Thesis (M.S. in Plant Breeding). 24 tables. Bibliography (70 ref.). Appendices. Received Jul 1994. Summary (En). (UPLB Call no. LG995 1994 A42A53)

DH0 [explant source IR43] and DH2s differed significantly in at least seven out of ten characters. Variation among DH2s was detected in at least six traits. The DH2s tend to have reduced height and panicle length, higher grain length, weight and yield. Significant pooled cytoplasmic gene effects were detected in at least three agronomic traits suggesting some alterations in the cytoplasmic genomes. Nine characters exhibited significant pooled nuclear gene effects, suggesting that mutations in the genes governed by an additive and/or dominance type of gene action may have occurred. Genetic variability observed in three characters was influenced by cytoplasmic and nuclear factors. Variability in six characters involved only the contribution of changes in the nuclear genes. Midparent heterosis in the F1 and F2 generations were significant in at least three characters, proving genetic diversity between DH0 and DH2 lines. The set of crosses using DH0 as the female parent exhibited a higher average midparent heterosis as compared to the reciprocals, indicating a notable influence of DH2 cytoplasm in mean performance. The chromosome behavior of DH0, DH2 lines and their F1s at meiosis was comparably similar. Laggards and bridges were observed in very low frequency which indicated that there was no observable gross chromosomal abnormality exhibited by the second cycle doubled haploid derivative using the anther culture technique. These results showed that the anther culture technique employed by UPLB-PhilRice in generating the second cycle doubled haploids of IR43 appears to be mutagenic and may be causing mutations in the nuclear genes and/or in the cytoplasmic genes

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