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Pearl millet (Pennisetum glaucum L. Leeke) x napiergrass (P. purpureum Schum.) interspecific hybrids (PMN) have great potential as a forage crop in the tropics. The effect of daylength on the flowering of cytoplasmic-nuclear male sterile (cms) pearl millet Tifton 23 A4, and three napiergrasses (N14, N20, and N74) was determined in monthly plantings for a period of one year. Fifty days after planting, the male parents (napiergrass) were cut to the ground level (Tl), to one meter aboveground (T2), or not cut (T3). Days from planting to flowering (PF) for pearl millet ranged from 44 to 47 across plantings and 50 or less for N14 and N74 (from August to December). Although flowering of the male parents was not influenced by the T2 and T3 treatments, the Tl treatment caused plants to flower later. With the exception of the Tl treatment, flower response to daylength was as expected. Seed of the PMN can be obtained from August through December in Puerto Rico but not during long days of (12 hours of day light or more) unless day-neutral male parents are used.

Dwarf Napiergrass (Pennisetum purpureum) selections N75, Nl 14, Nl27, Nl28, and tall cultivars, Merker (M) and Merkeron (N43) were evaluated on an Oxisol during a 2-year period at 45-, 65-, and 85- day cutting intervals (Cl) at Isabela, Puerto Rico. Dry forage yield (DFY) and crude protein yield (CPY) was superior in N43 than in the other grasses. Among the dwarf selections, Nl28 had the highest DFY, while N75 and Nl27 had the highest crude protein content (CPC). The 65-day CI appeared to be the most appropriate time to harvest the grasses. At this stage, M and N43 DFY and CPC were 7 t/ha and 9%, respectively. The dwarf selections could be potential candidates for use under grazing management due to their high leaf stem ratio as compared to the tall cultivars although their DFY was significantly lower than the tall cultivars.

Information on the effect of daylength on nonconverted and converted selections of sorghum is very limited. This study was designed to evaluate the effect ofdaylength on plant height (PHt), days to anthesis (DA), and other agronomic traits of local Millo Blanco nonconverted (MBNC) and three Millo Blanco converted (MBC) selections of forage sorghum (Sorghum bicolor (L.) Moench) and BTx406 (a 4-dwarf photoperiodinsensitive temperate grain sorghum used as the control) during an eight-month period in Puerto Rico. The MBC selections were based on approsirnately plant height of 50, 120 and 170 em. Plantings were made on the 21st day of each month from May through December, 1991. After an initial30-day growth period, plants were evaluated every 15 days until harvest. Days to anthesis of MBNC decreased from 175 (May planting) to 61 (October planting), then increased to 70 and 75 (November and December plantings, respectively). The mean plant height of MBNC followed a similar trend ranging from 278 em (August planting) to 138 em (November planting). Although a significant correlation was observed between days to anthesis and plant height in MBNC, the MBC selections and BTx406 (the control) were unaffected by planting date. Mean days to anthesis of the three MBC selections was similar throughout the year (61 days). This study demonstrated the possibility of making selections for height from converted sorghums prior to their formal release having by this wayan excellent opportunity for its utilization in a year round breeding program.

Perennial peanut species Araclzis glabrata (rhiromatous) and A. pinloi (stoloniferous) are attributed with high nutritional quality, palatability, persistence and competitiveness with grasses although little is known of their agronomic value outside of Florida and areas of South America. The main liability of Arachis is its slow rate of establishment, often more than one year. In Puerto Rico, studies were conducted on an Oxisol during a nine-month period to determine if rhizome crowns with attached plant foliage could successfully be established and to compare them with seedlings of stoloniferous accessions in their rate of plant spread and yield. In two separate studies, evaluations were made of nine selected entries and cv. Arbrook of A. glabrota and related species from Florida and six A. pintoi accessions from CIAT. Four of the rhizomatous entries established successfully. Three had relatively slow growth in the first 12-16 weeks, with an average of 35 % plot cover and high incidence of weeds. UF 99, however, had 75% soil coverage at 16 weeks and allowed little weed development. The commercial cv. Arbrook failed to establish. Three stoloniferous accessions, CIAT 18744, 18747, and 18748, exhibited a high rate of plant spread at 16 weeks (over 90% soil coverage) with little weed growth. At nine months, UF 99 had fully established (100% plot cover), and entries UF 3, UF 77 and UF 64 had a range of75-90 % coverage, with an average canopy height of 30 cm. No major insect damage or disease was observed on the plant material during the experimc:nt. The highest dry matter yield (DM:Y) was obtained from UF 99, which had an average yield of 5,568 kg/ha at nine months. DMY of the three other entries averaged only 2,360 kg/ha. For the CIAT accessions, DMY averaged 4,726 kg/ha. Based on these preliminary studies, UF 99 and CIAT 18744, 18747, 18748 exhibit potential for faster rate of establishment and adaptation.

Napiergrass (Pen11isetum purpureum Schumach.) (2n=28) has proven to be an excellent male parent in crosses with cytoplasmic male-sterile lines of pearl millet (P. g/aucum (L.) K. Schum.) (2n= 14) 'for the development of superior interspecific Pen11isetum forage hybrids (IPFH). These hybrids (3x=21) are sexually propagated and combine the leafiness and forage quality of pearl millet with the high dry matter yield and perennial nature of napiergrass. Three lPFH (101, 102, and -.103 developed by W. H. Hanna) and local photoperiod-sensitive forage sorghum Millo Blanco (Sorghum bicolor (L) M~nch) were compared at cutting intervals (CI) of 45, 65, and 85 days, equivalent to seven, five, and four harvests, respectively, at two locations (Oxisol and Ultisol) in Puerto Rico. Across locations, dry forage yields (DFY) of the lPFH averaged 6.0, 10.4, and 16.0 t ha-1 at the 45-, 65-, and 85- day CI, respectively, representing 119, 79, and 127 % more DFY than that of Millo Blanco. From the data obtained, it appears that the optimum time for harvesting these grasses is 65 days. At this stage, the DFY were 5.8, 9.5, 11.4, and 10.3 t ha-I for Millo Blanco and the three IPFH, respectively. The in vitro dry matter digestibility for the same CI ranged from 42 to 52 % and 'the crude protein content from 6 to 11 % . The perennial nature of the interspecific hybrids plus their production of excellent quality forage attest to their potential as valuable new forage grasses for the tropics.

This study was conducted to evaluate the yield potential of six Stvlosanthes quianensis introductions planted monthly from February to July, 1989, under short- and long-day periods, and harvested at 60 and 120 days after an initial 180-day cutting. Across planting dates, CIAT 184 had the highest mean DFY and CPC (7,160 kg/ha and 9.7%, respectively) at the 180-day cutting. The highest DFY and CPC were those of the February planting. Across planting dates and at the 60-day cutting, CIAT 1283 had the highest DFY (2,194 kg/ha) while the CPC of the six Stylos remained relatively constant (12.2-13.0%). At the 120-day cutting, across planting dates, CIAT 184 had the highest DFY (5,064 kg/ha) with a mean CPC of 11.7%. A positive linear relation was observed between days to flower and DFY. Significant differences were obtained among Stylos for all planting dates in terms of IVDMD (60-day harvest) except June and July. Across planting dates, all Stylos were significantly superior to CIAT 15 and CIAT 136. Based on this preliminary study, the optimal time for planting Stylo in Puerto Rico appears to be February-March.

Sorghum (Sorghum bicolor [L.] Moench.) research activities at the Tropical Agriculture Research Station (TARS), Mayaguez, Puerto Rico, are described. In cooperation with the Texas Agricultural Experiment Station, 423 daylength insensitive lines from the Sorghum Conversion Program were developed. Numerous new collections were evaluated and classified. Other activities include the evaluation of new cytoplasms and their reactions when crossed to converted lines, the evaluation of grain and forage hybrids, the comparison of daylength sensitive versus daylength insensitive forage hybrids and the development of single and three-way hybrids. Newly developed single and three-way forage hybrids yield over 25 tons ha-1 of dry forage in 180 days. Sorghum populations developed, or in process of development, at TARS in cooperation with other scientists include: 1. populations with reduced hydrocyanic acid (HCN) potential; 2. populations of high yield potential; and 3. populations with increased resistance to common tropical diseases of sorghum.

Cytoplasmic male-sterile sorghum ATx623 (Sorghum bicol or (L.) Moench) was crossed with male parents Millo Blaco (MB) (photoperiod sensitive), and Greehleaf (GL) (photoperiod insensitive). The genotypes were planted on the 15th day of each month during 1984 and harvested at 60 day intervals, Dry forage yield (DFY), crude protein yield (CPY), leaf area (LA), plant height (PHO, rust incidence (R) and in vitro dry matter digestibility (IVDMD) were calculated for each cutting. Analysis of variance showed significant differences among genotypes (G) and planting dates (PD) x G interaction for all traits except dry matter content (DMC) and IVDMD. All traits showed significant differences among PD. ATx623 x GL had nearly constant production (3-4 tonnes ha-1 harvest-1). ATx623 x MB fluctuated from appoximately 3 tonnes ha-1 per harvest from December to January plantings to 7.68 tonnes ha-1 harvest-1 at the June planting. Genotypes showed similar IVDMD at all harvests. During long day plantings photoperiod sensitive sorghums showed less R than the insensitive types. The excellent DFY, CPY and IVDMD, and low R incidence of photoperiod sensitive genotypes during long days make them valuable materials for intensively managed tropical sorghum. ATx623 and MB proved outstanding for developing superior F1 forage sorghum hybrids in Puerto Rico. ----- Sorgo fitopldsmico estaminado y esteril ATx623 (Sorghum bicolor (L.) Moench), fue cruzado con parentescos estaminados, - Millo Blanco (MB), (sensitivo a la luz) y Grennleaf (GL), (insensitivo a la luz) -. Los genotipos fueron plantados el quince de cada mes, durante el a1\o 1984 y cosechados cada sesenta dias. EI rendimiento de forraj e en seco (DPY), rendimiento de proteina en bruto (CPY), superficie de la hoja (LA), altura de la pl anta (PHt), incidencia de la Roya (R) y la digestibilidad de materia seca in vitro (IVDMD), fueron calculados para cada cosecha, Un an~J.isis de la variables mostrar6n una diferencia significativa, de los genotipos (G) y de las fechas de siembra (lPD) x interacci6n en todos los puntos mencionados anteriormente, excepto el conteniod G, de materia seca (DMC) y el IYMD. Todos los rasgos mostraron diferencias significativas entre las PD. AT623 x GL casi tuvieron una produccidn constante (3-4 ton/ha/cosecha), AT x 623 x MBfluctuardn de aproximadernente 3 ton/ha/cosecha en siernbras de Diciernbre a Enero, a 7.68/ton/ha/cosecha en la siernbra de Junio. Los genotipos mostraron un IVDMD durante todas las cosechas, Durante las siembras de tipo de dia largo, el sorgo sensitivo a la luz mostro una incidencia menor al ataque de la Roya que, el de aquellos del tipo insensitive. Los excelentes DPY, CPY y IVDMD Y la baja incidencia al ataque de la Roya de los genotipos sensitivos a la luz durante los dias largos, hacen de ellos un material de valor para las praderas de sorgo tropical, manejadas intensivamente, AT x 623 y MB mostraron ser sobresalientes para desarrollar un sorgo de forraje hfbrido Fl , en Puerto Rico.

Corn research activities conducted at the Tropical Agriculture Research Station (TARS), USDA·ARS, Mayaguez, Puerto Rico during the past five years are reported. The breeding programme utilizing recurrent selection has been successful in improving local and temperate zone populations. Progress has been made in transferring desirable genes to the local sweetcorn cultivar Suresweet. Numerous corn introductions from Central America and other tropical countries have been evaluated and high yielding selections identified for further studies. Based on numerous field studies, yields of over 8,000 kg ha-1 can be expected utilizing superior commercial hybrids under intensive management with the application of up to 120 kg N ha-1 at a population density of over 40,000 plants ha-1. ----- Este es un informe de investigacid'n del maiz, llevado a cabo durante los tlltimos cinco anos, en 1a Estaci6n de Investigacion de Agricultura Tropical (TARS), USDA-ARS en Mayaguez, Puerto Rico. EI programa de mejoramiento, de selecci6n reciproca-contigua, ha sido exitosa en cuanto se refiere al mejoramiento de poblaciones criolla y de la zona templada. Se hicierdn avanzes en el transferimiento de genes, beneficiosos para la variedad criolla de choclo, Suresweet. Numerosas introducciones de maiz de America Central y de otros paises tropicales han sido evaluadas y selecciones de alto rendimiento fueron identi ficadas para llevar a cabo estudios mas amplios. Basados en estudios de campo es posible obtener rendimientos mayores de 8000 kg/ha, utilizando htbridos comercial es superiores, llevados a cabo bajo un manejo intensivo, con aplicaciones de hasta unos 120/kg/N/ha y con una poblacidn de mas de 40,000 plantas/ha.

Response of corn (Zea mays l.) to day1ength has not been investigated in Puerto Rico. Five genotypes, two temperate (Ohio S9 and Ohio S10), two local (Mayorbe1a and Diente de Caballo), and hybrid X304C (PBH304C) were evaluated every 90 days during a 2-year period at Mayaguez and Isabe1a, Puerto Rico. Planting dates were March 21, June 21, September 21 and December 21. Daylight hours (DL) for the first 60-day growth periods corresponding to the four planting dates were: 746, 771, 687 and 669 hours, respectively. Significant effects of location (L), planting date (PD) and genotype (G) and significant interactions (L x PD and PD x G) were observed for grain yield (GY) and most traits studied. The genotype overall response was higher at Mayaguez compared to the Isabe1a location. Genotypes showed a quadratic response to PD. Genotypes responded to increases in day1ength up to the June planting (771 light hours). The highest GYs, 5971 and 5469 kg/ha, were obtained by PBU304C at Mayaguez and Isabela, respectively. Diente de Calla showed the strongest response to PD and the best yields were obtained by planting before the initiation of long days.

Twenty seven corn cultivars from the PCCMCA (Central America Cooperative Improvement Program) test were planted at two dates during 1982-83 at Isabela, Puerto Rico. The combined analysis of variance showed that there were significant differences between planting dates for grain yield, midbloom, leaf area index and rust reaction. Differences among cultivars were observed for all traits except test weight. Cultivar TICO V-6 from Costa Rica produced the highest grain yield (over 6 tons ha-1) at both planting dates.