Passiflora tripartita var. mollissima (banana passionfruit).
Authors: Popay Ian 
Published: March 2021

Abstract

Genetics: The chromosome number of P. tripartita var. mollissima is 2n=18 (Wagner et al., 1990). Physiology and PhenologyWilliams and Buxton (1995), almost certainly working with P. tripartita var. mollissima, found that in New Zealand establishment is restricted to areas of high light levels and soil disturbance. P. tripartita var. mollissima vines in the forest canopy were found to originate from adjacent open areas up to 15 m away. Baars and Kelly (1996) and Beavon (2007) in New Zealand reported that for P. tripartita var. mollissima, light availability appears to be important for the survival of seedlings. Reproductive Biology: Although P. tripartita var. mollissima does not appear to produce fruit apomictically (Beavon and Kelly, 2012), stems that are broken or cut can grow new roots if they contact moist soil (Williams and Buxton, 1995). Self-incompatibility has not been observed in the Tacsonia group (Coppens d'Eeckenbrugge et al., 1997), and stigmatic movement does not occur during anthesis as is observed in the Passiflora group. Research in New Zealand on P. tripartita var. mollissima by Beavon (2007) and Beavon and Kelly (2012) investigated mating systems and reproductive traits. They and other authors pointed out that humming birds are responsible for pollination in the species' native environments. According to Quintero (2009), honey bees are also important pollinizers helping to improve fruit size and quality. In New Zealand, visitors to flowers were almost exclusively introduced honey bees (Apis mellifera) and bumble bees (Bombus spp.). Beavon and Kelly (2012) compared fruit set, seed set and germination success between hand-selfed, hand-crossed, bagged and open flowers. Bagging flowers to exclude pollinators reduced fruit set from 18.0% to 3.0%. Fruit set in hand-selfed flowers was lower, at 17.5%, than in crossed flowers, at 29.5%. However, bees did not perform as well as either hand-selfing or hand-crossing, indicating significant pollen limitation. The flowers are large in relation to bees and bees can visit the nectar source in them without necessarily contacting either anthers or stigma. Clearly, however, pollination by bees is adequate to allow the species to flourish in New Zealand and elsewhere. The different pollination methods tested by Beavon and Kelly (2012) had no significant effect on fruit size, nor on the number of seeds per fruit, which averaged 108. Neither was there any consistent effect of pollination treatment on seed germination. In Hawaii, abundant fruit set is observed. This seems to be due to a mixture of spontaneous self-pollination and pollination by insects. The newly opened flowers have exposed stamens, favourable to cross-pollination by insects; if cross-pollination does not occur, each flower later pollinates itself through movement of the stigmas to touch the stamens (Duarte and Paull, 2015). Williams and Buxton (1995) found that fresh seed germinated over 12 weeks at 25°C under constant low light, but that 73% remained ungerminated after that time. LaRosa (1992), in her studies on germination with P. tarminiana, found broadly similar results. Beavon (2007) found that seeds cleaned of flesh germinated in slightly higher numbers than did uncleaned seed, but there were significant differences between germination in the field (much lower, at 9% of cleaned seed) and in a glasshouse (66% of cleaned seed).In its native environment, P. tripartita var. mollissima is capable of active growth, and of flower and fruit production throughout the year with little seasonal variation. Fruits are attractive to birds, pigs and small mammals, which consume the seeds with the fruit and may pass the undamaged seeds through their digestive tracts (LaRosa, 1984; Williams and Buxton, 1995; Beavon, 2007). Fruit production under cultivation in Bolivia is as high as 1000 kg of fruit/ha/week, and 13,000 kg/ha in 3 months during peak harvest (Casanas-Arango et al., 1996), indicating the potential for production and spread in areas of its introduction. Environmental Requirements: P. tripartita var. mollissima is a species of mesic and wet, cool (10-20°C), upper-elevation habitats. It is a cool climate crop with ideal average temperatures of 14-16°C, conditions found between 1800 and 3200 m in the Andes (Fischer et al., 2009), with an optimum of 2200-2400 m altitude (Bonnet, 1988; Schoeniger, n.d.). Coppens d'Eeckenbrugge (2001) reported that in its native environment it is not well adapted to grow under 2400 m, and that its fruit grow bigger at higher altitudes. It grows at 3400 m in Cusco, Peru (Missouri Botanical Garden, 2003) and has adapted well to altitudes of 1200-1800 m in Hawaii and New Zealand. In New Zealand, Baars et al. (1998) found that sites where it grew were generally characterised by high soil pH, warmer and lower altitude sites, nearness to coast, westerly aspects and early successional vegetation. The plant can stand light frosts (Munier, 1961) and temperatures of -5°C for a short time. At higher altitudes, fewer anthracnose problems are experienced (Campos, 1992). The optimal rainfall is between 1500 and 2000 mm (Quintero, 2009) uniformly distributed, otherwise irrigation is necessary for continuous fruit production. Dry periods occur in most of the Peruvian and Bolivian Andes where rain seldom reaches these amounts and normally occurs during only 6 months of the year (Duarte and Paull, 2015). Both Baars and Kelly (1996) and LaRosa (1992) provided evidence that growth and reproduction appear to be restricted to high-irradiance environments, with ideal growing conditions of 1200-1500 h of sunshine per year (Campos, 1992). Photoperiod does not seem to have an effect on flowering since it does flower for long periods of the year at different latitudes. Wind is very damaging to this plant, breaking young shoots and causing flower drop (MAG-INCCA, 1991). Fruit can also be damaged by rubbing with other plant parts. Pollinating insects are also affected by wind. Soil type and soil pH appear not to be critical to the growth of P. mollissima. Plants have been grown experimentally in soils of various consistencies, as well as in sand and vermiculite (Gardner, 1989). The plant needs a soil profile that is at least 50-60 cm deep, medium textured (loam to sandy loam) and rich in organic matter (MAG-INCCA, 1991). The soil should have a good water retention capacity since the vine does not stand long dry periods. The area should not be subjected to flooding and requires good drainage. Campos (1992) suggests an ideal pH of 5.5-6.5. Casierra-Posada et al. (2011) explored the effects of soil salinity on P. tripartita var. mollissima, having commented that current agricultural practices in Columbia are tending to increase soil salinity. They found that with increasing salinity, number of leaves, shoot length, specific leaf weight, leaf area and dry matter all decreased, concluding that banana passionfruit seedlings are moderately sensitive to salt stress.