Mitochondrial DNA Polymorphism in Male‐Sterile and Fertile Cytoplasms of Pearl Millet

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Abstract
Cytoplasmic male sterility (CMS) is used extensively in the production of pearl millet [Pennisetum glaucum (L.) R. Br.] commercial F1 hybrids. Although several male‐sterile cytoplasms are available in pearl millet, most of them are not stable enough for commercial use; therefore, additional male‐sterile cytoplasms are being sought. The traditional method of classifying male‐sterile cytoplasms using restorer gene responses is slow and cumbersome. This research was conducted to evaluate mitochondrial DNA restriction endonuclease fragment patterns for classifying cytoplasmic male‐sterile and fertile cytoplasms, to define restriction fragment patterns capable of distinguishing the cytoplasms, and to evaluate the relative effectiveness of restriction fragment and hybridization patterns, using maize mitochondrial gene probes to distinguish the cytoplasms. BamHI restriction patterns differentiated the male‐sterile cytoplasms, S‐Am, S‐A1, S‐A3, but grouped together S‐A2 and the five male‐sterile mutants derived from F‐B2. Those patterns also differentiated fertile F‐B2, but failed to differentiate F‐B1 and F‐B3. The CMS mutant, S‐M7, had a unique SmaI restriction pattern differentiating it from S‐A2 and the other four CMS mutants, and verifying its mutant origin. Hybridization patterns, using maize mitochondrial gene probes, differentiated the cytoplasms much the same as did the restriction patterns. Both restriction and hybridization patterns are of value in classifying the cytoplasms. Unique restriction fragments and patterns capable of differentiating the various cytoplasms were identified.