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Mechanisms of incompatibility among interspecific peanut(Arachis spp.) hybrids were investigated in an attempt to determine efficient methods for the introgression of germplasm from diploid Arachis species (2n = 20) into A. hypogaea L. (2n = 40). Hexaploid interspecific hybrids (2n = 60) with restored fertility were used in a backcross program, in reciprocal, with diploid Arachis species in an attempt to rapidly reduce the chromosome number from 2n = 60 to 2n = 40. All attempts to cross hexaploids and diploids failed to produce viable hybrids. The proposed mechanisms for such failure are: (i) lack of pollen germination on the stigma or restricted pollen tube growth (in crosses using diploid A. cardenasii as the female parent), and (ii) endosperm degeneration and/ore mbryo abortion( in all other crosses examined). When A. cardenasii Krap. et Greg. nom. nud. (coll. GKP 10017) (2n = 20) was used as a female parent, no pegs (the basal portion of the gynoecium that grows by the activity of an intercalary meristem and carries the fertilized ovule into the soil) werep roduced. When A . duranensis Krap. et Greg. nom. nud. (coll. K 7988) (2n = 20) or batizocol Krap. et Greg. (col l. K 9484 (2n = 20) was used as a female, very few pegs were produced and the hybride mbryosa bortedw ithin 10 days after pollination. When either of the two hexaploidh ybrids(A. hypogaea x A. batizocoi or A. hypogaea x A. cardenasii was used as a female, peg development was more frequent,b ut all developed pods contained tiny, shrivelled, black seeds. Embryo rescue techniques were applied as a means for overcoming embryo abortion. The seeds were successfully germinated in culture and shoots and roots were initiated.
Key Words: Arachis hypogaea L. Wild species Embryo rescue Tissue culture Germaplasm introgression
2 Graduate research assistant and associate professor, respectively, Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695.
Received for publication March 6, 1986.
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