La lima 'Tahiti', Citrus latifolia Tan. injertada en cinco patrones de cítricas: 'Swingle citrumelo' [Citrus paradisi Macf. x Ponsirus trifoliata (L.) Raf.], 'Carrizo' [C. sinensis x P. trifoliata (L.) Raf.] , 'HRS 812' [mandarina 'Sunki', C. reticulata x P. trifoliata (L.) Raf.], 'Limón rugoso' [C. jambhiri] y mandarina 'Cleopatra' [Citrus reshni Hort. Ex Tan.] se evaluó en las subestaciones de Isabela y Corozal, Puerto Rico. Los parámetros de altura, diámetro de copa, volumen de copa, eficiencia, número y peso de frutas por árbol, porcentaje de jugo, sólidos solubles totales, acidez y relación sólidos solubles totales/acidez (índice de madurez) fueron evaluados. En la Subestación de Isabela los mayores rendimientos se consiguieron en los patrones 'Limón rugoso' y 'Swingle', con 42.7 y 35.9 kg de fruta por árbol, respectivamente. Estos valores no difieren significativamente de los rendimientos conseguidos en los patrones 'HRS 812' (23.6 kg) y 'Cleopatra' (28.7 kg), mientras que superan significativamente los rendimientos en el patrón 'Carrizo' (21.6 kg). En la Subestación de Corozal los mayores rendimientos se consiguieron en los patrones 'Limón rugoso' (52.9 kg), 'HRS 812' (52.7 kg) y 'Swingle' (47.6 kg), siendo estos significativamente mayores que el de 'Cleopatra' (27.7 kg) pero no que el de 'Carrizo' (40.9 kg). En ambas localidades los parámetros que definen la calidad de fruta fueron aceptables y muy parecidos para ambas zonas. Dos años después de la siembra, en los árboles en Isabela se detectó a Candidatus Liberibacter asiaticus, bacteria asociada a la enfermedad conocida como "Huanglongbing" (HLB). A pesar de la presencia de la enfermedad, los árboles se mantuvieron en producción y no hubo declinamiento que se asociara a la enfermedad. Tras la detección de la enfermedad en esta localidad se estableció un programa nutricional más intensivo utilizado fertilizantes foliares y al suelo.

Pineapple [Ananas comosus (L.) Mere] is an important fruit crop cultivated in many tropical countries. This fruit crop requires large amounts of nitrogen (N) and potassium (K) to maximize yield. Although pineapple has low water requirements, extended drought can affect yield. Two experiments were conducted to study the effects of fertilizer application methods and drip irrigation management on pineapple yields. Pineapple cultivars MD-2 and Cabezona were planted at Isabela and Lajas, Puerto Rico, respectively. Fertilizer and irrigation treatments included: i) Controlapplication of 896 kg/ha of a granular fertilizer (12-6-10-3) at two, five and nine months after planting; ii) FS-R- application of 150-150-120-45 kg/ha at planting plus 20 foliar applications of urea and potassium sulfate (50 kg/ha) every three weeks, rainfed; iii) FS-DI- application of 150-150-120-45 kg/ha at planting plus 20 foliar applications of urea and potassium sulfate (50 kg/ha), drip irrigation applied every three weeks; iv) FERT- application of 150-150-120-45 kg/ha at planting, but urea and potassium sulfate (50 kg/ha) were applied throughout fertigation; and v) CRF- same amount of nutrients as FS-R but N was applied as a controlled release fertilizer every six months. At Isabela, treatment FS-R produced the highest fruit weight (2.5 kg per fruit) and 1.5% of N in tissue, but did not differ significantly from FS-DI and CRF. Plants under CRF registered the highest Brix (15.8°). Although foliar fertilizer tended to produce higher yields, controlled release fertilizer is recommended because it eliminates the need for frequent foliar application without compromising yield.

LIBERACIÓN DE LOS PATRONES DE CÍTRICAS 'SWINGLE CITRUMELO', 'CARRIZO' Y HRS 812 PARA PUERTO RICO

The 'Hamlin' sweet orange [Citrus sinensis (L.) Osb.] was evaluated in Isabela, Adjuntas and Corozal, Puerto Rico. This cultivar Is an early producer and Is used mainly by the Industry for juice. The cultivar was grafted to the rootstocks 'Swingle Citrumelo', 'Carrizo', Cleopatra' and 'Sun Chu Sha'. For six years, production, growth and fruit quality data [pH, total soluble solids (TSS), titrable acidity and TSS/acid ratio] were recorded to evaluate horticultural traits. Significant differences were detected In mean fruit number per tree between Corozal and the other sites. The highest yields were obtained at Corozal for the rootstock Sun Chu Sha. Yields at Isabela and Adjuntas were similar. In terms of growth, Swingle Citrumelo and Carrizo showed significantly smaller height and canopy volume. No significant differences were detected for fruit quality among the rootstocks at the three sites. At Isabela we observed the best maturity Index (TSS/acid ratio) for all the rootstocks (17.3). This cultivar could be recommended for planting in coastal areas such as Isabela for availability of ripe fruit In the months when there are none in the higher altitudes, from September to November. With regard to locality and yield, the best performance for this cultivar among all the rootstocks was observed at Corozal.

The chironja (clone 2-4) was evaluated during eight years of growth at Isabela and Corozal, Puerto Rico, in the coastal and central areas, respectively. The trees were grafted on the roostocks 'Swingle citrumelo' (Citrus paradise), 'Naronja' (Citrus paradisi x Citrus aurantium), 'Cleopatra', and 'Sun Chu Sha' mandarins (Citrus reticulata), and on the hybrid HRS 812 (Sunki mandarin x Beneck trifoliate orange). The trees of the Swingle-chironja combination died at both localities during the first year because of scion-rootstock incompatibility. The rootstock HRS 812 was one of the highest yielders, even though it was infected with severe strains of the Citrus Tristeza Virus (CTV) at both sites. Although the fruits on this rootstock were small, the amount of juice was significantly greater than that of the other rootstocks at both localities. Eight years after planting, the Naronja trees were affected by CTV; 38% of the trees were lost at Isabela, and 25% at Corozal. Nevertheless, trees on this rootstock were vigorous and good yielders, producing fruits of good size and moderate fruit quality. The high incidence of CTV and Phytophthora spp. was a limiting factor for the rootstocks susceptible to these diseases; thus there was a high mortality.