Validation of Maize (Zea mays L.) Hybrids for the Study on Variability, Trait Association, and Path Analysis

The present investigation was conducted with nine genotypes in randomized block design during Rabi, 2019-20 at the instructional-cum-research farm, Assam Agricultural University, Jorhat. All the characters exhibited significant genotypic mean squares in analysis of variance except anthesis silking interval, kernel rows per ear and 100 kernel weights. High heritability coupled with high genetic advance was observed for the traits plant height, ear height, ears per plant, ear length, kernels per row, chlorophyll content, leaf area index 60 days after sowing (LAI 60 DAS), LAI 90 DAS, harvest index, grain yield per plant and grain yield per hectare. Significant genetic association of grain yield per plant and grain yield per hectare with days to 50% pollen shed, days to 50% silk, days to 100% dry husk, ear height, kernels per row, LAI 60DAS and LAI 90 DAS. Genotypic path analysis revealed that the characters, days to 50% silk, days to 100% dry husk, plant height, ears per plant, ear diameter and harvest index had the highest positive direct effects on grain yield per hectare while days to 50% pollen shed and ear height had the highest negative direct effect on grain yield per hectare. The hybrids namely, PAC 751, CP 333 and PAC 751 ELITE, were found to be the three best hybrids to possess a high estimate of desirable traits such as days to 50% pollen shed, days to 50% silk, days to 100% dry husk, plant height, ear height, ear diameter, leaf area index at 60 days after sowing, lea area index at 90 days after sowing, grain yield per plant and grain yield per hectare.

Hazelnut floral phenology in southern Ontario

Hazelnut (Corylus avellana) is a monoecious, dichogamous plant species that flowers in winter and early spring. In traditional hazelnut growing regions, hazelnut cultivars generally express protandry where the male flowers bloom before the female flowers. Nut set requires that compatible pollen be shed when the stigmas of the main cultivar are receptive. In this study, the floral phenology and date of leaf budbreak of five selections and 19 hazelnut cultivars from Europe and North America were observed over four years in southern Ontario, and results were compared with cumulative growing degree days. In the continental climate of southern Ontario, most cultivars showed protogyny. Flowering dates varied over the years with pollination occurring in a period of 2 - 3 weeks in early spring. These cultivars were classified into early, mid, and late blooming types. A growing degree day model was a better tool than average daily temperatures to predict the flowering dates of catkins and female flowers. Averaged over years, most of the cultivars in this study have a female bloom that is likely too early for the pollen shed by most of the other cultivars. This would likely impact yields in a commercial orchard. However, ‘Jefferson’, ‘Gene’, and ‘Epsilon’ have late females that are receptive when other cultivars are shedding pollen.

GENETIC DIVERGENCE AMONG MAIZE (ZEA MAYS L.) INBRED LINES USING MORPHOMETRIC MARKERS

Genetic divergence study is imperative in breeding programmes in order to select distant parents. Forty maize inbred lines were assessed using morphometric markers to identify the potential inbred lines for yield and its component traits. The inbred lines were raised in α-RBD design replicated twice during kharif 2019. The morphological diversity analysis was done as per the standard statistical procedures using Mahalanobis D2-statistic. Analysis of variance revealed significant mean sum of squares due to genotypes for all the traits suggesting ample amount of genetic variability present among them. Moderate PCV, GCV and high heritability coupled with moderate genetic advance was observed for grain yield per plant, plant and cob placement height. Grain yield per plant exhibited significant positive correlation with all the traits except days to 50 per cent pollen shed and silking. Path analysis revealed high direct effects of days to 50 per cent pollen shed, harvest index, grains per row and 100 grain-weight on grain yield per plant therefore these morphometric traits would be the best selection indices to select high yielding genotypes. D2-statistics grouped 40 maize genotypes into three clusters. Cluster III has the highest cluster mean values for all the traits.Seven genotypes viz., 4186-4-05-1-1, LM-14, BAJIM-08-27, BIOM 10, LQPM24×1114-5, 9180-2, LDH 5(Vivek-21-1) were superior over the best check on the basis of mean performance and disease resistance and were diverse therefore, could be used in maize improvement program.

Detection of the Progression of Anthesis in Field-Grown Maize Tassels: A Case Study

The tassel of the maize plant is responsible for the production and dispersal of pollen for subsequent capture by the silk (stigma) and fertilization of the ovules. Both the amount and timing of pollen shed are physiological traits that impact the production of a hybrid seed. This study describes an automated end-to-end pipeline that combines deep learning and image processing approaches to extract tassel flowering patterns from time-lapse camera images of plants grown under field conditions. Inbred lines from the SAM and NAM diversity panels were grown at the Curtiss farm at Iowa State University, Ames, IA, during the summer of 2016. Using a set of around 500 pole-mounted cameras installed in the field, images of plants were captured every 10 minutes of daylight hours over a three-week period. Extracting data from imaging performed under field conditions is challenging due to variabilities in weather, illumination, and the morphological diversity of tassels. To address these issues, deep learning algorithms were used for tassel detection, classification, and segmentation. Image processing approaches were then used to crop the main spike of the tassel to track reproductive development. The results demonstrated that deep learning with well-labeled data is a powerful tool for detecting, classifying, and segmenting tassels. Our sequential workflow exhibited the following metrics: mAP for tassel detection was 0.91, F1 score obtained for tassel classification was 0.93, and accuracy of semantic segmentation in creating a binary image from the RGB tassel images was 0.95. This workflow was used to determine spatiotemporal variations in the thickness of the main spike—which serves as a proxy for anthesis progression.

Association studies between grain yield and agronomic traits of a MARS maize (Zea mays L.) population under drought and non-stress condition

<p>The study aimed at examining the associations between yield and other traits under drought stress and non-stress conditions. A total of 150 MARS testcrosses were evaluated under both conditions at the International Institute of Tropical Agriculture substation for two years under during the dry season. Genotypic and phenotypic correlation, multiple stepwise regression and path co-efficient analyses were carried out to examine the relationship among the traits under both environments. Results showed anthesis-silking interval, days to silking, husk cover and plant aspect were significantly associated with yield under drought condition at both genotypic and phenotypic levels. Yield was positively correlated with plant and ear height but had a negative correlation with plant and ear aspect at both levels under well-watered condition. Regression analysis showed that ears per plant, plant aspect, ear aspect, days to silking, leaf death and plant height had a direct effect on yield, contributing a total of 71.1 % of observed variation under drought, while ears per plant, ear aspect, plant aspect, days to pollen shed, days to silking and plant height contributed about 31.42 % to yield under well-watered conditions. The study concluded that these traits be used as selection criteria as it will aid improvement of maize yield.</p>

Flowering and yield of eastern filbert blight resistant hazelnut cultivars in southwestern British Columbia

Trees of six recently released hazelnut (Corylus avellana) cultivars (Eta, Gamma, Jefferson, Sacajawea, Theta, and Yamhill) were grown at five locations in southwestern British Columbia to evaluate female receptivity and pollen shed timing, disease resistance, and nut yield. The overlap of female receptivity and pollen shed of mating-compatible cultivars equaled or exceeded that reported elsewhere. Following 4–6 yr of field growth without fungicides at sites adjoining eastern filbert blight (EFB)-infected orchards, EFB symptoms were absent from four cultivars (Eta, Gamma, Theta, Yamhill), negligible on Jefferson, and substantial on Sacajawea. Two additional potential diseases, Phomopsis sp. and Phytophthora sp., were observed on several trees at multiple farms. Yields varied by cultivar and farm, averaging 2.9 kg per tree of sixth-leaf Jefferson and 1.0 kg per tree of fourth-leaf Yamhill; the highest yield per tree observed was 9.3 kg for fifth-leaf Jefferson. These data, the first describing flowering and yield of these cultivars from operational orchards and the only such data from British Columbia, demonstrate the potential for new hazelnut cultivars even where pressure from eastern filbert blight is high. Also revealed are two potential emergent diseases for which growers need to remain vigilant.

Corn Tassel: A New Source of Phytochemicals and Antioxidant Potential for Value-Added Product Development in the Agro-Industry

Corn tassel is a byproduct from hybrid corn seed production. It is also a new source of phytochemicals, including compounds with antioxidant activity. The aim of this study was to evaluate the phytochemical content and antioxidant potential of different corn tassel development stages. A 4 × 8 factorial experiment consisting of four tassel development stages and eight commercial corn varieties was carried out with a randomized complete block design with three replications. Data were collected for tassel weight, concentration and yield of total phenolics, total anthocyanin concentration, total carotenoid concentration, and antioxidant activity, as determined by the 2,2-diphenyl-1-picrylhydrazyl(DPPH•) radical scavenging assay and Trolox equivalent antioxidant capacity(TEAC) assays. Corn varieties and tassel developmental stages showed significant variations (p ≤ 0.01) in all parameters. P4546 presented the best variety for the total phenolic content (15.8 mg GAE/g DW sample), whereas Hibrix3 had the highest phenolic yield (6.78 kg GAE/ha). KGW1, a purple waxy variety, had the highest anthocyanin content (1528.0 µg CGE/g DW sample), anthocyanin yield (753.0 g CGE/ha), carotenoid content (74.9 µg/g DW sample), and carotenoid yield (53.7 g/ha). P4546 had the highest antioxidant activity: 92.4% for DPPH• and 76.1 µmol TE/g DW sample for the TEAC assay, respectively. The most appropriate time for tassel harvest to ensure the production of phytochemicals with high antioxidant activity should be from the 1st day of pollen shed until 50% of pollen shed. Phytochemicals and antioxidants that are extracted from corn tassel can be used as a functional food supplement, as natural pharmaceuticals, and in cosmetic products.

Corn Tassel: A New Source of Phytochemicals and Antioxidants Potential for Value-added Products Development in Agro-industry

Corn tassel is a by-product from hybrid corn seed production and a new source of phytochemicals including compounds with antioxidant activity. Four tassel development stages were evaluated in eight commercial corn varieties. Corn varieties and tassel developmental stages showed significant variations (P0.01) for all parameters. Total phenolic content and antioxidant activity were highest in field corn. KGW1, a purple waxy variety, had the highest anthocyanin content and carotenoid content at tassel development stages at 50% and 75% of pollen shed, whereas the tassel developmental stages at the 1st day of pollen shed and 50% of pollen shed had the highest of anthocyanin yield and carotenoid yield. The most suitable time for tassel harvest should be between the 1st day of pollen shed to 50% of pollen shed. Phytochemicals and antioxidants that are extracted from corn tassel can be used as a functional food supplement, natural pharmaceuticals and cosmetic products.

Respuestas correlacionadas para el rendimiento en la selección de híbridos de maices precoces subtropicales.

With the aim of designing selection criteria to identify the described genotypes with short vegetative period and longer grain-filling period without increasing the total growing cycle of the genotype. The information generated during 1995 at six locations in the subtropical region of Mexico was used. A serie of six experiments, integrated with a group of subtropical hybrids derived from a diallel between a group of elite tropical and subtropical inbred lines from CIMMYT, were evaluated in collaboration with INIFAP and the seed industry. In the combined analysis of six environments, early hybrids with a grain yield of 8.0 t/ha were identified; those hybrids were 14 days earlier to reach physiological maturity than the control check which yielded 7.4 t/ha. The genotypes with lower yields showed a short grain filling period compared to the vegetative period. Correlations among yield vs. days to physiological maturity, grain-filling period and the index calculated by dividing the between grain-filling /days to physiological maturity were 0.47, 0.53 and 0.41, respectively. This indicate an intermediate association between these traits; also, a high correlation values were observed between grain yield vs. plant and ear hight. The correlation between yield vs. days to silk and days to pollen shed were not significant. General combining ability (GCA) and specific combining ability (SCA) effects were significant for yield, days to silk and grain-filling period. Sufficient variation was observed to allow for the selection of genotypes with short vegetative periods and longer grain filling periods. The effects of GCA and SCA for grain-filling period suggest that this trait is an important criterion to select parents for producing short season hybrids.

Flowering Phenology of Eastern Filbert Blight-resistant Hazelnut Accessions in New Jersey

Hazelnuts (Corylus sp.) are monoecious and wind-pollinated with reproduction limited by a sporophytic self-incompatibility system. They flower during the winter and are dichogamous with the dates of flowering ranging from December to March in New Jersey depending on the genotype, geographic location, and year. Successful, consistent nut production depends on both genetic compatibility and the appropriate timing of flowering between pollinizing and nut-producing cultivars. While the disease eastern filbert blight (EFB), caused by Anisogramma anomala, has severely limited past hazelnut production in the eastern United States, resistant and tolerant genotypes are now available for testing. However, little is known of their flowering phenology in this region. In this study, the flower and budbreak phenology of 19 different EFB-resistant and EFB-tolerant hazelnut accessions was evaluated over 4 years, and the results compared with air temperature data collected during bloom. Results showed that the accessions followed a similar progression of bloom each year (both staminate and pistillate flowers), which allowed their placement into early-, mid-, and late-flowering groups. However, the date of bloom and duration of bloom, especially for pollen shed, differed each year, largely corresponding to average air temperature trends. Confirming previous reports from other cold regions, it was shown that consistently colder average temperatures delayed bloom until later in the winter, which then led to a compressed period of flowering once temperatures warmed. In contrast, relatively warm temperatures over the season led to earlier flowering as well as a significant lengthening of the duration of bloom, similar to responses reported in Mediterranean climates. Our study documents hazelnut flowering phenology under New Jersey’s variable winter climate, and the results provide a benchmark for selecting suitable pollenizers and breeding parents for future nut production, flowering research, and/or genetic improvement in this region.