International Center for Tropical Agriculture

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   List of promising Urochloa hybrids defined: Research and distribution of B. humidicola and Tetraploid B. ruziziensis X various accesions of B. decumbens or B. brizantha The main objective has been the breeding of tropical forages from Brachiaria species in order to produce hybrids which outperform in yield, biotic and abiotic resistances and nutritional quality. Brachiaria species of agronomic importance are apomictic and tetraploids. The forage group at CIAT adapted a breeding methodology that exploits these characteristics plus heterosis. This methodology follows a scheme of recurrent selection based in specific combining ability, in which a population of sexual clones is selected in every cycle based on the performance of their progeny when crossed against a tester genetically complementary. Every cycle of selection consist in three years (some times more in the case of B. humidicola): 1) open pollinated cross of sexual clones; 2) Test crosses formation against the tester; and 3) Multienvironmental evaluation of hybrids performance for further selection. For each of the breeding programs, a set of promising Urochloa hybrids were defined. The activities developed conducted in order to reach those materials are described as follows:  Brachiaria ruziziensis x decumbens x brizantha:  A final set of (BR09) hybrids was delivered to private sector in 2011.  A new set of hybrids (BR12) was generated during 2011, in a testcross crossing block at CIAT-Popayán.  Testcross hybrid seed was germinated in 2012 to originate the BR12 population.  These hybrid seedlings were transplanted to field trials at two sites (La Florida and El Porvenir farms, properties of Semillano in the Colombian Llanos.  Several thousand seedlings were transplanted at these two sites.  The population was culled, on visual assessment and open pollinated seed harvested from 128 “pre-selected” hybrids.  From this seed, progenies were established in 2013 at CIAT, with two objectives: i) To confirm (or otherwise) apomictic reproduction of selected hybrids;  ii) To multiply seed to deliver to DOW to initiate evaluation/development of cultivar(s) for future commercial release.    The 128 progenies were transplanted to the field on 29 and 30 April, in 5-plant plots, with two, three, or four replications (i.e., 10, 15, or 20 individuals per progeny).   Identification of segregating progenies (from sexual [or facultatively apomictic] BR12 selections) was done by visual assessment of sibling uniformity or segregation on several dates following transplanting. By August, progenies were culled to 103 based on apparent apomictic reproduction (uniform progenies) and plant vigor.  Seed harvest extended from August through October 2013.  Plants were sampled on three dates (i.e., different ages of regrowth) for nutritional quality assessments.  These selected hybrids were additionally assessed for reaction to nymphs and to adults of four spittlebug species, and for reaction to Rhizoctonia foliar blight.  Additional culling was imposed on the basis of one or more of these additional attributes. Ninety two BR12 hybrids were finally selected for dispatch to the private sector. Seed of a new set of testcross hybrids (BR15) was produced in a testcross crossing block at CIAT-Popayán during 2014.  The BR15 hybrid seedlings were produced in early 2015.  Seedlings were transplanted to two field sites (La Florida and El Porvenir farms, Llanos Orientales) in April 2015.  Culling was on visual evaluation of field-grown plants. One hundred thirty-three BR15, putatively apomictic testcross progeny were selected for advanced trials based on general vigor and leafiness during four bimonthly (three wet-season and one dry-season) evaluations during 2015-2016.  Open pollinated seed of these “pre-selected” BR15 hybrids was produced.   Advances during 2017: The selected hybrid genotypes were tested for reproductive mode (by progeny test), seed production and for spittlebug resistance (ANNEX 2: 81 hybrids from population Br15). During 2018 hybrid seed will be produced for 81 apparently (on observation of progeny-trial) apomictic BR15 preselections (of the original 133 preselections).  Nearly all of 131 BR15 preselections tested for spittlebug reaction were as or more resistent (by plant damage or nymphal survival) as Cv. Marandu, a testament to the high levels of resistance that has been achieved over the years in our sexually-reproducing breeding population.  The generally high resistance in these hybrids is particularly notable given that the male parent (the tester) of every hybrid is the very susceptible natural genotype cv. Basilisk. A set of apomictic seed would be available once import and export requirements are satisfied.     Brachiaria humidicola In mid-2011 we were in the process of synthesizing a broad-based, sexual breeding population of B. humidicola.  In 2012, a first set of Bh hybrids was produced (with the objective of selecting an apomictic “tester”), with 20 sexual clones exposed to pollination by six apomictic germplasm accessions in six isolated crossing blocks.  The resulting set of hybrid plants was generated in 2013 (Bh13).  These were assessed in field trials at two field sites in the Colombian Llanos Orientales, culled on visual assessment, and the “pre-selected clones vegetatively propagated to CIAT-Palmira.  OP seed was produced at CIAT-Popayán for progeny testing, at CIAT-Palmira, and apomictic hybrids identified on this basis.  A set of 45 of these Bh13 hybrids was selected for dispatch to DOW.   In 2014, a testcross crossing block was established at CIAT-Popayán.  Testcross seed was harvested during 2015, and a set of testcross hybrids (Bh16) generated in 2016. One thousand seven hundred ninety-four testcross progeny clones (Bh16) were established in each of two sites in the Colombian Llanos in May 2016.  Two visual assessments of overall agronomic performance (apparent biomass production, leaf:stem ratio, etc.) have been conducted and a “short-list” of 154 pre-selections (8.6%) has been identified by ranking the sum of the four ratings on each hybrid clone.  These pre-selections were genotyped with the University of Georgia marker of the “apospory-specific genomic region” (ASGR), and apomicts will undergo further assessment for spittlebug reaction; low pH; forage nutritional quality parameters, and, perhaps, BNI activity.  After further culling, open-pollinated seed for a confirmatory progeny test will be produced.   CONCLUSION Hybrid seed is ready to be sent to the private sector corresponding to: 92 hybrids from the population Br12 and 100 hybrids from population Br15, which belong to the fifth and sixth selection cycles, respectively, in the interspecific Brachiaria ruziziensis x decumbens x brizantha breeding program. In the B. humidicola breeding program a first set of 45 hybrids were obtained from the first selection cycle, and the set from the second cycle, corresponding to 27 promising apomictic hybrids, will be further selected according to progeny test once multiplication of seed is successful. ANNEX 1: 92 hybrids from the population Br12     Unit BR12 Name   Unit BR12 Name   Unit BR12 Name 1 937   32 1794   63 2176 2 1370   33 49   64 2243 3 2321   34 61   65 2254 4 2661   35 62   66 2255 5 2756   36 173   67 2305 6 91   37 181   68 2316 7 796   38 184   69 2367 8 1188   39 255   70 2461 9 1282   40 446   71 2462 10 1427   41 461   72 2937 11 2360   42 533   73 3069 12 2471   43 804   74 3377 13 2611   44 805   75 3436 14 2679   45 1176   76 3654 15 2762   46 1280   77 3659 16 2947   47 1325   78 3868 17 3018   48 1362   79 4012 18 3067   49 1399   80 4039 19 3136   50 1411   81 4400 20 3245   51 1418   82 4707 21 3358   52 1509   83 4856 22 3563   53 1532   84 4951 23 3809   54 1535   85 5023 24 4101   55 1620   86 5029 25 4653   56 1663   87 5049 26 5176   57 1685   88 5082 27 5213   58 1716   89 5350 28 5323   59 1844   90 5697 29 5925   60 1888   91 5873 30 5963   61 1889   92 5921 31 5967   62 1939             ANNEX 2: 81 hybrids from population Br15 Unit BR15 Name   Unit BR15 Name   Unit BR15 Name 1 58   31 2767   61 6547 2 60   32 2811   62 6571 3 361   33 2891   63 6590 4 378   34 3013   64 6758 5 395   35 3017   65 7006 6 503   36 3025   66 7121 7 582   37 3186   67 7316 8 722   38 3234   68 7318 9 757   39 3248   69 7659 10 780   40 3280   70 8529 11 800   41 3294   71 8543 12 823   42 3434   72 8650 13 972   43 3571   73 8756 14 1168   44 3597   74 8881 15 1462   45 3726   75 8887 16 1468   46 3810   76 8905 17 1628   47 3811   77 8919 18 1689   48 4368   78 8976 19 1712   49 4442   79 9125 20 1830   50 4483   80 9141 21 1851   51 5152   81 9142 22 1865   52 5232       23 1877   53 6346       24 2174   54 6401       25 2464   55 6402       26 2528   56 6434       27 2532   57 6487       28 2538   58 6504       29 2545   59 6508       30 2558   60 6543                         

Research and distribution of B. humidicola and Tetraploid B. ruziziensis X various accesions of B. decumbens or B. brizantha

https://cgspace.cgiar.org/bitstream/10568/102381/1/D4248%203.2.1_ListOfDefinedHybrids.pdf

Research and distribution of B. humidicola and Tetraploid B. ruziziensis X various accesions of B. decumbens or B. brizantha

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