Title: Characterization of new male sterile rice lines and validation of linked molecular markers for identification of their genetic seed purity
Author: Alireza Tarang
Abstract: The utilization of heterosis in hybrid rice breeding technology, is one of the options to achieve increased production per unit of area and hybrid rice varieties produce 20 to 30 percent more yields over those of improved or high-yielding varieties with the same growth duration. Seed product of male sterile lines in hybrid rice seed production is controlled of potential for the production of male-sterile lines (A), is assessed as a fertile line (B) and percentage of allogamy or suitable behavior of flowering male sterile lines and factors affecting it. Ensuring the genetic purity of hybrid seeds is a prerequisite for the successful production of hybrid rice. Hybrid seed often contaminated by crosses derived pollen from other varieties or the occurrence of selfing resulting from impurity parental line (Cytoplasmic Male Sterile). The objective of this study was to identify informative microsatellite marker (SSR) capable to distinguish hybrid rice parental lines and their utilization in seed purity assessment and to characterize the morphology of F1 hybrid rice to complement the description of varieties. In the process of hybrid rice production program, initial assessment of the traits related to outcrossing levels, sterility stability and genetic purity in male sterile lines of rice for selecting favorite lines is necessary. In the present research of Eighteen Iranian and exotic cytoplasmic male sterile lines, of different cytoplasmic source and their maintainers (B) and one Thermo-sensitive Genic Male Sterile (TGMS) line, TG51 were tested under randomized complete block design. The use of molecular markers based on PCR has been investigated to assess their purity. The results showed significant differences in plant height, flag leaf length, flag leaf width, fertile tiller number, floret length and width, panicle length, the exit status of the panicle, percentage of allogamy, total number, and panicle fertility percentage. Mean comparison of traits showed that selection and prioritization of the superior lines according to fertility percentage, panicle exsertion, percentage of allogamy, and floret number traits related to Fajr A and Neda A and IR58025 A. Due to proper height, panicle length, number of florets, and upper percentage of allogamy in the Dasht B, these lines introduced to the favorable line in the seed production program. Molecular tests based on PCR using four markers for the purity of the seed parent, CMS, and the distinction between male-sterile and maintainer lines were performed. A combination of CMS and RG136 markers and RMT6 markers could distinguish between the lines of CMS-WA and no efficiency of other male sterility sources. Results showed that the bands of drrcms marker distinction cytoplasmic male sterility lines between different sources of WA, DISSI, Gambiaca and produce different monomorphic fragments for each of the male-sterile and B lines. Therefore, these markers can be used for genetic purity and possible infection test of the seed parent and suitable alternative to be for GOT.
Keywords: Hybrid rice, Cytoplasmic male sterility, CMS-WA, TGMS, PCR based molecular markers