be applied in maize breeding programs.&nbsp;Results showed that all Studied genotypes of maize had significant differences in yield traits in which both genotypes (Z 263, Z 67) were remarkable in all studied traits like thousand grain weight (391.7, 390.7) g for each of them respectively. Results also revealed that most studied traits were significantly superior in Aleppo comparing to Edleb. Results of correlation showed positively and significantly relations between all studied traits except between each of row number per ear-1 and grain number per ear-1 with thousand grain weight

Analysis of Chlorophyll Content and Its Correlation with Yield Attributing Traits on Early Varieties of Maize (Zea Mays L.)

Chlorophyll has direct roles on photosynthesis and hence closely relates to capacity for photosynthesis, development and yield of crops. With object to explore the roles of chlorophyll content and its relation with other yield attributing traits a field research was conducted using fourteen early genotypes of maize in RCBD design with three replications. Observations were made for Soil Plant Analysis Development (SPAD) reading, ear weight, number of kernel row/ear, number of kernel/row, five hundred kernel weight and grain yield/hectare and these traits were analyzed using Analysis of Variance (ANOVA) and correlation coefficient analysis. SPAD reading showed a non-significant variation among the genotypes while it revealed significant correlation with no. of kernel/row, grain yield/hectare and highly significant correlation with no. of kernel row/ear and ear weight which are the most yield determinative traits. For the trait grain yield/ha followed by number of kernel row/ear genotype ARUN-1EV has been found comparatively superior to ARUN-2 (standard check). Grain Yield/hectare was highly heritable (&gt;0.6) while no. of kernel / row, SPAD reading, ear weight, number of kernel row/ear were moderately heritable (0.3-0.6). Correlation analysis and ANOVA revealed ARUN-1EV, comparatively superior to ARUN-2 (standard check), had higher SPAD reading than mean SPAD reading with significant correlation with no. of kernel/row, no. of kernel row/ear, ear weight and grain yield/ha which are all yield determinative traits . This showed positive and significant effect of chlorophyll content in grain yield of the maize.Journal of Maize Research and Development (2015) 1(1):134-145DOI: http://dx.doi.org/10.5281/zenodo.3426

Varietal evaluation of promising maize genotypes in mid hills of Nepal

The varietal evaluation of hybrid maize (Zea mays L.) genotypes with desired performance is one of the main objectives of maize breeding program. Fourteen hybrid maize genotypes were evaluated for 17 quantitative and nine qualitative traits in randomized complete block design with three replications at Sundarbazar, Lamjung, Nepal during May to September, 2019. The major objective was to identify superior genotypes based on genotypic and phenotypic variability, heritability, genetic advance, and correlation between grain yield and yield associated traits. We observed significant differences for 17 quantitative traits among the tested genotypes. Large variation was observed for grain yield among genotypes. Genotype RL-24-0/ RL-111 had the lowest yield (5.53 mt/ha) and Pioneer had the highest yield (11.98 mt/ha) whereas check variety Rampur Hybrid-10 yielded of 8.23 mt/ha. Grain yield showed highly significant positive correlations with stem girth (r= 0.67) and number of ears (r=0.6), but significant negative correlation with anthesis-silking interval (r= -0.55). The dendrogram grouped 14 genotypes into four clusters. Cluster I incorporated the highest number (five) of genotypes, which also had highest cluster mean (average yield of ~10 mt/ha) for grain yield. Traits namely test weight, ear aspect, anthesis-silking interval, number of ears, and tassel branching had high genotypic and phenotypic coefficient of variations, and heritability along with high genetic advances, indicating that these traits can be considered for maize breeding program