Mutation breeding

About: Mutation breeding is a research topic. Over the lifetime, 531 publications have been published within this topic receiving 6730 citations. The topic is also known as: variation breeding.

The Methods for Determining the Mutation Frequency after Seed Irradiation in Rice

Abstract: In mutation breeding, mutation frequencies are expressed as the proportion of X1 ears which segregate mutant progeny. Since mutations occur as sectors in X1 ear and the size of mutated sectors varies with increasing dose, the procedure used every ear for calculation of the mutation frequency might result in underestimates of mutation frequency. Using the method of the segregation frequency of mutants in mutated X1-ear-branch progenies, it could be shown that the primary branch was traced back to a single cell of rice seed embryo. Mutation frequencies were measured on the X1 ear, X2 plant or X1 ear-branch basis. The deviation from the linear relationship between dose and the frequency of mutations seemed to be less on the X1 ear-branch basis. Consequently, it was proposed to measure the mutation frequency per original treated cell as the proportion of primary branches of X1 ear which segregated mutant progeny. Furthermore, the mutation frequencies and the segregation ratios were less in the lower primary branches of X1 ear. It was supposed that even in haplontic selection the course of the elimination process was dependent on the environment in which the X2 seeds were produced.

Induced Mutations in Plant Breeding

Abstract: Many important traits for plant domestication and improvement have resulted from human selection for novel alleles of structural or regulatory genes. In addition to naturally-occurring genetic mutations, novel alleles have been induced in plants by chemical and physical mutagenesis. The goal of mutagenesis is to induce genetic variation in cells that give rise to plants, while minimizing chimeras, sterility and lethality. For several crop species, chemically-mutagenized populations of a few thousand lines were sufficient for finding the desired phenotype. The efficiency of mutation breeding can be improved by screening plants at the genetic level, prior to phenotypic analysis. High-throughput physical methods and, increasingly, next-generation sequencing are being used to identify lines with induced mutations in candidate genes. An alternative approach to increasing the precision of mutation breeding is through gene-specific mutation using engineered nucleases. Allelic diversity in candidate genes, whether induced naturally or experimentally, can be a resource in breeding programs for developing new agricultural traits.

Studies on the artificial mutation breeding in rice. : 1. Relation between R1 tillering system and R2 mutants treated with the radioisotope 32P.

Abstract: 1. In order to clarify the effective selection method of the mutation breeding, this experiment investigated the relation between the order of tiller and the induction of the mutations in the rice varieties 'Towada' and 'Hattukoda' treated with the radioisotope 32P. 2. Generally, the main stems and each of the lower primary tillers were mutated independently. But, sometimes, these stems when induced to the same type of mutations, they were often sectorial chimeratic on the induction of the mutation. 3. It seemed that the frequencies of the visiblemutations in the lower tillers were comparatively higher than that in the higher ones. 4. The inductions of the mutation in the secon. dary tillers were similar with that in the primary ones from which they grow. 5. Relatively high correlation was found between R1 spike fertilities and R2 Iines fertilities, while there. was no difference in R2 mutation rates by the different fertilities of R1 spike.

Chronic Gamma Irradiation Changes Phenotype and Gene Expression Partially Transmitted to Next-Generation Tomato Seedlings

Abstract: Compared to the studies on acute irradiation of seeds, fewer studies have reported on the chronic irradiation of seedlings, especially in fruit-bearing vegetables. We examined the effects of chronic gamma irradiation on tomato (Solanum lycopersicum ‘Micro-Tom’) seedlings exposed to gamma rays (50, 100, 150, and 200 Gy) for 4 weeks. As the total dose of gamma rays increased, leaf length, trichome density, and seed number were reduced in the irradiated seedlings (M1). Additionally, a change in fruit shape was observed. Chronic gamma irradiation reduced the expression of two trichome-related genes and affected the expression levels of 11 reactive oxygen species (ROS)-related genes. We examined the transmittance of these effects using M2 plants. The trichome density and fruit shape were similar between M2 and control plants; however, a reduction in leaf length and seed number was detected in M2 plants. Interestingly, changes in the expression of four ROS-related genes (ZAT10, Mn-SOD, POD3, and RBOH1) found in M1 were detected in M2 plants. Thus, the changes in phenotype and gene expression induced by chronic gamma irradiation were transmitted to the next generation. Additionally, we found novel mutants from M2 plants, suggesting that chronic gamma irradiation may be considered in tomato mutation breeding.