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Abstract

Papaya seedlings being tested for resistance to Phytophthora palmivora root rot were inoculated with sporangial suspensions which varied from 0 to 18,000/plant. Mortality counts and disease ratings of seedlings taken 1 month after inoculation showed that: (a) developmental resistance increased as seedlings became older and appeared totally developed by the time seedlings were 2 months old; (b) comparisons among papaya lines inoculated with increasing concentrations of inoculum demonstrated a dosage response; (c) 1-month-old papaya lines inoculated with a uniform concentration of inoculum (5,250 sporangia/plant) could be separated into 3 distinct groups. Line 8, ‘Waimanalo’-23, ‘WaimanaIo’-24, and line 40 were resistant; 45-T22 and ‘Kapoho Solo’ were moderately resistant and ‘Higgins’ was susceptible. The correlation between greenhouse and field mortality was r = 0.955, which supports the reliability of the method.

Open Access

Abstract

The inheritance of 8 monogenically controlled plant, fruit, and seed characters in Carica species is reported. The gene for red stem is dominant to that for green stem and the gene for red petiole is dominant to that for green stem and the gene for red petiole is dominant to that for green petiole. Genes for white and purple-blush flower colors are dominant to those for pale yellow; while the gene for red skin color of ripe fruit is dominant to that for yellow. However, the gene for red skin color is not dominant to that for orange skin color; the heterozygote has pink-skinned fruits. The gene for ridging on the fruit (carpel fusion lines) is dominant to that for wide groove, which in turn is dominant to that for narrow groove. Spiny vs. non-spiny seed coat produces an intermediate F1, indicating no dominance. The gene for succulent fruit pulp is dominant to that for dry pulp. The gene for bushy branching is dominant to that for sparse branching.

Open Access
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Abstract

Papaya plants (Carica papaya L.) were supplied with N, P, and K in factorial combinations from vegetative through bearing stages. An increase in N fertilization increased the stem growth rate at the vegetative stage only, but it increased the petiole weight at vegetative as well as bearing stages. K fertilization increased the stem growth rate at the bearing stage, but it did not affect petiole weight. P fertilization increased stem growth rate and increased petiole weight at the vegetative stage only. An increase in N fertilization resulted in increased petiole concentration of N and in decreased petiole concentrations of moisture, K, P, and Ca. P fertilization resulted in increased petiole concentrations of P, moisture, Ca, and Mg. K fertilization resulted in increased petiole concentrations of K and moisture, and in decreased concentrations of N, Ca, and Mg. The relationship between petiole dry weight and N concentrations was determined at 3 rates of P fertilization.

Open Access

Abstract

Shoot tips were removed from field-grown staminate, pistillate and bisexual selections of Carica papaya L. at intervals during a 21 month period, and were cultured in vitro on a sterile establishment formulation consisting of Murashige and Skoog basal medium (MS) supplemented with 50 μm kinetin and 10 μm naphthaleneacetic acid (NAA) in a growth room at 25°C and with a 16 hr photoperiod at 1.5 klx. Established expiants were transferred to proliferation medium consisting of MS with 2 μm 6-benzylaminopurine (BA) and 1 μm NAA. Establishment of expiants was influenced by season, sex type and degree or type of microbial infection. Proliferation rates varied for different clones and declined sharply after about 13 subcultures. Bacterial contamination was a severe problem; however the nearly ubiquitous Pseudomonas sp. contaminant did not cause mortality. Expiants could not be established from stock plants affected by a disease of unknown etiology that appeared in experimental plantings. Frequency of rooting on MS media with or without auxin declined with increased time in culture.

Open Access

An invertase gene was isolated and its mRNA activity and protein levels were determined during papaya (Carica papaya L.) fruit development. A complete invertase cDNA (AF420223) and a partial sucrose synthase cDNA (AF420224) were isolated from papaya fruit cDNA libraries. The invertase cDNA encoded a predicted polypeptide of 582 residues (MW 65,537 Da), and was 68% and 45% identical with carrot apoplastic and vacuolar invertases, respectively. Key amino acids indicative of an apoplastic invertase were conserved. A full-length gene corresponding to the putative apoplastic invertase cDNA was isolated and was organized into seven exons and six introns. Exon 2 (9 bp long) encoded part of a highly conserved region (NDPNG/A). Invertase mRNA and activity levels increased during fruit maturation and sugar accumulation just before ripening. In contrast, sucrose synthase mRNA levels were high during early fruit growth and low during the fruit sugar accumulation stage. A 73-kDa cell wall extractable protein that cross-reacted with carrot apoplastic invertase antisera substantially increased during papaya fruit maturation and declined in full ripe fruit. The increase in invertase protein levels occurred 2 to 4 weeks before maturity and was markedly higher than the overall increase in enzyme activity at this stage. Subsequently, the increase in enzyme activity was higher than the increase in protein levels between 2 weeks before maturity and fully ripe. The results suggested that mRNA level and invertase activity were related to maturity. The data suggested that the invertase was apoplastic, and that post-translational control of enzyme activity occurred, in which a significant accumulation of invertase occurred before the peak of enzymes activity.

Free access

Zinc in xylem and phloem of the citrus rootstock, rough lemon [Citrus jambhiri (L.)] was associated with a Zn-binding protein, designated citrus vascular Zn-binding protein (CVZBP). The apparent molecular mass of the CVZBP was 19.5 kDa after nondenaturing size exclusion chromatography and 21.8 kDa after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Ion exchange chromatography demonstrated that CVZBP was anionic, requiring 0.43 n NaCl for elution from quaternary aminoethyl Sepharose. Antiserum to the protein cross-reacted more with total protein extracts from leaf midveins than with total protein from the rest of the leaf lamina, further suggesting a vascular location of the Zn-binding protein. Quantitative analysis indicated that ≈2 to 3 mol of Zn were associated with 1 mol of native protein. Binding studies with the partially purified CVZBP demonstrated a capacity to bind several divalent cations: Cd, Ni, Pb, and Zn. Reaction with Ellman's reagent suggested that the protein has significant sulfhydryl group content that may be involved in metal binding. N-terminal sequencing demonstrates identity with papaya latex trypsin inhibitor, sporamin, or other Kunitz soybean proteinase inhibitors.

Free access

study, we evaluated the CC PI collection and identified significant levels of resistance to papaya ringspot virus (PRSV) in several accessions collected in northern India and in northern Africa, indicating that CC might be a viable source of resistance

Free access

SDH9 are expressed in the seed ( Nosarzewski and Archbold, 2007 ). Fifteen SDH genes are reported in the pear genome, which is much more than in other rosaceous and nonrosacaeous species such as strawberry ( Fragaria vesca L.) and papaya ( Carica

Free access

[ Fragaria × ananassa ( Song et al., 2009 )], and papaya [ Carica papaya ( López-Gómez et al., 2009 )] have primarily focused on genes related to fruit traits. In recent years, RNAi technology has led to greater accuracy and precision in the modification

Free access

melongena ), melon ( Cucumis melo ), papaya ( Carica papaya ), plum ( Prunus domestica ), potato ( Solanum tuberosum ), squash ( Cucurbita pepo ), sweet pepper ( Capsicum annuum ), and tomato ( Solanum lycopersicum )] are listed. Transgenic papaya with

Free access