Topcross Hybrids Research Articles

Association between traits related to fruit quality in papaya (Carica papaya L.) hybrids and their implications for selection

AbstractThe knowledge of the associations between the variables and the cause–effect discrimination allows the breeders to make efficient of new cultivars development with traits that meet the demands of producers and consumers. Therefore, the present work aimed to study the associations among the quality variables of papaya (Carica papaya L.) fruits and the effects on selection process. Eight variables related to fruit quality were evaluated in 62 topcross hybrids. The phenotypic and genotypic correlations and path analyses were performed to verify the associations between the variables and the effects on pulp volume. Canonical correlation analysis between primary and secondary quality variables was also carried out. Fruit firmness and soluble solids content showed a positive and significant genotypic correlation, providing evidence for selecting fruits with high averages for both variables. Fruit weight and pulp thickness (PT) were the variables that most contributed to the reduction and increased pulp volume percentage (PV%), respectively. The canonical correlation analysis showed an increase in PT associated with an increase in the fruit length and PV%variables. The physical–chemical variables showed a low association with others, which will make the selection process more laborious to obtain satisfactory gains between the groups of variables.

Genetic Variation in Among Seed Vigor of Single Crosses and Top Cross Hybrids of Sugar Beet

Genetic Variation in Among Seed Vigor of Single Crosses and Top Cross Hybrids of Sugar Beet

Combining ability and inheritance of yield-related traits in F1 of winter barley under conditions of Ukrainian Forest-Steppe

Purpose. To determine the peculiarities of the manifestation of combining ability and the mode of inheritance of yield-related traits in winter barley and to identify genetic sources and promising hybrid combinations for further breeding efforts under conditions of Ukrainian Forest-steppe. Methods. The research was conducted in 2018/19 and 2021/22 at the V. M. Remeslo Myronivka Institute of Wheat of NAAS of Ukraine. In accordance with generally accepted methods, the degree of phenotypic dominance, heterobeltiosis and effects of general combining ability in the top-cross hybrids of winter barley for key yield components were determined. Results. The variability of the manifestation level of the studied traits in parental components and hybrids in different years were established. According to the indicator of the degree of phenotypic dominance, the variability of the character of inheritance was revealed depending on the traits, hybrid combinations and growing conditions. Hybrid combinations with positive overdominance and dominance of individual yield components were highlighted. In particular, according to plant productivity these combination are: ‘Scarpia’ / ‘MIP Darii’, ‘Scarpia’ / ‘MIP Korsar’, ‘Aborygen’ / ‘MIP Corsar’, ‘Titus’ / ‘MIP Status’, ‘MIP Yanus’ / ‘MIP Status’, ‘Titus’ / ‘Paladin Myronivskyi’, ‘Maybrit’ / ‘Paladin Myronivskyi’ ‘MIP Yanus’ / ‘Paladin Myronivskyi’. The varieties with increased effects of general combining ability for yield-related traits under different growing conditions were distinguished. As follows: productive tillering – ‘Scarpia’, ‘MIP Darii’; grain number per ear – ‘MIP Yanus’, ‘MIP Hladiator’, ‘MIP Status’; 1000 grain weight – ‘Titus’, ‘MIP Korsar’, ‘MIP Status’; grain weight per plant – ‘MIP Yanus’, ‘MIP Status’, ‘MIP Darii’. Conclusions. Selected hybrid combinations with positive overdominance and dominance are of practical value for further breeding to increase individual components and plant productivity in general. The varieties with increased effects of general combining ability are valuable genetic sources for involvement in crossing for improving the certain traits.

Capacidade de combinação de progênies S3 de milho forrageiro em topcrosses para características da parte vegetativa e da planta inteira

Abstract The objective of this work was to evaluate the combining ability of S3 forage maize (Zea mays) progenies for traits related to forage yield and bromatological quality, with and without the ear, as well as to evaluate the ability of testers to discriminate progenies for these traits. The trials were carried out in the 2017/2018 and 2018/2019 crop seasons, in the municipality of Guarapuava, in the state of Paraná, Brazil. Topcross hybrids obtained from the crosses of 28 S3 maize progenies with three testers were evaluated. The following forage qualitative traits of the whole plant and of the plant without the ear were evaluated: neutral and acid detergent fibers, lignin, and in situ dry mass digestibility, as well as digestible dry mass yield of the whole plant. The progenies that stood out for forage qualitative traits were 85.1 and 42.1 for the whole plant and for the plant without the ear, respectively. For the qualitative and productive traits of whole-plant forage, progenies 91.1, 106.2, 126.2, 138.1, 152.1, 235.1, and 251.1 are promising to continue in the breeding program aiming to generate hybrids with a high yield and fiber quality. Testers LEM3 and AG8025 are efficient in discriminating progenies for forage yield and bromatological traits.

Breeding of sugar beet hybrids suitable for the production of biofuel

The development of bioenergy in Ukraine requires the cultivation of energy crops as renewable sources of energy. Sugar beet hybrids created using valuable sterile and fertile forms can have a breeding perspective as a raw material for the production of biofuel. Therefore, the goal is to create experimental hybrids of sugar beets with high energy output, suitable for obtaining alternative types of biofuel, and to select the best of them. When creating sugar beet hybrids, 6 pollensterile and fertile samples of different ecological and genetic origins were used. The stages of the breeding process were the breeding of the original parental components, their evaluation by combining ability, and the formation of sugar beet hybrids based on the best of them. The method of multi-tester top-crosses and field tests of experimental sugar beet hybrids were applied. It was found that the parental components of sugar beet significantly differed among themselves in terms of bioethanol yield, the indicators of which ranged from 2.06 to 2.43 t/ha (TCS lines) and 2.23 to 2.73 t/ha (pollinators). The highest energy yield in topcross hybrids of sugar beets was noted in combinations created with the participation of polliniferous samples Iv.24869 (61.5 GJ/ha) and Iv.24845 (58.4 GJ/ha). Their effects of ZKZ were reliably positive and amounted to 6.7 and 4.0 GJ/ha, respectively. Numbers 1233-Jan.3 (2x) and 1183 02024 (2x) were recognized as the best pollinators of sugar beets. In the genotypic structure of variability of the "sugar yield" trait, the total share of the influence of valuable additive gene complexes of sugar beet parental forms (51 %) was almost equal to the share of non-additive interaction of components (49 %). By the method of combinatorial breeding, two new hybrid genotypes of sugar beets, suitable for the production of biofuel from renewable sources, were created, in which the energy yield exceeded the group standard by 10.6 and 12.6 %. Key words: bioenergy, sterile forms, pollinators, sugar beet hybrids, combining ability, energy output.

Three-Way Top-Cross Hybrids to Enhance Production of Forage with Improved Quality in Pearl Millet (Pennisetum glaucum (L.) R. Br.)

Three-way top-cross hybrids of pearl millet were evaluated along with a popular single- cross check hybrid (PAC 981) for forage yield and quality traits under a multi-cut (three cuts) system across multiple years, seasons and sites in India. Total green forage yield (TGFY) varied from 36 to 53 t ha−1, and two hybrids outyielded the check hybrid for both total dry forage yield (TDFY) and forage quality (CP; Crude protein, and IVOMD; In vitro organic matter digestibility) traits. A set of promising three-way top-cross hybrids evaluated along with a set of promising open-pollinated varieties (OPVs) and top-cross hybrids for forage-related traits over two years under a multi-cut system revealed that the mean TDFY of three-way top-cross hybrids was higher than the mean TDFY of top-cross hybrids, followed by OPVs. Also, three-way top-cross hybrids had higher/or at par forage quality traits such as CP and IVOMD in comparison to other types of cultivars. TDFY had no correlation with CP and IVOMD across cuts in three-way top-cross hybrids, indicating that forage quantity and quality traits can be improved independently of each other. Overall, three-way top-cross hybrids were found to be a better pearl millet cultivar option than other types of cultivars.

Topcross pearl millet hybrids for Africa: A case study for Mali

Abstract Single-cross pearl millet hybrids are widely grown in India, but this cultivar type has not been adopted in Africa. Hybrids from India have proven to be highly susceptible to downy mildew disease in Africa, the continent where the disease originated. We investigated an alternative strategy of growing topcross hybrids where both the parents are of African origin and both are only partially inbred. We investigated root characteristics – length, diameter, area, volume and dry weight – under drought stress and well-watered controlled conditions in genotypes that included potential parents of topcross hybrids. Several, including population Civarex 06_05, had better developed roots under drought while also having good roots under more favourable conditions. Some of these genotypes were backrossed to a male-sterile line based on the A4 cytoplasm to produce male-sterile populations with stable male sterility. Civarex 06_05 had good combining ability when used as a female parent and produced high-yielding topcross hybrids. Two of the topcross hybrids were on restorer populations Toroniou, originating from Mali, and Maiwa from Nigeria. On the experimental station and in farmers’ fields, one was much superior in yield to the best local alternatives and both had superior downy mildew resistance. Current efforts on the seed production of these topcross hybrids are described, and the constraints to the commercialisation in Mali of promising topcross hybrids are discussed.

Varijabilnost odnosa visine klipa i biljke top cross hibrida kukuruza

In a large number of plant species, including maize, different phenotypic traits have undergone major changes through the breeding process, resulting in the creation of varieties and hybrids of good agronomic performance. This study aimed to examine the variability of the plant height (PH) and plant height to the uppermost ear (EH) of maize top cross hybrids obtained from crossing 31 local landraces with three genetically divergent testers (L217, L73B013 and L255/75-5). Top cross hybrids were tested in a two-year experiment, at four locations, in two replicates. The grand mean of top cross hybrids for PH and EH were 255.8 cm and 101.8 cm. Analysis of variance showed that all sources of variation (environment - year × location (E), landrace (B), tester effect (A), as well as their interactions) were highly significant (p≤0.01), except for triple interaction (A × B × E). The coefficients of variation for the PH and EH were 4.76% and 8.87%. A highly significant correlation was found between the examined traits (r=0.785; p <0.01). Linear regression of PH and EH shows that the increase of EH by 0.5 cm is followed by the 1 cm of PH increase. Based on the results, the general combining ability (GCA) of landraces for the examined traits, is under the influence of the additive effect of genes, i.e. tall landraces per se in crosses with all three testers give tall hybrids and inversely. In maize production, a trait of interest is the small EH/PH ratio. Landraces MB1960, MB642 and MB1890 showed the best GCA for a given trait, so they can serve as sources of a given trait in pre-breeding programmes.

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. The current study revealed significant genetic variability among the tested hybrids; hence, it can be used in future breeding programs to produce early maturing and high-yielding maize hybrids.Days to tasseling, genetic variability, heterosis, population cross, top cross Keywords: HBV, HCV, ICT, PCR, Risk factors, Mansehra

Selection of S3 progenies of super sweet corn based on agronomic performance of topcrosses

ABSTRACT The aim of this study was to select S3 progenies of super sweet corn based on agronomic performance, evaluated in topcrosses with the narrow genetic base tester Honey Sweeter (Seminis®). The experiment was carried out in Guarapuava-PR. We evaluated 22 topcross hybrids and three checks, in two sowing times, in randomized blocks design with three replications. Six traits were evaluated: total yield of husked ears, commercial yield of husked ears, grain yield, grain length, ear diameter and total soluble solids content. Considering the set of evaluated traits, the topcrosses with progenies D2-07, D3-28, D4-53 and D5-24 were superior to the others; therefore, these progenies should continue in the inbreeding process and be evaluated in crosses with elite inbred lines with potential to generate competitive super sweet corn single hybrids.

Understanding Heterosis, Genetic Effects, and Genome Wide Associations for Forage Quantity and Quality Traits in Multi-Cut Pearl Millet.

Pearl millet is an important food and fodder crop cultivated in the arid and semi-arid regions of Africa and Asia, and is now expanding to other regions for forage purpose. This study was conducted to better understand the forage quantity and quality traits to enhance the feed value of this crop. Two sets of pearl millet hybrids (80 single cross hybrids in Set-I and 50 top cross hybrids in Set-II) along with their parents evaluated multi-locationally for the forage-linked traits under multi-cut (two cuts) system revealed significant variability for the forage traits in the hybrids and parents. The mean better parent heterosis (BPH) for total dry forage yield (TDFY) was 136% across all the single cross hybrids and 57% across all the top cross hybrids. The mean BPH for in vitro organic matter digestibility (IVOMD) varied from −11 to 7% in the single cross hybrids and −13 to 11% in the top cross hybrids across cuts. The findings of TDFY and IVOMD heterosis in these sets indicated the potential of improvement of the hybrid cultivars for forage quantity and quality in forage pearl millet. The parental lines single cross parent (SCP)-L02, SCP-L06, and top cross parent (TCP)-T08 found superior in the forage quantity and quality traits can be utilized in the future breeding programs. Most of the forage traits were found to be controlled by using the non-additive gene action. A diverse panel of 105 forage-type hybrid parents (Set-III) genotyped following genotyping by sequencing (GBS) and phenotyped for crude protein (CP) and IVOMD under multi-cuts for 2 years identified one stable significant single nucleotide polymorphism (SNP) on LG4 for CP, and nine SNPs for IVOMD distributed across all the linkage groups except on LG2. The identified loci, once validated, then could be used for the forage quality traits improvement in pearl millet through marker-assisted selection.

Effects of artificial inoculation on trait correlations with resistance to Fusarium ear rot and fumonisin contamination in maize

AbstractBreeding for resistance to Fusarium ear rot (FER; Fusarium verticillioides Nirenberg) and fumonisin (FUM) contamination in maize (Zea mays L.) is labor intensive, time consuming, and expensive. The objective of this study is to explore three possible shortcuts to improve the efficiency of breeding for resistance to FER and FUM: relying on natural instead of artificial inoculation of Fusarium verticillioides, selecting inbred lines per se instead of topcross hybrids, and using grain test weight (TW) as an indirect selection criterion. We selected the 27 most resistant and 26 most susceptible S0:1 lines from the third cycle of a broad‐based recurrent selection population and topcrossed them to a common inbred line. The resulting topcross hybrids were evaluated in three North Carolina environments under artificial and natural inoculation of F. verticillioides. The entry‐mean heritabilities for FER and FUM are considerably reduced under natural conditions compared to artificial inoculation; therefore, artificial inoculation should be practiced for efficient selection for resistance. We found a high correlation between FER and FUM content of S0:1 lines per se and their topcross hybrids, suggesting that selection among early generation inbred lines per se is an efficient method to improve resistance in their topcross hybrids. The TW of inoculated S0:1 lines per se was strongly and negatively correlated with FER and FUM of their topcross hybrids, suggesting that TW can be utilized as an indirect selection criterion to improve resistance to FER and FUM contamination.

Topcross hybrids in papaya (Carica papaya L.): evaluation of the potential for increasing fruit quality in new cultivars

ABSTRACT Multivariate analyzes such as selection indexes are one of the ways to select superior papaya genotypes with adequate quality to the consumer market, becoming more efficient after inferences made in the population from the estimate of genetic parameters. Thus, this study aimed to estimate genetic parameters and select papaya topcross hybrids for traits related to fruit quality through selection indexes. The analysis of variance was performed, and the genetic parameters and means test were estimated. The indexes of Smith and Hazel, Pesek and Baker, Mulamba and Mock, and Williams were applied to determine the genetic gains. The genetic parameters indicated a greater environmental influence for firmness, and soluble solids content, where the fruit weight presented the highest genetic variation. The selection showed a reduction in gains for at least one of the essential traits in the quality of the fruits, such as fruit and pulp firmness, soluble solids content, or pulp volume percentage. The Mulamba and Mock index demonstrated satisfactory gains for all these traits with minimal reduction in the others, which is considered the most appropriate for the selection of eight papaya hybrids (UCHJ16-014, UCHJ16-034, UCHJ16-006, UCHJ16-026, UCHJ16-013, UCHJ16-012, UCHJ16-025, and UCHJ16-016).

Selection of S3 progenies of forage maize based on topcrosses with different testers

Maize forage is commonly used as silage in milk and beef cattle livestock production systems. Despite the wide variety of maize hybrids with high potential for grain production, few available hybrids have been developed exclusively for forage aptitude. The present study aimed to select S3 maize progenies derived from the single hybrid AS1572 based on the combining ability of forage traits in topcrosses with testers AG8025, 70.H26.1, and MLP102. The 135 resulting topcross hybrids were assessed in partial diallel in Guarapuava and Rio Bonito do Iguaçu, Paraná State, Brazil. Were evaluated the contents of neutral detergent fiber (NDF, %DM) and acid detergent fiber (ADF, %DM), forage dry matter yield (DMY, t ha-1), and in situ digestibility of forage dry matter (DIG, %DM). For all evaluated traits, the variability allowed us to select superior progenies. Progenies 3.1, 22.1, and 39.1stood out in terms of NDF, ADF, and DIG, whereas progenies 47.1, 73.1, 79.1, and 90.2 were efficient in increasing the forage dry matter yield. The testers AG8025 and 70.H26.1, of narrow genetic base, are the best to explore genetic variability among progenies.

Combining ability of recombined F4 papaya lines: a strategy to select hybrid combination

The growing demand for quality of papaya by the domestic and international markets requires the development of genotypes that are capable of incorporating traits, such as high yield and fruit quality. This study estimated the genetic parameters and the specific combining ability of F4 papaya lines crossed to the SS-72/12 tester to identify genotypes with higher genetic value for hybrid production. We evaluated 169 treatments consisting of 62 topcross hybrid combinations, 97 F5 lines, and 10 controls in a 13 × 13 lattice design with five replicates and two plants per plot. The following traits were evaluated: plant height (PH), stem diameter (SD), first-fruit insertion height (FFIH), number of marketable fruits (NMF), number of deformed fruits (NDF), number of fruitless nodes (NFN), average fruit weight (FW), and yield (YLD). Differences p < 0.05 were found in most traits evaluated. The specific combining ability estimates indicate that hybrids formed by the cross between SS-72/12 tester and the following lines are promising, considering the multiple traits: UCLA08-088, UCLA08-101, UCLA08-071, UCLA08-014, UCLA08-025, UCLA08-028, UCLA08-122, UCLA08-055, UCLA08-026, and UCLA08-092. These hybrids meet the demands for domestic and international markets and may be available to producers as new papaya cultivars.

Principal component analysis for selection of superior maize genotypes

Constant advances in studies on the behavior of maize genotypes and their interactions with the environment are of great importance for the best performance of the plant. This study verifies effects and causes of agronomic variables of maize hybrids on grain yields and performs the indirect selection of superior genotypes by principal component analysis (PCA). Two hundred and thirty maize genotypes were used, with two hundred and twenty- -nine topcross hybrids (consisting of crossings of two hundred and twenty-nine partially inbred genotypes with a tester) and one check in a randomized block design with two repetitions. The genotypes were evaluated during the 2016 and 2016/2017 crops considering the agronomic variables plant height, ear insertion height, ear position, lodging, breakage, and grain yield. Data were submitted to analysis of variance and means were compared by the Scott-Knott test (p<0.05) with subsequent multivariate exploratory analysis by PCA. In the principal component analysis, components explained 52.07% and 55.69% of the variance contained in the original variables for the 2016 and 2016/2017 crops, respectively. The variable that was most significant in both crops was ear insertion height, allowing the indirect selection of more productive genotypes. Indirect selection of the most productive genotypes was also conducted through variables that contributed significantly in the principal component analysis. Thus, the use of multivariate exploratory analysis is efficient in the characterization and selection of maize genotypes evaluated in different crop seasons.

Effects of Azospirillum brasilense applied along with herbicides on maize

The aim of this study was to estimate the correlation coefficients and slicing the phenotypic correlations into direct and indirect effects by path analysis between morphoagronomic and bromatological traits in corn hybrids for silage. Nineteen topcross hybrids and five controls were assessed in a randomized block design with four replications in two environments (Campos dos Goytacazes and Itaocara, RJ), in the 2013/2014 agricultural year. Phenotypic correlations and path analysis were estimated between morphoagronomic (average plant height; average first ear height; average stem diameter; ear yield with husk at silage point; grain yield at silage point; green mass yield) and bromatological (dry matter; crude protein; neutral detergent fiber; lignin; crude fat and mineral matter) traits. The highest correlation estimates were obtained between dry matter and crude protein and between dry matter and neutral detergent fiber, with magnitudes of 0.97 and 0.98, respectively. The coefficient of determination was high, indicating that the assessed components explain much of the variation in the dry matter content. Path analysis showed that traits with highest direct effect on dry matter content were the yield of green mass, crude protein, neutral detergent fiber, crude fat, and mineral matter associated to high correlations of 0.96, 0.97, 0.98, 0.90, and 0.96, respectively. The results showed the possibility of obtaining significant gains through indirect selection

Phenotypic correlations and path analysis between morphoagronomic and bromatological traits in corn hybrids for silage production

The aim of this study was to estimate the correlation coefficients and slicing the phenotypic correlations into direct and indirect effects by path analysis between morphoagronomic and bromatological traits in corn hybrids for silage. Nineteen topcross hybrids and five controls were assessed in a randomized block design with four replications in two environments (Campos dos Goytacazes and Itaocara, RJ), in the 2013/2014 agricultural year. Phenotypic correlations and path analysis were estimated between morphoagronomic (average plant height; average first ear height; average stem diameter; ear yield with husk at silage point; grain yield at silage point; green mass yield) and bromatological (dry matter; crude protein; neutral detergent fiber; lignin; crude fat and mineral matter) traits. The highest correlation estimates were obtained between dry matter and crude protein and between dry matter and neutral detergent fiber, with magnitudes of 0.97 and 0.98, respectively. The coefficient of determination was high, indicating that the assessed components explain much of the variation in the dry matter content. Path analysis showed that traits with highest direct effect on dry matter content were the yield of green mass, crude protein, neutral detergent fiber, crude fat, and mineral matter associated to high correlations of 0.96, 0.97, 0.98, 0.90, and 0.96, respectively. The results showed the possibility of obtaining significant gains through indirect selection

Partially inbred maize lines in topcrosses and hybrid performance

ABSTRACT In plant breeding programs, the selection of potential progenies in early generations of inbreeding is an essential step. Considering that, the adoption of topcrosses helps the breeder in the selection, this study aimed to verify the potential of S2 strains for synthesis of synthetic varieties and to obtain experimental information on yield and agronomic potential of topcross hybrids. As such, 75 topcross hybrids were generated from crossing 75 S2 lines with F2 generation of the commercial hybrid. The 75 hybrids were grown in a field, along with two commercial hybrids in a randomized complete block design with 4 replicates and in 4-meter plots. Flowering, plant height, height, diameter, length and weight in the ear, and grain yield traits were examined. Analysis of variance was performed, the combining ability was estimated, and, from the means, the Scott & Knott test was conducted. So, the topcross hybrids that distinguished themselves for grain yield were those composed by lines 67, 14, 44, and 69, presenting high CGA, therefore indicating good potential for producing synthetic or base population. For the other traits of agronomic interest that were assessed in maize, a potential for selection with different focuses was found: reduction of cycle and height and increase in length and diameter of the ear.

Topcross hybrids in papaya: Genes derived from backcrossing provide resistance to multiple diseases

Papaya (Carica papaya L.) is widely cultivated and consumed in tropical and subtropical regions of the world. However, a number of diseases prevent the expansion of the crop, the two most prominent of which are ‘black spot’ and ‘phoma spot’. Considering the increasing market demand for fruits free of agrochemical residues, genetic resistance emerges a promising control measure. Our study proposes to estimate the specific combining ability and its interactions with the environment to identify genotypes with genetic resistance to black spot and phoma spot in topcross hybrids. This paper describes an experimental trial implemented in a randomized-block design with six replicates, involving 10 superior lines obtained by backcrossing; four elite lines (‘SS-72/12’, ‘JS-12’, ‘Sekati’ and ‘41/7’), used as parents of already registered genotypes; 20 topcross F1 hybrids (crosses between the 10 lines and the elite hybrids); and two commercial controls. The result related to non-additive interactions resulting from genetic complementation between parents. The SS 72/12 × 4 genotype, a hybrid of the Solo group, was identified as potentially resistant to both diseases. The Sekati × 1 and JS-12 × 17 genotypes, hybrids of the Formosa group, were also promising, given their negative estimates for incidence of black spot on the leaves and fruits and incidence and severity of phoma spot on the leaves, showing less damage when affected by diseases. These results enable the registration of potentially resistant cultivars with high-quality agronomic attributes, which can broaden the range of papaya cultivars sold in Brazil.