S. R. Sree Rangasamy

Triple test cross analysis in rice

SummaryThe triple test cross analysis in rice brought out that significant epistasis is present for most of the characters in the three crosses except for 100 grain weight in two crosses (Co 39 × Co 41) and (Co 39 × Co 40) and plant height in one cross (Co 39 × IR 20). Epistasis of ‘i’ (homozygote × heterozygote) and ‘l’ (heterozygote × heterozygote) interactions are also detected in all the three crosses. The D component was significant for all the traits in the three crosses and H was significant in cross Co 39 × Co 41 for all characters. For tiller number in cross Co 39 × IR 20 and for tiller number and 100 grain weight in cross Co 39 × Co 40, the H component was not significant. In all the crosses D component was higher than H.

Plant regeneration from sorghum anther cultures and field evaluation of progeny

SummaryEmbryogenic calli were obtained from a hybrid line of Sorghum bicolor (L.) Moench anthers with mid to late uninucleate pollen cultured in N6 medium supplemented with 3.0% sucrose, 2.0 mg/1 2,4-D, 0.8% agar and incubated at 30°C, which was the optimum temperature. The regeneration of embryos was obtained from the embryogenic calli cultured in modified MS medium supplemented with 3.0% sucrose, 2.0 mg/1 BAP combined with 0.3 mg/1 IAA and 0.8% agar. A total of 248 doubled haploids and 12 haploid plants were regenerated. In a subsequent field study, the selfed progeny from anther culture (designated as the anther culture-2, [A2] generation) derived families was compared with both the F2 and the F1 for agronomic and morphological traits. Significant differences were noticed between the family means of both A2 and F2 for all the quantitative traits studied. The distinctive difference in the behavior of the A2 families in comparison with the F2 was established by within family variance, which was significant in F2 for days to 50 per cent flowering, plant height, panicle length, leaf area index, dry matter production, harvest index and grain yield and was non-significant in A2. Male sterility, one of the potentially important traits, currently exploited in the hybrid seed production of cereals, including CSH5 hybrid sorghum and the morphological traits (panicle shape, compactness, grain color, glume color and nature of the leaf sheath) segregated in the F2. Such segregation was not observed within A2 families and they bred true to their respective A1 plants, indicating the rapid attainment of homozygosity/uniformity. The present study establishes the gametophytic origin of anther culture derived families and indicates the possibility of rapid production of homozygous lines which can be used as recombinant inbreds.

Inheritance of the fuzzless-lintless character in cotton (Gossypium hirsutum)

SummaryA fuzzless-lintless mutant was identified in MCU.5 (Gossypium hirsutum) cotton in 1984. The inheritance of this character is reported in this paper. The fuzzless-lintless mutant was crossed with fuzzy-linted parents viz. MCU.5, MCU.7, Express Sindh (W), Piedmont Cleveland and Sindis Wild and the segregation pattern was studied in F2 and BC1F1 generations. The segregation ratios for fuzzy-linted and fuzzless-lintless were 15∶1 in the first cross, 63∶1 in the second, third and fourth crosses and 255∶1 in the fifth cross. These ratios indicated that this character is controlled by 2–4 gene pairs, and the fuzzless-lintless character is a recessive to fuzzy-linted character. The chi-square test was significant only in the BC1F1 generation with MCU.7 and Express Sindh (W). The test revealed that the observed values deviated significantly from the expected ratio of 7∶1, suggesting that this character is also influenced by modifier gene complex.

Diversity in sugarcane species and hybrids for peroxidase isozyme

Peroxidase isozyme was surveyed in 28 clones belonging to five species ofSaccharum L.and inter specific hybrid. Presence of more number of isozymes inSacharum reflected genetic complexity of this polyploid genus.Saccharum species could be identified from one another by the presence/ absence of specific isozymes. S.officinarum andS. robustum showed lesser genetic diversity.S. sinense was the most complex species with more number of isozymes and could be distinguished from its close relativeS. barberi. S. officinarum clones link Manjri Red, Baragua, Gungera and 57NG77 had isozymes characteristic of other species, as also reflected in the dendrogram, indicating introgression of genes from other sources in their origin. 2n = 64 cytotypes ofS. spontaneum were more similar, but were divergent from the rest including the other cytotypes of the species. F1 hybridity were intermediate between the parents, proving their hybridity. Commercial hybrids showed less diversity with species accessions in support to their interspecific origin. Peroxidase diversity among commercial hybrids quantified in terms of similarity indices may be useful in identifying diverse cross combinations for deriving heterotic hybrids in sugarcane breeding programmes.

Comparison of fertility between the F1, F2 and anther derived lines in the crosses of indica/japonica and japonica/indica in rice (Oryza sativa L.)

SummaryResponse of anthers in in vitro culture was examined in the indica-japonica hybrids of rice (Oryza sativa L.). Significant genotypic differences were observed for callus induction and regeneration among the different interracial hybrids of indica-japonica races. Induction frequency of haploids ranged from 57.7 to 72.9 per cent and doubled haploid androgenic lines ranged from 27.1 to 42.3 per cent in the anther culture of the different hybrids. The indica-japonica hybrids recorded partial pollen grain and spikelet fertility in F1 (29.9 to 41.5% and 19.4 to 48.7% respectively) as well as in F2 (42.7 to 50.6% and 37.1 to 54.4% respectively). In contrast, the androgenic doubled haploid lines recorded significant increase and the pollen grain and spikelet fertility was 76.3 and 78.6 per cent respecitively. The results suggested that the sterility barriers for realising genetic recombinants and fixation of fertile homozygous lines in indica-japonica hybridization programme could be overcome through F1 anther culture technique.

An estimation of the number of initials in grain Sorghum using mutagenic treatments

An investigation was carried out to estimate the number of cell initials in the mature embryo of dormant seeds of cultivated grain Sorghum with mutagenic treatments. Dry seeds of S. subglabrascens (Co. 18) were treated with a wide range of physical and chemical mutagens, X-rays, gamma rays, EMS, MMS, DES, NMU, NEU and MNG and also with combination treatments of gamma rays and EMS, MMS and DES. A total of 317 segregating M1 panicle progenies was studied in the M2 generation for the ratio of normal to chlorophyll mutant seedlings. The mutant phenotypes are albina, xantha, viridis, chlorina, striata, tigrina, xanthalba and alboviridis. A total of 161 M1 plant progenies showed a good fit, while the rest of the progenies (156) deviated significantly in both directions from file expected segregation of 3:1. This was interpreted as being due to the origin of M1 plants from both single cell initials and from multicellular initials following mutagenic treatments, the former segregating for 3:1, while the latter significantly deviating from 3:1. The data on the different mutant phenotypes also revealed the existence of single and multicellular initials in the matured embryo of grain Sorghum. The excess of deficiencies noticed in the mutant phenotypes in the segregating M1 panicle progenies might be due to a large extent to the chimeric nature of multicellular initials and to a less extent also due to factors operating on gametes and zygotes following mutagenic treatments. An assessment of M1 fertility as related to the distribution of chi square deviations on 3:1 ratio indicated that the M1 plants with low fertility are frequently derived from single cell initials and the M1 plants with high fertility may commonly arise from multicellular initials.

Effect of X-irradiation on the size of the mutated sector in diploid and tetraploid rice

An investigation was carried out of the effect of X-irradiation on the size of the mutated sector in three diploids (A.S.D.8, T.N. 1 and G.E.B. 24) and the autotetraploid of G.E.B 24 of Oryza sativa L., by analyzing the M2 segregation ratios of chlorophyll mutants. A total of 612 segregating M1 panicle progenies in the diploids and 284 panicle progenies in the tetraploid was studied in the M2 generation for the ratio of normal to chlorophyll mutant seedlings. Of the 573 segregating M1 panicles analysed by chi square test in the diploids, 206 showed good fit with a 3∶1 ratio, while the rest of the progenies (367) deviated significantly in both directions from the expected 3∶1 segregation. This was interpreted as the result of M1 panicles developing from both single cell and multicellular initials following X-irradiation, the former segregating for 3∶1, the latter significantly deviating from 3∶1. An assessment of fertility (as judged from the number of M2 seedlings per mutated M1 panicle), related to the distribution of chi square deviations from the 3∶1 ratio in the diploids, indicated that the M1 panicle progenies deriving from single cell initials had low fertility but those originating from multicellular initials ranged from low to high fertility. A comparison of the distribution pattern of the M2 segregation ratios of chlorophyll mutant phenotypes in the diploid and autotetraploid G.E.B. 24 indicated that, in the tetraploid, a larger sector and only one, or fewer cell initials than in the diploid species, are involved.

Embryology ofOryza sativa Linn.—Diploid and autotetraploid forms

The embryo sac development in cultivated species of rice and its autotetraploid forms has been investigated in detail. The investigation brought out, the causes for the low seed set in the autotetraploid forms as owing to the defects in the development of embryo sac in the differentiation and development of zygotes. Frequently post-fertilisation defects have also been met with. Despite the course of embryogenesis being similar in the diploid and autotetraploid forms, the differences in seed fertility in autotetraploids are considered te be due largely to gametic sterility and also due to the zygotic inviability, abortion and degeneration.The embryo sac development in cultivated species of rice and its autotetraploid forms has been investigated in detail. The investigation brought out, the causes for the low seed set in the autotetraploid forms as owing to the defects in the development of embryo sac in the differentiation and development of zygotes. Frequently post-fertilisation defects have also been met with. Despite the course of embryogenesis being similar in the diploid and autotetraploid forms, the differences in seed fertility in autotetraploids are considered te be due largely to gametic sterility and also due to the zygotic inviability, abortion and degeneration.

A comparison of mutation induction in diploid and tetraploid rice

SummaryA comparative assessment of the frequency and spectrum of chlorophyll mutations in the M2 and M3 of three diploids and one tetraploid of rice after X-irradiation was made. As well as a linear relationship of the frequency of mutations with the dose of mutagen, a saturation effect was also evident. Among the three diploids, the maximum frequency of mutations was observed in T. N. 1, followed by G. E. B. 24 and A. S. D. 8. The diploid of G. E. B. 24 showed a higher frequency of mutations than the tetraploid when measured on the M1 plant basis only. The diploids showed a higher rate of mutations in the M2 than in the M3.There was no relationship between the frequency of different types of chlorophyll mutations and the dose of X-rays. Albina, occurred in greater proportion than the other types of mutations in the diploids as well as in the tetraploid. The diploid showed a wider spectrum in the M2, whereas the tetraploid recorded the maximum types of mutations in the M3. Striking differences in the spectrum and the relative frequency of each type were observed among the three diploids and also between the diploid G. E. B. 24 and its tetraploid.The frequency and spectrum of induced mutations in the diploid and autotetraploid provided an insight into the genetic behaviour of the diploid and autotetraploid of G. E. B. 24, indicating that the genetics of diploidisation of the existing diploid rice may give evidence on the nature of the evolutionary pathway.