|Authors: ||Y.A. Patil, V.S. Dalvi, V.K. Borole, B. Krishna, A.V. Dhake, P.V. Sane, A.P. Sane|
|Keywords: ||onion (Allium cepa L.), cytoplasmic male sterility (CMS), coxI, AOX|
Onion (Allium cepa L.) is an out crossing diploid (2n=2x=16) biennial vegetable of great economic importance in the Allium genus.
Yields of several vegetables have been improved through the use of hybrid seeds (F1 hybrids) by utilizing hybrid vigor.
The production of F1 hybrid seed of short day onion has not been commercially possible due to unavailability of well characterized male sterile and restorer lines.
The present study was conducted to identify and characterize CMS lines in short day white onion.
Six cytoplasmic male sterile lines were identified from 18 lines used for study from the germplasm collection of Jain R&D centre.
Sterility/fertility of these lines along with other germplasms was confirmed by visual as well as by microscopic examination of pollen.
Using published molecular markers the six sterile genotypes were found to possess the sterile (S) cytoplasm while the rest of the genotypes possessed the fertile (N) cytoplasm.
None of the 12 fertile lines could restore fertility in any of the sterile lines.
The chimeric male sterility marker gene “orf725” consisting of a fusion of coxI-orfA501-atp6 gene was present as such in all six identified sterile lines of onion.
Gene expression study revealed reduced expression of normal coxI gene and abundant expression of chimeric “orf725” in sterile lines.
An increase in AOX expression responsible for cyanide insensitive respiration (and reduced ATP generation) was found to be higher in sterile lines compared to fertile lines in flowers.
The lower normal coxI and higher AOX expression in sterile lines might be responsible for reduced mitochondrial ATP generation during anther formation and may affect pollen viability.
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