Peroxidase activities in relation to plant height and grain weight in bread wheat (Triticum aestivum L.)

Summary The relationship of peroxidase activity with plant height and grain weight has been studied in seven different varieties of bread wheat belonging to diverse genotypes, and their F₁ crosses. The association between plant height and peroxidase activity was highly significant and negative. Based on the similarity index values of peroxidase isoenzymes, the seven wheat genotypes could be classified into two groups: the first group consisting of triple and quadruple dwarf varieties and the other of tall, single and double dwarf. A negative correlation between peroxidase activity and grain weight was also observed. However, the results of this study indicate a possibility of developing a dwarf plant type with low peroxidase activity and well filled grains.     

Isozymic classification of pearl millet (Pennisetum glaucum,Poaceae) landraces from Niger (West Africa)

The principal landraces of the pearl millet,Pennisetum glaucum (L.)R. Br., from Niger have been analysed for their genetic structure at eight enzyme systems coded by 12 loci and 46 alleles. Three groups have been identified: (1) early-maturing pearl millets, cultivated between 8° and 13°E longitude, including the oases from Aïr mountains; (2) early-maturing millets situated more to the west (1° and 8°E longitude), and (3) late-maturing millets. Group 1 shows the highest isozyme diversity. The differences between the accessions represent 8.8% of the total diversity and the differences between the three groups 4.5%. The accessions from groups 1 and 3 are the least distant. When considering pearl millets from areas outside Niger, the chadian and sudanese millets are enzymatically close to the Niger group 1. The pearl millets from Niger group 2 are close to millets from east Mali, northern Burkina Faso and Senegal, and the Niger group 3 to the late-maturing millets group from West Africa. This study should help breeders to select the landraces for improvement and parents for crosses from cultivars of Niger and introduced germ plasm.     

Variability and covariability for plant height,heading date,and seed weight in wheat crosses

Summary Variability, covariability, heritability, and expected genetic gains from selection for heading date, plant height, and kernel weight were estimated in progenies derived from six wheat crosses. The crosses differed in the magnitude of the genetic variabilities of their progenies, but all crosses had significant variabilities for all traits. Heritability estimates were calculated by the variance components method. The estimates of heritability were relatively high for all three traits and averaged 86% for heading date, 77% for plant height, and 70% for kernel weight. The presence of significant genetic variabilities and high heritability estimates indicated that selection would be effective for the three traits.The segregates derived from crosses between medium tall parents showed transgressive segregation that would permit isolation of short-statured types. Transgressive segregation also occurred for heading date and kernel weight.Heading date and plant height were positively and highly significantly correlated in four crosses out of six. But both plant height and heading date had, in general, low negative correlations with kernel weight which would not preclude the development of short wheats with high kernel weight from these crosses. The association between characters was mostly genetic in cause.     

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

Summary 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 (31) 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 934 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).Submitted as J.A. No. 429 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Inheritance of a dwarf seed stalk character in onion

Results are reported of crossing a dwarf seed stalk line (mean height 44.8 cm) from Israel with five inbred lines of the Rijnsburger type each having normal tall seed stalks (mean heights 83.1–105.9 cm). The seed stalk height of F₁ generations from these crosses was slightly greater than that of the Rijnsburger parents but segregation occurred in the F₂ giving plants which could be considered ‘dwarf’ and ‘normal’ with respect to seed stalk height. Selfing individual F₂‘dwarf’ plants produced F₃ progenies whose mean heights were in the dwarf range, and were significantly correlated with those of their F₂ parent. The results obtained in the F₂ and F₃ families suggest that although a major recessive gene for dwarfness may be present, substantial minor gene and environmental variation is also involved.     

Genetic variability among sorghum accessions from the Sahelian agroecological region of Burkina Faso

The authors collected Sahelian sorghum landraces of Burkina Faso in 1984 and 74 of these accessions were characterized in 1985–1986 at Gampela in Burkina Faso (West Africa). The five races of cultivated sorghum were represented in this zone but 63.5% of the accessions were Guinea type. Great intra-and inter-accession variability was found. Plants were tall and had long panicles and small to intermediate seeds. There was a strong association between days-to-flowering, number of internodes, panicle length and height. The 100-kernel weight showed an antagonism with days to flowering and tillering. Multivariate analyses were made which enabled the accessions to be classified into four groups. The group most adapted to the sahelian zone, sahelian group, was semi-late, developed intermediate size of vegetative organs, had moderate tillering and had the best yield per plant.     

Inheritance of grain filling duration in spring wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L. em thell)

To understand the genetic control of grain filling duration (GFD), i.e., the number of days from anthesis to physiological maturity, we studied the F₁, F₂, BC1 and BC₂ generations of six spring wheat crosses from nine varieties/genotypes. Generation mean analysis for gene effects indicated that one or more types of epistasis were significant in all crosses. In each pairing, the F₁ and F₂ means were either intermediate or closer to the mean of the parent having the longer GFD. Our narrow-sense heritability estimate was reasonably high, at 47.67 (based on diallel analysis). This demonstrated that progress could be made from the selection in these crosses for either long or short GFD. The two early varieties that had identical maturity durations differed in their GFD values, indicating that maturity dates are not good criteria when choosing parents for modifying GFD. To utilize favorable additive × additive effects during this selection, we suggest that a single seed descent (SSD) or bulk popula-tion approach be adopted. In comparison, dominance effects would prove quite useful in hybrid wheat breeding programs.     

Cross prediction studies on spring barley

Summary The genetical and environmental control of three height characters, two maturity characters and neck length in five barley pair crosses was studied using both F₂ triple test cross and model fitting analysis.Significant additive and dominance effects were found for all six characters with some evidence of epistasis for each character. Generally, dominance was incomplete for the height characters but was significantly directional for increased height in those crosses where dwarfing genes were segregating. Variable dominance effects were found for both the maturity characters. Complete dominance was found in three cases, otherwise incomplete dominance was found. Significant directional dominance for earliness was found for both maturity characters in one cross but this was attributed to the presence of a daylength insensitivity factor in one of the parents. Most of the genetic variation for neck length was additive, though some evidence of dominance was found.Broad sense and narrow sense heritability estimates generally were found to be high for the height and maturity characters but low for neck length. It was concluded that early generation selection for height at ear emergence, for final height and for awn emergence was worthwhile. Early generation selection for neck length was not recommended from the results of this study.     

Genes for dwarfing and photoperiod flowering response inPharbitis nil choisy

Dwarfing and sensitivity to the duration of a single inductive dark period for flowering ofPharbitis nil in F₂ progeny of a cross between the tall strain Tendan, and the dwarf, Kidachi appear to be controlled by the alleles at two independent loci. Progeny of a similar cross between the tall strain Violet and the dwarf Kidachi at F₂ and F₃ also showed single locus segregation for tall: dwarf plants. In this cross, differences in photoperiodic response could be identified in F₃ families but they were not simply inherited. There was some evidence of difficulties with classification of the F₂ plants, but also, the flowering of the F₁ between the two less sensitive strains Tendan and Violet indicated complex inheritance of their photoperiodic response. Complementary dominant alleles at three independent loci may be necessary for flowering in even shorter dark periods with the sensitive strain Kidachi. The dwarf strain Kidachi has a reduced gibberellin (GA) content (Barendse and Lang 1972), it flowers in a short dark period without terminal flowering, and it responds positively to GA application both for flowering and growth. However, since control of dwarfing and photoperiodic sensitivity can be separated genetically, there is no strick link between the gibberellin responsiveness of Kidachi for its growth and flowering. Despite the complexity of flowering genetics in Violet×Kidachi, a short-dark-period-sensitive, terminal flowering and tall F₇ line was obtained in a pedigree previously held heterozygous for the dwarf: tall character but not selected for flowering time. Thus, flowering in a short dark period can also be obtained in the presence of the non-dwarfing allele from strain Violet, again demonstrating genetic independence.     

Mode of inheritance of dwarf stature and allelic relationships among various spontaneous and induced dwarfs of cultivated rice Oryza sativa L.

Summary Genetic study of spontaneous and induced dwarfs included the mode of inheritance of dwarf stature and the allelic relationships among various dwarfs. Qualitative genetic analysis involving crosses of fourteen dwarfs with a common tall variety IARI 11124 showed that the degree of dominance in the F₁ hybrids varied with the cross. With the exception of the crosses of IARI 6579 and IARI 10560 with the tall variety, all crosses exhibited incomplete dominance. The segregation pattern in F₂ populations of height classes showed dwarfness to be a monogenic recessive trait functioning, however, in association with modifier complexes of varied strength. From F₂ behaviour of all possible crosses involving the fourteen different dwarfs, the allelic relationships were deduced. Three major groups of dwarfs could be recognised. Group I, comprised of FF 36, IARI 5842, IARI 5906-2B, IARI 5923, IARI 10061, IARI 10560 and IARI 11445, was allelic to I-geo-tse and Dee-Gee-Woo-Gen with modifiers of predominantly negative effects, while group-2, comprised of dwarfs IARI 5901-2, IARI 5924, IARI 6579 and IARI 7312B, was also allelic to Dee-Gee-Woo-Gen and I-geo-tse but with large and equal number of modifiers of positive and negative effects. The induced mutant, Central Africa Mutant (CAM) which constituted the third group seemed to possess a dwarfing gene that was non-allelic to those of the above mentioned two groups of dwarfs, with equal strength of modifiers of plus and minus effects. Unlike the dwarfs of spontaneous origin, which are invariably allelic to Dee-Gee-Woo-Gen, the induced dwarf was nonallelic. Thus, induced mutagenesis appears to give rise to dwarfing genes different from those found in the naturally occurring dwarfs.     

Contributions to Grain Yield from Pre-anthesis Assimilation in Tall and Dwarf Barley Phenotypes in Two Contrasting Seasons

Twenty-four barley genotypes were produced from crosses betweentwo sets of parents each having a different, non-allelic dwarfinggene. Four genotypes were phenotypically tall, twelve were singledwarf and eight were double dwarf. By a combination of carbon-14labelling and growth measurement the contribution to grain drymatter from assimilation before anthesis was estimated for eachgenotype in two years, 1976 and 1977. Pre-anthesis assimilation was estimated to have contributed44 per cent of grain dry matter in 1976, a very dry, hot year,but only 11 per cent in 1977, a wetter, cooler year. These percentageswere equivalent to about 133 and 74 g m^–2 in 1976 and1977. It is shown that some previous estimates of the contributionfrom pre-anthesis assimilation are too low for crops of barleygrown in the field in dry years, while in wet years, the contributionis unlikely to be less than 10 per cent. In neither year did the genotypes differ in the extent to whichpre-anthesis assimilation contributed to grain filling. In bothyears, grain yields of the tall genotypes were 8–9 percent greater than those of the double dwarf ones, and stem weightsat maturity 30 per cent greater. Hordeum vulgare L., barley, grain yield, carbon assimilation     

A single treatment of rice seedlings with 5-azacytidine induces heritable dwarfism and undermethylation of genomic DNA

Summary A single exposure of germinated rice seeds (Oryza sativa) to either of the DNA demethylating agents 5-azacytidine (azaC) or 5-azadeoxycytidine (azadC) induced dwarf plants. At maturity, seeds treated with azaC exhibited normal morphological characteristics in comparison with untreated controls except that their height (total stem length) was reduced by about 15%. The M₁ progeny, obtained by self-fertilization of an azaC-induced dwarf plant, segregated into dwarf (35%) and apparently tall types (65%). The M₂ progenies, obtained by self-fertilization of dwarf M₁ plants, were also dwarf, while those from tall M₁ plants were only tall. Genomic DNA isolated from mature leaves of azaC-treated seeds showed about a 16% reduction in the 5-methylcytosine (m⁵C) content in comparison with DNA from untreated samples. A similar reduction in the m⁵C content was also observed in the M₁ and M₂ progenies. Thus, both undermethylation and dwarfism induced by azaC treatment were heritable. The results suggest that azaC induced demethylation of genomic DNA, which caused an altered pattern of gene expression and consequently a reduction in plant stem length.     

Genetics of grain amaranths

Summary Two landrace populations of Amaranthus cruentus L. were crossed to generate F₂ populations for quantitative genetic analyses of variation. Evidence for significant inbreeding depression in comparisons of F₁ and F₂generation means suggested some role of nonadditive gene action for days to first anthesis, leaf length, leaf width, petiole length, plant height, panicle length, and panicle weight. A pooled F₂ population was subjected to bidirectional mass selection for time of first anthesis (two cycles) and leaf length (one cycle). Responses to selection were asymmetrical and the second cycle response for anthesis time was smaller than for the first cycle. Overall, selection gains were significant and gave estimates of heritability in the range of 0.35 to 0.66 for anthesis time and 0.08 to 0.19 for leaf length. This suggested a large additive term in the total genetic variance especially for anthesis time where early and late flowering selection lines diverged by 20.5 days.Correlations between the selected traits (anthesis time, leaf length) and single plant yield or yield components were also studied to evaluate correlated responses to selection. Selection for optimal flowering time in amaranth cultivation areas is very likely to result in rapid yield improvement.     

The Heritability of Abscisic Acid Accumulation in Water-stressed Leaves of Pearl Millet [Pennisetum americanum (L.) Leeke]

Using detached leaves, two cultivars of pearl millet [Pennisetumamericanum (L.) Leeke], B282 and Serere 39, were assessed forvariation in the capacity to accumulate ABA in response to waterstress. Significant differences in ABA accumulation were detectedbetween cultivars and between different inbred lines withina cultivar, but within lines there was much less variation inthis character. In crosses between individual lines of B282(low ABA) and Serere 39 (high ABA), ABA accumulation in theF₁ was mid-way between parental values, indicating additivegenetic control and lack of dominance. Selfed progeny of a B282 x Serere 39 cross were selected forcontrasting ABA accumulation in the F₂ to F₄ generations. Asixfold range in ABA accumulation was found amongst 207 F₂ progeny.This increased to nearly ninefold at F₃ and F₄. Regression analysisindicated high heritability of ABA accumulation and rapid approachto homozygosity. As the cross studied involved a dwarf (B282) and a tall (Serere39) parent, segregation occurred for height as well as for ABA,though not entirely independently. Tall F₃ progeny had significantlyhigher ABA contents than dwarf progeny and high ABA was thereforeassociated with other traits (e.g. large leaves, high leaf percent d. wt) characteristic of tall plants. Nevertheless, therewas a substantial range of ABA content within both groups whichwas uncorrelated with height and other characters. The potential use of the selections in studies on drought responseis briefly discussed. Pennisetum americanum (L.), Leeke, pearl millet, abscisic acid accumulation, water stress, genetic differences, inheritance     

Dwarfism and male sterility in interspecific hybrids of Epilobium

Summary Reciprocal differences for male sterility, dwarfism and morphological traits have been studied in intra- and interspecific crosses of five Epilobium species. Male sterility occurred in two interspecific hybrids with E. montanum as the male parent while dwarfism has been found to varying degrees in three interspecific crosses with E. watsonni. In contrast to transient differences in plant height and leaf morphology in reciprocal hybrids of the cross between E. hirsutum and E. parviflorum, male sterility and dwarfism persistently occur as reciprocally different traits which may be influenced by determinants of the cytoplasm. The molecular characterization of the plastid DNA of the parental lines and the F₁ hybrids indicate that the plastome of male sterile and dwarf plants is identical to that of the female parents. Furthermore, in spite of these developmental disturbances, the expression of plastid genes coding for polypeptides of thylakoid-membrane complexes is unchanged. Thus, it seems unlikely that the genetic compartement of the plastids is responsible for the expression of the male sterile or the dwarfed phenotype.     

Exogenous GA3 Application Can Compensate the Morphogenetic Effects of the GA-Responsive Dwarfing Gene Rht12 in Bread Wheat

The most common dwarfing genes in wheat, Rht-B1b and Rht-D1b, classified as gibberellin-insensitive (GAI) dwarfing genes due to their reduced response to exogenous GA, have been verified as encoding negative regulators of gibberellin signaling. In contrast, the response of gibberellin-responsive (GAR) dwarfing genes, such as Rht12, to exogenous GA is still unclear and the role of them, if any, in GA biosynthesis or signaling is unknown. The responses of Rht12 to exogenous GA₃ were investigated on seedling vigour, spike phenological development, plant height and other agronomic traits, using F_2∶3 and F_3∶4 lines derived from a cross between Ningchun45 and Karcagi-12 in three experiments. The application of exogenous GA₃ significantly increased coleoptile length and seedling leaf 1 length and area. While there was no significant difference between the dwarf and the tall lines at the seedling stage in the responsiveness to GA₃, plant height was significantly increased, by 41 cm (53%) averaged across the three experiments, in the GA₃-treated Rht12 dwarf lines. Plant height of the tall lines was not affected significantly by GA₃ treatment (<10 cm increased). Plant biomass and seed size of the GA₃-treated dwarf lines was significantly increased compared with untreated dwarf plants while there was no such difference in the tall lines. GA₃-treated Rht12 dwarf plants with the dominant Vrn-B1 developed faster than untreated plants and reached double ridge stage 57 days, 11 days and 50 days earlier and finally flowered earlier by almost 7 days while the GA₃-treated tall lines flowering only 1–2 days earlier than the untreated tall lines. Thus, it is clear that exogenous GA₃ can break the masking effect of Rht12 on Vrn-B1 and also restore other characters of Rht12 to normal. It suggested that Rht12 mutants may be deficient in GA biosynthesis rather than in GA signal transduction like the GA-insensitive dwarfs.     

Regulation of internodal lenght by peroxidase enzymes in grain sorghum

Summary A relationship between height genes (dw locus) and perioxidase was demonstrated by extracting and determining peroxidase specific activity in internode tissue from different height isogenic lines of sorghum Sorghum bicolor (L.) Moench]. Tall plants (2 dwarf) had less peroxidase per gram tissue than their short counterparts (3 dwarf); their F₁ offspring internodes were closer but had more peroxidase than the tall parent. Peroxidase in the F₂ offspring was inversely related to their height and followed a simply-inherited pattern similar to that for height.Among different tissues analyzed, peroxidase concentration in roots was higher than in leaves and internodes, whole internode higher than in pith, and seed embryo higher than in endosperm. Peroxidase activity of nonviable seeds was negligible.Isoelectric focusing provided a more detailed peroxidase zymogram than did gel electrophoresis. Differences in peroxidase bands among tall and short parental plants, F₁ and F₂ segregating groups all appear to be reflected by intensity differences rather than by position or number of bands.Activities of nitrate reductase and acid phosphatase did not correlate with height. That finding provides a control and suggests that peroxidase activity is not associated with height by chance but may have a functional relationship.Contribution no. 1628-j, Dept. of Agronomy and no. 188-j, Dept. of Biochemistry, and no. 962-j, Dept. of Grain Science and Industry, Kansas State University, Kansas Agricultural Experiment Station, Manhattan, Kansas 66506.     

Genetic parameters estimation for some wild wheat species and their F1 hybrids grown in different regions of Saudi Arabia

Wheat (Triticum aestivum L.) is the most important crop for human nutrition that underpins the food safety of Saudi Arabia. The investigation here was to determine heterosis effects using different genetic methods: heterosis over better, mid parents, the genetic advance, and genotype, phenotypic coefficient of variation for estimation some traits among six wheat landraces and their F₁ hybrids. In 2019, these landraces were sown using hand and after 100 days, the emasculation and crossing were made among these six landraces using hand emasculation of anthers. In 2020, seeds for these genotypes (six wheat landraces and their F₁) were sown under normal irrigation accordingly done in 2019. The results showed that the most important parent was Mabia resulted with the highest value in number of tiller/ plant, 1,000-grain weight, and fresh shoot weight. The highest value of plant height among six parents was Naqra while highest value at the same trait among F₁ hybrids was P₃ XP₆. The estimations of heterosis showed that out of 15 crosses, one cross (P₁XP₅) was significantly better yield than all crosses for these four traits. The genotype coefficient of variation (GCV) ranged from 12.5% to 8.7% while phenotypic coefficient of variation ranged from 17.7% to 11.3%. The correlation coefficients was found between fresh shoot weight and number of tiller and plant height and umber of tiller. Wild wheat still serve as a source of useful germplasm with proven adaption and productivity and thus assembles of the wild wheat assortments are the initial step of breeding program.     

A study of genetic diversity among host-specific populations of the witchweedStriga hermonthica (Scrophulariaceae) in Africa

Striga hermonthica is a root hemiparasite that attacks onlyGramineae, includingSorghum and millet for which it is a principal cause of lowered yield. Enzyme electrophoresis was used to investigate genetic diversity inStriga hermonthica and to determine the level of differentiation between host-specialized populations. Nine genetic loci coding eight enzymes were interpreted and data obtained from three populations: oneSorghum-adapted population from Sudan and two populations from Burkina Faso, oneSorghum-adapted and the other millet-adapted. Levels of polymorphism were similarly high in all three populations (P=0.625, A=2.6–2.8, H=0.293–0.401). Genotypic frequencies at most loci conformed to Hardy-Weinberg expectations in each population, consistent with outcrossing as predicted from previous studies of floral biology. Occasional heterozygote deficiencies were probably the result of Wahlund effect. The mean value of F_ST over the three populations was 0.068, indicating a slight to moderate level of genetic differentiation among the populations. The two Burkina Faso populations were more closely related (S=0.940, D=0.006) than either was to the Sudan population, suggesting that geographic separation is more important than host specialization in contributing to population differentiation. TheSorghum-adapted population was slightly closer to the Burkina FasoSorghum-adapted population (S=0.873, D=0.047) than to Burkina Faso millet-adapted population (S=0.851, D=0.074). The absence of substantial genetic divergence between host-specific populations ofStriga could result either from recent evolution of host-specialized strains or from strong selection for physiological specialization in the face of substantial gene flow between the populations.     

Inheritance of partial resistance to the leaf aphids Macrosiphum euphorbiae and Uroleucon sonchi in lettuce

The genetics of partial resistance (PR) of lettuce to the leaf aphid species Macrosiphum euphorbiae and Uroleucon sonchi was studied in F₁ and F₂ generations of six crosses between four cultivars. Partial resistance inherited mainly additively. With M. euphorbiae the estimates of broad-sense F₂ heritability were low and non-significant in crosses between parents of the same resistance level (S x S and PR x PR), and high (0.69-0.76) in crosses between parents of different resistance level (PR x S). The level of resistance in lettuce cultivars ‘Charan’ and ‘Marbello’ led to a marked reduction in percentage of plants with colonies of M. euphorbiae in a field experiment. With U. sonchi the highest estimates of F₂ heritability were found in ‘Charan x ‘Avoncrisp’ (0.51) and ‘Charan’ x ‘Chou de Naples' (0.48). In the cross ‘Charan’ x ‘Marbello’ (PR x PR) no significant segregation for resistance to M. euphorbiae was found, indicating that these cultivars may have the same genetic constitution for resistance to M. euphorbiae.‘Charan’ has additional genes for resistance to U. sonchi, that are not, or only weakly linked to the gene(s) for resistance to M. euphorbiae. The heritability estimates for the partial resistance to M. euphorbiae and U. sonchi indicate that it is possible to effectively select for these traits in plant breeding programmes.