SOMACLONAL VARIATION IN GLYPHOSATE TOLERANCE OF POTATO (SOLANUM TUBEROSUM L. CV. 'SUPERIOR') (IN VITRO, HERBICIDE, MUTATION)
Abstract
An in vitro system was used to determine if variation exists in plants regenerated from somatic cells of potato (Solanum tuberosum L. 'Superior'), which could be exploited to obtain somaclones tolerant to glyphosate. Tolerance to glyphosate of somaclonal populations were compared to a tuber piece propagated population by applying 0.56 kg ha('-1) glyphosate to field-grown plants. The quantitative variation to glyphosate of each population was partitioned into variation transmissible through clonal generations, variation due to environment, and the interaction of transmissible and environmental variation. In the first series of studies, the mean tolerance to glyphosate of the somaclonal and tuber control populations was similar. The glyphosate tolerance of the somaclone population exhibited a transmissible (possibly genetic) variation, while the tuber control population did not. The presence of transmissible variation in the somaclonal population led to the second set of experiments to determine if selection pressure would increase glyphosate tolerance of the somaclones. In these studies, there was transmissible variation in all populations. Glyphosate inclusion in the regeneration medium during formation of shoot primordia resulted in increased somaclone tolerance. Other factors which contributed to variable response to glyphosate included virus infection and vigor differences. These did not account for the total amount of variation observed. The somaclone response to glyphosate also was dependent on initial explant, suggesting that at least part of the somatic variation preexisted in the tuber tissue prior to regeneration. The ratio of transmissible-to-phenotypic variation (a measure of broad-sense heritability) was less than 10% in all populations. But, because of the environmental control and selection intensity possible, our in vitro selection method did result in increased glyphosate tolerance in the plant populations. In order to obtain an agriculturally useful degree of glyphosate tolerance, recurrent in vitro selection, along with further field evaluation, is required.
Degree
Ph.D.
Subject Area
Botany
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