| Another feasible approach to study the phylogeny of
cultivated hexaploid wheat1) Guillermo S. RYAN Instituto de Fitotecnia, Castelar, Argentina The phylogeny of cultivated hexaploid wheat is always an exciting subject. It is not necessary to refer here to well known pioneering research work made by KIHARA, SARKAR, STEBBINS, MCFADDEN, SEARS and others. The main approaches to the problem can be divided as follows : a) cytogenetic studies, including genome and karyotype analysis, chromosome affinity, interspecific crosses and so on, b) deductions based on analogies between different phenotypes. It is believed that plant reaction to narrowly specific pathogens might be used as a third feasible approach that could shed light on controverted results obtained with the above techniques, as suggested by VAVILOV'S use (1914) of fungi as "physiologic reactors" in systematic botany. If it is assumed that characters of disease reactions in hexaploids or tetraploids derivate from their diploid ancestors, this gives way to screen the possible genome contributors, in order to trace the source of these characters. To test this working hypothesis, seedlings of 129 strains from the Aegilops collection of the Instituto de Fitotecnia, were infected in the greenhouse with conidia of wheat powdery mildew (Erysiphe graminis tritici) from the most common physiologic race found in Argentina. Table 1 summarizes results obtained; strains are grouped in four sections according to KIHARA (1949 and 1957). Before drawing conclusions, the following remarks must be emphasized: a) samples employed came from plots open pollinated during several years, b) Aegilops strains originated from ten sources, listed in Table 2, c) no attempts were made to purify this material or to eliminate identical strains from different sources, d) botanical names are those indicated by the sources mentioned in Table 2, e) some species contribute with only one strain while others are represented by more than ten, f) no representatives from Comopyrum and Amblyopyrum sections were included. In spite of the aforementioned factors, it is possible, nevertheless, to make the following statements: a) most of Aegilops species appear to be resistant to wheat mildew, b) there are, however, some diploid species with one or more susceptible strains. |
| 1) Paper No. 339 of the Institute de Fitotecnia, CIA, INTA, Castelar, Argentina. |
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