Origin and process of obtaining

This variety originated from the triple cross (NCB 228/RCB 224) F₁//SXB 244, which was made at the International Center for Tropical Agriculture (CIAT), in Cali, Colombia. The development process began in F₁ as a ‘gamete’ or F₁ plant harvested individually, to create a unique family derived from F₁ and then continued with F₂ in which selection was made under drought conditions in Palmira, Colombia. The F₃ plants were established in Popayan, Colombia, where they were inoculated with Colletotrichum lindemuthianum and individual plants resistant to anthracnose caused by this fungus were selected.

F₄ was planted in Santander de Quilichao, Colombia, in acid soil, with low phosphorus content and inoculated with the Phaeoisariopsis griseola Ferraris fungus, which causes the angular spot disease. The selections in F₅ were planted in Palmira, to determine the grain yield under drought conditions, from the superior selections an individual plant was taken to obtain a uniform F₆ (Steve Beebe, Com. Pers. ^{Villar et al., 2013}).

The line from which Frailescano was generated was introduced to Mexico in 2009, along with another 110 lines and to the state of Chiapas in 2010, with the SCN 6 code; through a national performance test of black bean genotypes, to determine their yield, tolerance to diseases and adaptation to acidic soil.

Agronomic characteristics

The plants of the Frailescano variety are of indeterminate growth habit, bushy and erect, type II (^{Singh, 1982}), with medium guides, small leaves and an average plant height of 49.8 cm. Flowering occurs on average at 38 days after sowing, physiological maturity at 70 days and they are ready to be harvested at 80 days after sowing. Its flowers are purple in color, its stems green and its pods are white at physiological maturity and creamy white at harvest, with black, opaque, small-sized and ovoid-shaped grains.

One of the most outstanding characteristics of this variety is its resistance to the bean golden yellow mosaic disease (BGYMV) and its adaptation to the acid soils of the humid tropics of the state of Chiapas (^{Villar et al., 2013}). On the other hand, as it is an early cycle variety, its sowing in the summer cycle allows the producer to harvest the beans in the heatwave season, to avoid problems of excess humidity and in the autumn-winter cycle, with residual humidity, escape the occurrence of periods of terminal drought, which commonly occur in the entity (Figure 1) (^{López et al., 2002}).

Figure 1 Diagram of bean planting with the Frailescano variety (early cycle) and another commonly used (intermediate cycle), in two cultivation cycles. 

Productive behavior

During 2011 and 2012, the Frailescano variety was compared with the commercial varieties Negro Papaloapan and Negro Comapa, used as regional controls, due to its high yield potential and wide adaptation in the tropical areas of Veracruz and Chiapas, through a uniform test of regional yield that was conducted in eight environments of the state of Chiapas, under conditions of rain, residual humidity and irrigation.

Table 1 shows that, in most cases, the Frailescano variety outperformed the two commercial controls. In rainy conditions, the Frailescano variety surpassed the yield of the Negro Papaloapan and Negro Comapa varieties by 17 and 28.4%, respectively. With residual humidity, the percentages of superiority of the Frailescano variety, with respect to these same varieties, were 10.5 and 15.3% and when irrigation was used, 15.8 and 13.2%, respectively. According to the Student’s t test, the general average yield of the Frailescano variety (1 150 kg ha^-1) was statistically similar to that of the Negro Papaloapan variety and significantly higher than that of the Negro Comapa variety (^{Reyes, 1990}).

These experimental results indicate that, in the center of the state of Chiapas, the Frailescano variety has a similar yield and adaptation potential than the Negro Papaloapan variety and superior to that of Negro Comapa; both varieties were developed by the INIFAP Bean Program for southeastern Mexico (^{López et al., 2007}; ²⁰¹²).

Reaction to BGYMV

In the summer cycle of 2012, under seasonal conditions, in the town of Emiliano Zapata, municipality of Villa Corzo, Chis., the reaction of the Frailescano variety was evaluated, together with the Negro Papaloapan and Negro Comapa varieties, to the incidence bean golden yellow mosaic (BGYMV), at 20, 28 and 35 days after sowing. The Negro Papaloapan and Negro Comapa varieties showed symptoms of the disease from 20 days after sowing, whose incidence percentage on the last evaluation date was 40 and 23%, respectively, while the Frailescano variety only presented symptoms weak golden yellow mosaic, with an incidence rate of 13%, up to 35 days after sowing (^{Schoonhoven-Van and Pastor-Corrales, 1987}) (Table 2).

Therefore, in cultivation areas with a high incidence of whitefly (Bemisia tabaci), a vector of BGYMV, the Frailescano variety is a better sowing alternative than the Negro Papaloapan and Negro Comapa varieties.

Adaptation to acidic soil

In 2012, in the Emiliano Zapata locality, the productive response of the Frailescano variety was compared with the creole Veracruzano, commonly used in central Chiapas (^{Villar et al., 2013}), in an acid soil (with a pH of 4 and 20% aluminum saturation), without and with the application of 1 t ha^-1 of agricultural lime. Both under natural conditions of edaphic acidity and with the application of lime, the Frailescano variety exceeded the yield of the creole Veracruzano by more than 96%. The yield reduction, due to acidic soil stress, was lower in the Frailescano variety than in the creole Veracruzano (Table 3). These results indicate that, in the acidic soils of central Chiapas, the Frailescano variety is a better sowing alternative than the creole Veracruzano.

Validation of the Frailescano variety

From 2014 to 2016, the Frailescano variety was validated in farmers’ fields, in five environments in the state of Chiapas (two under irrigation conditions and three with residual moisture stored in the soil and the rains that occurred during the crop cycle). In all cases, the creole Vaina Negra commonly used in the entity was used as a control. In the two humidity conditions, the Frailescano variety outperformed the regional creole. It should be noted that, in the town of Alfonso Moguel, in autumn-winter 2016, there was severe drought during the reproductive phase of the crop, under these restrictive humidity conditions, the Frailescano variety obtained 58% more grain yield than the creole Vaina Negra.

The general average yield of the Frailescano variety was 1 438 kg ha^-1, significantly higher (51.1%) than that obtained by the regional creole (Table 4). These results made it possible to confirm at a semi-commercial level and under the soil, humidity and management conditions of the farmers, the greater productive capacity of the Frailescano variety, compared to the creole materials commonly used in the state of Chiapas.

Agroecological conditions

The Frailescano variety has adaptation in the tropical areas of the state of Chiapas, as well as in regions with similar environmental conditions in the southeast of Mexico. It can be sown in the summer cycle, under rainstorm and autumn-winter conditions with residual humidity, in areas with altitudes ranging from 0 to 1 200 m, rainfall of at least 350 mm during the crop cycle and average annual temperature between 24 and 26 °C.

It can also be sown in areas that have water and irrigation equipment, where the availability of a sheet of water of around 350 mm is ensured, distributed in six or seven irrigations, with an interval of between 10 and 15 days each during the crop cycle, depending on the humidity conditions in the soil and the ambient temperature (^{López et al., 2002}; ^{Ruiz et al., 2013}).

Seed availability

In the Central Experimental Field of Chiapas, original seed of the Frailescano variety is available, to produce basic and registered seed, in case producer associations or seed companies wish to acquire it, to produce certified seed. The registration number of this variety in the SNICS National Catalog of Plant Varieties, for seed production and commercial use is: FRI-088-060314.

Conclusions

The Frailescano variety showed an average experimental yield of 1 150 kg ha^-1, significantly higher than that of the Negro Comapa variety, greater tolerance to golden yellow mosaic, than the Negro Papaloapan and Negro Comapa varieties and better adaptation in conditions of acidic soil and drought. severe, then the regional creoles.

This variety can be cultivated in tropical and subtropical areas of the state of Chiapas and regions with similar conditions in southeastern Mexico, with an altitude of up to 1 200 m, under conditions of rain, residual humidity and irrigation. Its precocity allows the producer to reduce the risk of loss of yield due to the occurrence of periods of terminal drought and its opaque black bean, small in size, meets the characteristics of the type of bean that producers and consumers demand in the state of Chiapas.