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Estimation of genetic parameters such as genetic variability of germplasm allows inferring genotype-enviromental interaction for a given variable. The information is important for the process of choosing the variables to be applied to the superior genotype selection. This study aimed at evaluating characteristics related to genetic resistance of papaya to black spot during time testing, as well as estimating genetic parameters associated with some characteristics. The experiment was carried out in RCBD design at Agua Limpa farm, Espirito Santo state, Brazil, using six genotypes: ‘STZ-03’, ‘SS-PT’, ‘Golden’ (‘Solo’ group) ‘Maradol’ (‘Formosa’ group) ‘STA-04’ ‘STA-10’ (landraces), and four repetitions. The 6 treatments were arranged in single row, spacing 2 m between rows and 1.5 m within plants. Nine evaluations were performed during 9 months. We quantified plants on a monthly basis for the characters such as symptom appearance of black spot (FS) on leaves; the incidence of leaves with black spot symptoms (IBS); the severity of black spot on the fifth leaf (SBS5F) and on the leaf with axil attached to the first open flower (SBSFO). By means of the evaluation values, we built a Boxplot graphic to characterize the magnitude of the variables and to describe the dispersion of the data set throughout the evaluations. Analysis of variance, genetic parameter estimate and comparative test of mean were also conducted. The Boxplot graphic allowed classification and magnitude of the variables and described the dispersion of the data set during evaluations. The results showed that SBS5F and the SBSFO were the characteristics that generated reliable results to select genotypes in all evaluations. They showed high H² (Coefficient of genotypic determination), CVg (Coefficient of genotypic variance), CVr (Coefficient of relative variance) and AS (Selective accuracy). The months July, August, September and October showed higher representativeness to evaluate attributes related to resistance to black spot in papaya leaves.

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The antifungal activity of fungi with biocontrol potentials should be studied. Therefore, this study aimed at establishing alternative agent to replace the chemical control of papaya black spot. We investigated the antagonistic activity of the fungi Hansfordia pulvinata (H-611), Acremonium sp (A-602, A-617 and A-598), Simplicillium lanosoniveum (S-599), Lecanicillium lecanii (L-622), and Sarocladium implicatum (I-609) on the phytopathogenic fungus A. caricae, by evaluating the mycoparasitism, the enzymatic activity and the production of volatile and non-volatile compounds. For the evaluation of mycoparasitism, each antagonic fungi isolate was microcultured along with conidia of A. caricae. Then, events of mycoparasitism were evaluated at 24h, 48h, 72h, and 96h after inoculation under an optical microscope. We estimated the enzymatic activity (protease and lipase) of the fungi in a particular culture medium for each enzyme. The activity of the protease was reflected in the mean diameter of the halo. The lipase activity was measured by the halo/colony relation. In order to detect volatile compounds in the antibiosis test, A. caricae was cultured under a medium along with the isolates described. For the test of non-volatile compounds, we evaluated the germination of A. caricae in culture medium by diffusion under cellophane paper. As a result, the mycoparasitism of the H-611, A-602, A-617, A-598, S-599, and L-622 isolates was confirmed on the microcultures. We observed higher activities of protease in the I-609, S-599, A-602, and A-598 isolates. The H-611 and A-602 isolates presented higher activities for lipase. We did not observe effect of volatile compounds in any of the tested isolates. In the non-volatile compound test, there was production of antifungal metabolite highlighting the A-617 isolate, which inhibited the germination of the conidia of A. cariae by 100%.

This study aimed to verify if the genetic divergence between papaya lines, obtained by means of molecular markers, is correlated with heterosis in the hybrids for characteristics related to production, fruit quality and disease resistance. Eight parents and 56 hybrids obtained from diallel crosses were evaluated in randomized blocks, with four replicates. The number of commercial fruits (NCF), the average fruit weight (AFW), the productivity (PROD), the fruit firmness (FIRM) and the total soluble solids (TSS) were evaluated, as well as the severity of black spot on leaves (BSS) and fruits (BSSFr), phoma spot (PSS) and powdery mildew on leaves (PMS). Correlations were estimated between genetic divergence, obtained based on Vivas, M.; Cardoso, D.L.; Ramos, H.C.C.; Santos, P.H.D.; Silveira, S.F.; Moraes, R.; Pereira, M.G. Genetic diversity between papaya lines and their correlation with heterosis in hybrids for disease resistance and morpho-agronomic traits. Summa Phytopathologica, v.44, n.1, p.110-115, 2018. SSR, and heterosis, estimated for each characteristic in four possibilities of crossings within the diallel: i) all crossings; ii) between parents of the 'Solo' group; iii) between parents of the 'Formosa' group; and iv) between parents of 'Solo' with 'Formosa' group and 'Formosa' with 'Solo' group. Results indicate the possibility of exploring heterosis both in crossings between groups and in crossings within groups. The low magnitude of the estimates of correlation between heterosis and morphological characteristics of the hybrids with genetic distance obtained by SSR in the parents indicates that the behavior of hybrids cannot be inferred based on the genetic divergence between parents.Keywords: Carica papaya, diallel, hybridization, plant breeding.Papaya (Carica papaya L.), one of the tropical plants with major importance for the national and world's fruit production, is cultivated in several Brazilian states. One of the bottlenecks of this crop is the lack of commercial varieties and hybrids that meet the requirements of the domestic and external market; thus, breeding programs with this attempt should be intensified. Breeding programs in papaya aim to obtain lineages and use them in hybridization programs with the focus on hybrid vigor or heterosis, a phenomenon that provides great productivity to hybrids from the crossing of highly divergent parents.In papaya, the possibility of exploring heterosis is already reported for morpho-agronomic characteristics (5, 17), physiological seed quality (19) and disease resistance (13,27,29,26). Falconer (9) suggests that, at any degree of dominance above zero, heterosis is a function of allele frequency between the parents; therefore, there is a positive correlation between genetic divergence and heterosis. For this reason, lineage diversity estimates can be used as a predicting tool of superior crosses in plant breeding programs (14). Studies with lineages obtained from the populations BR-105 and BR-106, correlating productivity and genetic divergence es...

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Selection for papaya resistance to multiple diseases in a base population of recurrent selectionABSTRACT: Papaya has a narrow genetic base concerning disease resistance, with few genetically distinct cultivars for planting in the world. Losses in crop production caused by fungal and viral diseases, added to the absence of resistant cultivars available to producers, have reduced the competitiveness of crops. Therefore, this study aimed to estimate the direct and combined genetic gains in the base population of the recurrent papaya selection and to indicate promising individuals for resistance to phoma spot and black spot. The population used in this study originated from the crossing of dioecious, female individuals and holders of a gene pool for resistance to phoma spot and black spot.These were crossed with elite individuals with a gene pool for production traits and fruit quality. The experiment was carried out without an experimental design, containing one plant per plot. Three measurements were taken on 255 individuals for five traits of disease resistance, being: four associated with black spot (incidence and severity on the leaf and fruit) and one associated with phoma spot (severity on the leaf). With the observations obtained, the REML/BLUP procedure was performed to estimate the temporary and permanent environmental effects. Such values were used to know the genetic parameters of the population and to elaborate a combined selection index, as well as to compare the gains with the direct selection. The results indicate low repeatability for the traits and that the gains obtained from the use of the combined selection index better rank the genotypes in comparison to the gains obtained by direct selection.

Papaya (Carica papaya L.) breeding is a complex task; furthermore, Carica papaya has a sexual chromosome and is difficult to make crosses. One of the most critical papaya crop diseases is black spot, which is caused by Asperisporium caricae (Speg.) MaublSince . Therefore, we used half-sib families to combine genetic gains on the yield and resistance traits to papaya black spot. In this scenario, the present study proposed to select papaya genotypes more resistant to black spot from half-sib families.Five parents with superior attributes related to black spot resistance were pollinated with a pollen mixture from five parents considered "elite" for agronomic traits, thus generating five half-sib families. The half-sib families were evaluated for black spot resistance in a greenhouse with two control cultivars ('Golden' and 'Maradol'), for 75 d, at 15-d intervals, totaling five evaluations. The families exhibited genetic variability for all traits associated with disease resistance, surpassing even the Golden and Maradol controls. The traits associated with severity by papaya black spot are more efficient to distinguish resistance genotypes using principal components analysis, like mean incidence of black spot (MSBS) (cosš = 0.794) and area under the disease progress curve (AUDPC) (cosš = 0.697). The recommended progeny for resistance to black spot are M-1.4, M-1.5, M-3.1, M-3.3, M-2.5, and M-4.5, as they showed lower values of mean severity of black spot, MIBS, and AUDPC. These progenies from half-sib families overcame the resistant control genotype Maradol as potential to combining resistance to papaya black spot with superior agronomic traits. INTRODUCTIONBlack spot, caused by the fungus Asperisporium caricae (Speg.) Maubl, is a disease of high economic relevance for the papaya crop (Carica papaya L.) worldwide. The disease Abbreviations: AUDPC, area under the disease progress curve; MIBS, mean incidence of black spot; MSBS, mean severity of black spot.