1a. Objectives (from AD-416):
To improve the utility of Gossypium (G.) barbadense chromosome substitution lines for G. hirsutum breeding. To develop and release to the public a random mated population(s) that has unique combinations of alleles from the two species. To develop a breeding scheme that facilitiates the recombination of alleles from G. barbadense and G. hirsutum.
1b. Approach (from AD-416):
Seventeen chromosome substitution barbadense (CS-B) lines have been crossesd to five elite cultivars from different commercial breeding programs in the U.S. ('DP 90', 'SureGrow 747', 'PSC 355', ST474, and FM 966). The CS-B lines ae CS-B01, CS-B02, CS-B04, CS-B06, CS-B07, CS-B16, CS-B17, CS-B18, CS-B25, CS-B05sh, CS-B11sh, CS-B12sh, CS-B14sh, CS-B15sh, CS-0B22sh, CS-B22Lo, and CS-B26Lo. The designations sh and Lo indicate that only the short or the long arm of a chromosome from Gossypium (G.) barbadense is in the CS-B line. We will begin the random mating with two or three F1 hybrids from each of these 17 CS-B lines with two or three of the five cultivars. We will use the bulk pollen methodology of Miravalle to accomplish random mating, thus we will have 51 familes many of which will be half-sibs. The F1 hybrids will have one of five elite cultivars as one parent and a particular CS-B line as the other parent. From the cultivar parents we expect to gain adaptability, yield, and other necessary properties. From the CS-B parent we expect to gain alleles from particular chromosomes or chromosome arms from G. barbadense. These chromosome or chromosome arms should contain many alleles for fiber quality because of the very high fiber quality of the G. barbadense parent.
3. Progress Report:
We crossed 18 chromosome substitution from barbadense (CS-B) lines with FM966, SG747, and PSC 355. The CS-B lines were CS-B 01, 02, 04, 06, 07, 10, 16, 17, 18, 25, 5sh, 11sh, 12sh, 14sh, 15sh, 22sh, 22Lo, and 26Lo. F1 of these crosses were planted in Mexico in the winter nursery (2008-09) and the F1 plants were randomly intercrossed using bulked pollen. This was Cycle 0. After the first cycle of random mating we pooled the three variety lines within each CS-B family into 18 half-sib families and kept the 18 individual populations as half sib families during the following cycles of random mating. Random mating was among all 18 families. We have now completed 5 cycles of random mating. After the fifth cycle (C4) seed were self pollinated in the winter nursery to provide seed for release. A germplasm release called Random Mated Barbadense Upland Population (RMBUP-C4) has been approved for release. As soon as all parties have signed the document, we will send it to all cotton breeders and geneticists in the U.S. The seed for release were prepared by mixing equal numbers of seed from each of the 18 half-sib randomly mated C4S1 lines. Thus, the release will be one random mated population; however, we also have selfed seed of the 18 individual half-sib families that went into the released population. We plan to send 1,000 of the population to each person who requests seed. This will provide them with a good sample of the diversity in the random mated population. We have also prepared a germplasm registration manuscript which is nearly finished. This will be sent to Journal of Plant Registration for registration and publication. We will also send one pound of seed from RMBUP-C4S1 to the National Center for Germplasm Registration at Fort Collins, CO. In 2012, we also planted the S1 generation of the 18 C4 half sib families in the field in 2012 and will self pollinate 25 plants in each to begin the development of recombinant inbred lines (RIL) for each family. We expect to develop at least 10-15 RIL per family. We also have planted in 2012 a random sample of selfed seed following each random mated cycle to measure yield and fiber properties. The released RMBUP-C4 is a unique random mated population which should have considerable introgression of Gossypium barbadense alleles into it. It should be valuable germplasm to commercial breeders to broaden the genetic base used in cultivar development.