Papaya Hybrids Research Articles

The effect of indigenous Arbuscular mycorrhizal fungi (AMF) on phyto-accumulation in Carica papaya hybrids

Papaya (Carica papaya L.) is a climacteric fruit with a resilient and distinctive aroma. The consumption of the fruit is global due to its high nutritive and medicinal values. However, there has been low production of quality papaya fruits due to unavailability of crucial mineral elements in the soils. The current study therefore, focuses on the effect of indigenous arbuscular mycorrhizal fungi (AMF) as a biofertilizer on the quality of papaya fruits. In order to verify AMF effectiveness on papaya fruits, four treatments were used: AMF inoculum only, composted farm yard manure (FYM) only, combination of AMF inoculum and compost FYM and control where only soil and sand media were used at a ratio of 1:1. Jomo Kenyatta University of Agriculture and Technology (JKUAT) and Malkia papaya hybrids were used. The papaya seeds from JKUAT and Malkia papaya hybrids were sown in trays and transplanted at 3 leaves stage into 5 litre pots within a green house. The AMF spores were bulked using sorghum plants to obtain the AMF inoculum. The treatments were added into the soil media of the papaya plantlets at a ratio of 1:3, every 4 weeks after first transplanting until they were 20 weeks old. They were then transplanted to 100 litre containers, where completely randomized design was used and replication of six papaya plants for each treatment and hybrid. Watering, weeding and cooling the green house with water fumes was carried out when necessary; as the papaya plants grew until the fruits attained physiological maturity. The fruits were separately harvested and ripened to a predetermined stage. They were then analysed for moisture content, crude fibre, minerals (nitrogen, phosphorous, potassium, magnesium, calcium, iron and zinc), ascorbic acid, total carotenoids and total polyphenols. Data obtained was subjected to two-way ANOVA at p ≤ 0.05 significance level; means were separated using Tukey's HSD test in Genstat's 15th edition. JKUAT hybrid with AMF inoculum treatment had 3.07%crude fibre and 8.42mg/100g phosphorous content while JKUAT hybrid with both AMF inoculum and manure treatments had 4.9 % crude fibre and 9.88 mg/100g phosphorous content. Malkia and JKUAT hybrids with compost FYM treatment had potassium content of 98.31mg/100g and 109.4 mg/100g respectively while the controls had 31.58 mg/100g and 35.32mg/100g respectively. Incorporating soil media with manure and AMF inoculum improved the nutritive quality of papaya fruits and this was contingent on papaya hybrids. Key words: biofertilizer, inoculum, mineral elements, nutritive quality, physiological maturity

Nutrient content and biochemical analysis of papaya (Carica papaya L.) hybrids grown in central Kenya

Papaya (Carica papaya L.) is a known powerhouse of nutrients and biochemicals which have health benefits necessary in a human diet. Mineral and vitamin deficiencies, like stunting, wasting and underweight in children, are common in Kenya yet available fruits like papaya can provide those nutrients. This study evaluated the nutritional and biochemical compositions, sugars and the 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activities of 2 newly developed papaya hybrids (JKUAT 7 and JKUAT 8) grown in Kenya and Solo variety, as control; in a completely randomised design which were subjected to one way ANOVA at p?0.05. Results from this study showed significant differences for JKUAT 8 with zinc, iron, potassium and vitamin C contents at 3.28, 3.62, 1145.10 and 448.30 mg/100 g respectively. Solo variety had significantly higher ?-carotene (68.75 mg/100 g), lycopene (25.47 mg/100 g) and flavonoid (0.0178 g/100 g) contents. JKUAT 7 had more phenolic and tannins contents at 0.4434 g/100 g and 81.65 mg/100 g respectively. The DPPH activities ranged from 20 to 80 mg/mL with JKUAT 7 having the highest activity at 20 mg/mL and the least, Solo at 80 mg/mL. JKUAT 7 also exhibited higher total sugar contents in a range of 4.86 to 11.57%: with glucose and fructose at 5.74 and 5.83 % respectively. Our results suggested high nutritional and biochemical profiles of the newly developed JKUAT 7 and JKUAT 8 compared to Solo, the commercial variety. The high nutritional and biochemical contents recorded in the study papayas can be utilised in enhancing human nutrition and health thereby reducing metabolic disorders.

<i>In vitro </i>Propagation of <i>Carica papaya</i> L. Variety ‘Horana Papaya Hybrid 01’ Using Shoot Tip

In vitro plantlet regeneration ability of the local hybrid papaya variety Horana Papaya Hybrid 01 was evaluated using shoot tips from greenhouse-raised seedlings. Shoots tips surface sterilized in 20% Sodium Hypochlorite (Clorox®) for 20 min were established in Murashige and Skoog (MS) basal medium containing 6-Benzylaminopurine (BAP; 0.0,0.5,1.0,1.5 mg/L) in combination with 1-Naphthalene Acetic Acid (NAA; 0.0,0.1,0.5 mg/L) for shoot multiplication. Considering the high mean number of shoots per explant (4.8 ± 0.5) and absence of calli, 1.0 mg/L BAP was the best treatment for direct organogenesis. Proliferated shoots were transferred to a 1.5 strength MS medium containing 0.25 mg/L BAP and Gibberellic Acid (GA3; 0.0, 0.15, 0.30 mg/L) for further elongation. Elongated shootlets were placed in half-strength MS medium supplemented with Indole-3-Butyric Acid (IBA; 0.0,1.0, 2.0, 3.0 and 4.0 mg/L) for rooting. The highest root induction response (86%) and roots suitable for acclimatization were observed with 2.0 mg/L of IBA. Plantlets were acclimatized in poly cups containing a sterile potting mixture (soil, sand, compost, and coir dust; 1:1:1:1) and a survival rate of 75% was achieved under in vitro conditions. The findings of the present study can be optimized to develop a suitable in vitro micropropagation protocol for rapid clonal propagation of this papaya variety for producing true to type planting material.

Heterosis for seed and seedling traits in papaya

The current study was aimed to explore the heterosis expressed in the seed and seedlings of 36 papaya hybrids originating from the 6 inbred lines. The results revealed the manifestation of heterosis, occurred in the seed and seedling stage of papaya. The cross combinations, P-9-5 × P-7-2, P-9-12 × PN and PN × P-9-5 exhibited positive average heterosis and heterobeltiosis for physical seed traits. The genotypes, P-9-5, P-9-12, P-9-5 × P-9-12 and P-9-12 × P-9-5 were observed with positive mid-parent heterosis and heterobeltiosis for the seedling traits. The hybrid, P-7-9 × PN and PS3 × P-7-9 showed positive average heterosis (5.89% and 9.91%) and heterobeltiosis (3.41% and 2.09%) for germination percentage, respectively. Whereas in case of seedling length and weight (fresh and dry), the hybrid combination, P-9-5 × P-9-12 exhibited the positive heterosis. The heterosis effect estimated helped us to identify the superior performing hybrids like, PN × P-7-2, PN × P-9-5, P-7-2 × PN, P-7-2 × P-7-9, P-7-9 × P-9-5, P-9-5 × P-7-2, P-9-5 × P-9-12, P-9-12 × PN, P-9-12 × P-7-2, P-9-12 × P-95and PS3 × P-7-9, in the initial stage of seedling development.

Sex Identification of in vitro Plants of Carica papaya L. MSXJ Hybrid through Molecular Markers

Objective: To identify the sex of in vitro plants of papaya (Carica papaya L.) MSXJhybrid obtained via somatic organogenesis, through SCAR type molecular markers. Design/Methodology/Approach: Eight-month old MSXJ papaya hybrid plants in thefructification stage were collected in Cotaxtla, Veracruz, Mexico. They weresuperficially disinfected with abundant running water, detergent during 30 min, andthen alcohol at 70% was added for one minute, commercial chlorine at 30% for 30min, and they were rinsed with sterile distilled water; then the meristems werecultivated in MS medium and after 30 d a subculture was made. The DNA extractionwas made with the CTAB method, and the DNA PCR was done with the Deputy et al.(2002) method, and the primers T1, T12 and W11 were used.Results: The T1 primer was the positive control and the T12 and W11 primersallowed the amplification of fragments that identify hermaphrodite, feminine and maleplants, while the T12 and W11 primers were specific for hermaphrodite plants.Study Limitations/Implications: It is required to standardize the method for it to beinexpensive.Findings/Conclusions: The sexuality of papaya plants can be differentiated until thestage of flowering, which is why the implementation of molecular markers wouldfacilitate plant selection if it is implemented at a large scale. Costs, maintenance timeand elimination of plants of unwanted sex are reduced this way.

Genetic Uniformity of the MSXJ papaya hybrid (Carica papaya L.) during Micropropagation

Objective: To analyze the genetic uniformity of MSXJ hybrid papaya in vitro plants, obtained by direct organogenesis.Design/Methodology/Approach: The MSXJ papaya hybrid demonstrates quality characteristics for the national and exports market. In vitro culture of plant tissues represents a useful tool for their multiplication and conservation, but somaclonal variation can diminish their genetic and agronomic uniformity. In order to analyze the genetic uniformity of in vitro plants of this hybrid, ten ISSR primers were used for in vitro plants micropropagated during nine subcultures. DNA was extracted using the CTAB method. Data were analyzed using the program PopGene v 1.3.1.Results: Eighty-five loci of 200 to up to 2000 pb were generated, with 37 polymorphic loci. In the cluster analysis, three groups were observed which separate subculture one, subcultures two to eight, and subculture nine; the Gst value of 0.87 indicated genetic uniformity as far as subculture eight.Study Limitations/Implications: Papaya is one of the most important tropical fruits worldwide; however, these plants need to be healthy and genetically uniform to guarantee commercial success. In vitro propagation allows obtaining healthy and uniform plants, but it is necessary to study genetic uniformity during their micropropagation.Findings/Conclusions: The in vitro multiplication of the MSXJ papaya hybrid permitted the regeneration of vigorous plants in 30 d. Molecular profiles indicate that as far as subculture eight, there is genetic uniformity. As such, no more thaneight subcultures are recommended during micropropagation.

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).

The papaya selection based on fruit characters: a way to assembly new preferred variety

The recent program for assembly new papaya variety was aimed to improve its quality, which based on consumer preference on papaya fruit characters namely size (small to medium), flesh thickness, flesh color (reddish, orange and chewy), and the taste (sweet). To get that kind of papaya variety, a plant breeding program could be applied to assembly. Indonesian Tropical Fruit Research Institute (ITFRI) had conducted several papaya hybridizations in order to obtain a wide genetic variability. The study was carried out in Sumani Experimental Filed of ITFRI, Solok Regency, West Sumatra, and performed to select high-quality papaya hybrids based on the fruit characters. The tested genotypes were selected based on its heritability index on fruit size (length, diameter, and weight), flesh thickness and total dissolved solids (TSS). As the results, six papaya varieties were selected based on fruit character, which mirroring best quality of papaya fruit.

Comparative Growth Performance of Papaya Hybrids and their Parents under Reciprocal Crossing System

Papaya is a very popular fruit in the tropical and subtropical regions of the world and has witnessed an increase in demand. This has fuelled an interest to develop region specific hybrids with desirable vegetative growth and vigour. Hence a field experiment was carried out at College of horticulture and forestry, Navsari Agricultural University in Gujarat during 2018-2020 in randomized block design with three replications to know the mean performance of parents and hybrids for comparative growth performances of papaya. Wherein, thirty papaya hybrids were developed from six morphologically distinct parents through full diallel crossing technique and all the parents and hybrids were evaluated for their germination and growth parameters. The variability was distinct in all hybrids and parents for germination percentage, days taken to germination, periodical plant height and girth, number of leaves, petiole length and internodal distance. Amongst all the parents, Pusa Delicious, CO-8 and Lucknow Local exhibited improved germination, better vegetative growth and dwarf stature, respectively. Among the hybrids, Pusa Delicious x Lucknow Local was found to have dwarf stature with minimum internodal length however, the reciprocal cross: Lucknow Local x Pusa Delicious recorded maximum plant girth and number of leaves. Based on their mean performance, these parents can be used for further breeding programmes and hybrids could be exploited for cultivation.

Evaluation of Phytoseiidae mites and Chrysoperla carnea (Stephens) on the control of Tetranychus urticae in Carica papaya L.

In order to evaluate the establishment and biological effectivenessof the predators Phytoseiulus persimilis, Neoseiulus californicus and Chrysoperla carnea on populations of Tetranychus urticae, a trial was established at the farm “La Pola” (with a cumulative precipitation of 445.9 mm), located in the municipality of Roldanillo, Valle del Cauca, Colombia. Anexperiment was performed under field conditions between September 2017 and May 2018 and using the papaya hybrid Tainung-1 between the stages of vegetative growth and fruit filling. Four treatments were established: T1: 12 releases of P. persimilis and N. californicus; T2: 10 releases of C. carnea; T3: treatment with no predator releases (control); and T4: grower’s practice (15 applications of pesticides) in a randomized complete block design with three replicates per treatment. Samples were collected every eight days by measuring the following variables: infestation percentage, number of fruits/plant, population of T. urticae, P. persimilis, N. californicus, and C. carnea/leaf and the diameter of the stem (every 30 d). The largest T. urticae populations were found in T3 and the lowest ones in T4. The populations of immature and adult T. urticae did not show significant differences between T1 and T2 but there were significant differences between T3 and T4. The variables diameter of the stem, number of leaves per plant, percentage of infestation, and number of fruits per plant showed significant differences between treatments. The T1 and T2 were equal to T3. T4 had the highest number of leaves and fruits per plant. The released predators did not control the populations of the mite T. urticae under the conditions of the present experiment.

Combining ability for fruit yield and quality in papaya recombinant inbred lines from the sexual conversion backcrossing

In Brazil there is a limitation in the choice of commercial papaya hybrids for cropping. This factor is responsible for the crop vulnerability to the pests and diseases attack, being of great importance the investigations that aim at the availability of new genotypes. In papaya breeding programs to developed new hybrids, the lines should be evaluated by their combining ability. This step is important to select the superior parents for superior hybrid production. The objective of this research was to evaluate the combining ability of recombinant inbred lines by using elite testers in order to select papaya hybrid combinations with productive capacity and fruit quality, to supply the new cultivars demand, mainly from the Solo group. 34 genotypes were evaluated in a randomized complete block design with six replicates and three plants per plot. The specific combining ability (SCA) was estimated based on 12 traits related to fruit quality and yield. The hybrid combinations SS-72/12 × UCLCF01-01, SS-72/12 × UCLCF01-02, SS-72/12 × UCLCF01-09, Sekati × UCLCF01-04, Sekati × UCLCF01-10 and JS-12 × UCLCF01-17 were superior for presenting positive estimates of the SCA effects for the number of commercial fruits, fruit weight, pulp and fruit firmness and soluble solids that are the most important traits for the crop. These Solo and Formosa hybrid combinations have great potential to supply the consumer market demand, especially the small fruit hybrids, constituting national and international novelty as the first Solo hybrids.

Identification of papaya hybrids resistant to Stagonosporopsis caricae by heterosis: a possible reality?

Papaya requires frequent applications of fungicides because of its high susceptibility to disease. However, no products capable of effectively managing the fungus Stagonosporopsis caricae are commercially available to date. Because of this limitation and the continuous demand for products free of chemical residues and that achieve higher yields, genetic improvement is necessary to obtain resistant and productive genotypes. The present study used lineages produced by backcrossing and hybrids obtained from the cross between these backcrossed lines and four elite genotypes (SS72-12, Sekati, JS-12, and 41/7) to identify genotypes with increased resistance to phoma spot. The analysis of the effects of heterosis evidenced the possibility of achieving high genetic gains. The evaluation of the incidence and severity of phoma spot indicated that hybrids Sekati × 1, 41/7 × 10, and JS-12 × 21 presented negative heterosis for phoma spot in all evaluated seasons. Considering standard heterosis, the hybrids Sekati × 1 and Sekati × 4 were the most resistant to disease. The Solo group genotypes SS × 04 and SS × 06 presented negative heterosis in at least one season for common and standard heterosis, evidencing that these cultivars were resistant to phoma spot. The obtained results on heterosis and papaya production allowed identifying promising cultivars.

English

Papaya (Carica papaya L.) is among the most grown fruit crops worldwide with high economic and nutritional value. In Kenya, the papaya industry relies heavily on imported varieties and farmers’ selected seed whose quality is not known. Therefore, the morphological and quality characteristics of mature fruits of eight newly developed papaya hybrids and their control, Sunrise solo were assessed using papaya descriptors (International Board for Plant Genetic Resources). The results showed significant differences in fruit sizes among the newly developed papaya hybrid lines and the control, Sunrise solo with Line 4 having the longest and heaviest fruits. Fruits from Sunrise solo, lines 2, 3, 7 and 8 ranged from small to medium in size, while those of lines 4 and 6 were large. Line 1 had the shortest shelf life of 4 days while Line 7 had the longest shelf life of 11 days. The total soluble solids (TSS) varied from 7.4 in Line 8 to 12.3% in Lines 5 and 7. Hence, most newly developed papaya hybrids Lines showed traits that were comparable to or exceeded those of Sunrise and could be suitable for both local and export markets. However, there is a need to evaluate and characterize the newly developed papaya hybrid lines in different agro-ecological zones in order to monitor the influences of the environment, pests and diseases.   Key words: Carica papaya L., new papaya hybrid lines, morphological characteristics, shelf life, fruit quality.

Evaluation of NPK doses on the production of papaya ‘Caliman 01’

The study aimed to evaluate the effect of different NPK doses on the yield components of papaya hybrid ‘Caliman 01’. The experiment was carried at the company WG Fruticultura, located in the Chapada do Apodi region. Five nitrogen doses (94, 590, 837, 1088 and 1575 kg N ha-1), five phosphorus doses (10, 72, 96, 133 and 195 kg P2O5 ha-1) and five potassium doses (75, 527, 752, 978 and 1429 kg K2O ha-1), were combined according to the experimental matrix Pan Puebla II, in 16 combinations and distributed in a randomized block design, with five repetitions. The plots consisted of six papaya plants and the four central plants were evaluated. The fertilizers urea, monoammonium phosphate and potassium chloride were used as NPK sources, respectively. The doses of N and K were split into 30 applications, one every two weeks. Phosphorus doses were split into two applications, the first at 75 days after transplantation (DAT) and the second one at 150 DAT. Fruit production was evaluated during eight months. The best results were obtained for NPK doses of 1088, 72 and 527 kg ha-1, respectively. Increasing N doses linearly increased the number of fruits per plant and yield, while increasing P and K doses reduced yield by a quadratic and linear model, respectively. The combination of NPK doses 590-72-75 kg ha-1 provided the best economic results with the highest rate of return for papaya production.

Somatic embryogenesis in the commercial papaya hybrid UENF/Caliman 01 relying on plantlet production from sexed adult hermaphrodite donor plants.

Somatic embryogenesis from explants from hermaphrodite papaya mother plants is an alternative for the production of true-to-type plants without the need for sexing. This study aimed to analyze hormonal and osmotic inducers in different somatic embryogenesis stages in the commercial hermaphrodite hybrid papaya UENF/Caliman 01. Leaf disks from in vitro shoots originated from ex vitro hermaphrodite plants were cultured in induction medium supplemented with different concentrations of 2,4-D (6, 9, 12, 15, and 18 μM) and 4-CPA (19, 22, 25, 28, and 31 μM). After 90 days, the formation of somatic embryos was verified. The 2,4-D induced the formation of light brown calli with low frequency (20%) of somatic embryogenesis. However, 4-CPA (25 μM) induced 96% of embryogenic calli, which were transferred to maturation medium (MM) and cultured for 30 days. The MM contained ABA (0.5 μM) and AC (15 g L-1) and produced 36.6 somatic embryos callus-1, mainly on cotyledonary stage. Cotyledonary embryos were transferred to germination medium supplemented with gibberellic acid (GA3) (0.0, 1.44, 2.88, and 4.32 µM), and the conversion into plantlets was enhanced with GA3 at 2.88 µM.

Evaluation of Physicochemical, Nutritional and Sensory Quality Characteristics of New Papaya Hybrids Fruits Developed in JKUAT

The world is faced with a lot of challenges including lack of sustainable development and inability to feed its growing population leading to malnutrition. The issue of accessing high quality nutritious foods such as fruits has become a major challenge for many African people. Papaya (Carica papaya L.) is among the most popular fruits grown in Kenya and excellent in nutritional content. However, its potential has remained unexploited due to inadequate quality planting materials, high post- harvest losses and prevalence of pests and diseases. Researchers at Jomo Kenyatta University of Agriculture and Technology developed promising papaya hybrids whose physicochemical, nutritional content and sensory characteristics have not been evaluated. Thus, the aim of this study was to determine the physicochemical, nutritional content and sensory quality characteristics of the new papaya hybrids and their control, Sunrise Solo. The physicochemical attributes evaluated included; total soluble solids, total titratable acid, pH and total soluble solid/total titrable acid ratio. While the nutritional content evaluated included (Vitamin C and β-carotene content) and sensory quality characteristics were evaluated. The standard AOAC methods was used to determine nutritional content and an effective analysis with 9- point hedonic scale was used on sensory evaluation. There was significant difference (P< 0.05) in nutritional content of new hybrids papaya fruits and Sunrise solo. The maximum and minimum Vitamin C content of 131.63 mg/100g and 52mg/100g were exhibited by line 6 and 8 respectively. β-carotene content ranged between 1.69 and 3.39 mg/100g as exhibited by line 1 and lines 2 and 8 respectively. The findings of this study revealed that the nutritional content of the new papaya hybrids exceeded the one of Sunrise Solo while their sensory quality characteristics compared favourably to the one of Sunrise Solo. Based on these findings, lines 1, 2,5,6,7 can be recommended for commercialization.

Explant Type, Culture System, 6-Benzyladenine, Meta-Topolin and Encapsulation Affect Indirect Somatic Embryogenesis and Regeneration in Carica papaya L.

A protocol to propagate papaya hybrid plants through indirect somatic embryogenesis was developed considering the effect of explant type, culture system, particular cytokinins and encapsulation, in different stages of the process. Optimal 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations for non-embryogenic callus formation ranged between 9.0 and 27.1 μM in half-cut seeds, while higher concentrations were harmful. Non-embryogenic callus was also obtained with 22–158 μM 2,4-D from hypocotyl segments. Callus with embryogenic structures was only obtained in half-cut seeds cultured in the darkness on half-strength Murashige and Skoog culture medium supplemented with 2,4-D, while hypocotyl segments and isolated zygotic embryos failed to produce this type of callus regardless of the 2,4-D and sucrose (30 and 70 g l-1) concentrations tested in this study. Both, embryogenic callus development and quantity of somatic embryos formed per embryogenic callus, which ranged between 11 and 31 units after 14 months, required 2,4-D, but without any effect of the concentration. Histological studies confirmed the multicellular origin of the somatic embryos. In further steps, liquid medium induced over four times more somatic embryos than agar-gelled medium and showed significantly higher production of globular somatic embryos (85 vs. 57%). Both, 6-benzyladenine (BA) and meta-topolin (Mtop) stimulated sprouting (40–45%) of the somatic embryos (development of shoots only) in concentrations of up to 2.7 and 10 μM, respectively. Sprouting probability showed a 2nd order polynomial trend despite the range of concentration used for each cytokinin. This is the first report about the positive effect of Mtop on the apical shoot development of Carica papaya somatic embryos known to the authors. Radicle growth was observed in 5% or less of the cultivated embryos, regardless of the BA concentration. Finally, all encapsulation conditions tested (2.5, 3.5, and 4.5% sodium alginate, combined with 50 and 100 mM CaCl2) reduced sprouting of somatic embryos when compared to the non-encapsulated ones, whereas capsule hardness showed low correlation with embryo sprouting. Embryos were further cultivated until they became plantlets approximately 5 cm long. They were acclimatized and afterward planted in the field, where they flowered and produced fruit.

Sensory acceptance and qualitative analysis of fruits in papaya hybrids

Over the last three years, Brazil has been ranked among the three largest producers of papaya. This study aimed to evaluate the acceptance and commercial standard of papaya fruits according to their sensory traits and provide information about the organoleptic and qualitative aspects of the fruit. Ten papaya genotypes grown in Linhares-ES were investigated, arranged in a randomized block design with four replications. Ten fruits from each genotype were randomly collected from each replication, which totaled 40 fruits per genotype. The fruit harvest was performed at stage 1 of maturation. The following genotypes were assessed: hybrids UC13, UC14, UC15 and UC16, from the 'Solo' group; hybrids UC03, UC10 and UC12, from the 'Formosa' group; and 'Golden', 'Calimosa' and 'Tainung 01', which were used as controls. The sensory evaluation of the genotypes was carried out in full balanced design by 50 evaluators. When submitted to sensory analysis, the hybrids showed high performance compared to the controls of each group. Traits such as aroma, flavor and overall impression were crucial in the selection carried out by the appraisers of the hybrids assessed. The hybrids UC10, UC12, UC14 and UC16 were the most accepted and preferred, respectively, in purchase intention.

Adaptability and stability of papaya hybrids affected by production seasonality

Abstract The present work aimed to estimate the adaptability and stability of new papaya hybrids. The experiments were carried out at the company Caliman Agricola S/A, in the municipalities of Linhares-ES and Pureza-RN, with seven hybrids from inbred parents of the groups ‘Solo’ and ‘Formosa’ and three controls (‘Golden’, ‘Calimosa’, and ‘Tainung 01’). The experiment consisted of a randomized block design with four replications and ten plants per plot. The variables mean fruit weight (MFW), number of commercial fruits (NCF), and production (PROD) were measured at 270, 360, 450, and 540 days after planting. Afterward, the adaptability and stability of the hybrids were estimated using the Lin and Binns, Eberhart and Russell, and Mixed Models. MFW was less affected by the evaluation periods and showed high behavior predictability. The hybrids UC10, UC12, UC14, UC15, and UC16 were the most adapted and predictable and can be recommended for the regions where the experiment took place.

Heterosis and genetic diversity for selection of papaya hybrids for resistance to black spot and phoma spot

In this work, two experiments were set up in order to select papaya hybrids and verify heterosis expression for black spot (Asperisporium caricae) and phoma spot (Stagonoparopsis caricae) resistance. Experiments were set up in randomized blocks with two replications. Black spot and phoma spot incidence and severity on leaves were evaluated, and fruit damaged area by black spot was estimated. These characteristics were used to estimate genetic distance with complement of Jaccard’s Index. For black spot resistance, 77 % of hybrids showed heterosis for at least one of three evaluated characteristics and 58 % of hybrids showed heterobeltiosis effect. For phoma spot severity, there was heterosis manifestation in 56 % of hybrids, and 30 % of them showed heterobeltiosis effect. Therefore, heterosis was found in most of the hybrids, emphasizing the possibility of using hybridization to develop resistant genotypes. We observed that the best estimates of heterotic effects were obtained by crossing genetically distant individuals, indicating the existence of a positive relationship between genetic distance and hybrid performance. Together, the results highlight the hybrid ‘Americano’ x ‘Waimanalo’ as having a strong potential to reduce the intensity of these two diseases.