germplasm. For instance, Iowa Stiff Stalk Synthetic is considered a source population of inbreds with above-Breeders need more information on selecting testers to identify average performance for combining ability (Hallauer lines for formation of synthetics and need more user-friendly methods to study general combining ability (GCA) and specific combining and Miranda, 1988). Lonnquist (1961) defined a synability (SCA) of genotypes. Forty-three lines were crossed to two thetic as an open-pollinated population formed by internarrow-based (S3 line and S3 ϫ S3 hybrid) and two broad-based crossing lines and maintained subsequently by mass setesters, which were open-pollinated varieties (OPVs). Topcrosses lection. In this paper, synthetics are defined as OPVs (line ϫ tester, L ϫ T) were evaluated in eight acid soil environments. formed by recombining lines with high GCA and main-The additive main effect and multiplicative interaction (AMMI) and tained from one generation to the next by open pollithe site regression (SREG) models were used to study the GCA of nation. the testers and lines and the SCA of the L ϫ T interaction. The SREG The use of testers in a maize recurrent selection probiplot contains the effect of the lines plus the L ϫ T interaction and gram has been well documented (Jenkins and Brunson, displays both GCA and SCA, whereas the AMMI biplot contains the 1932;Matzinger, 1953;Rawlings and Thompson, 1962; effect of the L ϫ T interaction and displays only the SCA. One synthetic was developed by recombining six lines identified as superior Allison and Curnow, 1966, Hallauer, 1975; Hallauer and by each tester. The four synthetics were evaluated in 12 acid and nine Miranda, 1988;Russell et al., 1992, Menz et al., 1999. nonacid soil environments. The synthetic developed with the S3 lineThese authors concluded that choice of a suitable tester as tester yielded the highest and the one developed with an OPV as should be based on simplicity in its use, its ability to tester yielded the lowest. The AMMI and SREG models seem to classify the relative merit of lines, maximize genetic gain, provide an effective tool to visualize and study GCA and SCA of geand enhance the expected mean yield of a population notypes.

No abstract

An emphasis in maize breeding for areas with acid soils is the development of varieties with tolerance to P-deficiency plus high yield potential in acidic as well as normal soils. This study was carried out to assess the (i) genetic diversity within a set of tropical inbred lines developed from acid soil-tolerant populations; (ii) F1 yield performance, mid-parent heterosis (MPH), high-parent heterosis (HPH), and specific combining ability (SCA) in a diallel set of crosses under P stress (low P) and non-stress (high P) conditions; and (iii) the effect of P stress on the relationship between genetic distance (GD) and hybrid performance. Using field evaluation and molecular marker studies, the results show that these germplasm from the South American maize breeding program of CIMMYT for improving tolerance to acid soils had only a moderate level of genetic diversity. The utility of GD as a predictor of hybrid value is best up to a certain threshold, as correlations with GD became inconsistent when the inbred parents were greatly divergent. There was no correlation between GD and F1 grain yield, MPH, HPH and SCA when the GD was [0.77. The high correlation of GD with F1 grain yield and with SCA in specific subsets of crosses having a narrower range of GD shows that GD can be put to practical use in predicting hybrid performance. The highest correlation between GD and SCA, seen in the subset of crosses between lines within a cluster, was reasonably stable even when the environment had a severe effect on yield.

No abstract

INTRODUCTION Primary central nervous system (CNS) sarcomas are rare mesenchymal non-meningothelial tumors accounting for less than 0.2% of intracranial lesions. Diagnosis and management are challenging due to the current lack of substantive clinical, histological and molecular data. METHODS We retrospectively identified all patients with diagnosis of primary CNS sarcoma at the Hospital Fundación Pediatrico la Misericordia (HOMI) in Bogota, Colombia. We collected patient demographics, disease characteristics, and outcomes for analysis. RESULTS Between 2008 and 2020, twenty-four consecutive patients were diagnosed at the HOMI representing 6% of all CNS tumors diagnosed over the same time period. The median age at presentation was 9.48 years (range:1.6–13.4). The median time of symptoms prior to diagnosis was 2 weeks (0.1–24). The most common presentation was headache (21/24- 89%) and vomiting (19/24- 79%). The frontal lobe was involved in 63% of patients (15/24) and only one patient presented with a cerebellar lesion. Histologically, these tumors were characterized by a pleomorphic spindle cell architecture and high mitotic activity. All samples lacked immunoreactivity to GFAP, CD34, EMA, and S100 and all samples had strong nuclear immunopositivity for TLE-1; BCL-2 was reactive in eighteen cases. Gross total resection was attained in fifteen patients, most patients received focal radiation therapy and ICE chemotherapy. Progression-free survival at 12 and 24 months was 57% and 31% respectively. Overall survival was 77% at 12 months and 39% at 24 months. Thirteen patients relapsed, 11 presented with local failures, and 2 with intracranial recurrences outside of the radiation field. CONCLUSION Our study identifies TLE-1 as a diagnostic marker of primary CNS sarcoma, a highly malignant supratentorial tumor of childhood. Further molecular studies are urgently needed to elucidate the biology of this disease and the unusually high incidence observed in the Colombian pediatric population.