The use of wild species in the breeding ( papaya L.- ): a cytological evaluation

Telma N. S. Pereira, Monique F. Neto, Lyzia L. Freitas, Messias G. Pereira

Universidade Estadual do Norte Fluminense Darcy Ribeiro - Campos dos Goytacazes - RJ -Brazil

Introduction

Papaya is a species grown in tropical and subtropical regions. The cultivars of this species are all susceptible to ring spot mosaic virus; however, there is in the Caricaceae family wild species that exhibit resistance genes to the virus as Vasconcellea cauliflora, V. cundinamarcensis, V. quercifolia, and V. stipulata. But, interspecific/intergeneric hybrids are not obtained between the wild species and the cultivated one, thus preventing the introgression of important genes in the cultivated form. The objectives of this study were to generate cytogenetic knowledge by karyotype determination and species meiotic behavior.The study was conducted on C.papaya, V.quercifolia,V.cundinamarcensis, V.cauliflora,V.goudotiana, and V.monoica by routine laboratory methodology.

Methodology

Seeds Germination Pdb=8h Fixation

Observation Coloration Enzimatic

Figure 1- Caricaceae species. A) Carica papaya; B)Vasconcellea monoica; Figure 2- Papaya products. Figure 3- Mitotic protocol. Figure 4- Meiosis protocol. C)Vasconcellea quercifolia;D)Vasconcellea cundinamarcensis; E) Vasconcellea goudotiana; F)Vasconcellea cauliflora.

Results

Table 1 - Karyotype formulas, mean sets lenghts and similarities indices of Caricaceae species. Table 2 - Characteristics evaluated during meiosis and post-meiosis in C. papaya, V. Goutodiana,V. monoica and V. Quercifolia. Karyotype Rec Syi Species Meiosis Recombination Meiotic Pollen Species formula THC TF (%) index index abnormalites index index viability C. papaya 9M 17.18 45.51 82.66 82.69 C.papay a 4.76% 26.0% 94.8% 96.0% V. cauliflora 9M 18.94 46.00 76.55 85.71 V. cundinamarcensis 9M 18.69 46.65 84.11 87.27 V. goudotiana 24.0% 26.2% 85.7% 68.0% V. goudotiana 4SM+5M 23.08 40.25 82.44 67.32 V. monoica 28.5% 25.8% 77.5% 70.9% V. monoica 9M 17.11 44.24 75.88 79.24 V. quercifolia 13.0% --- 94.1% 90.2% V.quercifolia 9M 16.18 46.00 82.33 96.33

A D

B E

C F

Figure 6- Caricaceae meiosis. A)Diakinesis with 9 chromosomes pairs.B)Pre metaphase I; C) Metaphase I with 9 Figure 7- Meiotic irregularities. A) Sticky chromosomes; B) Lagging chromosomes; Figure 5 - Ideograms of six Caricaceae. A) C. papaya; B)V. monoica; C) V. cundinamarcensis; D) V. cauliflora; chromosomes; D) Anaphase I; E)Prophase II; F) Metaphase II; G) Anaphase II and H) Telophase II. Bar:5µm C-E) Irregular segregation; F) Monads; G) Dyads;H) Triads and I) Polyads. Bar: 5µm E) V. goudotiana; F) V. quercifolia. Bar:5µm

Conclusions

- The karyotypes are similar and symmetrical for all the species;

- The species are genetically stables and there are no differences in the chromosomal homology between species that explain the unsuccessful results registered for interspecific/intergeneric hybridization between Caricaceae species.

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