Characterization of avocado (Persea americana Mill.) in Nagari Giri Maju, West Pasaman Regency based on fruit morphological characteristics

The avocado plant is cross-pollinated; thus, each plant has a different genetic fashion. This research was carried out in 2020 in Luhak Nan Duo District, West Pasaman Regency. The research aimed to obtain information about the morphological characteristics and describe the diversity of avocado plants in Nagari Giri Maju, the center of avocado production in Luhak Nan Duo District, West Pasaman Regency. The research used a survey method with purposive sampling as a sample collecting design. Morphological characterization was carried out on avocado fruit. Exploration and characterization conducted successfully identified 238 accessions of avocado that showed variability in fruit shape, ripe fruit skin color, ripe fruit flesh color, fruit flesh texture, and fibrous within fruit flesh. Wide variability was detected only for fruit weight. Ten potential avocado accessions were obtained from the characterization with the following characteristics, i.e., oval fruit shape, grade A fruit weight, green color of ripe fruit peel, and buttery and non-fibrous fruit flesh texture. Hence, the accessions can be recommended for new potential avocado varieties. Based on qualitative traits, cluster analysis resulted in seven groups with a 38% degree of similarity.


Introduction
The avocado (Persea americana Mill.) originates from the humid tropics of Mexico, and now the plants have spread throughout the world [1].Avocados comprise three race types, namely, Guatemalan (P.americana var.guatemalensis), Mexican (P.americana var.drymifolia), and West Indian (P.americana var.americana) [2].Mexican avocado race tolerates low temperatures and has a high oil content.The Guatemalan race is less cold tolerant, while the West Indian is tolerant of salty soils but sensitive o low temperatures.All three races have the same number of chromosomes, which is 24 (2n=2X=24), so the three races can be easily crossed.The commercial avocado varieties found throughout the world are a cross between the Mexican and Guatemalan races [3][4] [5].
Avocado fruit contains high unsaturated fat such as oleic acid (78%); hence, it affects immunity and contributes to medical treatment of cancer, HIV, and infection [6] [7], and reduces heart attack [8].Based on West Sumatra province's statistics, avocado production in the previous five years indicated fluctuating values.In 2019, avocado production in West Sumatra reached 54,203 tons [9].One of the avocado-producing areas in West Sumatra is West Pasaman Regency.Avocado production in West  [10].
The producer of avocado in Luhak Nan Duo District is Nagari Giri Maju.Avocado plants in Nagari Giri Maju are planted semi-intensively in smallholder plantations far from the residential areas [11].Based on a survey and interviews with avocado farmers, the total land planted with avocados in Nagari Giri Maju is approximately 886 hectares, and only 15% attain the reproductive phase.Avocado of Giri Maju (GM) has been marketed to Java and began to globalize when consumed by Asian Games athletes in Palembang in 2018.The advantages of GM avocado are smooth fruit skin without spots buttery and non-fibrous flesh fruit texture.
Avocado plants in Nagari Giri Maju are generally cultivated using seeds, contributing to high diversity among plants [11].The existence of cross-pollination also generates a high diversity of avocados in this area.However, this has not been clearly identified and characterized.The research aimed to obtain information about the fruit's morphological characteristics, describe the diversity of avocado plants in Nagari Giri Maju and recommend accessions as new potential avocado varieties.

Materials and Method
This research was carried out in 2020 at Nagari Giri Maju, Luhak Nan Duo District, West Pasaman Regency.The research used a descriptive method with purposive sampling, viz.plants attained reproductive phase and produced fruits minimum for three seasons.The accession was determined based on individual avocado plants sampled and prioritized to obvious differences.The number of samples was determined based on the size of the population.Determination of the number of samples in the population was measured using Yamane formulae [12], that is: (1) n = number of samples; N = total number of populations; d = margin of error The margin of error value was set at 0,25 (25%) with an accuracy rate of 75%.Estimates of the total population were known from direct interviews with avocado farmers.
Exploration and characterization of avocado plants were carried out by collecting data and determining which plants fulfilled the requirements for observation.The characters observed were morphological, both qualitative and quantitative, according to avocado descriptor by the International Plant Genetic Resources Institute [13] and the International Union of the Protection of New Varieties of Plants [14].Three fruit samples were taken from different picking-time within one accession.The characteristics of fruit picking were that fruits are almost ripe, indicated by dull and dark green skin color.Data from the characterization were analyzed using descriptive statistics [15], with the diversity criteria, refers to Hayati et al. [11].The similarity analysis used the NTSYSpc2.02software [16].

Results and Discussion
The avocado cultivation type in Nagari Giri Maju was a smallholder plantation.The coverage area of each farmer's garden is different, ranging from 1 -10 hectares, dispersed in many locations.The age of the plants ranges from 1 -20 years, and they begin to bear fruit at 2.5 to 3 years from seed propagation and reach the highest production starting at four years.
Based on observations on 238 avocado accessions derived from 21 different plantation owners, variations in fruit characters were pinpointed (Table 1).Narrow-obovate dominated the fruit shape (23%) of nine fruit shapes.Before ripening, all accessions performed dark green in fruit color.Generally, accessions performed alteration of color after ripening into dark purple (28.6%), lightpurple (17.2%), reddish (16.8%), bright green (14.3%) and yellowish-green (3.8%) (Figure 1).Fruits with green skin color contain more chlorophyll than other pigments.During the fruit ripening process, chlorophyll degradation will occur; thus, the chlorophyll content decrease and affect the alteration of fruit color into the other color depending on the pigment contents [17].Based on the wholesaler in Nagari Giri Maju, consumers prefer green skin after ripening due to a longer shelf-life of fruit than black or other colors [18].Ripe fruit with black skin color is easy to spoil [19].Avocados with green skin are in great demand by consumers from the Caribbean, and Central and South America [20], indicating that consumers' preferences for green skin color depend on ethnicity and country of consumers [21].Consumers also prefer a buttery texture and not-fibrous flesh fruit because it is savory and slightly sweet.High fibrous in flesh fruit will lessen consumer preference [18].
Based on the 01-3168-1992 avocado SNI standard, there are three grades of avocado fruit.Grade I weighs 451-550 grams per fruit, grade II 351-450 grams per fruit, and grade III 250-350 grams per fruit.According to the wholesaler, grades A, B, and C consist of 3, 4, 5, or more fruits per kg.Grades A and B meet supermarket preferences.Big avocado fruit is found separately in many fruit forms, usually in spheroid, obovate, clavate, and rhomboidal shapes.The dominant color of ripe fruit skin on large fruit is green and dark purple.Oval or slightly oval is preferred to distinguish it from the Tongar variety, which is also widely cultivated in Nagari Giri Maju.The fruit shape is a commercially crucial morphological character that appeals to market consumers [22].
Variation among 238 avocado accessions in Nagari Giri Maju showed narrow variability for fruit characteristics, except fruit weight [Table 2].Wide variability indicates a high probability of obtaining avocado fruit with a particular fruit size in Nagari Giri Maju.Wide variability for fruit weight is due to plant genetics and environmental factors, such as plant performance, competition between plants, fruit maturity, cultivation techniques, climatic conditions, and other environmental factors.Ten accessions from 238 total accessions meet the fruit criteria as potential varieties with the characteristics were oval or slightly oval fruit shape, grade A fruit size, buttery texture and not fibrous, and green fruit skin color when ripe fruit characteristics.These ten accessions can be recommended to be evaluated further for two seasons (years) as new varieties for local variety registration.The accessions are MS6, MS9, SW10, PR1, PR4, PR8, ZL5, KB7, BD14, and AM7 [Figure 2].Parameters of fruit weight, seed weight, and fruit skin (rind) weight are components to determine the value of the edible portion.The edible portion is a measure to assess the percentage of edible parts of the fruit.The edible portion of avocados is the fleshy mesocarp.The ten recommended accessions have an edible portion range of 62 to 80%.KB7 accession has the lowest edible portion percentage, while the highest is AM7.Accessions SW10 and MS6 have 64% and 65% edible portions, respectively.Accession PR1, PR4, and Zl5 have an edible portion of 69%, while PR8, BD14, and MS9 have 71, 72, and 73% edible portions, respectively.Analysis of qualitative traits for fruit characteristics on 238 accessions from Nagari Giri Maju was carried out to determine the genetic distance of accessions.Analysis of the morphological similarities among accessions resulted in seven groups with a 38% degree of similarity [Figure 3].In the first group, there were 30 accessions, 26 accessions in the second group, 52 accessions in the third group, 30 accessions the fourth group, 24 accessions in the fifth group, 51 accessions in the sixth group, and the seventh group consisting of 25 accessions.Accessions within one group (cluster) derive from different gardens, indicating high genetic variability of avocado accession within a similar garden (one farmer).Each group has different characteristics; hence accessions in the same group will have different characteristics from other groups.The similarities were found in the fibrous characters and the flesh fruit texture among the first, second, third, fourth, and seventh groups.The first group has a lot of fibrous with a watery flesh fruit texture, while the second has a lot of fibrous with a buttery texture.The third group had less fibrous with a buttery texture, and the fourth group had medium fibrous with a buttery flesh fruit texture.The sixth group had a watery flesh fruit texture.The similarity among accessions was determined by medium fibrous with a watery flesh fruit texture for the seventh group.In contrast, the similarity among accessions in the fifth group was determined by ripe fruit skin color, i.e., dark purple or black.

Conclusion
Exploration and characterization conducted successfully identified 238 accessions of avocado that showed variability in fruit shape, ripe fruit skin color, ripe fruit flesh color, fruit flesh texture, and fibrous within fruit flesh.Wide variability was detected for fruit weight, and narrow variability for fruit length, fruit diameter, and fruit flesh thickness.The research obtained ten accessions recommended for new potential avocado varieties from the West Pasaman Regency.

Figure 3 .
Figure 3. Dendrogram of 238 avocado accessions from Nagari Giri Maju based on qualitative traits on fruit characteristics.

Characterization of avocado (Persea americana Mill.) in Nagari Giri Maju, West Pasaman Regency based on fruit morphological characteristics
Pasaman Regency reached 391.34 tons in 2018, with Luhak Nan Duo District as the largest producer, with 77.34 tons

Table 1 .
Variations in fruit morphological characteristics of 238 accessions of avocado plants from Nagari Giri Maju.

Table 2 .
Phenotypic variability of quantitative fruit character on 238 accessions of avocado from Nagari Giri Maju, West Pasaman Regency.