PRODUCTION AND IDENTIFICATION OF PRIMARY TRISOMICS IN DIPLOID AGROPYRON-CRISTATUM (CRESTED WHEATGRASS)

Six of the seven possible primary trisomics in Agropyron cristatum wer e produced. Based on morphology, arm length ratios, and C-banding patt erns, they were identified as primary trisomics for chromosomes A, B, C, D, E, and G. Agropyron cristatum is one of several species constitu ting the crested wheatgrass complex. All species in this complex conta in one basic genome (P). A study was conducted to produce and identify a primary trisomic series that will be used to map genes to individua l chromosomes. A population of 157 plants were generated by crossing a utotriploids (PPP) with diploid (PP) A. cristatum: 58 were diploid (2n = 14), 76 were primary trisomics (2n = 15), 17 were double trisomic ( 2n = 16), 4 were triple trisomics (2n = 14 + 3), 1 was telocentric tri somic (2n = 14 + 1 telo), and 1 was tetratrisomic (2n = 14 + 4). Karyo type analysis of acetoorcein-stained chromosomes was carried out using the CHROMPAC III computer program; for analysis of C-banded karyotype s, the computer imaging analysis program PCAS (Plant Chromosome Analys is System) was used to identify the primary trisomics. Of the 47 prima ry trisomics analyzed, 21 plants had one extra satellited chromosome E , 18 with the satellited D chromosome, 3 each for chromosomes B and G, and 1 each for chromosomes C and A. Chromosome pairing was studied in trisomics B, D, E, and G. Trisomics for chromosomes B and G were simi lar in their mieotic behavior. Each had a trivalent frequency of about 60% and pollen stainability of less than 40%. Trisomics for chromosom es D and E had a trivalent frequency of about 30% and pollen stainabil ity of over 70%.