Cytogenetics of Reciprocal Triticum - Hordeum Hybrids

Abstract

The present study was executed for intergeneric crosses reciprocally among four species of Triticum and ffordeum at the first step. Chemical treatment with GA3 yielded better result regarding seed setting. On an average 7.9 l % seeds were found to set and 68.24 % seeds were found to germinate. Most of the hybrid seeds were shriveled, weak, smaller in size, sometimes intermediate and few of them resembled to that of their respective female parent. Seedling viability ranged from 45.45-58.33%. The FI plants were vegetatively weak and resembled morphologically somewhat to their female pare1i.t. The spikes were very weak and the spikelets were found to arrange themselves on the rachis very laxly. All the hybrid plants were found to be sterile in nature. The present study was carried out for making a keen observation on interphase nuclei of F 1 s and their respective parents. Mean values for chromocentre number were found to be higher than that of their respective 1-/ordeum parents and but lower than that of their T iticum parents. The number of chromocentres were always less compared to their chromosom���� number in all the F 1s. The percentage of heterochromatin per nuclear area in different hybrids ranged from 24.69 % (H. nudum x T durum) to 28.38 % (T. aestivum x IJ. 1111d11111). Nuclear vulome (NV) and interphasc chromosome volume (ICY) were found lo be proportionally related the number and size of chromosomes. Mean values for inlerphase chromosome volume (ICY) in the hybrids were found to decrease when compared to Triticum species but increased when compared to florcleum species. The present study was performed for chromosome identification both m the hybrids and their respective parents by quantitative karyotype analysis. This technique also helped to propose the standard karyotype of each hybrid and their parents. The identifiable number of chromosome were found to be 13 pairs in Triticwn durum, 18 pairs in Triticum aestivum and 7 pairs in both. the Hordeum species. On the other hand, the chromosome numbers were counted lo be 22-28 in the hybrids of T. aestivum ><: H. vulgare, Ii vulgare x T. aestivwn, T. aestivwn x 1-1. 1111d11111 and /-I. nudum x T. aestivuin and 15-21 in the hybrids of T. durum x fl. vulgare, H. vulgare x T. durum, T. durum x 1-f. nudum and fl. nudwri x T. durum. The number of identified chromosomes were 7,7,6,5,6,5,6 and 5 in F 1s of T. aestivum x I-1. vulgare, fl. vulgare x T. aestivum, T aestivum x /-I. nudum, /-I. nudwn x T. aestivum, T. durum x H. vulgare, H. vulgare x T. durum, T durum x H. nudum and H. nudum x T. durum, respectively. The present study was dealt with chromosome association and chiasma frequency. The frequency of univalents were higher than the bivalents, trivalents and quadrivalents in all the F 1 s. Ivlean values for univalent ranged from 17.1-25.9, for bivalent ranged from 0.2-0.7, for trivalent ranged from 0.1-0.2 mid for quadrivalent ranged from 0.1-0. l. Chiasmata per cell decreased significantly in F1 s when compared to their respective parents. Frequencies for homologous chromosome pairing were found to be very low ( 1.15 to 2.0). Mciocytes reflected the meiotic instability in all the hybrids. At the end of the present study meiotic irregularity and pollen sterility were determined. Parents of Triticwn and Hordeum species showed negligible amount of meiotic irregularities. l3ut meiotic irregularities were of high frequency in all the hybrids. Highest percentage of meiotic irregularities was among hybrids found in FI of H. vulgare x T. aestivum and lowest in F1 of Ii vulgare x T durum. In parents of Triticum and Hordeum species pollen sterility was found with very low percentage. On the contrary, hybrid plants showed high pollen sterility. The values obtained for it ranged from 87.50- 94.93.