Guava Fruit Anthracnose and the Effects on its Nutritional and Market Values in Ibadan, Nigeria

Abstract

The etiology of guava fruit anthracnose was investigated at Ibadan in the humid forest of Southern Nigeria. Result of the investigation revealed that Colletotrichum gloeosporioides was responsible for the anthracnose and the fruit rot diseases of guava fruit. Eighty percent of the guava plants were found infected with anthracnose disease and over 40% of the fruit produced on those trees were severely infected. The non-infected guava fruit was significantly higher than the anthracnose infected guava fruit in carbohydrates, crude fibre, ash, fat, protein, Ca, Fe and P. A significant reduction in the price of guava was found associated with anthracnose infected fruits in all the 3 major market surveyed. Key word: Guava % fruits anthracnose % Colletothrichum gloeosporioides % market surveyed INTRODUCTION the fruits right on the tree prior to ripening. This disease Guava (Psidium guajava) a vitamin C enrich fruit non-attractive to both farmers and in the home gardens. plant is grown abundantly throughout western Nigeria. It has been reported that anthracnose has becomes a It is an important fruit in many parts of the world where serious obstacle to guava cultivation, food values and the climate is suitable for its production [1]. Guava is one market price are falling and cause a great threat to of the leading fruits of Mexico [2]. The guava fruits germplasm preservation in Bangladesh [4]. contain moisture (85%), proteins (7%) and carbohydrate The present research was initiated to investigate (11%) [1]. Guava fruits are processed into guava paste the etiology of fruit anthracnose, its effects on the and guava cheese, which are staple sweets and guava, nutrition and the market value of guava fruit in Ibadan jelly which is almost universally marketed [2]. It is also the humid forest of south-western Nigeria. made into fruit leather [3] and syrup for use on waffles, ice cream, puddings and in milkshakes [2]. Guava juice MATERIALS AND METHODS and nectar are among the numerous popular canned or bottled fruit beverages of the Caribbean area [2]. Survey of fruit anthracnose of guava in Ibadan In South Africa, a baby-food manufacturer markets the lowland rain forest zone of western Nigeria was carried a guava-tapioca product and a guava extract prepared out in the year 2000, 2001 and 2002. Ibadan (7° 20'N, from small and overripe fruits is used as ascorbic-acid 3° 50'E: 200 mm above sea level) is in a transition zone enrichment for soft drinks and various foods. Also, between the humid forest and derived savannah guavas are mixed with cornmeal and other ingredients to agro-ecologies of Nigeria. It has a mean annual rainfall of make breakfast-food flakes [2]. Despite the economic 1200 mm and mean daily temperature of 34°C (max) and importance of this crop, it’s production is limited by 24°C (min), with over 2 million people. some biotic factors in humid forest region of Nigeria. Guava fruit showing symptoms of infection and Most of the guava fruits produced in the humid forest the non-infected ones were collected from home gardens region of south-western Nigeria is associated with fruit in Apata, Ojo and Moniya all within Ibadan metropolis. anthracnose. This anthracnose was commonly found on These were then kept in sterile sampling bags and has made guava production in the region almost World J. Agric. Sci., 1 (2): 169-172, 2005 170 brought to the plant pathology laboratory of the institute Market survey: The market survey of the anthracnose of Agricultural research and Training/ Obafemi Awolowo infected guava fruits were conducted in the year 2001 and University, Moor plantation Ibadan, Nigeria. Three guava 2002, respectively. The price of both anthracnose infected trees mainly grown in the zone were used for the guava fruits and the non infected ones were obtained in experiment in each of the above locations. 3 main markets located at Ojo, Sango and Apata in Ibadan The sampled fruits were surface sterilized for 3 min metropolis. with 1% NaOCL and rinsed in 4 successive changes of sterile distilled water. The surface-sterilized fruits RESULTS AND DISCUSSION showing symptoms of canker were then sliced into 2 mm pieces, then plated on sterile potato dextrose agar (PDA) The first observable symptom of the guava fruit in Petri dishes and incubated for six days under anthracnose on the field was small, slightly sunken, dark alternating 12 hr light and dark periods at 26°C. The fungal or blackens (necrotic lesions) on immature fruits. The isolates were examined under a stereo binocular spots often enlarge up to 1-2 cm in diameter and their microscope. The identity of these fungi was determined central portion becomes dark black due to the presence of using cultural, morphological and description in existing black acervuli. The spots are usually numerous and publications [5, 6]. Pathogenicity tests were carried coalesce, leading to the eventual rotting of the fruit. Both out on the identified isolates as described below. green and ripe guava fruits were usually affected with Pathogenicity Test: Six freshly harvested guava fruit diseased portions are comparatively harder than soft. intact to the twigs were surface sterilized by swabbing The symptoms were initially observed in mid-March and with 70% alcohol and placed in the conical flask by the end of June over 80% of the fruit on the field containing sterile water when the distal end of the twigs were infected. Green unripe fruits once infected undergo immersed in water. Fruits were inoculated with one single forced ripening and then dry up rapidly becoming organism in the way it was done in situ inoculation. mummified. Inoculations fruits were done following the procedures When the cavity of the fruit is open, the canker was of Hossain [7]. The inoculated fruits were then placed in seen to extend to the inner cavity of the fruit. Seeds from moistened plastic container and incubated at 25°C in the infected fruits harboured the pathogen. Gallenkamp incubators for 72 hr. After which observations The pathogen found mainly associated with the fruit on the development of infection were made. anthracnose was C. gloeoisporioides. In Culture, the The experiments consist of 6 guava fruit intact to the fungus produced whitish mycelium at the early stage of twigs inoculated with sterile PDA agar discs and growth followed by pinkish coloured conidia that incubated as decribed above. The extent of rot was grows in a concentric manner on PDA. Black acervuli determined by measuring the size of infection (mm). developed from the centre of the plate towards the Nutrient composition: Three guava fruit each from samples. While the other fungal isolates includes Apata and Moniya were used for the analysis; at 3 days Fusarium spp, Pestalotia psidii and Macrophomina interval for 9 days along with 10 freshly picked fruits. spp. Pathogenicity tests revealed the presence of C. The fruits were kept in clean containers, de-seeded and gloeoisporioides as the pathogen responsible for guava weighed. The fleshy pulp was cut into pieces and dried fruit anthracnose in the humid region of south-western in a hot air oven at 60°C for 3 days. The dried fruits pulp Nigeria. When re-isolated the fungus was identical to the was ground into powder. The pulverized samples of the initial isolate. guava fruit (in-triplicates) and those of the freshly picked Out of 12 guava trees examined 10 of them were non-infected fruits were analyzed for moisture, found associated with severe anthracnose infection and carbohydrate, ash, crude fibre, proteins and crude fat on most of the trees over 40% of the fruit produced were according to AOAC [8] procedure. The mineral analysis infected. was also carried out according to standard AACC [9] The non-infected guava fruit was significantly higher method at the livestock analytical laboratory of the than the anthracnose infected guava fruit in the institute of Agricultural Research and training percentage carbohydrates, crude fibre, ash, fat, protein, Obafemi Awolowo University, Moor Plantation, Ibadan, Ca, Fe and P (Table l). Market survey also revealed that Nigeria. the anthracnose-infected fruits attracted low prices infected fruits often with several necrotic lesions. The periphery. The pathogen was isolated from 95% of the World J. Agric. Sci., 1 (2): 169-172, 2005 171 Table 1: The effect of anthracnose on the nutrient composition of guava in Ibadan Nigeria Apata-Ibadan Moniya Ibadan Chemical -----------------------------------------------------------------------------------------------------------------------------------------composition (%) Non-infected fruit Anthracnose infected fruit Non-infected fruit Anthracnose infected fruit Moisture 77.890 91.290 78.290 90.190 a a a a Crude Fiber 7.010 2.320 7.000 2.310 b c c c Protein 1.660 0.300 1.260 0.320 c c c c Fat 1.000 0.430 0.890 0.410 c c c c Ash 0.670 0.230 0.680 0.240 c c c c Carbohydrates 11.290 10.240 11.420 10.260 b b b b Calcium 0.023 0.002 0.023 0.002 c c c c Phosphorus 0.032 0.012 0.032 0.012 c c c c Iron 0.001 0.004 0.001 0.004 c c c c Means in the same column followed by the same letter are not significantly different from one another at p<0.05 Table 2: The effect of fruit anthracnose on the market price of guava fruits in three major markets in Ibadan, Nigeria Infected fruits/ Non-infected fruits/ market prices (N/10 fruits) market prices (N/5 fruits) Market ----------------------------------------------------------------location 2001 2002 2001 2002