Fruit weight (FW)

The values ranged from 146.3 g for the Temprana cultivar to 251.4 g for the Marrs cultivar in 2020 and from 146.6 g in the Queen cultivar to 238.8 g with the Marrs cultivar in 2021 (Table 1). Based on the weight of the fruit, the cultivars were placed in three groups during the two years of study: a first group with high values represented by Marrs (2020 and 2021), another group with intermediate values, where were the cultivars San Miguel, Queen, Hamlin and Parson Brown (2020) and Pineapple, San Miguel and Parson Brown (2021), and a third group with low values, composed of the cultivars Pineapple and Temprana (2020) and Queen in 2021.

These results coincide with those reported by ^{Medina et al. (2007}), who reported the Marrs orange with the largest fruit size (289 g) compared to the cultivars Queen (217.8 g), Pineapple (198.4 g) and San Miguel (196 g) in dry subtropical climate conditions.

Polar diameter (PD)

The values ranged from 62.6 mm in the Temprana cultivar to 75.3 mm with the Marrs cultivar (2020) and from 65.7 mm for Temprana to 77.8 mm in Marrs (2021). The cultivars formed three groups in 2020 and six groups in 2021. In the first year, the group with the highest values corresponded to the cultivars Marrs, Hamlin, Parson Brown, Queen and Pineapple, the group with intermediate values was formed by the San Miguel cultivar and the third group with the lowest values, by the Temprana cultivar. In the second year, the Marrs cultivar remained with the highest value of the polar diameter, the second group was constituted by the cultivars Parson Brown and Pineapple, in the third group was the Hamlin cultivar, in the fourth group the San Miguel cultivar, in the fifth group the Temprana cultivar and in the sixth group the Queen cultivar (Table 1). These are typical characteristics of the varieties under study regardless of the rootstock used and the age of the trees.

Equatorial diameter (ED)

A similar response was recorded in the equatorial diameter of the cultivars during the two years of study, where the values ranged from 65.7 mm in the Temprana cultivar to 79.4 mm for the Marrs cultivar (2020) and from 65.4 mm with the Temprana cultivar to 77.8 mm in the Marrs cultivar (2021). According to the data obtained, cultivars were placed in four groups in 2020 and five in 2021. In the first group the highest values were for the Marrs cultivar (2020 and 2021), the second group was made up of the cultivars San Miguel, Hamlin, Queen and Parson Brown (2020) and San Miguel, Pineapple and Parson Brown (2021), the third group with the cultivars Pineapple (2020) and Hamlin (2021), in the fourth group with the cultivars Temprana (2020) and Queen (2021), and in the fifth group of 2021 it was made up of the Temprana cultivar (Table 1).

Peel thickness (PT)

The values ranged from 3 mm in the Temprana cultivar to 4.5 mm with the Marrs cultivar (2020) and from 2.9 mm for the Temprana cultivar to 4.3 mm in the Hamlin cultivar (2021). In 2020 the cultivars were placed in three groups, the first group was made up of those that presented the highest values for this variable (Marrs, Hamlin, Pineapple, San Miguel and Parson Brown), the second group formed by the Queen cultivar which registered an intermediate value, the third group included the Temprana cultivar which had the lowest value for peel thickness. In the second year, the first group was represented by the Hamlin cultivar with the highest value; the second by the cultivars Marrs and Queen, the third by the Parson Brown cultivar, the fourth by the Pineapple cultivar, the fifth by the San Miguel cultivar and the sixth by the Temprana cultivar which presented the lowest value (Table 1).

The thickness of the peel is one of the most important fruit quality characteristics in early orange varieties, the fruits preferred by producers are thin-skinned and easy to peel. Although there is no specific value reported as ideal for peel thickness, ^{Ariza et al. (2010}) state that values of 5 mm in late orange Valencia are considered normal.

In this regard, ^{Padrón-Chávez and Rocha-Peña (2009}) point out that the Marrs variety fruits mainly in bunches, in the outermost parts of the tree, the peel of the fruit is smooth, not very thick and the fruits are easy to peel. For their part, ^{Futch and Tucker (2020}) report that the lower thickness of the peel is mainly due to phosphorus deficiency. This implies that possibly the sour orange tree as rootstock is ineffective to absorb phosphorus (^{Pérez-Zamora, 2004}), but in this case, it is a favorable characteristic for the quality of the fruit.

Number of seeds (NS)

The values ranged from 3.2 seeds for the Temprana cultivar to 17.9 seeds in the Queen cultivar (2020) and from 2.6 seeds in the Temprana cultivar to 16.7 seeds for the Pineapple cultivar (2021). The cultivars showed a similar trend in the two years of study and were distributed into five groups in 2020 and four in 2021 (Table 1). The first group with the highest values was integrated by the cultivars Queen and Pineapple, this information was recorded during the two years of study; the second was formed by the cultivars San Miguel and Parson Brown, the third by the Marrs cultivar, the fourth included the Hamlin cultivar and the fifth the Temprana cultivar in 2020. In the second year, the cultivars Hamlin and Temprana formed a single group. The fruits of the cultivars Queen, Pineapple, San Miguel and Parson Brown had the highest number of seeds with respect to the Temprana cultivar, which showed the minimum value obtained, the cultivars Marrs and Hamlin had intermediate values.

According to ^{Agustí et al. (2003}) and ^{Ladaniya (2008}), seedless fruits are the most accepted by consumers, while fruits with large amounts of seed are commercially unviable. In this regard, ^{Padrón-Chávez and Rocha-Peña (2009}) point out that the fruits of the Marrs variety are characterized by having few or no seeds in the citrus-growing region of the state of Nuevo León. This is an important factor for the Marrs cultivar to be accepted by the consumer, as varieties with few seeds or no seeds are preferred over those that have abundant seeds in the fruit (^{Davies and Albrigo, 1994}; ^{Agustí et al., 2003}; ^{Ladaniya, 2008}).

Notwithstanding the above, in Mexico the presence of seeds in the fruit is not a determining factor in consumer preferences. In the case of fruit whose final destination is the processing plants, the external quality requirements are of secondary importance and the production of lower quality consisting of fruit stained or beaten during the harvest goes practically to this destination (^{Ramírez-Díaz and Rocha-Peña, 2009}).

Total soluble solids (TSS)

In this case the values were from 11.9 °Brix in the cultivars Hamlin and Parson Brown to 13.7 °Brix with the Marrs cultivar (2020) and from 12 °Brix for the San Miguel cultivar to 14.3 °Brix in the Queen cultivar (2021). The cultivars showed a variable trend in the two years of study, which led to the formation of five groups in 2020 and four groups in 2021. In the first group the highest values were recorded in the cultivars Marrs (2020) and Queen (2021), in the second were the cultivars Pineapple and Temprana (2020) and Marrs (2021), in the third were the cultivars Queen (2020), Parson Brown, Hamlin, Temprana and Pineapple (2021), in the fourth the San Miguel cultivar (2020 and 2021) and the fifth group formed in 2020, the cultivars Hamlin and Parson Brown (Table 1).

Although the values corresponding to the last two cultivars could be considered relatively low, these values meet the minimum required by the Mexican Standard (^{NMX-F-118-1984}). Relative levels of total soluble solids are related to the taste and palatability of citrus fruit juices, so they are considered as an indicator of maturity and taste quality (^{Al-Mouei and Choumane, 2014}).

The minimum maturity index required for the Marrs variety is reached at the beginning of September in the citrus-growing region of Nuevo León, but due to its low acidity; at this time its quality is not very good, it is sweet but somewhat tasteless; however, the flavor improves considerably if its maturation is allowed to advance more to harvest the fruit during November (^{Padrón-Chávez and Rocha-Peña, 2009}).

Amount of juice (AJ)

The values ranged from 49.7 ml in the Temprana cultivar to 110.6 ml for the San Miguel cultivar (2020) and from 42.2 ml in the Temprana cultivar to 115.7 ml with the Marrs cultivar (2021). The amount of juice recorded in the different varieties was variable in the two years of study and resulted in the formation of five groups in 2020 and three in 2021. In the first year of study, the group with the high value was formed by the San Miguel cultivar, the second group by the cultivars Marrs, Parson Brown and Queen, the third group by the Pineapple cultivar, the fourth group by the Hamlin cultivar and in the fifth group was the Temprana cultivar (Table 1).

The second year, the first group formed by the Marrs variety, the second group by the cultivars San Miguel, Parson Brown, Pineapple and Queen and the third group by the cultivars Hamlin and Temprana (Table 1). Despite the great importance of the amount of juice in the quality of the fruit, to date there is no regional or local information available in this regard, the only certain thing is that there are juice processing plants that destine all their production for export, mainly to the United States of America and to a lesser extent to Canada, Japan and the European Union (^{Gaitán, 2002}).

Fruit hardness (FH)

The values ranged from 3.5 kg cm^-2 for the Hamlin cultivar to 4.5 kg cm^-2 in the Parson Brown cultivar (2020) and from 3.3 kg cm^-2 in the Marrs cultivar to 4.1 kg cm^-2 with the Parson Brown cultivar (2021). The cultivars showed a variable trend in the two years of study and a single group was formed in 2020; that is, no significant difference was observed. However, in the second year, three groups were formed; the first was formed by the Parson Brown cultivar, the second by the cultivars Hamlin, Temprana, San Miguel and Pineapple and the third by the cultivars Queen and Marrs (Table1).

Fruits that are less firm are more susceptible to deterioration during postharvest handling (^{Villalba et al., 2014}). ^{Barbosa et al. (2003}) point out that firmness, as an indicator of fruit maturation, determines the optimal levels of quality for consumption and is related to the conditions of transport and postharvest handling, therefore, the hardness of the fruit is a highly desirable characteristic in cultivars since it gives a high value for commercialization.

The results obtained in the present study suggest that, in the Citrus Germplasm Bank of the General Terán Experimental Field, there is a wide variation between the early-maturing orange materials in relation to their fruit quality characteristics, which constitutes a viable alternative to diversify the orange crop in the citrus-growing region of the state of Nuevo León. This diversification would be essential for the sustainable production of orange cultivars in two well-established harvest periods, one comprising at least six months (September-February) with the use of early-maturing cultivars and another of five months (March-July) with the use of late-maturing Valencia-type cultivars.