| Evaluation and utilisation of diploid species of wheat
S.M.S. TOMAR*, M. KOCHUMADHAVAN and P.N.N. NAM BISAN* Indian Agricultural Research Institute, Regional station, Wellington, The Nilgiris, India Diploid progenitors of wheat have successfully been exploited for incorporating resistance to rusts into common wheat. To find out the effectiveness of resistance available in the diploid wheats, 98 accessions belonging to Triticum monococcum, T. urartu, T. boeoticum, T. speltoides (Aegilops speltoides), T. longissimum, T. bicorne, Ae. sharonensis and T. tauschii (Ae. squarrosa) were evaluated for resistance under natural incidence of stem, leaf and stripe rusts infection over a period of four seasons at Wellington (Nilgiri Hills), a 'hot spot' location for wheat diseases in south India. Most of the accessions of T. speltoides, T. longissimum and Ae. aucheri exhibited a high degree of resistance to all the three rusts whilst the majority of T. tauschii strains did not possess adequate resistance to any of the three rusts. However, more forms were found resistant to leaf rust than to stem and stripe rusts. The einkom wheats : T. monococcum, T. urartu and T. boeoticum were found to carry a high degree of resistance to leaf and stripe rusts. A number of specific genes such as Lr9, Lr21, Lr22a, Lr28 for leaf rust, Sr33, Sr34 and Sr35 for stem rust and Yr8 for stripe rust have been transferred by various wheat workers from diploid wheats to common wheat. These specific genes conferring resistance to rusts were also screened against rusts under natural incidenee of stem, leaf and stripe rust infection over a period of six seasons at same location. The genes Lr21 and Lr22a conferred moderate degree of adult plant resistance to leaf rust races existing in the Nilgiris, however, theses genes have been reported ineffective to most of the Indian races in seedling stage (SAWHNEY et al. 1977). Except the gene Sr34, all the genes were found to confer effective resistance to the rust-race-flora prevailing in the Nilgiri hills. Thus, diploid wheats are potentially useful and offer an excellent source of resistance to wheat rusts. A programme of transference of resistance to rust from T. speltoides into common wheat was initiated in the year 1982. A tetraploid wheat variety of T. durum was crossed to a strain of T. speltoides. The F1 triploid hybrid (2n=21) exhibited complete resistance to all the three rusts under field conditions. The two triploid hybrid plants were crossed to T. aestivum variety Sonalika. To ensure good seed set the florets were pollinated twice. Seven seeds were obtained out of which only three survived when planted. The cytological analysis made at frist meiotic metaphase stage revealed that the hybrid progenies varied in chromosome constitution (Table 1). |
| * Present address-Division of Genetics, IARI, New Delhi-12 |
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