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Screening Passiflora Species For Drought Tolerance, Compatibility With Purple Passion Fruit, Fusarium Wilt Resistance And The Relationship Between Irrigation, Drenching And Media Composition In The Control Of Fusarium Wilt

by Gesimba, Robert Morwani

Abstract (Summary)
Drought and Fusarium wilt are the main constraints in growing purple passion fruit (Passiflora edulis) in Kenya. There is need for drought and Fusarium wilt-resistant rootstock. In an effort to develop a drought and Fusarium wilt resistant Passiflora rootstock, a series of experiments were conducted at The Ohio State University and Egerton University in Kenya, to study vegetative propagation, graft compatibility, drought tolerance, Fusarium wilt resistance in Passiflora species and to identify an integrated control method for Fusarium wilt. In the vegetative propagation, graft compatibility and drought tolerance studies, 20 Passiflora species were screened. Species of the subgenus Passiflora rooted in higher percentages than species of the Decaloba subgenus (81 vs 64%). Cuttings from vines and liana type species rooted in higher percentages than cuttings from annual species when treated with 0.1% indole-3-butyric acid powder (82, 73 vs 44%). Cuttings of Passiflora gerbertii L., Passiflora caerulea L. and Passiflora subpeltata Ortega. could be rooted in high percentages and were compatible rootstocks with the purple passion fruit. Passiflora incarnata, P. caerulea and P. subpeltata had higher drought-tolerance than the other species. In the Fusarium wilt resistance studies, nine Passiflora species were screened using Fusarium oxysporum f. sp. passiflorae isolates from four locations in Kenya. Passiflora edulis f. flavicarpa and P. suberosa were resistant to Fusarium wilt implying that the P. edulis f. flavicarpa plants currently being used by farmers may not be true-to-type and hence susceptible. Passiflora incarnata and P. mollisima were moderately resistant to Fusarium wilt. Passiflora suberosa, P. incarnata and P. caerulea can be improved for use as rootstock alternatives for purple passion fruit. For Fusarium resistant P. suberosa, breeding should focus on improving graft compatibility and drought tolerance. For drought-tolerant P. incarnata, improvement should focus on improving compatibility and Fusarium wilt resistance. Since P. caerulea is compatible with P. edulis and is drought-tolerant, improvement should focus on Fusarium wilt resistance. In the study the effect of irrigation and substrate type in the occurrence and suppression of Fusarium wilt in a passion fruit orchard, two substrates, native soil in Kenya and a formulated substrate comprising of 20% soil, 60% pumice and 20% decomposed bovine manure were evaluated. Substrate treatment was by pasteurization, or three chemicals; Root-guard and Rodozin (both under trials) with Terraclor SuperĀ® as a commercial control. Irrigation methods comprised of a novel integrated container-irrigation system (ICIS-pot) and black plastic mulch with integrated irrigation system (ICIS-mulch), micro irrigation (dripper), basin irrigation and no irrigation as control. Three month old seedlings were inoculated with 2.0 x 106 cfu. of Fusarium oxysporum f. sp. passiflorae macroconidia obtained from infected passion fruit plants. ICIS-pot and ICIS-mulched plots in the field and greenhouse as well as plots treated with Root-guard and Rodozin had low pathogenic Fusarium colony populations. Also ICIS-mulched plots had the highest colony populations of non-pathogenic Fusarium per gram of substrate. In the greenhouse and field, the ICIS-pot and ICIS-mulch irrigation methods significantly reduced Fusarium wilt occurrence 75 days after substrate treatment. ICIS-pot irrigated passion fruits had longer vines in the field. Thus, the use of ICIS-pot and ICIS-mulch together with either Rodozin or Root-guard treatment give short term suppression of Fusarium wilt and increase passion fruit vegetative growth.
Bibliographical Information:

Advisor:

School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:passiflora drought rootstocks fusarium wilt

ISBN:

Date of Publication:01/01/2008

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