Abstrait

Screening of Carica papaya x Vasconcellea cauliflora hybrids for resistance to papaya ringspot virus (PRSV).

R. Jayavalli*, T.N. Balamohan

Carica papaya x vasconcellea cauliflora and intergeneric F1 hybrids of these species were screened for resistance to severely infected papaya ringspot virus isolates of papaya ringspot virus. Artificial screening for papaya ringspot virus was carried out 27 days after sap inoculation. Out of twenty nine F1 hybrid plants of CO 7 x Vasconcellea cauliflora, only six plants were found free from PRSV symptoms. Similarly, out of fifty five F1 hybrid plants of Pusa Nanha x Vasconcellea cauliflora only twenty three were found free from the symptoms and seventy plants out of 335 plants of CP50 x Vasconcellea cauliflora were found free from PRSV symptoms. The resistance of the hybrids and parents and their hybrids viz., CO 7 x Vasconcellea cauliflora, Pusa Nanha x Vasconcellea cauliflora and CP50 x Vasconcellea cauliflora were subjected to DAS ELISA test. ELISA titre value varied from 0.216 to 0.927. among the parents, the resistant male parent Vasconcellea cauliflora had recorded the lowest titre value of 0.216. However, the susceptible female parent CO 7 recorded the highest titre value of 0.972 followed by Pusa Nanha 0.952 and CP50 0.942. Among the hybrids ELISA titre value ranged from 0.218 to 0.29. Thus, the intergeneric hybrids and Vasconcellea cauliflora plants were resistant to PRSV. Molecular marker viz., ISSR markers were used to check and verify the hybridity. ISSR markers showed confirmity on three hybrid progenies viz., CO7V3, CO7V5 and CO7V6 from CO 7 x Vasconcellea cauliflora. Five female hybrid progenies viz., PNV3, PNV8, PNV9, PNV11and PNV13 and 3 male hybrid progenies viz., PNV1, PNV6 and PNV21 from Pusa Nanha x Vasconcellea cauliflora were confirmed through the ISSR markers. Three female hybrid progenies viz., CPV1, CPV23 and CPV56 and four male hybrid progenies viz., CPV12, CPV26, CPV31, and CPV39 from CP 50 x Vasconcellea cauliflora were also confirmed through the ISSR markers. Hybridity confirmed F1 hybrids are tolerant to PRSV at field conditions.