Heterotic groups are necessary for high vigor in hybrid rice. However, hybrids produced from crosses between parents from different rice subspecies (i.e., Indica × Japonica) have extensive incompatibility issues exhibited by low seed sets. The study objectives were to evaluate the heterosis in grain yield and yield-related traits between hybrids produced from low and high parental genetic distances (PGDs) and demonstrate the heterotic group approach in rice. From PGDs, eight and three hybrids were assigned to the low and high PGD hybrid groups, respectively. Neighbor-joining clustering and model-based population structure analyses classified the hybrid parents into four heterotic groups, with the low and high PGD hybrid groups found consisting of intra-subpopulation and inter-subpopulation crosses, respectively. Replicated yield trials conducted at Beaumont, Texas, transpired in 2019 and 2020. The hybrids exhibited normal seed sets, with at least one of each hybrid’s parents determined to possess the wide compatibility S5n allele necessary for normal seed sets in wide crosses. Trait and standard heterosis values estimates included the number of days to heading, plant height, tiller density, and grain yield. Higher trait values and heterosis for tiller density and grain yield occurred in the high than the low PGD hybrid group, especially in the inter-subpopulation crosses with indica rice. PGD had consistent positive correlations with heterosis for grain yield (r = 0.41 to 0.60) and tiller density (0.28 to 0.36) in both years. PGDs aid in determining highly heterotic cross combinations for tiller density and grain yield and in forming heterotic groups. Heterotic grouping is advisable through cluster and structure analyses of genome-wide markers instead of identifying genetically-distant crosses based on pedigree information.

Keywords: Heterosis, heterotic group, hybrid, rice, yield, Oryza sativa L.

Key findings: Rice hybrids from wide-compatible parents in japonica × indica crosses were studied. Heterosis was higher in hybrids produced from parents with extreme genetic distances (PGDs). PGDs help form heterotic groups and in selecting highly heterotic crosses.

The climate is continuously changing, consequently increasing the drought-affected areas. As such, it challenges breeders to develop adaptive and drought-tolerant sunflower (Helianthus annuus L.) cultivars through evaluation and inducing genes tolerant to drought. Hence, the recent study aimed to assess the sunflower hybrids during 2019–2020 under well-watered and stressed conditions in a splitplot design with four replications at the Sindh Agriculture University, Tandojam, Pakistan. The observed data determined heterotic effects among 15 F₁ hybrids for days to 75% flowering, days to 75% maturity, stem diameter, head diameter, biological yield plant^-1, seeds head^-1, seed index, and seed yield plant^-1. The mean squares due to genotypes, treatments, and genotype by treatment were significant for all the traits, which exhibited that genotypes performed significantly across the environments for the above-cited traits. The F₁ hybrids, such as, Mehran × Pehawar-93, gave maximum negative heterotic effects for phonological traits which will benefit the development of short-duration sunflower hybrids. Further, F₁ hybrids like Thatta × UC-666 displayed higher heterotic effects for head diameter, stem diameter, number of seeds plant^-1, seed index, and biological plant^-1 and PSF-025 × B2 and HO.1 × B2 gave higher heterotic effects for the number of seeds head^-1 and seed yield plant^-1 under stress environment.

Keywords: Sunflower (Helianthus annuus L.), split-plot design, well-watered and stressed-conditions, heterosis, heterobeltiosis, yield-related traits

Key findings: Four sunflower (Helianthus annuus L.) hybrids, Mehran × Peshawar-93, Thatta × UC-666, PSF 025 × B-2, and HO-1 × B-2 showed promising that could benefit future breeding programs for hybrid crop development.

Accurate data and relevant insights on parental corn inbred lines’ and hybrids’ genetic purity and diversity are essential for hybrid development and seed production. Here, the genetic purity and diversity of 19 parental yellow corn inbred lines were assessed using SSR markers. A total of 91 SSR markers were utilized, of which 61 were highly polymorphic and had high polymorphism information content value (PIC = 0.379). Genetic purity and diversity parameters were calculated from the generated SSR marker data. Observed pairwise genetic distances ranging from 0.257 to 0.808 implied high genetic dissimilarities among the accessions. Cluster analysis separated the parental lines into three distinct subclusters, which can potentially be a basis for generating heterotic groupings among the parental lines. Eight (8) out of the 19 parental lines showed considerable residual heterozygosity of ≤10%. Inbred line CML 431 displayed complete homozygosity across all 61 SSR markers. Inbred lines that have residual heterozygosity of >15% need purification through further breeding and selection. Out of the resultant F1 hybrids analyzed, only four (4) showed genetic impurity of ≤10%. It may be attributed to the intrinsic genetic impurity of parental line CML 452 (21.67%). In contrast, hybrids generated from two genetically pure parents (e.g., CML 431 and CML 575) showed low to no off-types. Overall, genetic purity and diversity determination of promising parental lines can be valuable for future yellow corn breeding programs in the Philippines.

Keywords: corn, SSR markers, genetic purity, genetic diversity, hybrid development

Key findings: The genotyping strategy employed in the study proved cost-efficient and effective in terms of identifying whether the corn genotypes are genetically pure or contaminated. Corn breeders can utilize the generated clusters as a basis for designing cross-combinations. Finally, the achieved set of SSR markers determined can help further assess successful hybridization among the corn genotypes used in this study.

In light of the scarcity of irrigation water, extreme wastage of water, saline soils, and the dominance of traditional water management methods, the presented research transpired in 2020 in the Directorate of Agriculture, ALHashimiya area, Hilla City, Iraq. The latest study aimed to investigate the effects of subsurface drip irrigation system (SDIS) and flood irrigation system (FIS), with three drip irrigation distances of 18, 20, and 22 cm on two rice (Oryza sativa L.) cultivars, i.e., ‘Tarm Hashemi’ (TH) and ‘Daillman Mazandarani’ (DM). The irrigation systems (SDIS and FIS) significantly impacted the growth and productivity traits of the rice crop. The SDIS ensures the addition of an appropriate amount of water to the plants by keeping wet the root zone without wasting water compared with the flood irrigation system. The interaction of rice cultivar Tarm Hashemi, SDIS, and drip irrigation distance (DID of 18 cm) resulted in the best performance for root growth traits, i.e., root length and root fresh and dry weight (17.66 cm and 1.80 and 0.85 g, respectively). It also provided the highest plant vigor index (PVI), biological, and grain yield (71.15 cm, 1,747.23, and 608.26 g.m^-2, respectively). Cultivar Tarm Hashemi proved superior to cultivar Daillman Mazandarani in managing the morpho-yield traits. The subsurface drip irrigation system during the growing season helped increase the productivity of the rice crop compared with the traditional irrigation system. Compared with FIS, the SDIS not only improved and enhanced the growth and grain yield, but also saved abundant water and nutrients.

Keywords: Rice (Oryza sativa L.), cultivars Tarm Hashemi (TH) and Daillman Mazandarani (DM), subsurface drip irrigation system (SDIS), flood irrigation system (FIS), drip irrigation distance (DID)

Key findings: The study focused on achieving the best growth results for the rice (Oryza sativa L.) crop, with the highest productivity emerging with the subsurface drip irrigation system and the planting distance of 18 cm. The reaction of rice cultivar Tarm Hashemi (TH) to the subsurface drip irrigation system gave the highest studied characteristics compared with the rice cultivar Daillman Mazandarani (DM).

Potassium (K) performs multiple essential functions in the plant, including enzyme activation and osmotic regulation. Citrus fruit quality gains considerable influence from potassium (K) fertilizer rate, application method, and sources used. The conducted field experiment assessed the impact and response of different levels of K applications on the quality and yield parameters of citrus fruit, determining a suitable time, stage, and K fertilizer dose for citrus trees. Comparing traditional K fertilizer, i.e., sulfate of potash (SOP), with new-generation potassium (NG-K) employed the use of foliar and soil (basal) applications. Treatments included (i) T1: Control (0 NPK), (ii) T2: Recommended NP and without K, (iii) T3: 500 g K as sulfate of potash (SOP) (basal), (iv) T4: New generation K (NG-K) fertilizer @1.5% (foliar), and (v) T5: 400 g NG-K fertilizer (basal). Observations revealed that citrus trees responded positively in growth characteristics, including fruit quality and physiological attributes, under both foliar and basal K fertilizer applications of different K sources. Notably, NG-K fertilizer proved a better source of K, whether applied as a basal dose or foliar spray. For growth characteristics like the fresh weight of leaves and fruit mass, obtaining the highest values of 35.2 and 172 g, respectively, resulted when applying a basal dose of NG-K. On the other hand, maximum total sugar content (13 mg L^-1) and juice content (40%) occurred under foliar-applied NG-K. Foliar application of K fertilizer proved to be more effective for better growth and fruit quality parameters than the basal application of SOP.

Keywords: Citrus, growth characteristics, potassium, fertilizer, formulation

Key findings: K fertilizer application improved the citrus fruits’ quality and quantity attributes irrespective of source, dose, and application method. However, among K fertilizer sources, newgeneration K fertilizers proved superior over commercial K sources (SOP). Regarding the application method, the foliar application gave better results and effectively improved the quality and growth attributes of the citrus fruits.

The tendency to use natural organic wastes is one of the environmentally safe applications in crop production. Therefore, the presented study aimed to determine the effect of adding mushroom and sulfur residues to gypsiferous soil and their efficiency in improving the production of broccoli ‘Balimo F1’ (Brassica oleracea var. ‘Italica’). The study set out in a randomized complete block design with three replications. The 10 combined treatments of the spent mushroom substrate (SMS) and sulfur residues consisted of 0% and 15% (SMS), and 0, 1000, 2000, 3000, and 4000 S kg ha^-1. The interaction of the spent mushroom substrate with sulfur showed significant differences for most growth and yield-related traits of broccoli, including leaf length, leaves per plant, roots per plant, head diameter, head weight, total yield, and harvest index, as compared with the control treatments. Among all the treatments in broccoli, the highest total yield (148,702 kg ha^-1) resulted in the treatment SMS – 15% + Sulfur – 3000 kg ha^-1, followed by the total yields of 111,608 and 105,663 kg ha^-1 produced by the treatments SMS – 15% + Sulfur – 4000 kg ha^-1 and SMS – 15% + Sulfur – 2000 kg ha^-1, respectively. However, the minimum total yield in broccoli (28,295 kg ha^-1) came from the treatment SMS – 0% + Sulfur – 3000 kg ha^-1, followed by a total yield of 33,793 kg ha^-1 obtained in the treatment SMS – 0% + Sulfur – 4000 kg ha^-1. Overall, and compared with the control, a significant influence occurred due to the interaction of spent mushroom substrate and sulfur with levels of 15% and 3000 kg ha^-1, respectively.

Keywords: Broccoli, spent mushroom substrate (SMS), composting, sulfur, inorganic fertilizer, organic manure, gypsiferous soil

Key findings: For growth and yield-related traits of broccoli, a significant influence occurred due to the interaction of spent mushroom substrate (SMS) and sulfur at the levels of 15% and 3000 kg ha^-1, respectively.

Phosphate-solubilizing and nitrogen-fixing bacteria are crucial in increasing soil fertility and restoring soil properties damaged by salinity and other abiotic environmental factors. The presented study aims to explore and identify the morphological characteristics of phosphate-solubilizing and nitrogen-fixing bacteria in saline soil. This study took place from August until November 2022 in the field and laboratory of the Faculty of Agriculture, Universitas Muhammadiyah Sumatera Utara, Medan, Indonesia. Isolation of potential microbes proceeded to characterize phosphate-solubilizing and nitrogen-fixing bacteria. Sampling began with the soil planted with rice and palm oil at the sampling location. Morphological parameters observed were color, form, margin, surface, and elevation of pure colonies. The result showed that exploring various species in saline soil revealed 19 colonies and 14 cells of phosphate-solubilizing bacteria and 16 colonies and 14 cells of nitrogen-fixing bacteria. The pure colonies of the phosphate-solubilizing and nitrogen-fixing bacteria showed differences in the morphological characteristics, i.e., color, form, margin, surface, and elevation. The potential microbes obtained sought to increase soil fertility and crop production.

Keywords: Phosphate-solubilizing bacteria, nitrogen-fixing bacteria, morphological characteristics, saline soil

Key findings: Exploration and identification of morphological characteristics is a must action to analyze potential microbes in depth to improve the quality of saline soils to increase crop productivity.

Shallot production has many challenges, including the anthracnose disease caused by the pathogen Colletotrichum gloeosporioides Penz. Disease characteristics include severe twisting of leaves, neck elongation, and necrosis of leaves. This disease can cause yield loss of up to 100 percent. In addition to chemical control practices, resistant shallot varieties will be very useful in decreasing losses. However, information about existing shallot varieties resistant to C. gloeosporioides is limited. The study objectives are to identify the shallot varieties resistant to C. gloeosporioides and identify morphological characters and secondary metabolites of the leaves that may associate with the defense mechanism in shallot. Fourteen shallot varieties underwent a single factor use in a randomized block design in the field and laboratory experiments. The experiment transpired from January to June 2021. Planting healthy shallot bulbs of all genotypes in a polybag containing sterile media continued by artificial inoculation of C. gloeosporioides after the plant had 3–5 leaves. The field test showed that the Sumenep variety has the best resistant level to C. gloeosporioides, with a disease severity score of about 30.19%. On the other hand, the Blue Lancor variety is most susceptible, with a disease severity score reaching 95.05%. The study also found an indication that a possible resistance of shallots to C. gloeosporioides relates to the thickness of the palisade tissue (r =-0.8, P < 0.001), with the induced mechanism associated with the detection of the presence and increase of carbamic acid concentrations.

Keywords: Carbamic acid, defense mechanism, palisade tissue, secondary metabolite, Sumenep variety

Key findings: Identifying the resistance of leaf cellular morphology showed that palisade tissue is a character associated with shallot resistance to C. gloeosporioides.

Currently, the selection of tomatoes with a high content of biologically active substances and antioxidant properties at the large green and breaker stage is relevant since mature tomatoes cannot tolerate storage and transportation. For this purpose, 11 tomato genotypes, chosen in a preliminary study in 2018–2020 from the Genetic Collection of Plant Resources of Federal State Budgetary Scientific Institution Federal Scientific Vegetable Center (FSBSI FSVC), Moscow, Russia, and Tomato Genetics Resource Center (TGRC), the University of California, Davis, USA, for further studies during 2020–2022 for antioxidant pool changes: measuring the contents of chlorophyll, lycopene, β-carotene, ascorbic acid, and lutein. The experiment arranged in a randomized complete block design proceeded in the film unheated greenhouses. The results showed five promising tomato genotypes, i.e., VFN Hi Sugar, VS-420, Paul Robeson, Black Cherry, and VS-410. The genotype Black Cherry fruits with breaker ripeness contained 42% lycopene and 93% β-carotene, while the genotype Paul Robeson at the same stage contained 80% β-carotene. The three other tomato genotypes, viz., VFN Hi Sugar, VS-420, and Paul Robeson, also gave a higher content of ascorbic acid in the fruits at the breaker ripening stage.

Keywords: Tomato, ascorbic acid, β-carotene, chlorophyll, lutein, lycopene, total phenols

Key findings: The studied dynamics of various pigments with biological activity according to the tomato ripening stages revealed promising genotypes identified and selected for further studies.

The present study aimed to determine the genetic divergence of seven maize genotypes (Al-Maha, Sumer, Al-Fajr, Baghdad, 5018, 4 × 1 single hybrid, and 4 × 2 single hybrid) under two varied levels of nitrogen fertilization (92 and 276 kg N ha^-1). The experiment occurred in 2022 in a randomized complete block design (RCBD) with a split-plot arrangement and three replications at the College of Agricultural Engineering Sciences, University of Baghdad, Iraq. The nitrogen fertilization levels served as main plots, with the maize genotypes allocated as the subplots. The results revealed that genetic variance was higher than the environmental variance for most traits, and the coefficient of phenotypic variation was close to the genetic variation coefficient under the two levels of nitrogen fertilization. Heritability (broad sense) at the 92 kg N ha^-1 (N1 level) was the highest for traits. i.e., ear height, grains per row, grains per ear, individual plant yield, yield per unit area, days to 50% male flowering, leaf area, ear length, rows per ear, and 100-grain weight, with values of 92.556%, 90.760%, 90.123%, 95.007%, 95.007%, 88.976%, 89.974%, 88.748%, 85.521%, and 89.690%, respectively. For the N level of 276 kg ha^-1 (N2 level), the heritability in a broad sense was high for the traits, viz., days to 50% male flowering (91.546%), plant height (96.150%), ear height (91.038%), ear length (92.454%), individual plant yield (98.108%), yield in the unit area (98.108%), and plant dry weight (85.488%). The cluster analysis divided the maize genotypes into four and five cluster groups under the nitrogen fertilization level of 92 and 276 kg N ha^-1, respectively. These different groups of maize genotypes could be due to the genetic divergence among the genotypes resulting from their varied genetic makeup and origin.

Keywords: Maize (Zea mays L.), genetic diversity, nitrogen fertilization levels, heritability, broad sense, cluster analysis, yield related traits

Key findings: The presented study can identify the genetically diverged maize genotypes with some other genetic parameters, which could benefit hybridization for transferring better yield-related genes to improve grain yield through various breeding methods.