Normal Inbred Lines Research Articles

Nuclear gene induced plastid alterations in Pennisetum americanum

A nonlethal stripe mutant (700430) of Pennisetum americanum was crossed reciprocally with other normal inbred lines to establish its inheritance pattern. A recessive nuclear gene, when homozygous, led to defective plastid development with variable penetrance and expressivity. Intraplant and interspikelet crosses revealed maternal plastid transmission. When stripe plants were crossed with pollen from normal inbreds, green and yellow progeny were obtained; selfing stripe plants or crossing with its green sib produced yellow, stripe, and green progeny. These results suggest that in egg cells with exclusively defective plastids, the plastids do not revert back inspite of acquiring a dominant allele from the pollen parent, while in egg cells with a mixture of green and yellow plastids, the yellow plastids could develop into functional plastids under the influence of a dominant allele.Key words: altered plastids, variable penetrance, plastid transmission, plastid reversion.

Inheritance and transmission of plastid alterations in a green–white stripe mutant of pearl millet (Pennisetum americanum)

The breeding behaviour of the GWS-14 stripe mutant of pearl millet was tested in crosses with different normal inbred lines. The F2 segregations revealed two independently assorting recessive nuclear genes controlling the stripe phenotype with variable expressivity. Striping appeared 25 days after germination or later, suggesting the delayed expression of mutant genes. When stripe plants were crossed with pollen from normal inbreds, normal and white F1 progeny were obtained, while reciprocal crosses gave exclusively normal F1 progeny, suggesting that the white plastids are maternally transmitted in the absence of homozygous recessive nuclear genes in homoplastidic (altered plastids) egg cells. The absence of stripe progeny indicates the possible reversion of such plastids in heteroplastidic egg cells.

Mise en évidence d'une liaison génétique entre un gène de nanisme et des marqueurs enzymatiques chez le mil pénicillaire (Pennisetum glaucum L.)

The genetic linkage relations between the dwarfing (D2, d2) and seven enzymic marker genes were evaluated in three crosses between semidwarf and normal inbred lines of pearl millet (Pennisetum glaucum L.). The seven genes code for the following isoenzymes: alcohol dehydrogenase (Adh A), esterase (Est A), malate dehydrogenase (Mdh D) cathodic peroxydase (Pec A), phosphoglucoisomerase (Pgi A), phospholucomutase (Pgm A), and shikimate dehydrogenase (Skdh A). Semidwarf and normal plants were identified by a discriminant analysis based on 16 morphological height components. Mendelian segregations have been observed for all eight genes. Linkage was shown between Pgi A and Pgm A (4 ± 4 centimorgans (cM)), between Skdh A and Adh A (11 ± 7 cM), between D2 and Skdh A (9 ± 5 cM) and between D2 and Adh A (17 ± 8 cM). The latter three genes are linked in the following order: Adh A – 11 cM – Skdh A – 9 cM – D2. The linkage between the recessive dwarfing gene (d2) and the codominant Skdh A alleles will help in the creation of isogenic semidwarf lines of cultivars. It is highly probable that the D2d2 genotype could be separated from the D2D2 genotype.Key words: isozymes, linkage groups, early selection.

Comparative Resistance of Opaque‐2 and Normal Inbred Lines of Maize to Ear‐rotting Pathogens 1

Comparative Resistance of Opaque‐2 and Normal Inbred Lines of Maize to Ear‐rotting Pathogens ¹

Dynamics of seedling emergence of opaque-2 and analogous normal maize in cold tests and effect of fungicide seed treatment on their cold tolerance

SummarySix opaque·2 (O2) inbred lines and the single, three-way and double-cross hybrids derived from them were compared for emergence at low temperatures with their analogous normal inbred lines and hybrids. The results demonstrate that there is an increasing difference in emergence between the o2 and the normal forms with an increase in the period of incubation, the o2 types being inferior, in general, to the normal.A treatment of seeds with fungicides like Quinolate V4X, TMTD–Lindan and Vitavax 75W before sowing improved the cold tolerance of both the o2 and normal analogues, but the o2 forms remained far below the level of the normal.

Protein quality traits and their relationships with yield and yield components of opaque-2 and analogous normal maize hybrids and inbred lines

Diallel cross hybrids obtained by crossing six opaque-2 (o 2) converted inbred lines were compared with a similar series of crosses made between the analogous normal inbred lines together with the parents, for a number of protein quality and oil traits. The results obtained show that there is only a minor decrease in percent protein or yield of protein per hectare caused by the presence of the o 2 gene in recessive homozygous condition, compared with its normal counterpart. On the other hand, percent lysine in the whole kernel, lysine yield per hectare and percent lysine in protein are increased by 53, 45 and 55 percent, respectively, in the o 2 inbred lines and hybrids compared with their normal analogues. Percent oil and oil yield remain almost unaltered by the presence or absence of the o 2 gene. As well as lysine, the content of other amino acids, such as aspartic acid, arginine, glycine, threonine, valine and histidine are also, in general, increased by the presence of the o 2 gene in recessive homozygous condition.The results obtained have shown that a number of correlation coefficients between the protein quality traits and yield components related to kernel characteristics are negative and significant, especially in the presence of the o 2 gene in recessive homozygous condition. Only two correlation coefficients have been found that could be used with advantage by opaque-2 maize breeders. They are a stronger positive correlation of percent protein with percent lysine, and lysine yield per hectare with 1000 grain weight, in o 2 maize than in normal maize.The results presented here also show that there is more heterotic dilution in the o 2 hybrids than in the normal analogues for traits like percent protein, percent lysine (whole kernel basis) and percent lysine in protein. It has been observed that the inbred lines with the o 2 gene in recessive homozygous condition and a superior protein quality tend to produce hybrids of superior quality.

Some genetic and biochemical characteristics of a new source of maize opaque-2 mutant

The opaque kernels separated from the F1 of crosses of our opaque-2 strains with normal inbred lines contained 45, 50 and 74 percent more lysine in the whole kernel than the translucent kernels from the same ear. The opaque kernels from these crosses contained almost the same level of lysine as the parental opaque-2 strains.Some of our opaque-2 strains contain 63 to 122 percent more lysine than the tested dent or flint normal inbred lines. In comparison with opaque-2 Purdue, four opaque-2 strains had almost the same lysine content and a strain labelled as SP-1 No. 15 contained 25 percent more lysine and 73 percent more tryptophan. Some of our opaque-2 strains contained 55 to 100 percent more tryptophan in the whole kernel than opaque-2 Purdue.In contrast to lysine content, the transmission of the tryptophan content from opaque-2 strains to opaque kernels from their crosses shows variability.We found weak positive correlation (r = +0,3057) between lysine and tryptophan content in opaque-2 kernels.Our opaque-2 strains had a higher lysine content in the endosperm than did opaque-2 Purdue 22.1 - 36.6% more, and compared with normal lines they had 109.5 - 142.6% more.It is apparent that a new source of opaque-2 mutant gene, which has the same genetic and biochemical characteristics as the opaque-2 mutant discovered by Mertz, Bates and Nelson (1964), has been found in a completely new, genetically divergent, strain derived from a large number of populations.

Variations in Lignin and Other Structural Components of Brown Midrib Mutants of Maize1

Three brown midrib (mutant) genotypes of maize (Zea mays L.) in inbred Tr background, bm1, bm3, and bm1/bm3 were harvested at 10, 35, and 55 days post‐silking and compared to the normal inbred line, Tr. Plants were separated into leaf blade, leaf sheath, stem, and a composite of husk, kernel, cob, and tassel tissue. Structural and nonstructural constituents were determined for component parts, and a weighted mean was obtained for the whole plant. Acid detergent lignin (ADL) values of the whole plant for normal, bm1, bm3, and bm1/bm3 were 6.08, 5.13, 4.37, and 4.60%, respectively, for plants harvested 35 days post‐silking. The leaf blade, stem, and leaf sheath tissue of the three brown midrib genotypes contained lower ADL (P < .05) than the normal maize. Similar differences existed at 10 and 55 days post‐silking. The brown midrib genotypes, bm3 and bm1/bm3, were consistently lower in ADL than was bm1 over harvests and plant parts. Other structural and nonstructural constituents measured were variable. The normal counterpart had higher ADL/acid‐detergent fiber (ADF) and ADL/cellulose ratios than the three brown midrib genotypes for leaf blade, stem, and leaf sheath tissue.

The nucleolus organizer region of maize (Zea mays L.): Chromosomal site of DNA complementary to ribosomal RNA

A maize genetic marker strain (designated as the 2NOR strain) was found to carry a cytologically-visible “duplication” of the nucleolar organizer region (NOR). The 2 NOR condition is a simply inherited cytological marker which is transmitted normally through mega- and microsporogenesis and is associated when homozygous with a nucleolus approximately 64% greater in volume than that of two representative normal inbred lines of maize.—Utilizing DNA · rRNA hybridization techniques and the 2 NOR strain plus two unrelated inbred lines with normal NOR's, the chromosomal site of DNA complementary to rRNA was shown to be localized in the NOR. To our knowledge, this is the first report on the localization of rDNA cistrons in the NOR of plants. An estimate was made of 17,000 rDNA cistrons per diploid nucleus for normal maize.—The 2 NOR strain was shown to possess approximately twice as many rDNA cistrons (34,000) as normal maize. The usefulness of this 2 NOR condition for plant protein improvement programs is being investigated.