Evaluation of Avocado (Persea americana) for Growth and Yield at Teppi, Southwestern Ethiopia

ABSTRACT Avocado is a member of the Lauraceae family. It is a crop with enormous economic significance all over the world. The aim of this work was to evaluate the performance of avocado cultivars for yield and yield components. Six avocado cultivars and one local check cultivar were compared in Teppi Agricultural Research Center. The experiment was laid out in randomized complete block design with three replications. The analysis of variance showed that, for most growth traits except girth above union and girth below union, significant variation has been recorded. The combined analysis over seasons revealed that significant difference between cultivars for most of the characters tested. The over years combined analyses of variance revealed that there was significant difference (P < .05) among cultivars for yield performance. Among the cultivars, the highest yield (29.13 tha−1) was recorded for Ettinger. In contrast, the lowest yield was recorded for local (6.20 tha−1). The cultivars, Ettinger, Hass and Fuerte performed better as compared to other cultivars. Therefore, these cultivars should be multiplied and disseminated for further popularization. The gaps in cultivar improvement, agronomic management and post-harvest handling also need due attention to improve the productivity of avocado in target area.


Introduction
Avocados (Persea americana) are indigenous to Central America, the northern coast of South America, and the West Indies.It belongs to the Lauraceae family (Maranca, 1980).Avocado is rich in unsaturated lipids, improves and maintain healthy heart and circulatory system and it is valuable source of energy.It is rich in calorie, vitamin E, ascorbic acid, vitamin B6, B-carotene, and potassium.Avocadoes are high in monounsaturated fatty acids, dietary fiber, important nutrients, and phytochemicals (, 2019;Fulgoni et al., 2013).It contains 15-30% oil, vitamins A, B6, B12, C,K, E, Folacin and Niacin, minerals, high caloric value 123-387 kcal/kg of edible avocado and has low sugar content (Mooz et al., 2012) and Tan et al. (2017).It plays significant role in economic growth, food security and nutrition (Bergh, 1992).Economically, avocado is playing a pivotal role in the socio-economic life of the farmers in the study area.Currently, the cultivation of avocado is spreading through the country with satisfactory adaptation to different agro-ecologies.Most wet parts of Ethiopia provide favorable weather condition for avocado cultivation (Etissa, 1999).Ethiopia has suitable agro-ecology for the production and cultivation of different tropical, sub-tropical and temperate fruits Teklay et al. (2016).In Ethiopia, avocado covers the area of 17.26% of the fruit crops next to banana.More than 777,430.692ton of fruits was produced in the country.Avocado took up 10.47% of the fruit production and its production is mainly concentrated in southern part of Ethiopia followed by Oromia, Amhara and Benishan Gul-Gumuz (CSA, 2018).The current Avocado national productivity in Ethiopia is 4.52 tha −1 (CSA, 2018) which is very low as compared to the world average production (7 tha −1 ) (FAOSTAT, 2019).
In Ethiopia avocado production is constrained by, shortage of improved cultivars and dependence on local cultivars which are poor yielding and poor quality that does not satisfy the international and domestic market demand in volume and quality (Jalata, 2021).In addition to these, absence of broad genetic base, poor knowledge on nutritional value of fruits, lack of improved planting material and production technology, lack of appropriate postharvest technology, disease and insect pest and marketing problems are among the constraints associated with fruit production in Ethiopia (Derbew and Soon, 2015).Small holder farmers in south western Ethiopia, specifically around Teppi area have been cultivating the local cultivar of avocado which is low in yield.Hence the need to introduce improved avocado cultivars to the target area is crucial to boost the production and productivity.As a result the study was designed to select high yielding and quality avocado cultivars for the target area.

Study Area
The field experiment was conducted from 2015 up to 2020 at Teppi Agricultural Research Center, in south western Ethiopia.Teppi is located at an elevation of 1,200 m above sea level.The research center receives an annual rain fall of 1,678 mm with average maximum and minimum temperature of 30°C and 16°C, respectively Table 1).The soil of the experimental site is reddish brown sandy clay loam classified as Nitosol with pH varying from 5.6 to 6.

Experimental Treatment and Design
A total of six avocado cultivars which were introduced from Melkassa Agricultural Research Centre and one local cultivar was used for this experiment.The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications.The activity was established during 2015.Improved cultivars (Hass, Bacon, Ettinger, Pinkerton, Nabal, and Fuerte) were utilized as scion bud sticks for grafting purposes, with root stocks from local cultivars.Spacing of 7 m between the rows and 7 m within rows was used.Four plants were used per plot for the study.The planting hole with 60 cm depth and 60 cm width were prepared two months before planting and grafted seedlings of each cultivars were planted in to the prepared pits.Agronomic practices like weeding, watering and other tree management was followed as per recommendation.

Data Collection and Analysis
Data collection was done during the year 2019 and 2020.Several parameters were recorded from the planting date to harvest time.The data were collected for two successive years to increase the precision of the data.The major parameters collected are listed as follows: plant height, stem girth at 30 cm above graft union, stem girth at 30 cm below graft union, branch number, number of fruits per tree, fruit weight, and total yield per tree and physical quality traits like: fruit length and diameter and analyzed using statistical analysis system (SAS) software.

Results and Discussion
For vegetative, yield, and yield component metrics, the Analysis of Variance (ANOVA) revealed significant variations across the cultivars (P = .05)(Table 2).This shows the existence of large variability among the cultivars for the parameters considered.The Analysis of Variance for yield and yield-related traits revealed significant differences (P = .05)between cultivars.For most of vegetative traits, significant variation has been observed between cultivars.However, the Analysis of Variance revealed no significant differences between cultivars for girth above union and girth below union.

Tree Height (M) and Canopy Diameter (M)
The ANOVA showed that tree height was significantly (P < .05)influenced by avocado cultivars (Table 2).The cultivar Bacon had tallest plant height (6.48 m), while the cultivar Fuerte was shorter than others (4.9 m).Shorter trees are preferred over taller kinds because they are easier to harvest fruit from, reduce post-harvest loss owing to unmanageable tree height, and allow for easier implementation of agronomic management measures.All of the cultivars in this investigation demonstrated a significant difference in plant height.The genetic heterogeneity among the cultivars could be the reason for the differences in plant girth.This result is agreement with findings of Chen et al. (2007), who reported the significant effects of avocado genotypes on plant height and canopy diameter.The effect of cultivar indicated non-significant difference on avocado canopy spread, except the variety Bacon had significant difference from local cultivar.The canopy width ranged from 3.13 m for local cultivar to 4.31 m for Bacon (Table 2).

Number of Branches, Girth Above Union (Cm) and Girth Below Union (Cm)
The highest number of branches was recorded for the cultivar Bacon (5.25), in contrast, the lowest number of branches was recorded for local cultivar (3.06).There was no significant difference between cultivars for girth above union and girth below union.Hass cultivar showed maximum, which however was not statistically different from other cultivars.This finding disagreed with the result reported by Chen et al. (2007) who reported that there was significant difference in canopy spread between cultivars.The productivity of avocado had shown significant correlation with canopy width.The wider the canopy, the higher will be the percent of incident light intercepted and which would probably enhance more fruit setting (Biazin et al., 2018).Total Yield (tha −1 ) The total yield of avocado was significantly (P < .05)determined by cultivar during the two years.Significantly highest and lowest fruit yield was recorded from Ettinger, followed by Hass and Fuerte cultivars.However, the lowest yield was recorded from local cultivar (Table 2).The highest yield (29.13 ton/hectare) was recorded for cultivar Ettinger.In contrast, the lowest yield was recorded for local (6.20 ton/hectare).The yield obtained from this study were within ranges reported by (Lovatt et al., 2015).They also reported varying yield of different cultivars.From the present study, the yield of all cultivars was lower in the first year as compared to the yield obtained in the second year.This could be probably due to development of vegetative traits like number of branches that contribute for yield of the trees with increasing age.The variation in total yield between cultivars attributed to the environmental condition, genetic potential of the cultivars and agronomic management practices.This finding was in agreement with the result reported by Lovatt et al. (2015) who reported the varying yield between different cultivars.The combined analysis of two year results revealed that the cultivars Ettinger, Hass, Fuerte, Bacon, Nabal and Pinkerton had 369.84, 275, 261.45, 215, 104.19 and 84.03% yield advantage over the local cultivar respectively.Ketema et al. (2010) also reported that, these cultivars are known for bearing uniform and good quality fruits.

Conclussion
Avocado has high potential for improving food security, increasing household income, employment opportunities, poverty reduction and nutritional security.The best performed cultivars like Ettinger, Hass and Fuerte should have to be multiplied and disseminated to the target area.Avocado cultivars that have high yielding, quality and good resistance to different diseases and insect pests have to be released and disseminated to boost avocado production and productivity.In addition to variety improvement, agronomic management, improving pre and post-harvest handling of the crop should be given attention.

Table 1 .
Summary of weather and soil information.

Table 2 .
Mean phonological and vegetative parameters of avocado cultivars at Teppi.