New sources of dwarfing genes in pearl millet (Pennisetum americanum).

Thirteen naturally occurring dwarf lines of pearl millet [Pennisetum americanum (L.) Leeke], identified from the world collection, varied for several morphological and agronomic characters. Extreme dwarfs were characterized by a tufted growth habit which could be distinguished from the time of germination, while the other dwarf lines could be distinguished only after anthesis. The F1 hybrids between the tall and dwarf genotypes were tall, indicating that dwarfness is a recessive trait. In 10 out of the 13 crosses, the F2 segregation ratio was three tall to one dwarf (3∶1) suggesting that the dwarfness is controlled by a single recessive gene, while the height differences in 3 of the dwarfs (IP 8056, IP 8210 and IP 8214) were controlled by more than one gene as they showed continuous variation for plant height in F2. When the remaining 10 single gene dwarfs were crossed to either d 1 ('Tift 238') or d 2 ('Tift 23 DB') dwarfs, only 2 crosses produced tall F2 hybrids and they segregated for height in F2 indicating that these 2 dwarfs are non-allelic to d 1 and d 2. Reciprocal crosses of these 2 dwarfs produced tall F1 hybrids and showed a dihybrid segregation of 9∶3∶4 in F2 indicating that the dwarfing genes of these 2 parents are non-allelic to each other. These non-allelic dwarfs were assigned the gene symbols d 3 (IP 10401), and d 4 (IP 10402).