Determination of hetero and autotoxicity effects in some japonica, javanica and indica types of rice cultivars

Autotoxicity and heterotoxicity induced root exudates plays an important role in regulating crop yield and the quality of plants. The aim of this study was to determine the effects of hetero and autotoxicity of allelo chemicals leaking from the roots of three sub species of Oryza sativa L. namely Indica, Japonica and Javanica and check their effects on 13 morphologic characteristics and some phenolic acids of these plants on their growth and development under in vitro conditions. Each of the sub species showed variable effects of hetero and autotoxicity on the morphological and chemical attributes of the three subspecies. Neither heterotoxicity, nor autotoxicity showed severe lethal effects on the morphological attributes of rice. If a comparison of the three species is made, the Japonica was least and the Indica was highly autotoxic. The Javanica lied in between the two. The maximum depression was noted for all morphologic characters, when 5 plants of Indica were grown with three plants of Javanica in the first experiment. The second experiment compared Japonica and Indica, which showed similar observations for both autotoxicity, and heterotoxicity with variable lethal effects on the morphological attributes of the two subspecies. If a comparison between the two is made, the expression was irregular. Japonica was maximum toxic when the 7 plant of Japonica were grown with a single plant of Indica. However, dry weights of roots, shoots and plant showed maximum toxicity when the 3 plants of Japonica were grown together with 5 plants of Indica sub species. The third experiment with Javanica and Japonica showed that 5 Javanica plants grown with three Indica plants were grown together, they showed maximum depression on plant shoot length, root length and plant length. However, rest of the parameters showed maximum depression when 6 plants of Javanica were grown together with 3 plants of Japonica subspecies. The experiment made use of three sets of Indica-Javanica, Japonica-Indica, and Javanica-Japonica to compare the morpological performance of each of the subspecies on the other, it was found when equal number of plants were used they induced moderate depression in each set of the expreriment. This transitional depression decreased with each increase in number of Indica plants compared to Javanica plants. This transitional depression was irregular when Japonica-Indica were used and increased with each increase in number of Javanica-Japonica set. In terms of phenolic acid compounds, using all 3 subspecies alone and using Indica-Javanica, Japonica-Indica and Javanica-Japonica as mixtures showed a change in the ratios of phenolic compounds (benzoic acid, caffeic acid, cinnamic acid and syringic acid). Significant effects of auto and heterotoxicity were observed on plant growth parameters by using the seeds singley or in combination for auto or hetero toxicity of the respective in vitro grown plants. The results can be used to quantify phenolic acids secreted by explants and to counteract them. The results will help to solve or reduce the widespread necrosis issue on explants in tissue cultures, and to increase the regeneration potential of explants.