Mitochondrial DNA-RFLP Analysis Distinguishes New CMS Sources in Pearl Millet (Pennisetum glaucum (L.) R. Br.)

Restriction fragment length polymorphism (RFLP) of mitochondrial (mt) DNA provides a rapid and effective method to assess heterogeneity among male sterile cytoplasms. Six isonuclear A-lines (81 A₁, with Tift 23A₁, cytoplasm, ICMA 88001 (= 81 A_v) with Violaceum cytoplasm, 81A (=81 A₄) with monodii= violaceum cytoplasm, Pb 310A₂ and Pb 311A₂ with A₂ cytoplasm from L 66A, and Pb 406A₃, with A₃ cytoplasm from L 67A), nine cytoplasmic male-sterility sources from Large-Seeded Genepool (LSGP 6, LSGP 14, LSGP 17, LSGP 22, LSGP 28, LSGP 36, LSGP 43, LSGP 55 and LSGP 66) and two each from Early Genepool (EGP 33 and EGP 15) and Population Varieties (PV 1 and PV 2) were characterized for variation in their mitochondrial genomes following Southern blot hybridizations using homologous (pearl millet 13.6 kb, 10.9 kb, 9.7 kb and 4.7 kb clones) and heterologous (maize atpB and coxl clones) mitochondrial DNA (mtDNA) probes. Following cluster analysis based on similarity indices for the RFLP banding patterns observed, we identified seven cytoplasmic groups within LSGP. Two (LSGP 43 and LSGP 66) of these were quite distinct from each other as well as from other cytoplasms. This clearly indicates that besides serving as a source of diversity for agronomic and adaptation traits, broad-based gene pools can also provide diverse sources of cytoplasmic male sterility. These new CMS sources were also compared with standard CMS systems and cytoplasm-specific restriction fragments were identified.