Progress in the development of PRSV-P resistant papaya (Carica papaya L.) through intergeneric hybridization
2004
Siar, S.V. | Sajise, A.G.C.Philippines Univ. Los Banos, College, Laguna (Philippines). Inst. of Plant Breeding | Nerradura, L.E., Covacha, S.A., Drew, R.A., Brion, C.M.O.
Vasconcella quercifolia is a wild relative of Carica papaya that carries gene/genes for resistance against Papaya Ringspot virus Type P (PRSV-P)- the most dreadful disease of papaya worldwide. Successful production of fertile F1 intergeneric hybrids of C-papaya V. quercifolia was done in Australia and six intergeneric hybrid lines (401, 404, 410, 468, 469 and 507) were introduced in the Philippines to introgress PRSV resistance to four inbred lines with good horticultural traits by conventional breeding thru series of backcrossing and evaluation of the resulting progenies. Two intergeneric hybrids (410 and 468) remained virus-free in IPB experimental field two years after planting. Susceptible intergeneric hybrids (401,404,469 and 507) succumed to PRSV seven months to two years after field planting. PRSV symptoms were observed and confirmed by ELISA test results. Backcrossing activities were focused on intergeneric line 410 as pollen source because of its ability to consistently produce viable pollen (1.2 to 2.2%) in sex-stable male trees. Seven hundred fifty six fruits were harvested and 100,096 seeds were dissected from the different crosses made. Among the four papaya inbred lines (4108, 4172, 5648 and 5893), inbred lines 5648 comprised the highest portion of the embryos rescued (64.76%) and did not show severe PRSV symptoms after two years in the field. Viable embryos were also recovered from the other three inbred lines. Out of 315 genotypes, one genotype (BC1 5648x410) showed putative resistance to PRSV after three mechanical inoculations. ELISA test confirmed the absence of the virus in the promising resistant genotype three months after field planting. Morphological characteristics of the BC1 hybrid are similar to papaya however, it has a shorter juvenile stage.
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