FIG. 1. Diagramatic description of the sorghum conversion program.


SORGHUM CONVERSION PROJECT


PUERTO RICO


Will Flower Will Not Flower
 In U.S. In U.S.


4


X

P.R.


A


 F( -(P.R.)

Short-Early F2(Texas)

 -(P.R.) X Exotic
 F3-(P.R.)X Exotic


 TEXAS(USA)

 Exotic Which Will Flower
 In U.S.




 GOAL

 OA



After 5 backcrosses to Exotic


1
FI-(PR R.)

L F2(Texas)Continued for cycles
 2 a- rm 0 -- -A I


each
 F3
 is crossed back to Exotic


 in which a genetic male sterile is used as the female. Three
 random mating cycles were completed in Puerto Rico, two
 under long days. Seed of PR2BR has been distributed to
 many places in the tropics.
PR3BR. Population PR3BR was released in 1977 by the ARS,
 USDA as germplasm for breeders, primarily in the tropics.
 The population was developed at TARS. In the summer of
 1974, sorghum population PR1BR was planted in alternate
 rows with TP4R (Texas Population 4). The steriles in each
 row were bagged and, when in full bloom, pollinated by
 bulk pollen from adjacent rows. Equal quantities of seed
 from each of the head pollinated were bulked together and
 planted to begin PR3BR. Four random mating cycles were
 completed under long days in Puerto Rico in June 1977.
 Seed of this population is also available in limited amounts
 from TARS.
PR4BR. Population PR4BR was released in 1978 by the Univer-
 sity of Puerto Rico (UPR), Agricultural Experiment Sta-
 tion, and TARS. The components of two populations in-
 clude 88 sorghum cultivars from difference sources such as
 the SCP, the "All Disease Nursery" of the University of
 Texas, breeding lines from the UPR-AID and TARS sor-
 ghum projects. The selection of the 88 cultivars was based-


290


 on possible resistance to head and foliar insects and
 diseases. the initial screening and first crosses using TP4R
 as female were done at the UPR, Isabela Experiment Sub-
 station by Morales, Powell, and Cruz. The subsequent
 development of the population was done at TARS. Three
 random mating cycles were completed by May 1978. Seed
 of PR4BR has been distributed to many places in the
 tropics.
PR5BR. In 1983 PR5BR was released by the UPR Crop Protec-
 tion Department and TARS. The components of PR5BR
 are KP-5 (Kansas population 5) and Millo Blanco (MB).
 The KP-5 population is a potentially good source of
 resistance to maize dwarf mosaic and anthracnose caused
 by Colletotrichum graminicola (Ces.) G.W. Wilson. Millo
 Blanco is a vigorous local forage and grain sorghum with
 photoperiod-sensitivity, and considerable drought toler-
 ance. Local trials show its excellent yield compared to other
 forage species in Puerto Rico (Sotomayor-Rios and Telek,
 1977). In January 1976, more than 200 crosses of MB with
 photoperiod insensitive male sterile plants from KP-5 were
 completed. The F, seed was bulked and planted under
 long days at Isabela in May 1977. By 60 days after planting
 more than 300 plants had flowered: these were self-

 PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY-VOL. XX


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