HORTICULTURAL EVALUATION OF ‘FHIA-21’ (AAAB) PLANTAIN IN PUERTO RICO 1,2

Control of black Sigatoka disease in plantains is imperative for adequate yield. Black Sigatoka is caused by the fungus Pseudocercospora fijiensis (Morelet) Deighton, formerly known as Mycosphaerella fijiensis Morelet. The disease does not immediately kill the plants, but by reducing the effective leaf area it interferes with photosynthesis 2011). If not controlled, the disease has the potential to devastate plantain fields.In Puerto Rico, main plantain cultivar ‘Maricongo’, false-horn clone susceptible to black Sigatoka. a combination of synthetic pesticides the sanitary removal of leaves, or parts of to control the disease. of French-type plantain may result in increased yield of and by tolerance of clones to black Sigatoka. Resistance to this disease appears associated with French-type ents as the source of resistance in Musaceae breeding programs Weeds were controlled by hoeing around the plant and the use of registered herbicides for the rest of the field. Nematodes and soil-borne insects were controlled by following current recommended practices. Drip irrigation was used. Because a major objective of this study was to evaluate ‘FHIA-21’ for its tolerance to black Sigatoka, no practices were carried out to control this disease. At flowering (inflorescence apical emission) functional leaves were counted, and the height of the plant and diameter of the pseudostem were measured. The height was measured as the distance from the ground to the point where the flower emerged. The diameter of the pseudostem was measured at one meter above ground. At six months after planting, and at flowering, plants were evaluated for susceptibility to black Sigatoka following procedures by Carlier Evaluations were made at Corozal, Gurabo and Isabela considering plantings made on similar dates. At each location, plots at the center of the field were selected, and among these plots 12 plants per cultivar were marked for sampling. For each of 12 the youngest leaf spotted (YLS) was identified, number of functional leaves and number of standing leaves (NSL) were counted, and the index of non-spotted leaves (INSL) calculated. The youngest leaf spotted is the first (youngest) leaf from the top of the plant having at least ten black Sigatoka necrotic lesions. Functional leaves those erect petiole and more 50% free black Sigatoka INSL refers to the proportion of standing leaves black Sigatoka and was as INSL = (YLS – / NSL 100. This index an estimation filling an estimate black for

. The Banana Streak Virus infection in Musaceae is characterized by discontinuous chlorotic areas that turn into necrotic streaks on leaves and the split of the pseudostem (Lockhart, 1995). Nonetheless, because of its high yield potential, 'FHIA-21' continues to be used for processed plantain products especially in the Dominican Republic (Garming et al., 2013). Thus, the Department of Agriculture of Puerto Rico was interested in evaluating 'FHIA-21' to increase local raw material for processed plantain products. This study was conducted to evaluate 'FHIA-21' for plant characteristics, susceptibility to important diseases, and its production potential in four agricultural zones of Puerto Rico as compared to the local cultivar 'Maricongo'.
Field trials were conducted between 2013 and 2015 at the Corozal, Gurabo, Isabela and Juana Díaz research farms of the Agricultural Experiment Station of the University of Puerto Rico. Locations differ in geographical conditions and in soil characteristics (Table 1).
Soil in the planting area was prepared conventionally (University of Puerto Rico, 1995 At planting, each plant received 50 g of triple superphosphate. Each plant was individually side-dressed with 57 g of 12-5-20 fertilizer applied approximately at two, five and eight months after planting. Weeds were controlled by hoeing around the plant and the use of registered herbicides for the rest of the field. Nematodes and soil-borne insects were controlled by following current recommended practices. Drip irrigation was used. Because a major objective of this study was to evaluate 'FHIA-21' for its tolerance to black Sigatoka, no practices were carried out to control this disease. At flowering (inflorescence apical emission) functional leaves were counted, and the height of the plant and diameter of the pseudostem were measured. The height was measured as the distance from the ground to the point where the flower emerged. The diameter of the pseudostem was measured at one meter above ground.
At six months after planting, and at flowering, plants were evaluated for susceptibility to black Sigatoka following procedures summarized by Carlier et al. (2003) and by Viljoen et al. (2017). Evaluations were made at Corozal, Gurabo and Isabela considering plantings made on similar dates. At each location, plots at the center of the field were selected, and among these plots 12 plants per cultivar were marked for sampling. For each of the 12 plants, the youngest leaf spotted (YLS) was identified, number of functional leaves and number of standing leaves (NSL) were counted, and the index of non-spotted leaves (INSL) calculated. The youngest leaf spotted is the first (youngest) leaf from the top of the plant having at least ten black Sigatoka necrotic lesions. Functional leaves were those with an erect petiole and more than 50% free of black Sigatoka lesions. The INSL refers to the proportion of standing leaves without the typical late-stage symptoms of black Sigatoka and was calculated as INSL = (YLS -1) / NSL x 100. This index provides an estimation of available photosynthetic leaf area prior to fruit filling and is an estimate of black Sigatoka tolerance for cultivated Musaceae (Viljoen et al., 2017).
Plants with symptoms associated with the Banana Streak Virus were identified and counted throughout the crop cycle. Symptoms included necrotic streaks on the  Cation Exchange Capacity leaves, stunted plants, splitting of the pseudostem, cigar leaf necrosis, absence of bunch or underdeveloped (abnormally-shaped) bunch. Many of these symptoms were described by Lockhart (1995).
Yield results were from the three plantings at Gurabo. Treatments for bunch pruning were applied between the second and third week after bunch emergence. Pruning consisted in the removal of the male floral bud and the apical hands. The pruning of hands in 'FHIA-21' was done so that their bunches retained six, five and four hands. Bunches for the 'Maricongo' plants were not pruned because this cultivar has an inflorescence that disintegrates as the bunch matures. Bunches were harvested when estimated ready for market. Freshly harvested bunches were weighed and fruits counted. The number of hands of 'Maricongo' were counted. For yield, analysis of variance was carried out using a mixed model. Aleatory effects were planting and replicates within planting. Fixed effects were 'FHIA-21' with bunches pruned at six, five and four hands and unpruned 'Maricongo'. To compare the number of fruits per bunch and yield, two analyses were made. The first analysis included all plants whether or not the plant yielded or was unproductive. In this analysis yield was zero for unproductive plants. The second analysis included yield for plants that were productive and harvested. Means were compared by using the least significant difference at the 0.05 probability level.
Across locations, 'FHIA-21' consistently flowered later in the crop cycle and had more leaves at flowering than 'Maricongo' ( Table 2). The latter observation is consistent with previous reports indicating that 'FHIA-21' flowers later than commercial false-horn clones (González-Vélez, 2014;Calvo, 2010). This result also indicates that the crop cycle for 'FHIA-21' is longer than that of 'Maricongo'. The INSL for 'FHIA-21' was 93 or higher, indicating that the available photosynthetic leaf area prior to fruit filling was high (Table  3). These observations confirm that 'FHIA-21' is highly tolerant to black Sigatoka. 'Maricongo' had an INSL from 91 to 73 at six months. However, this index went from 35 to 52 at flowering. Thus, results indicated 'Maricongo' was more susceptible to black Sigatoka than 'FHIA-21' (Table 3).
At all locations 'FHIA-21' plants showed symptoms associated with Banana Streak Virus (Table 4). Common symptoms were the necrotic streaks on the leaves, stunted plants, cigar leaf necrosis, splitting of the pseudostem, absence of bunch and abnormally shaped bunch. 'Maricongo' plants did not present symptoms of this virus. Percentage of 'FHIA-21' plants showing symptoms of the Banana Streak Virus and becoming unproductive varied from 54% at Corozal to 26% at one of the Gurabo plantings (Table 4). Even though our results confirmed 'FHIA-21' is highly tolerant to black Sigatoka, the relatively high percentage of unproductive plants associated with Banana Streak Virus reduces the chances this cultivar will become commercial under the current agricultural system for plantain production in Puerto Rico. Local cost for plantain production is high; thus, a high percentage of productive plants is necessary to recover investment and to generate adequate returns.
In this study, the number of hands per bunch of 'FHIA-21' plants was set to six, five and four through bunch pruning. Unpruned 'Maricongo' bunch had on average 6.8 hands (Table 5). Yield analysis counting all plants whether or not plants yielded or were unproductive: Under this analysis, 'FHIA-21' plants with their bunches pruned to six hands had more fruits and higher bunch weight than 'FHIA-21' plants pruned to four and five hands, and more than 'Maricongo' (Table 5). Yield analysis counting plants that were productive and harvested: Under this analysis, the higher the number of hands in 'FHIA-21' bunches, the higher the number of fruits (Table 5). 'FHIA-21' plants pruned to six and five hands did not differ in bunch weight, and bunches from both treatments weighed significantly more than those from 'FHIA-21' plants pruned to four hands, and also more than 'Maricongo'.