PJB-2018-953
Identification of spontaneous chromosome doubling, optimization of artificial chromosome doubling and evaluation of R1-nj marker system in maize maternal haploids at high temperature
Khunsa Khakwani
Abstract
In-vivo maternal doubled haploid technology is new to maize breeders of Pakistan. One of the steps in this technique is to double the chromosome number of the haploid seedlings. This is mostly carried out through the use of Colchicine as a doubling agent. This step requires skill, money and laboratory setup which may cause hindrance for maize breeders of developing countries with limited resources. Spontaneous doubling can be an alternate procedure which is natural occurring and germplasm specific. The present study was aimed at the identification of spontaneous doubling in local germplasm. In this technique the R1-nj visual colored marker is used to sort haploid seed from diploid seeds. The expression of this visual color marker is dependent on certain factors including temperature. In the region during the growing season of spring maize (Feb-June) temperature may reach up to 40 0C. Induction crosses were planned in the season to check the expression and reliability of R1-nj visual color marker system in high temperature regime. Two haploid inducer lines with 4-6% HIR were used as male parents and crossed with a F2 generation of a single hybrid FH-949. The R1-nj visual colored marker was used to sort haploid from diploid kernels. To check the spontaneous chromosome doubling rate these haploid kernels were grown in the field. In the laboratory, colchicines treatment of haploid seedlings was optimized, the data for seedling survival and DHo seed formation was collected and generalized linear model GLM was used to interpret treatment results. SAS 9.2 was used to estimate confidence intervals for the binomial proportion having zero frequencies. The R1-nj dominant anthocyanin marker performance under the high temperature was found to be 91 percent effective. The spontaneous doubling percentage of maternal haploids was recorded 0.4%. The cob development of maternal haploids is a major factor bringing out spontaneous duplication. If its percentage is increased, spontaneous duplication in the field will be as promising as artificial duplication of chromosomes with the help of colchicines in the laboratory.
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