Papaya Varieties Research Articles

Papaya seedlings growth using a low-cost, automatic watering controller

The study assessed growth and physiological parameters of 'Sunrise Golden' and 'Tainung 01' papaya seedlings grown in 280mL plastic tubes and watered using a low-cost automatic irrigation system adjusted to operate at substrate water tension for starting irrigation (STI) of 3.0, 6.0 or 9.0 kPa. The water depths applied by the dripping system and drainage were monitored during germination and seedling growth. Germination, emergence velocity index (EVI), leaf area, plant height, shoot and root dry weight, stomatal conductance, relative water content (RWC) and relative chlorophyll content (RCC) were evaluated. Soil nutrient levels were determined by electrical conductivity (EC). Water use efficiency (WUE) corresponded to the ratio of plant dry mass to depth of water applied. STI settings did not affect papaya germination or EVI. System configuration to 3.0 and 6.0 kPa STI exhibited the highest drainage and lowest EC and RCC, indicating soil nutrient loss and plant nutrient deficiency. Drainage was greater in tubes planted with the 'Tainung 01' variety, which developed smaller root systems and lower stomatal conductance than 'Sunrise Golden' seedlings. The highest values for shoot dry weight and WEU were obtained at 6.0 kPa STI for 'Sunrise Golden' (0.62 g and 0.69 g L-1) and at 9.0 kPa in 'Tainung 01' (0.35 g and 0.82 g L-1). RWC at 9.0 kPa STI was lower than at 3.0 kPa in both varieties. The results indicate that the low-cost technology developed for irrigation automation is promising. Even so, new studies are needed to evaluate low-flow irrigation systems as well as the nutrient and water needs of different papaya varieties.

Relación del Color y del Estado de Madurez con las Propiedades Fisicoquímicas de Frutas Tropicales

In this study, the relationships of color and maturity stage with the physicochemical properties of tropical fruits (puerco and corazon varieties of mango, passion fruit, papaya and plantain) were investigated. The color of tropical fruits was measured using image acquisition system, expressed in CIELAB color space. The pH and the maturity index showed good fitting with the color parameters using linear and polynomial models. The pH increased slightly with increasing maturity stage, while titratable acidity decreases in mango, passion fruit and papaya, due to cushioning effect of citric acid. In the plantain, the pH decreases with increasing maturity index. However, titratable acidity increases with increasing maturity stage. This occurs as result of the degradation of starch in sugars and their conversion into pyruvic acid.

Use of morpho-agronomic traits and DNA profiling for classification of genetic diversity in papaya

We examined the genetic diversity of papaya (Carica papaya) based on morpho-agronomic and molecular data. Twenty-seven genotypes grown in Brazil were analyzed with 11 AFLP primer combinations, 23 ISSR markers, 22 qualitative, and 30 quantitative descriptors. For the joint analyses, we used the Gower algorithm (Joint Gower) and the average value of the individual dissimilarity matrix for each type of data (Average-Joint Gower); 359 AFLP and 52 ISSR polymorphic bands were found. Approximately 29.2 and 7.7% of the AFLP and ISSR bands, respectively, were genotype-specific and may therefore be used for papaya variety protection. Although there was a significant correlation between the qualitative and quantitative descriptor dissimilarity matrices (r = 0.43), the morpho-agronomic data were not highly correlated with the molecular data. Moreover, correlation between AFLP and ISSR dissimilarity matrices was nearly null (r = -0.01). Joint Gower analysis of all data showed high correlations, especially for AFLP markers, most likely due to the larger number of bands, generating a strong bias in the diversity estimates. The Average-Joint Gower analysis allowed a better balance between the correlations for the continuous and the discrete variables. The results generated by clustering analysis distinguished 5 genetically distinct groups. While we found that papaya genotypes are significantly variable for many traits, we observed that Average-Joint Gower analysis allowed for genotype clustering based on the most widely used criterion for classifying papaya genotypes, which is fruit type ('Formosa' or 'Solo'). This information helps provide an accurate estimate of the genetic diversity and structure of papaya germplasm, which will be used for further breeding strategies.

Effect of BAU-Biofungicide, Neem Oil and a Nematicide on the Root-Knot (Meloidogyne javanica) of Papaya (Carica papaya)

In a pot experiment, BAU-Biofungicide (Trichoderma harzianum) neem oil and curaterr (carbofuran) 5G were tested against root-knot (Meloidogyne javanica) of two papaya varieties Kashempuri and Deshi papaya. Seedlings were inoculated with second stage larvae of M. javanica. Neem oil (5 ml/ 10g seeds) and BAU-Biofungicide (1:4) were used as seed treatant and curaterr as side dressing. Both the bio-agents significantly increased the root and shoot growth of papaya plant and reduction of galls and eggmasses and suppressed the development of J2, J3, and J4 and adult females of M. javanica. Efficacy of BAU-Biofungicide was to reduce the gall and nematode development and to increase plant growth was similar to nematicide curaterr. BAU-Biofungicide gave higher effect in most of the growth characters compared to neem oil and prevented the development of adult females and juveniles like nematicide curaterr. DOI: http://dx.doi.org/10.3329/bjar.v37i2.11230 Bangladesh J. Agril. Res. 37(2): 271-277, June 2012

Isolation and functional characterization of bacterial endophytes from Carica papaya fruits

To isolate and characterize the endophytes from papaya fruits and to determine the fermentative potential of the strains. Endophytes provide potential sources for novel natural products for the use in agriculture and nutrition. There is very limited information on isolation and characterization of bacterial endophytes from papaya. We describe isolation and characterization of eighteen endophytes of papaya fruit from four economically important papaya varieties viz 'Red lady', 'Solo', 'Coorg Honey' and 'Bangalore'. The phylogenetic analysis based on the 16S rRNA sequence revealed that isolated endophytes are genetically distinct and cluster as discrete clades in the dendrogram. The Bacillus species is a predominant bacterial endophyte across papaya varieties. The seeds and the endocarp of papaya fruits harbour Kocuria, Acinetobacter and Enterobacter species. The Staphylococcus species were detected in the fruit mesocarp of two papaya varieties used in the study. The endophytes isolated from papaya fruits were capable of producing extracellular enzymes like amylase, cellulase, pectinase and xylanase. Three isolates, Bacillus (PE-LR-1 and PE-LR-3) and Kocuria (PE-LR-2), were selected for fruit fermentation, and antioxidant potential of the fermented product was evaluated. PE-LR-3 fermented product has the free radical scavenging activity of 61·2% and a microbial cocktail of PE-LR-3 with Saccharomyces cerevisiae MTCC 2918 enhances the antioxidant potential to 75·7%. These findings suggest that different parts of papaya fruits harbour an array of bacterial endophytes that could be important agents in attributing the high nutritive status to the fruit and can serve as potent microbial cocktails for developing value-added fermented products of this important fruit. This study describes isolation of a bacterial endophyte from papaya fruit that is capable of improving the antioxidant potential of raw papaya after fermentation.

Glycemic Index values of some Jaffna fruits

Background: The incidence of diabetes mellitus has recently increased in developing countries. Scientific data on glycemic index values of common meals is essential to modify the diets for diabetes mellitus patients. This study aimed to evaluate the glycemic index (GI) values of fruits such as ‘Kathali’ (Yellow plantain), ‘Kappal’ (Golden plantain), and ‘Itharai’ (Green plantain) varieties of plantains, jack fruit and papaya. The results will be helpful to physicians and the general public to decide the benefits of the consumption of fruits, particularly by diabetic and coronary heart disease patients.Methods: Healthy volunteers (20 Nos.) of 21.05(±0.92) years, 53.90 (±9.36) kg body weights, 153.92 (±9.15) m heights, and 20.55 (±2.22) kgm-2 body mass indexes were selected with their written consent. After overnight fasting, 75g glucose and each test fruit containing 75g digestible carbohydrate were administered at different instances and blood glucose levels were measured half hourly for two hours. The glycemic response and GI values were calculated and analyzed by Randomized Complete Block Design using SAS analytical package.Results: The mean GI values of the ‘Kathali’, ‘Kappal’, ‘Itharai’ varieties of plantains, jack fruit and papaya were 54.45 (±9.26), 50.43 (±5.79), 48.47 (±10.13), 65.36 (±8.00) and 34.80 (±12.78) % respectively. The GI value of papaya differed significantly (P<0.05) from other fruits. The GI value of ‘Itharai’ variety of plantain differed significantly (P<0.05) from other fruits except the ‘Kappal’ variety of plantain.Conclusion: The three varieties of plantains and papaya were low GI fruits, and jack fruit was found to be an intermediate GI fruit. The presence of dietary fiber, esp. soluble fiber, reduces the glycemic response and glycemic index of foods. Keywords: Glycemic index, glycemic response, fiber, fruits.

Evaluation of arbuscular mycorrhiza and other biocontrol agents against Phytophthora parasitica var. nicotianae infecting papaya ( Carica papaya cv. Surya) and enumeration of pathogen population using immunotechniques

Root rot of papaya, caused by Phytophthora parasitica var . nicotianae, is the most widespread and important disease of papaya and is particularly damaging to many papaya varieties popular in southern India, such as Coorg Honey Dew and Surya. The objective of this study was to evaluate biocontrol agents (BCAs) under controlled and field conditions for their efficacy against Phytophthora infecting papaya cv. Surya and to detect and quantify the reduction in the pathogen population by immunological techniques. Glomus mosseae, Trichoderma harzianum and Pseudomonas fluorescens were inoculated at the time of planting in the nursery and at the time of transplanting in single, dual and tripartite combinations allowing colonization up to 90 days. Plants were challenged thereafter with Phytophthora inoculum multiplied on specialized Phytophthora medium. Uninoculated plants and those inoculated with pathogen only were controls. All the BCAs in general improved plant growth and reduced severity of disease compared to uninoculated control in both pot experiments and under field conditions. Plants preinoculated with G. mosseae + T. harzianum, provided the best results when challenged with Phytophthora, with increased plant height, girth and yield and also reduced disease severity over plants not inoculated with BCAs. Studies with Phytophthora antibodies conjugated with fluorescein isothiocyanate (FITC) and enzyme-linked immunosorbent assay (ELISA) further substantiated the reduction in infection and population of Phytophthora in BCA pretreated plants. Beneficial effect of BCAs may be due to the resistance acquired by the plant and reduction in the population of the pathogen caused by their colonization.

Genetic characterization of papaya plants (Carica papaya L.) derived from the first backcross generation

The limited number of papaya varieties available reflects the narrow genetic base of this species. The use of backcrossing as a breeding strategy can promote increases in variability, besides allowing targeted improvements. Procedures that combine the use of molecular markers and backcrossing permit a reduction of the time required for introgression of genes of interest and appropriate recovery of the recurrent genome. We used microsatellite markers to characterize the effect of first-generation backcrosses of three papaya progeny, by monitoring the level of homozygosity and the parental genomic ratio. The homozygosity level in the population ranged from 74 to 94%, with a mean of 85% for the three progenies (52-08, 52-29 and 52-34). The high level of inbreeding found among these genotypes increases the expectation of finding more than 95% fixed loci in the next generation of self-fertilization of superior genotypes. The mean proportion of the recurrent parent genome found in first-generation backcross progeny was 50.1%; 52-34 had a larger genomic region in common with the recurrent genitor and the lowest level of homozygosity. The progeny 52-08 was genetically closest to the donor genitor, and it also had the highest level of homozygosity. We found that linking conventional procedures and molecular markers contributed to an increase in the efficiency of the breeding program.

Quality of papaya variety 'Rathna' as affected by postharvest handling

Tropical Agricultural Research and Extension is a peer-reviewed international scientific journal covering a wide range of subject areas in tropical and subtropical agriculture published quarterly by the Faculty of Agriculture, University of Ruhuna, Sri Lanka. The journal is also available on the Faculty of Agriculture, University of Ruhuna website https://www.agri.ruh.ac.lk/tare/index.htm .

The Nutritional and Functional Properties of the Seed Flour of Three Varieties of Carica papaya

The Nutritional and Functional Properties of the Seed Flour of Three Varieties of Carica papaya

Cloning and expression analysis of phytoene desaturase and ζ-carotene desaturase genes in Carica papaya

The fruit flesh color of papaya is an important nutritional quality trait and is due to the accumulation of carotenoid. To elucidate the carotenoid biosynthesis pathway in Carica papaya, the phytoene desaturase (PDS) and the ζ-carotene desaturase (ZDS) genes were isolated from papaya (named CpPDS and CpZDS) using the rapid amplification of cDNA ends (RACE) approach, and their expression levels were investigated in red- and yellow-fleshed papaya varieties. CpPDS contains a 1749 bp open reading frame coding for 583 amino acids, while CpZDS contains a 1716 bp open reading frame coding for 572 amino acids. The deduced CpPDS and CpZDS proteins contain a conserved dinucleotide-binding site at the N-terminus and a carotenoid-binding domain at the C-terminus. Papaya genome sequence analysis revealed that CpPDS and CpZDS are single copy; the CpPDS was mapped to papaya chromosome LG6, and the CpZDS was mapped to chromosome LG3. Quantitative PCR showed that both CpPDS and CpZDS were expressed in all tissues examined with the highest expression in maturing fruits, and that the expression of CpPDS and CpZDS were higher in red-fleshed fruits than in yellow-fleshed fruits. These results indicated that the differential accumulation of carotenoids in red- and yellow-fleshed papaya varieties might be partly explained by the transcriptional level of CpPDS and CpZDS.

Carotenoid, flavonoid profiles and dietary fiber contents of fruits commonly consumed in Thailand

Soluble and insoluble dietary fiber and flavonoid contents in 21 varieties of Thai fruits, as well as carotenoids in five varieties of ripe durians were determined. Fresh fruits were purchased from five local markets in Bangkok during July 2008–May 2009. Dietary fiber content ranged from 0.71 to 3.58 g/100 g edible portion, with all five varieties of durian, guava, ripe banana and papaya being good sources of dietary fiber. Durian (Chanee, Kradom, and Puang manee variety) having yellow to deep-yellow color pulp had the highest carotenoid content. Durian, pomelo, guava and ripe banana were good sources of flavonoids; especially pomelo (Thong dee and Tuptimsayam variety) showed the greatest total flavonoid content (13,994.21 and 15,094.99 μg/100 g edible portion). Data in this study demonstrated that Thai fruits are not only a good source of dietary fiber but also a good source of carotenoids and flavonoids.

SEED GERMINATION, SEEDLING GROWTH AND VIGOUR OF PAPAYA UNDER NORTH EAST INDIAN CONDITION

Papaya (Carica papaya L.) is a popular fruit of tropics and subtropics of the world. India is in the forefront of papaya producing nations. Papaya nursery is normally raised through seeds. There are improved varieties of papaya which are being used for commercial cultivation through out the country. But none of the varieties are commercially grown in the north eastern India due to undulating topography, high rainfall, poor transport, marketing facility etc. Hence, the present study was pursued in papaya with the objective of identifying cultivars suitable to north eastern region of India with better germination percentage, seedling growth and vigour. The experiment was executed at the Horticulture division of ICAR Research Complex for NEH Region, Barapani, Meghalaya during 2001-2002 with fourteen papaya cultivars comprising varieties and hybrids of red and yellow flesh types gathered from across the world. The indigenous collections comprised cultivars from Tamil Nadu Agriculture University, Coimbatore (Co-1, Co-2, Co-3 Co-4, Co-5, Co-6, and Co-7), cultivars from G.B. Pant University of Agriculture and Technology, Pant Nagar (Pant Papaya), Indian Agriculture Research Institute, New Delhi (Pusa Dwarf) and Indian Institute of Horticultural Research, Bangalore (Coorg Honey Dew and Pink Flesh Sweet) whereas Sunrise Solo, Thailand and Washington were the other varieties from foreign sources. The seeds were soaked overnight in different concentrations of gibberellic acid (0, 50, 100, and 150 ppm) and sown in perforated polythene bags containing potting mixture. The cultivars differed significantly with respect to their 1000 seed weight, seed germination, time taken for seed germination, seedling length including seedling vigour. Soaking the seeds with GA 3 had a significant effect in improving the germination percentage of papaya cultivars. Increasing the GA 3 concentration from 0 to 100 ppm significantly improved the germination (66.17%) over the control (42.40%) and above 100 ppm the seed germination decreased. GA 3 treatment had a favorable effect in hastening the germination of papaya and the time taken for germination was maximum in untreated control (31.86 days) whereas GA 3 at 100 ppm recorded the minimum period for germination (29.73 days). GA 3 treatment had a significant effect in enhancing the seedling length and it was maximum with GA 3 100 ppm (17.38 cm) as against control recording only 10.98 cm. It is concluded that the papaya varieties viz., Coorg Honey Dew, Pant Papaya, Co-2 and Co-7 possess better seed germination, seedling growth and vigour are highly suitable for commercial cultivation in north eastern region of India and their germination and seedling health can be improved by treating with GA 3 100 ppm.

HURRICANE OMAR WIND TOLERANT PAPAYA

During the mid and late 1990s the US Virgin Islands experienced frequent hurricanes which destroyed most of the papaya crops. From this experience, papaya breeding focused on developing short and compact lines with fruit set within 1 m of the soil. A papaya plot was established in a double-row system, 2 m between plants in a row, 1 m between rows and 3 m between sets of double rows. Papaya trees, 7 months after transplanting, latent with fruit and in the first month of harvest, were subjected to hurricane Omar force winds in October 2008. Papaya varieties over 2 m in height 'Tainung 1', 'Tainung 5', 'Known-You 1' and Kapoho had 10-20% broken stem and 70-80% were blown down. Three compact papaya lines, 1-1.5 m tall, had no broken stems and only up to 15% of the plants blown over. These results indicate that short productive trees, with a lower center of gravity, were able to tolerate hurricane force.

PAPAYA DISEASES IN BIHAR: AN OVERVIEW

Papaya occupies an important position among fruits grown in Bihar. Over the past two decades this crop has experienced considerable reduction in yield due to attack of various diseases. According to an estimate, yield reduction up to 50% has been observed within last 18 years. So a systematic survey was conducted during 2000-08 in different districts of Bihar viz., Samastipur, Muzaffarpur, Vaishali, Siwan, Saran, Katihar, Saharsa, and Bhagalpur to quantify losses due to major diseases of papaya in the state. During the survey two viral diseases were recorded i.e. leaf curl and Papaya ring spot virus. Leaf curl incidence varied between 12 to 27%, while PRSV incidence was most rampant showing cent per cent incidence in all the districts under the survey. Disease symptoms were some times visible in the nursery too. No variety showed tolerance/resistance against the disease. Due to severe disease incidence, area under papaya cultivation is shrinking every year. The entire papaya varieties viz. Pusa Dwarf, Pusa Nanha, Pusa Delicious, Red Lady, Coorg Honey Dew and the local ones were found susceptible. In Samastipur district, after first fruiting, all the leaves of the plant dropped due to severe PRSV attack and gradually the papaya plants succumbed to death. In some cases, papaya plants produced new tiny leaves (rosettes at the top) but affected plants produced very poor yield i.e. less than 10 kg/plant. It is very difficult to continue the crop stand even up to 2 nd year fruiting due to heavy pressure of PRSV in the state. Among fungal diseases damping off, collar rot and fruit rot, were frequently observed in all the districts under survey with varying level of incidence. Damping off disease was recorded only in nursery, while collar rot disease was recorded at various stages of plant growth. Fruit rot disease was incited by a number of fungi though Colletotrichum gloeosporioides was predominant. Fruit rot was observed at different stages of fruit growth but immature fruits were highly prone to this disease. This study may serve as a guide for planning effective management of papaya diseases in this part of the country.

RADIATION INDUCED MUTATION FOR IMPROVING PAPAYA VARIETY IN VIETNAM

A papaya breeding program was initiated at the Southern Fruit Research Institute, Vietnam in 2006 using gamma rays to induce mutation. Germinated seeds of popular local papaya variety Dai Loan Tim were irradiated with gamma rays ranging from 10 to 60 Gy. Radio sensitivity test of germinated seeds showed that LD 50 was 30 Gy, two doses below LD 50 value viz. Ten and 20 were selected for field planting. A total 1000 M 1 plants were planted and screened in the field. Among these, four mutant plants, which were particularly outstanding in vigor with medium dwarf stature, bearing the first flower at a height of 50-60 cm from the ground and improved fruit quality when compared to control were selected. The average fruit weight of four mutant lines ranged from 1.3-1.9 kg/fruit, average total soluble solids from 10.8-11.6 Brix %. Usefulness of these economic mutants for improving precocity and reducing plant height in papaya breeding program is discussed.

EFFECT OF N, P, K AND SPACING ON GROWTH AND YIELD OF PAPAYA (CARICA PAPAYA L.) CV. PANT PAPAYA 1

A field experiment was conducted at G.B. Pant University of Agriculture & Technology, Zonal Research Centre - Nagina during 2000. Three doses of nitrogen i.e. 200, 250 and 300 g and two doses of phosphorus and potash i.e. 200 and 250 g/plant were applied with different combinations. Papaya variety Pant Papaya 1 was sown in the nursery on 20 th July 2000 and the seedlings were planted at three spacings viz. 3×1.5, 2.5×1.5 and 2×1.5 m with two plants per hill on 20 th September 2000. The maximum plant height (144.11 cm) was noted under the N3 P2 K2 (300 g N and 250 g each of P & K/plant) which was followed by N2 P2 K2 (250 g each of N, P & K). Flower initiation at maximum height (84.88 cm) was noted under the treatment of N3 P2 K2 which was followed by N3 PI K2 (81.66 cm) but significantly at par with N2 P2 K2. The maximum days (246.11) taken to flower initiation was N2 P2 K2 treatment which was followed by N3 P2 K2 and N1 P2 K2 treatments but they were statistically at par with each other. The highest average number of fruits (44.66) was recorded in N2 P2 K2 treatment which was followed by N3 P2 K2 and N1 P2 K2 treatments. The maximum average fruit weight 1298.88 g was recorded under N3 P2 K2 treatment which was followed by N2 P2 K2 treatment but it was significantly at par with each other. On the other hand, the minimum average fruit weight (682.22 g) was noted under N1 PI K1 treatment.

OVERVIEW OF THE SOUTH AFRICAN PAPAYA INDUSTRY

The papaya industry is a small but lucrative industry in South Africa. The fruit is currently marketed on the local/domestic market. The primary production techniques range from land preparation to planting and thinning techniques right through to harvesting and postharvest techniques. The postharvest handling of the papaya in South Africa is carried out in a bulk pack house where the fruit is dipped into a fungicide bath to reduce postharvest decay. After sorting a wax is applied to the papaya fruit to assist with appearance. The fruit is then packed into crates for storage in the ripening rooms. From these ripening rooms the fruit is moved to a pre-pack facility for pre-packaging for specific supermarkets. This is the postharvest value adding process. There are pest and diseases that affect the industry. New markets need to be established either local or export markets to manage the increasing volumes of papaya. The South African climate is not ideal for the production of papaya which remains the biggest challenge that the industry faces. There are very limited papaya production areas within the country. Future prospect would be to make use of cold tolerant papaya varieties, optimum use of irrigation and fertilization, improve the disease control methods and establish new markets through awareness programs and marketing strategies.

PAPAYA CAROTENOIDS FOR COMBATING VITAMIN A DEFICIENCY AND AGE RELATED MACULAR DEGENERATIVE DISEASES

Vitamin A deficiency (VAD) and age-related macular degeneration (AMD) are the two health problems related to vitamin A. Many studies were conducted on papaya with respect to nutritional composition, vitamin A precursors, xanthophylls profile, glycemic response, fruit maturity and processing effects on nutritional composition. Present study revealed that papaya contains 0.6/100 g protein and 0.1/100 g fat hence the available energy is around 32 kcal for 100 g ripe papaya. Papaya variety Honey Dew contains good amounts of vitamin C (64 mg/100 g). There are wide variations in carotenes and xanthophylls profile. Some varieties contain lycopene, a powerful singlet oxygen quencher in addition to β-cryptoxanthin (1040 μg/100 g), a xanthophyll attributed in correcting ulcers in the stomach. Papaya is one fruit which not only contains zeaxanthin but also lutein. Papaya contains moderate glycemic index value for longer lasting energy. Fruit maturity studies indicate that total carotenoids content was almost doubled (22 mg/100 g) while β-carotene and β-cryptoxanthin levels increased about three fold during ripening when compared to the values in light yellow ripe fruit. During storage for 24 h (senescence), it was observed that the total carotenoids content was not altered significantly (p<0.001). After 72 h, further decrease was observed in these two carotenoids as well as total carotenoids content of the fruit. Vitamin A activity decreased as the storage time was extended from 24 to 72 h. Papaya fruit pieces stored in refrigerator retained higher percentage of carotenoids than papaya fruit juice. Papaya pulp dried in solar cabinet drier retained carotenoids better than sun drying. A soft texture of fruit and its rich quantities of water soluble vitamins and fat soluble carotenoids with dietary fiber and moderate glycemic index value makes papaya an ideal fruit for pediatric population for VAD and geriatric population for AMD.

IDENTIFICATION OF DISEASE TOLERANCE LOCI TO PHYTOPHTHORA PALMIVORA IN CARICA PAPAYA USING MOLECULAR MARKER APPROACH

Papaya diseases such as root rot and aerial blight caused by Phytophthora palmivora, powdery mildew caused by Oidium caricae, and fruit anthracnose caused by Collectotrichum gloeosporioides, and leaf black spot caused by Asperisporium caricae, reduce yields and increase production costs due to the lack of genetically resistant cultivars. Among these diseases, Phytophthora is particularly devastating because it becomes established in wet, rainy weather when the fungicides are ineffective. The goal of this study is to identify and develop molecular markers linked with P. palmivora tolerance in Carica papaya. We used an F2 population derived from an F1 of the most tolerant Hawaiian cultivar Kamiya, crossed with a highly susceptible cultivar SunUp, to evaluate genetic reaction to Phytophthora infection using a laboratory leaf inoculation, followed by a fruit inoculation. These same progeny were scored for DNA markers associated with resistance using methods of amplified fragment length polymorphism (AFLP) and several polymorphic bands linked with tolerance traits in F2 population has been identified. These markers are further characterized to form sequence characterized amplified region markers. Breeders could utilize these markers to select papaya varieties that carry a P. palmivora-tolerant phenotype. These markers may also assist in the identification and cloning of genes involved in plant defense mechanisms, which would further elucidate the defense mechanisms towards oomycete pathogens.