GROWTH AND YIELD RESPONSES OF THREE GENOTYPES OF PASSION FRUIT (PASSIFLORA VAR. FLAVICARPA AND VAR. EDULIS) TO THREE LEVELS OF POTASSIUM FERTILIZER TREATMENT UNDER TWO ENVIRONMENTS

ABSTRACT

Two  environments  (high  tunnel  and  open  field)  and  three  levels  of  potassium  fertilizer (0kg/ha, 100kg/ha and 200kg/ha) were evaluated for their effects on early growth and yield of three genotypes of passion fruits – conventional, purple and hybrid KPF-4 . Seedlings grown under the two environments showed significant (p<0.05) differences for the morphological growth parameters at varying months after treatment application. Highest numbers of unifoliate leaves 42.2, were observed in the open field than in the high tunnel 12.7.  However, Longest vine 300.9cm was observed in plants inside the high tunnel compared to the open field that gave 105.6cm.   Number of bifoliate and trifoliate leaves were not significantly different  in  the two  environments  but  more were produced  by  plants  inside the tunnel. Furthermore, number of unifoliate, bifoliate and trifoliate leaves, number of branches and vine length varied among the three genotypes; KPF-4 had the highest values than the other genotypes.  Different levels of potassium fertilizer (muriate of potash) applied did not show significant difference   although plants that received 200kg k2O/ha of potassium fertilizer produced more bifoliate and trifoliate leaves while vine length, number of unifoliate leaves and branches were higher on those that received 100kg k2O/ha than those with no fertilizer. Comparison of fresh weight of vine, leaf and total dry matter yield indicated that KPF-4 seedlings grown under the tunnel gave the best results. The combined effects of potassium and genotype revealed that conventional genotype with 100kg k2O/ha produced more juice volume and weight while the hybrid with 200kg k2O /ha had longer, wider and thicker fruits than those with no fertilizer.  Percentage weight loss varied significantly (p<0.05) among the three rates of potassium fertilizer. Increase in weight loss was observed in plants with no fertilizer than those with fertilizer. Evidences from the study revealed that high tunnel and different rates of potassium fertilizer enhanced growth and yield quality of passion fruits. The hybrid KPF-4 grown with 100kg k2O/ha gave the best results than other genotypes.

INTRODUCTION

Passion fruit is one of the extremely important   and versatile types of tropical fruits grown all over the world whose demand is growing both in export and domestic markets. It is a vine species of passion flower that is native to Southern Brazil through Paraguay to Northern Argentina (Manica, 1981).  This exotic fruit belongs to the family of Passifloraceae of the genus Passiflora.   Passion fruit is a shallow-rooted, woody perennial plant that climbs by means of tendrils to almost any support (Morton, 1987).  This crop is propagated either by seed or through cuttings and can grow up to a height of about 5-7m per year once established and must have strong support. The plant is short- lived for about 5-7years. There are several varieties of passion fruits but the most commonly cultivated edible types are the yellow passion fruits (Passiflora. edulis Sims f. flavicarpa Deg.) and the purple passion fruits (Passiflora. edulis Sims f. edulis) .

The purple variety is smaller, less acidic, varies in taste and juiciness, has intense aromatic scent and does better at higher altitude whereas the yellow type is bigger, has similar taste, less aromatic, more acidic, has more vigorous vine, tend to yield higher and is more resistant to diseases (Maciel et al., 1997) and also grows well in hot low-lying areas (Bradtke, 2010). Both  varieties  are  green  before  ripening  and  are  grown  for  commercial  and  domestic purposes.

Commercial quantities of passion fruit are mostly produced in greenhouses where rainfall is low to moderate and dry season is long (Paull and Duarte, 2012).   In recent times, passion fruits are not only cultivated in an open field but also in a growing system similar to green house popularly known as high tunnel used in horticultural industries to protect microclimatic variables as well as increasing yields than field crops (Jiang et al., 2003).

Among fruits, it has been considered an attractive farming choice since it provides a fast economic  return.  The  fruit  can  be  eaten  fresh  or  consumed  as  fruit  juice  and  other

formulations containing the fruit. Fresh passion fruit juice is a good source of protein (5.2 g/cup of fruit juice), rich in mineral salts  and vitamins such as Vitamin A (3002IU) and C (70.8mg), which are important for the healthy development of children, pregnant women and the elderly (Khalid et al. 2004).  Nearly, half of the fresh fruit yield can be converted to juice that is high in antioxidants. With high export value, it can serve as potential source of foreign earnings. In addition to high vitamin C content, passion fruit also contains the B vitamin niacin that helps in the creation of certain enzymes, as well as in the formation of important chemical  messengers  in  the  brain.  However,  these  exotic  fruits  also  contain  a  lot  of potassium, iron and phosphorus. The seeds are used to manufacture soap, paint, cooking oils and rich in insoluble dietary fibre(64g/100g) that serve as an effective functional ingredient to promote intestinal amylase activity and reduction of caecal pH and caecal ammonia content (Chau and Huang, 2004; Chau et al., 2005).  Passion fruit leaves contain oil that can be used for domestic, industrial and medicinal purposes and reported to have the ability to cure diseases such as urinary tract infection, chronic inflammations, asthma and hypertension (Decuypere, 2000). Passion fruit, being a highly valued crop across the world, is rarely cultivated in warm high rainfall environments; In Nigeria, it is still an unexplored kind of fruit farming in spite of its importance.   Its production is low and mostly restricted to the moist savannah zone and its average yield is nearly ten-fold lower than production obtained in other parts of the world.  Apart from the fact that passion fruits, just like any other fruit, has its good and bad seasons, lack of appropriate fertilizers treatment could possibly be one of the limiting factors because fertilization is one of the agronomic practices in fruit farming that influences productivity, quality and shelf life of fruits.

According to Baiyeri et al. (2011) fertilizer treatments influenced seed quality, seedling emergence and growth quality of passion fruits. The sensitivity of passion fruit plant to potassium fertilizer under low to moderate atmospheric conditions is well known but its

response under conditions of high rainfall, relative humidity and temperature is less reported. The questions now are can three genotypes of passion fruit seedlings thrive in a high tunnel under the warm high rainfall conditions of Nsukka and environments.  Also, what would be the levels of potassium fertilizer requirement, if they are to be grown under high tunnel conditions and in the field?

Therefore, the general objective of this study was to evaluate the growth and development pattern of three genotypes of passion fruit seedlings to potassium fertilizers under the warm, humid, high rainfall environmental condition in Nsukka. However, the specific objectives of this study were to:

1.        Determine the effect of high tunnel on the growth pattern of three genotypes of passion fruit;

2.        Evaluate the effect of three levels of potassium fertilizer on  the    growth    and    dry matter accumulation of the three genotypes of passion fruit; and

3.       Investigate the effect of three rates of potassium on post harvest and nutritional quality of the three genotypes of passion fruit.

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