Mechanical Strengths, Hydraulic Conductance and Growth of Passiflora edulis f. edulis Grafted on Five Different Rootstocks at Three Different Cleft Lengths and Their Susceptibility to Wind Damage in Nakuru Kenya

Abstract

This study was carried out to determine the relationship between graft union mechanical strengths, hydraulic conductance and plant growth of Passiflora edulis f. edulis grafted on different rootstocks and cleft lengths and their susceptibility to wind damage in Nakuru Kenya. Vertical rupture, horizontal tensile strength, hydraulic conductance and growth of Passiflora edulis f edulis grafted on P. edulis f. flavicarpa, P. ligularis, P. mollisima, P. subpeltata and P. caerulea rootstalks with 1, 1.5 and 2 cm cleft lengths were determined 13 weeks after grafting and compared with self-grafts. Vertical rupture force was highest in P. edulis f. flavicarpa self grafts in all the three cleft lengths. Grafts with 1 and 1.5 cm cleft lengths had no significant difference in horizontal tensile strength. Self grafts with 1.5 cm clefts had higher hydraulic conductance than cross grafts. Scion growth was significantly high when the union length was 1.5 and 2 cm in P. ligularis by P. edulis and P.  flavicarpa by P. edulis graft combinations. Vertical force generated by wire displacement showed that enough force was generated that could damage the vines The strength of wind needed to break the weakest was higher than the maximum recorded in Nakuru County implying that cross grafts of P. edulis f. flavicarpa by P. edulis f. edulis with 1.5 cm cleft lengths are not prone to wind breakages in Nakuru, Kenya. However, the growers need to graft their passion fruits with 2 cm cleft lengths since wire displacement develops enough vertical force that could damage the vines. Results indicated that the best rootstock for Passiflora edulis was Passiflora flavicarpa.