Origin of the varieties Guanay-1, Guanay-2 and Guanay-3

To obtain these varieties, 30 trees (10 per variety) that were vigorous, ungrafted and with visible absence of pests and diseases were selected in a commercial orchard in the locality of Venustiano Carranza (21° 32’ 2.77” north latitude, 104° 58’ 39.73” west longitude, 893 masl) of the municipality of Tepic, Nayarit. The study trees were 19 years old, their origin comes from genotypes of soursop established in orchards of the ejido Platanitos (21° 31’ 24.25” north latitude, 104° 58’ 27.37” west longitude, 1 075 masl) of the municipality of Tepic, Nayarit.

In 2016, a selection of the trees was carried out, considering the distinctive morphological characteristics of the fruits; subsequently it was monitored for two years, it was observed that the fruits of the selected trees retained the distinctive morphological characteristics of each variety, in 2018, the morphological and physicochemical characterization of the fruits (6 fruits per tree of each variety) at maturity of consumption was carried out. As a basis for the characterization of the fruits, the descriptors of cherimoya (Annona cherimola Mill.) registered and proposed by the International Union for the Protection of New Varieties of Plants (^{UPOV, 2019}) were used.

Titratable acidity was determined by the official method ^{AOAC (2005)}, by volumetric titration with sodium hydroxide (NaOH) and phenolphthalein as an indicator, the results were expressed in percent citric acid. Firmness was assessed with a texture meter (Chatillon^® MT 150 L) with a conical tip 6 mm in diameter of the base and 5 mm in length from the base of the cone to the apex. With the data obtained, an analysis of variance and comparison of means with Tukey’s test (p≤ 0.05) were performed using the Statistical Analysis System (SAS^® V. 9.2) software.

Description of varieties

The shape of the fruits of the variety Guanay-1 was heart-shaped with a round apex, the habit of the fruits was present in stems and branches, the weight was 1 438.79 g, the length of 17.09 cm, with a diameter of the cross section of 11.07 cm, the fruits had small stylar protuberances on the surface, which measured 0.5 mm in length (Figure 1 A). The fruits of the variety Guanay-2 presented an irregular shape with a conical apex, the habit of the fruits was present both in stems and branches; they averaged a weight of 1 948.01 g, a length of 25.31 cm and a diameter of 13.17 cm, the protuberances presented by the fruits on the surface measured 2.05 mm in length (Figure 1 B).

The shape of the fruits of the variety Guanay-3 was conical with a round apex; the habit of the fruits was present in stems and branches, the weight of this variety was 902.27 g, with a length of 21.17 cm and a diameter of 10.96 cm, the protuberances present on the surface of this variety measured 7.56 mm in length (Figure 1C). The analysis of variance showed significant differences between varieties (p≤ 0.05). Generally, the shape of soursop fruits is described as oval-heart-shaped and some fruits have an irregular, asymmetrical curved shape due to inappropriate carpel development or voids produced by insects (^{Lawrence, 2007}).

The weight and dimensions of the fruits are also varied and weights between 0.4 and 2 500 g, longitudinal diameters of 10 to 26 cm and equatorial diameters of 8 to 15 cm have been reported (^{Nolasco-González et al., 2019}). The variability presented by the fruits of soursop, in their morphological characteristics, is due to the fact that they come from plants reproduced by seed, which leads to the fruits presenting high variation in shape and size (^{Terán-Erazo et al., 2019}).

Figure 1 Soursop varieties Guanay-1 (A); Guanay-2 (B); and Guanay-3 (C). 

The fruits of the variety Guanay-1 had fewer seeds (86), greater firmness (24.62 N) and lower titratable acidity (0.62%), while the fruits of the variety Guanay-2 showed a higher number of seeds (166), high titratable acidity (0.96%) and lower firmness (7.82 N) with respect to Guanay-1. The variety Guanay-3 showed the largest number of seeds (231) and the largest protuberance size (7.5 mm) unlike the other two varieties, the titratable acidity and firmness was similar to the variety Guanay-2 (Figure 2 and 3).

Statistically, there were significant differences (p≤ 0.05) between varieties. The number of seeds per fruit showed high variability since it has been reported that they can have more than 200 seeds and that this depends on the size of the fruit (^{Nolasco-González et al., 2019}). ^{Jiménez-Zurita et al. (2016)}) report a titratable acidity between 0.3 to 1.2%, for their part these same authors indicate values of 21.61 and 7.19 N in mature fruits, which coincide with the data of this research (0.62-0.96% citric acid) and (24.61 and 7.83 N) respectively.

Figure 2 Weight (A); length (B); diameter (C); and seed number (D) of three soursop varieties (Guanay-1, Guanay-2 and Guanay-3). Each point represents the mean of 11 to 26 observations and its standard error. Different literals present significant differences (p≤ 0.05). 

Figure 3 Firmness (E); titratable acidity (F); and protuberance length (G) of three soursop varieties (Guanay-1, Guanay-2 and Guanay-3). Each point represents the mean of 11 to 26 observations and its standard error. Different literals present significant differences (p≤ 0.05).