Semi-dwarf Cultivars Research Articles

Parent‐Progeny Regression Estimates and Associations of Height Level with Aluminum Toxicity and Grain Yield in Wheat1

Concerns regarding possible associations between plant height and A1 tolerance in wheat (Triticum aestivum L. em Thell) led to this investigation. Standard height, low grain yield potential, A1 tolerant cultivars ‘BH 1146’ and ‘Atlas 66’ and semidwarf, high grain yield potential, A1 sensitive cultivars ‘Tordo’ and ‘Siete Cerros’ were crossed in a diallel fashion. Parents, F1's, F2's and reciprocal backcrosses were tested for their seedling reaction to 6 ppm of A1. Plant height and grain yield were determined for the same populations at maturity.Parent‐progeny regression estimates for A1 tolerance and plant height were high (b = 0.903) but intermediate (b = 0.507) for grain yield. Genotypic, phenotypic and environmental correlations, between A1 tolerance with plant height and grain yield, respectively, were not significant. Grain yield and plant height correlations ranged from 0.274 to 0.813 and were significant (P = 0.01).Results suggest it would be possible to select plant types which combine A1 tolerance and semidwarf height levels; however, large F2 populations will be required. Tordo appears to be the most promising dwarfing source for the development of semidwarf cultivars adapted to soils with high A1, but poor seed quality could be a limiting factor using this source of germplasm.

Diffusion and Adoption of Semidwarf Rice Cultivars as Parents in Asian Rice Breeding Programs1

The first widely grown semidwarf cultivars of rice (Oryza sativa L.) were ‘Taichung Native 1’ (TN1), released in 1956, and ‘IR8’, in 1967. To determine the impact of new semidwarf cultivars on the genetic diversity of the world's rice crop, the International Rice Research Institute (IRRI) traced the diffusion and adoption of improved rice cultivars as parents among national breeding programs at 14 agricultural research centers in seven Asian nations from 1965 to 1975.Sixty‐one percent of the 1965–67 crosses and 84% of the 1974–75 crosses involved at least one semidwarf parent. Crosses that involved a tall cultivar decreased. In 1965–67, 28% of the total gene pool was semidwarf and 40% tall. Ten years later, the percentage of semidwarfs almost doubled and that of talls dropped sharply. Apparently, breeders were increasingly crossing semidwarf parents to other semidwarfs.TN1 and IR8 were the most popular gene sources in 1965–67; each was used in about 20% of the crosses. Use of TN1 and IR8 dropped to only 1 to 3% by 1974–75, while use of other IRRI semidwarfs increased significantly. But the strongest trend was the growing use of locally developed semidwarfs — from 2% of the 1965–67 crosses to 49% in 1974–75. The genetic makeup of those local semidwarf parents was traced back two generations; 76% were progeny of IR8 or other IRRI rices.Breeders in India adopted TN1 and IR8 earlier, and more extensively, than breeders in the six other countries. By 1974–75, 75% of Indian crosses involved a local semidwarf. In the six other countries, IRRI remained the major source of semidwarf breeding material but breeders increasingly used local semidwarfs. The semidwarf indica rices largely replaced japonica, ponlai, and other races in the breeding programs.

Growth and yield of a semi-dwarf and a standard height wheat cultivar in the Murrumbidgee Irrigation Area

A semi-dwarf cultivar (WW 15) and a standard height Australian wheat variety (Timgalen) were grown at two nitrogen levels and under three irrigation regimes in the Murrumbidgee Irrigation Area. Numerous plant measurements were taken to determine which attributes were associated with the superior yield of semi-dwarf wheat in this environment. WW 15 yielded 42% more grain than Timgalen and nitrogen fertilizer increased the yield of both varieties. The irrigation treatments did not affect yield because rainfall was above average. Total dry matter production and leaf area of WW 15 were similar to those of Timgalen, but WW 15 put a much greater proportion of its dry matter into grain. A greater number of grains per spike was the yield component responsible for the higher yield of WW 15. The increase in grain yield with the addition of nitrogen fertilizer was due to a general improvement in all aspects of crop vigour (e.g. tiller density, leaf area, total dry matter). There was no interaction between cultivars and nitrogen rates in their effect on grain yield.

A study of grain number in two contrasting wheat cultivars

The origin of the grain number difference between two contrasting wheat cultivars (WW 15, Mexican semidwarf; Timgalen, Australian) was studied in terms of (i) the production and distribution of dry matter during the pre-anthesis development of the ear; (ii) the number of florets initiated; and (iii) interaction between grains during grain set. Grain yield was much more closely related to harvest index than to total dry weight, and harvest index appeared to be largely a function of the number of grains produced per unit area. The difference in grain number between the cultivars bore no relation to the number of florets initiated by them. Nor was the inhibition of grain set in the distal florets of spikelets by rapid growth of grains in basal florets involved. Large differences in grain number occurred between the cultivars where there was no detectable difference between them in the production and distribution of dry matter during pre-anthesis ear development, i.e. the semidwarf cultivar was superior in setting grains for some reason other than the pattern of distribution of dry matter between grain and straw.

SOMATIC INSTABILITY IN THE BRAZILIAN SEMI-DWARF WHEAT IAS 54

The mitotic chromosome behavior of the Brazilian semi-dwarf wheat cultivar IAS 54 (Triticum aestivum L. em Tell) is described. In root tip cells dicentrics, fragments, isochromosomes, a satellite tandemly duplicated, chromatid exchanges, aneuploidy, ring chromosomes and breaks in almost all chromosomes of the complement were observed. Since anaphase cells that were not pretreated showed bridges, disorderly condensation and micronuclei, the possibility that pretreatment was responsible for the abnormalities was eliminated. Other possible genetic factors and virus infection as causal agents were discussed.

Inheritace of Plant Height in Cotton. II. Diallel Analyses Among Six Semidwarf Strains1

Semidwarf cultivars of upland cotton (Gossypium hirsutum L.) have been developed to meet the requirements of narrow‐row, high‐population cotton production. Six semidwarf stocks, the diallel set of F1 hybrids among those stocks, and a “normal‐height” stock were used to compare plant height and crop maturity characters among the semidwarf stocks and the normal‐height stock and to evaluate the inheritance of those characters among the semidwarf stocks. The characters studied were plant height, mainstem and fruiting‐branch internode length, number of mainstem nodes, node of the first fruiting branch, and mean maturity date. Diallel analyses were used to estimate genetic and environmental components. Comparisons between the normal‐height and the semidwarf stocks showed that the semidwarf stocks were gen. erally shorter in plant height, had shorter mainstem and fruiting‐branch internodes, initiated their fruiting branches at a lower mainstem node, and were earlier in crop maturity than the normal‐height stock. Diallel analyses indicated that the genetic variation for the plant height and maturity traits among the semidwarf stocks was primarily additive, with a small, although significant, dominance component associated with all the traits except number of mainstem nodes. Heritability was relatively low for plant height and mainstem internode length, intermediate for number of mainstem nodes and node of the first fruiting branch, and. high for fruiting‐branch internode length and mean maturity date.

Adaptation of semidwarf wheat cultivars to rainfed conditions

With a view to determining the comparative adaptation of semidwarf wheats to rainfed conditions, adaptation analyses were carried out on grain yield data of the 6th and 7th International Spring Wheat Yield Nurseries of the International Maize and Wheat Improvement Centre. Sites were chosen which had not received irrigation: across a combined total of 44 such sites, yield variation was closely related to growing seasonal rainfall. Using these sites, yields of thirty-three common cultivars. Norin 10-derived semidwarf cultivars plus tall ones, were regressed against site mean yield to give a regression slope (b) and deviations from the regression (sd 2) for each cultivar. Semidwarf cultivars generally showed higher mean yields and larger regression slopes (b > 0.9) than tall cultivars from lower latitudes. Tall cultivars from higher latitudes showed the lowest mean yields and the lowest b values (< 0.7). No consistent trends in sd 2 were evident. Despite the greater regression slopes of semidwarf wheats, the best yields under all but the lowest yielding (driest) conditions were given by certain semidwarf cultivars; these had high mean yields and b values close to 1.0 (for example Tobari 66, Inia 66, Pato ArGentino and Sonalika). In contrast other semiwdarfs (notably Chenab 70) of similar mean yield, plant height and phenology, were not well adapted to the drier conditions as indicated by b values close to 1.3. The usefulness of the regression technique and the implications of these results for selection of semidwarf wheats adapted to drier conditions are discussed.

Gametocidal properties of RH-531, RH-532, RH-2956, and RH-4667 on spring wheat (Triticum aestivum L.)

Several chemicals were evaluated for their gametocidal properties to control pollination in hybrid wheat (Triticum aestivum L. em Thell.) seed production. In a preliminary study, four chemicals were applied to three cultivars of spring wheat at two application times. RH-532 was the most effective of the four gametocides, reducing fertility to a 0 10% level for all three cultivars. In a second experiment, RH-532 was applied to one cytoplasmic male-sterile and three normal spring wheats at four rates (0.56, 1.12, 2.24, and 4.48 kg/ha) and at two times of application. Alternate strips of pollinator were planted throughout the experiment. All treatments decreased fertility. plant height, and spike length of the three normal wheats. RH-532 did not inhibit spike emergence of two semidwarf cultivars or one of conventional height. Cultivars did not respond similarly to treatments. Yields of cross-pollinated seed were only 1 21% of the normal yield when fertility levels on treated plants reached 0 10%. Hybrid seed content of the harvested seed ranged from 2 55%. On the treated male-sterile line, yield was significantly reduced in comparison with the open-pollinated check. Inhibitory properties of this chemical suppressed the fertilization potential of the female as well as inducing male sterility. The differential response of genotypes to treatments indicates that cultivars should be screened for male and female sensitivity to this chemical. If differential sensitivity is found, breeding and selection to improve this trait may be possible. Different environmental conditions may alter the response of cultivars to this chemical, with less effect on the female structures.

Contrasting Responses of Morphologically Similar Wheat Cultivars to Temperatures Appropriate to Warm Temperature Climates With Hot Summers: a Study in Controlled Environment

This study attempted to determine if and why there are differences among three cultivars of wheat in their responses to temperature. The three semidwarf cultivars examined, Kalyansona, Condor and Janak, are currently used commercially. Temperature regimes chosen matched the range to which plants in warm temperate climates with hot summers would be exposed at different stages of development. Plants were grown in a phytotron in sunlit cabinets. Responses to temperature were different among the cultivars. Kalyansona was relatively un- responsive to temperatures during the floret phase, being little affected in the sizes of upper leaves, in floret production and grain set, in overall plant growth or in grain yield. The sole character to respond to temperature in this cultivar was kernel weight, which declined with increasing grain phase temperature. In contrast, Condor demonstrated marked plasticity during the floret phase in all plant characters measured. Its plasticity was such that, at the lower temperatures, it outyielded Kalyansona by a substantial margin while at the higher temperatures its yield was relatively poor. On a plant basis, Janak performed similarly to Condor. Rates of photosynthesis were relatively unaffected by temperature in any cultivar. This wide range of response among three superficially similar cultivars has promising implications for the tailoring of cultivars for different temperature zones. The importance of different plant characters to temperature stability is considered in the discussion.

PERFORMANCE OF CROSSES BETWEEN STANDARD-HEIGHT AND SEMIDWARF SPRING WHEATS

Three semidwarf wheat (Triticum aestivum L.) cultivars were each crossed to three standard-height cultivars, and bulk F2 and F3 generations of each cross were compared with parents in the field at two locations. Yield component and grain yield data of parents vs. bulks were evaluated to determine whether a relationship existed between bulk and parent populations. Yield component data did not consistently relate to grain yield in either bulks or parents. However, correlation coefficients of 0.89 and 0.81 suggested a strong yield relationship between standard-height parents vs. their bulks and semidwarf parents vs. their bulks, respectively. We conclude that the average performance of the parents generally predicted the average performance of the F2 and F3 bulks for culm number, kernel weight, and grain yield. Heterosis was indicated for spikelets per head in crosses with P.I. 295619. There were no differences between semidwarf and standard-height cultivars in ability to impart yield component and grain yield potential to their offspring.

Melhoramento do cafeeiro XXXVI: produtividade do café de porte pequeno com poda dos ramos inferiores

Cafeeiros portadores dos fatores caturra (Ct), san ramon (Sr), laurina (Ir), dos cultivares pacas e villa sarchi e híbridos diversos foram estudados em Campinas, visando à seleção de cafeeiros de porte pequeno e de alta produtividade. Estudou-se também o efeito da poda de ramos inferiores sobre a produtividade e desenvolvimento das plantas. Utilizaram-se delineamento látice retangular triplo 5x6, 30 tratamentos, nove repetições, sendo as parcelas constituídas por duas covas, com uma planta por cova. As progênies derivadas do catuaí amarelo H 2077-2-12 e H 2077-2-5, que vêm sendo extensivamente cultivadas, apresentaram, em quatro anos, produções médias de 41,2, e 41,6 kg de café cereja, respectivamente. Os dados também mostraram que o caturra amarelo tem produção semelhante à dos cultivares pacas e villa sarchi. Entre as demais progênies analisadas, as de prefixo LCH 2077-2-5, H 2077-2-12-158, H 2077-2-5-47 e H 2077-2-12-283 salientaram-se quanto à produção no período de quatro anos. De modo geral, as progênies mais produtivas aos quatro anos foram aquelas que se destacaram por suas produções acumuladas aos seis anos. O mesmo ocorreu com as progênies menos produtivas. Após o quarto ano de colheita retiraram-se, ao acaso, em uma das plantas de cada parcela, todos os ramos inferiores até a altura de 60 cm, enquanto a outra planta permaneceu intacta. A média de produção de café cereja das plantas podadas foi de 7,1 kg e a das não podadas de 7,2 kg, no período de dois anos. A prática de retirada dos ramos laterais inferiores até 60 cm não contribuiu para alterar a produtividade e o desenvolvimento das plantas. Também não se verificou interação entre as produções das plantas podadas e não podadas, em relação aos tratamentos.

Some physiological aspects of growth and yield in wheat crops: a comparison of a semidwarf and a standard height cultivar

A field experiment showed the semidwarf cultivar Penjamo 62 to outyield the taller Australian cultivar Gamenya at nitrogen levels up to 896 kg N ha-1. This was attributed primarily to a faster rate of grain growth particularly in the later stages. Lodging resistance of Penjamo 62 accounted for only 16-58 per cent of the differences observed at the lower nitrogen levels. Although these two cultivars showed only small differences in both photosynthesis and in the duration of photosynthetic activity of microplots in the greenhouse, large differences in the efficiency of utilization of post-anthesis photosynthesis for grain production were inferred from growth analysis. Moreover, grain growth of Penjamo 62 was far more sensitive to a post-anthesis drought than that of Gamenya, even though similar levels of water deficit and reductions in photosynthesis were recorded in microplots of both cultivars.

Relation of Flag Smut Incidence to Semidwarf Growth Habit in Wheat Isolines1

AbstractIncidence of flag smut [Urocystis agropyri (Preuss) Schroet.] was related to the presence of semidwarf genes of wheat (Triticum aestivum L. em. Thell.) derived from ‘Norin 10’/‘Brevor,’ 14 and ‘Suwon 92.’ For 2 years at two sites, tests were conducted on five isoline populations of four genetic backgrounds with varying degrees of flag smut susceptibility. Isolines with two semidwarf genes had higher incidences of smut than standard‐height phenotypes in 9 of 10 comparisons (P = 0.05). One‐gene semidwarf isolines were more heavily smutted than standard‐height lines in 7 of 10 comparisons (P = 0.05). The two‐gene, one‐gene semidwarf, and standard‐height phenotypes averaged 62.9, 56.3 and 47.6% smutted tillers, respectively, for all populations during the 2 years. The proportions of smuttedtillers of all populations for both years for two‐gene and one‐gene phenotypes vs. the standard‐height phenotypes were 1.32 to 1.00 and 1.18 to 1.00, respectively. The two‐gene semidwarf isolines were significantly more heavily smutted than their one‐gene semidwarf sibs in 6 of 10 comparisons (P = 0.05). On an overall basis, the proportion of smutted tillers of the two‐gene vs. one‐gene phenotype was 1.12 to 1.00. The relation between semidwarf genes and increased incidence of flag smut was indirect and should not preclude the development of two and one‐gene semidwarf cultivars with adequate resistance. Breeders should recognize that semidwarf types may be potentially more vulnerable to losses from flag smut than nonsemidwarf types.

Melhoramento do cafeeiro XXXIV: comportamento de cafeeiros de porte pequeno, em Monte Alegre do Sul

Analisaram-se o desenvolvimento e a produtividade de progênies de cafeeiros de porte reduzido pertencentes aos cultivares san ramon, caturra e são bernardo, na região montanhosa de Monte Alegre do Sul. Tomou-se como padrão a progênie n.° 662 do cultivar burbom vermelho, de porte médio. Usou-se o delineamento em blocos ao acaso, parcelas subdivididas, com quatro e uma planta por cova em cada parcela a fim de avaliar a reação de 18 progênies nessas duas modalidades de plantio. De modo geral as progênies tiveram altura pouco maior quando plantadas a quadro mudas. Os dados de produção de café maduro no período de 15 anos indicaram que apenas algumas progênies não mostraram diferenças de produção quando plantadas a uma ou a quatro plantas por cova, enquanto outras revelaram diferenças significativas a favor do plantio a quatro mudas. Também mostraram que as progênies dos cultivares de porte pequeno produziram menos do que a de burbom vermelho 662. Os valores do coeficiente de correlação e o da interação entre a modalidade de plantio e produção das progênies indicaram que as melhores progênies plantadas a uma muda no geral também o são quando plantadas a quatro mudas por cova. Observou-se, ainda, que no plantio a quatro mudas as porcentagens de grãos chatos mostraram-se pouco menores e, as de grãos moca, pouco maiores, em relação ao plantio a uma única planta por cova.

Effect of sowing rate on the growth and yield of standard and semidwarf wheat cultivars

Abstract Two standard Wheat cultivars (‘Gamenya’ and ‘Triple Dirk’) and three semidwarf wheats (‘Matipo’, ‘Karamu’, and ‘Ciona-S’) were drilled at 77, 150, 216, and 284 kg/ha in the spring. Production and survival of tillers on permanently tagged plants were recorded at weekly intervals, and the number and weight of grains on the main stem and on the first, second, and remaining tillers of these plants were determined before the crop was harvested. Grain yield of the semidwarf wheats was 16% higher on average than that of the standard wheats, with no indication of any variety × sowing rate interactions for grain yield or any of its primary components (ears per unit area, grains per ear, and weight per grain). The tillering pattern of the semidwarf wheats was directly comparable with that of the standard wheats, and the yield superiority of the semidwarfs was largely due to their consistent advantage in total grain weight per ear. The ears on the main stems contributed 44% of grain yield at the lowest sowi...

Dependance on cultivar of wheat yield response to superphosphate

In seven experiments on calcareous grey clays the yield response of Olympic to superphosphate was compared to that of a number of other conventional and semi-dwarf wheat cultivars. The response to superphosphate rates, containing up to 48 kg P ha-1, was greatest with a number of semi-dwarf cultivars but a range of responses was recorded within both groups of cultivars. In comparison with Mexico 120, Olympic, in most experiments, achieved maximum yields at lower levels of applied superphosphate.

Inflorescence development of semidwarf and standard height wheat cultivars in different photoperiod and nitrogen treatments

A comparative study was made of the growth and development of the shoot apex/inflorescence in two contrasting spring wheat (Triticum aestivum L.) cultivars: Marquis—a standard height, day-length-sensitive type; and Pitic 62—a semidwarf, Norin 10 derivative with relatively low day-length sensitivity. The effects of 8-, 12-, 16-, 20-, and 24-h photoperiods and of two nitrogen levels in 12 and 20 h on both cultivars were determined, as well as those of two phosphorus levels on Marquis in 20 h.Apical primordium production continued for a longer duration in Pitic than in Marquis, and the initiation of spikelet primordia was delayed. Spikelet development was more synchronous in Pitic than in Marquis in all treatments. Apical spikelet formation always coincided in both cultivars with the initiation of rachis internode extension. Inflorescence development after termination of spikelet primordia formation was as fast in Pitic as in Marquis (or faster in short photoperiods).In general, increasing N increased the rate and duration of primordium production (apical spikelet formation occurring later at high N), and delayed inflorescence development and extension. These effects were more pronounced in Pitic, resulting in much greater N responses for spikelet and grain numbers per spike, and for grain yields per spike. Effects of high P were similar to those of high N. Increasing photoperiod increased the rate, but decreased the duration of primordium production, and accelerated the development and the extension growth of the inflorescence.The results are discussed in relation to a postulated involvement of endogenous gibberellins and inhibitors in the regulation of inflorescence growth and development.

The effect of increased soil nitrogen associated with medic ley on the performance of a standard and a semi-dwarf wheat cultivar

Two cropping rotations of fallow-wheat and four years of barrel medic (Medicago truncatula) pasture were used to obtain two levels of soil total nitrogen on a grey clay at Longerenong College, Dooen, Victoria. A semi-dwarf cultivar, Mexico 120, and a standard cultivar, Olympic, were then compared at the two levels of soil nitrogen over four years from 1964 to 1967. Mexico 120 outyielded Olympic by 1490 kg ha-1 in 1964 at the higher soil nitrogen level; however, it did not yield any better than Olympic at low soil nitrogen in that year nor at either soil nitrogen level in the other years. Mexico 120 had higher tiller survival, larger grain size, and shorter straw than Olympic in all years. In 1965 and 1966 its harvest index and the percentage of plant nitrogen in the grain responded more to higher soil nitrogen than that of Olympic.

Response of four wheat cultivars to applications of (2-chloroethyl)trimethylammonium chloride (CCC)

The effect of CCC on the grain yield of two Australian and two Mexican semi-dwarf cultivars, with two seeding rates, and two levels of N fertilizer, was studied in the held. Grain yield increases, particularly in CV. Timgalen, were produced by CCC through the control of lodging, an increase in the number of grains per ear and an increase in the number of ears per unit area. Even where only a small effect on height was produced in CV. Pitic 62, the grain yield was increased as a result of more ear-bearing tillers. No significant grain yield increases were found in R.K.F. The delay in ear emergence in some cultivars as a result of CCC did not change the number of florets formed but it may have improved floral fertility as indicated by the higher number of grains per ear at harvest. The differential response of the cultivars to CCC is demonstrated by the plant height data. In decreasing order of height reduction they were Robin, Timgalen, Pitic 62 and R.K.F.

Diffusible and Extractable Growth Regulators in Normal and Dwarf Shoot Apices of Peach, Prunus persica Batsch

Brian and Hemming (1), upon educing genetic dwarfs to behave as normal plants by applications of gibberellic acid, proposed that dwarfism was hormonally regulated. Phinney and his co-workers (12) expanded this idea by proposing that dwarfism in corn (Zea mays) is controlled by nonallelic genes, each of which governs a different step in gibberellin biosynthesis. They found that in this species the dwarf character, when transmitted as a recessive factor, can be altered by successive application of GA so that the seedling develops, flowers, and fruits as a normal plant. However, seedlings which inherit the dwarfing character as a dominant factor do not respond to GA treatments. Similarly, dwarf peas (Pisum sativum) respond to GA applications but the normal seedlings do not (2, 8). In rice (Oryza sativa), both the dwarf and semidwarf cultivars respond to exogenous GA. In contrast to the above species, applications of GA to normal peach (Prunus persica) seedlings accelerate shoot growth and inhibit flower bud formation (3), whilt the same treatments to dwarf progenies evoke a meager growth response. Moreover, the dwarf character in this species is transmitted as a simple recessive Mendelian factor; hence, it is likely determined by an allele and a single gene. It appears that while the genetic heritability of dwarfism in peach is simple, the mechanism controlling this character is dissimilar to that of other sp:cies mentioned above. To explore this dwarfing mechanism in peach, the levels of free diffusible and extractable gibberellin-like substances, IAA and ABA, in the shoot apices of dwarf and normal seedlings were compared.