Three-way Hybrids Research Articles

Agronomic evaluation of streak resistant maize germ plasm derived from the improved Vaalharts maize composite

Streak resistant maize inbred lines released by the Grain Crops Institute in 1995 were evaluated in the absence of streak disease as hybrid combinations in field trials. The evaluation of single crosses between three lines in each of a B73 and Mo17 background identified one line which transfers resistance to northern leaf blight (Exserohilum turcicum) in all combinations. Modified single crosses of the same lines using I137TN as tester yielded significantly less than a commercial standard hybrid. In three-way hybrid combinations of B73 related lines crossed to MSV-resistant germplasm in seven other genetic backgrounds, and using I137TN as tester, several hybrids yielded equivalent to a commercial standard. Significant differences in the incidence of ear rot (Stenocarpella maydis) were observed. The results comfirm that MSV-resistant breeding material derived from the improved Vaalharts composite are competitive with commercially proven susceptible varieties.

Effects of KK-42, an imidazole derivative, on rearing and reproductive performance of Bombyx mori L. during the hot, wet season

Experiments on the effects of KK-42, an anti-juvenile hormone imidazole derivative, on the rearing and reproduction of Bombyx mori L. were carried out in a hot, wet summer in West Bengal, India. A single dose of 3 μg KK-42/larva induced precocious metamorphosis in a bivoltine hybrid (KPGB x P5) race of B. mori when applied topically to freshly moulted (less than 1-h old) fourth instars, and increased their rearing performance over control tetramoulters. However, cocoon and shell weights, shell ratio and filament length were reduced by the anti-JH treatment. Final body weight and head capsule width of the treated fourth instars were significantly higher than those of the controls. Bivoltine trimoulter males also showed good capacity for mating with multivoltine Nistari females. The possibility of obtaining three-way multi-bi hybrid eggs during the wet part of summer in a tropical climate is discussed.

Components of rate-reducing resistance to Cercospora leaf spot in sugar beet: incubation length, infection efficiency, lesion size

SUMMARY Four sugar beet cultivars exhibiting increasing levels of rate-reducing resistance towards Cercospora beticola (‘Cyrano’ or ‘Univers’, ‘Bushel’, ‘Monodoro’, and ‘Break’) were used in monocyclic infection experiments to study the following resistance components: incubation length (IP, the degree-day cumulation, base 5°C, during the time between inoculation and appearance of spots), infection efficiency of conidia (INF, the number of necrotic spots per cm 2 of leaf at the end of a single infection cycle), and lesion size (LS, the area of single spots). All the resistance components were influenced by cultivar significantly; whereas no differences in lesion type were found. Resistance delayed the appearance of spots by a maximum of 12 days compared to the susceptible cultivar. IP 50 was delayed by a degree-day cumulation of 28°C, 60°C and 100°C in ‘Bushel’, ‘Monodoro’, and ‘Break’, respectively. More resistant cultivars showed a reduced INF compared to both less resistant and susceptible cultivars, of about 44% in ‘Monodoro’ and 79% in ‘Break’. Furthermore, in ‘Break’ the LS was 45% smaller than that of the susceptible cultivar. Differences between cultivars were consistent from one experiment to another. Within cultivars variability was an important source of variation; it was attributed to both ‘between plants’ and ‘between leaves within plants’ variability. The former was due chiefly to the genetic heterogeneity of the cultivars used, which are open-pollened three-way cross hybrids; the latter, to differences in the age of the leaves of a plant.

Evaluation of in vitro selection regimes for a mitochondrial trait (methomyl resistance) in cms-T maize

Several factors affecting the success of selection in plant populations were examined for their relevance to in vitro selection. Three in vitro selection schemes and two growth assessment procedures were evaluated for effectiveness in selecting for a mitochondrial trait in maize: resistance to the insecticidal compound methomyl. Regenerable maize callus was derived from immature embryos of the three-way hybrid P39/IL766A2 x W182BN containing Texas male sterile cytoplasm (cms-T). Either low, gradually increasing, or high selection pressures were used to grow callus over a period of 3–5 months. There was no significant difference in recovery of resistant plants using these 3 methods. Growth of callus on medium containing methomyl was assessed by increase in fresh weight during the final month of selection or by increase in number of callus pieces over the course of selection. These quantitative measures of growth were unreliable indicators for gain in resistance within the callus population. A procedure for recovery of methomyl resistant and male-fertile cms-T plants is suggested.

Construction of partial triallel crosses (ptc) using a class of balanced incomplete block designs (BIBD)

The Triallel Mating Design introduced by Rawlings and Cockerham (1962) is useful for the estimation of , and first order epistatic components and . It consists of a set of n∗= n(n - l)(n - 2)/2 distinct three-way hybrids. The number of crosses becomes too many to be accommodated within the resources of the breeder as n increases rapidly. In the paper an attempt has been made for the construction of Partial Triallel Crosses (PTC) using a special clus of Balanced Incomplete Block Designs (BIBD) called Partially Doubly Balanced Incomplete Block Designs (PDBIBD) which preserves the property of full Triallel Mating Design. It has been shown that for the estimation of variance components that λ(k - 2) >=2 and the degree of fractioning is equal to λ(k - 2)/(v - 2). A list of PDBIBD's which will be useful in the construction of PTC is given in the Appendix.

Restriction fragment length polymorphisms as genetic markers in Vicia

Genetic variability at the nucleic acid level has been examined in 16 Vicia faba accessions and in four Vicia species. Both six and four base-pair cutting restriction enzymes together with cDNA clones were used to assess the level of polymorphism detectable in Vicia section Faba. Nei's estimate of the number of shared fragments and principal co-ordinate analysis were used to examine and quantify the relationship between the Vicia accessions. The degree of polymorphism detected was considerably reduced when the four wild Vicia species were excluded from the analysis. One Vicia faba genotype, A × B × C, a three-way hybrid, was responsible for the majority of the RFLPs identified within the Vicia faba genotypes. The identification of hybridisable but diverse parents will improve the efficiency of creating a linkage map based on molecular markers. The nature of the polymorphism detected in Vicia is discussed together with the role of molecular markers in Vicia faba improvement programmes.

Use of Rank Indexing for Comparative Evaluation of All-male and Other Hybrid Types in Asparagus

Abstract Numerous asparagus (Asparagus officinalis L.) hybrids have been developed worldwide during the past 20 years. Most are clonal hybrids. The French (INRA) breeding program has successively introduced double, clonal, three-way all-male, and F1 (mixed or all-male) hybrids. Because these hybrids are evaluated at different locations during different years, a composite comparison of all cultivars is not feasible. A ranking index has been developed to make useful the huge volume of heterogeneous data that has been accumulated from the many trials during the past 10 years. This index is based for each hybrid on 2 years of comparative harvest data at four locations from about 40 hybrids and check cultivars at each location and each year. Using these rank indexes, the different types of hybrids can be compared one with another and with foreign hybrids. These indexes show that 1) all-male F1 and three-way hybrids tend to have high total yield and earliness; 2) F1 mixed hybrids are likely to have relatively large spear diameter; 3) double, clonal, and foreign hybrids produce the most attractive spears; 4) the general superiority of all-male hybrids is confirmed; 5) the four characters that are the major breeding objectives—early yield, high total yield, large spear size, and attractive spear appearance—are difficult, but not impossible, to combine into one hybrid. The indexes also show that, in spite of general trends, individual hybrids outstanding in all characteristics can be found in each type of hybrid.

Heterosis in Single, Three-way and Double Cross Hybrids of Silkworm, Bombyx mori L.

An investigation was carried out in India, to study the extent of heterosis expressed in single, three-way and double cross hybrids with respect to important economic characters. The results were discussed in terms of relative heterosis (heterosis over mid-parent value) and standard heterosis (heterosis over standard check variety). Significant negative relative heterosis was observed for total larval duration in single and majority of the three-way crosses; whereas it was positive and significant in double cross hybrids. The commercial characters like cocoon and pupal weight, shell percentage, filament length and denier, recorded positive relative heterosis in most of the single and three-way crosses; whereas they were negative and significant in most of the double crosses. In general, higher degree of heterosis was expressed in single crosses followed by three-way and double crosses for the characters studied.

Partial amphiploids from wheat (Triticum aestivum) × rye (Secale cereale) crosses

Two groups of three-way hybrids were produced by crossing F1 hybrids of 'Petkus' × 'Prolific' rye (2n = 14) and 'Prolific' × 'Puma' rye (2n = 14) onto 'Chinese Spring' wheat (2n = 42). Meiosis was studied in 89 plants from 29 families from the first combination and in 36 plants from 11 families in the second cross. In three families from the first combination ('Petkus' × 'Prolific') five partial amphiploids with chromosome numbers of 2n = 35, 36, 36, 38, and 41 were identified. The mean bivalent frequencies in five hybrids were 6.71, 7.73, 8.10, 9.94, and 13.00, suggesting that the number of bivalents was generally equal to the number of chromosomes in excess of the expected chromosome number of 2n = 28. These five plants were partial or incomplete amphiploids and their origin was attributed to duplication of a portion of the wheat complement after fertilization.Key words: partial amphiploids, hybrids (intergeneric), Triticum, Secale, chromosome pairing.

Título en español

Se estudió el efecto de cantidades de N e intervalos de corte sobre la producción de forraje y proteína bruta, el contenido en proteína bruta, la altura de la planta y el área foliar de tres híbridos sorgo-sudán. El nitrógeno se aplicó a 0, 80 y 160 kg/ha y los cortes se hicieron cada 60, 75 y 90 días. El experimento se hizo en dos localidades de Puerto Rico. Las diferencias fueron significativas entre localidades, híbridos, cantidades de nitrógeno, intervalos de corte y cosechas y entre las interacciones de localidades x híbridos, localidades x N, localidades x intervalos de corte, localidades x cosechas, cosechas x N, e intervalos de corte x N para la mayoría de las características estudiadas. La producción de forraje seco aumentó significativamente, especialmente con la aplicación inicial de N, y con los intervalos de corte. El contenido en proteína bruta fue más alto a los 60 días y disminuyó según aumentó el intervalo de corte. El híbrido triple (A Tx624 x 8 Rhodesian sudan) x Common sudan registró la mayor producción de forraje seco y proteína bruta y contenido en proteína bruta en comparación con los cruces sencillos A Tx624 x Common sudan. Se estima que a base de la información obtenida la ganancia neta proveniente del sorgo forrajero para producir leche puede ser de $1,522.00/ha.

Título en español

Cinco híbridos sencillos, cinco híbridos triples y el híbrido comercial DeKalb SX-17 se evaluaron en términos de forraje verde (GF), materia seca (DM), proteína bruta (CP), altura, área foliar, número de vástagos, razón hoja-tallo y potencial de ácido prúsico (HCN-p) durante 217 días en lsabela, Puerto Rico. Se llevaron a cabo 4 cortes, el primero a los 60 días y los siguientes cada 52 días, aproximadamente. Se utilizaron las yerbas sudan "Greenleaf" y "Common" como progenitores masculinos y las líneas androestériles "ATx624" y "ARhodesian sudangrass" como progenitores femeninos. En adición, se utilizaron las líneas " BTx624" y "BRhodesian sudangrass" como mantenedoras de las respectivas líneas A. El segundo corte registró la mayor producción de forraje seco (DF) y el menor contenido de CP. Al combinar los cuatro cortes, el híbrido sencillo ATx624 x Common, el híbrido triple (ATX624 x BRhodesian) x Common y el híbrido sencillo ARhodesian x Common fueron los mayores productores en términos de DF, resultando significativamente superiores al híbrido comercial DeKalb SX-17. La producción de DF del híbrido sencillo ATX624 x Common (17,303 kg/ha en 217 días) fue superior en 11 y 13%, respectivamente, con relación a los híbridos que resultaron segundo y tercero en producción de DF. A base de las comparaciones ortogonales, los híbridos sencillos fueron en promedio superiores a los híbridos triples en producción y otras características estudiadas. Los híbridos triples registraron en promedio menos HCN-p (250 ppm) al compararse con los híbridos sencillos (285 ppm). Estos valores son ligeramente superiores al nivel de 200 ppm, nivel sobre el cual el HCN-p puede ser tóxico para el ganado. Los resultados indican, que los híbridos que registraron los rendimientos más altos tienen magníficas potencialidades para usarse como forrajeras en la Isla. La producción de DF del híbrido sencillo ATX624 x Common de 17,303 kg/ha en un período de 217 días o de 80 kg. ha-1 dia-1 con una CP de 12% es excelente, especialmente cuando la yerba se puede cortar en los trópicos a intervalos cortos.

NORTHERNVEE AND EARLIVEE SWEET CORNS

Northernvee and Earlivee are first-early sweet corn cultivars for fresh market and home garden. Northernvee, a three-way hybrid, is slightly earlier but more variable than Earlivee. Both are 12-to 14- rowed and have better eating quality than most early cultivars.

‘Tuckcross 756P’ Tomato1

Abstract ‘Tuckcross 756P’ is an early, large, pink-fruited three-way hybrid tomato (Lycopersicon esculentum Mill.) that is adapted for greenhouse culture in the northern U.S. and Canada. Since 1971 it has performed well in experiment station and commercial greenhouse trials (2, 3, 4). With early production of good quality fruit, ‘Tuckcross 756P’ is also resistant to fusarium wilt and tolerant to leaf mold.

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.

‘TAMU Triple Cross’ Pickling Cucumber1

Abstract ‘TAMU Triple Cross’ is a three-way hybrid pickling cucumber (Cucumis sativus L.) developed for mechanical harvesting. It is the first American pickling-type hybrid cucumber developed from three inbreds. ‘TAMU Triple Cross’ exhibits several outstanding characteristics including high yield, desirable fruit shape, dark green color, excellent processing qualities both as brinestock and fresh pack, broad spectrum resistance to cucumber diseases, and finally, an improved and less expensive system for production of hybrid seed (1,2,3).

Combining ability type of analysis for triallel crosses in maize (Zea mays L.)

Data on 30 three-way maize (Zea mays L.) hybrids formed from 5 inbred lines were subjected to the combining ability type of analysis. The relative importance of general and specific line effects in maize three-way hybrids was studied by the Ponnuswamy and Das (1973) method. It was also shown that this analysis provides the breeder with the basic information necessary to choosing proper breeding materials and in deciding the order in which they should be combined to get desirable three-way hybrids.

Factors Affecting Butylate Injury to Corn

Injury to corn (Zea maysL.) hybrids from butylate (S-ethyl diisobutylthiocarbamate) was investigated as a function of planting depth, soil pH, and temperature. Field and growth chamber studies indicated that the potential for butylate injury increased with increasing planting depth regardless of hybrid. Greenhouse and growth chamber experiments suggested that as soil pH decreased butylate injury increased, depending upon the hybrid. Butylate injury was also a differential response among hybrids, depending on temperature. Certain hybrids may be injured more at higher temperatures and other hybrids more at lower temperatures. Butylate injury to corn, therefore, appears to be due to a three-way interaction, stress x hybrid X butylate.

A Y To Δ Transformation of a Three-Way Hybrid Junction

A three-way power divider/summer in the Wilkinson configuration can be symmetrically fabricated in stripline if the Y resistive balancing network is replaced by a /spl Delta/ resistive network. Port-to-port isolation in a stripline circuit at 2 GHz exceeded 27 dB; loss was below 0.15 dB.

A comprehensive breeding system

An outline of a comprehensive breeding system developed and used by the Kenya Maize Research Section is presented. This system has four main phases: 1. Evaluation of local and exotic varieties so that the breeding material is the best available. 2. Compositing the selected breeding material into two or more populations or varieties in such a manner that each population has considerable genetic variation for the traits requiring improvement and that the crosses of these populations will show heterosis. 3. Recurrent selection in each population to increase the frequency of favorable genes so that the populations and population crosses are improved with each cycle of selection. 4. Release of a commercial variety of one of the following forms: (a) the cross of two populations as a variety cross hybrid; (b) single, three-way or double cross hybrids from inbred lines developed from the elite material after each cycle of selection; or (c) a synthetic variety derived from the advanced generation of the population cross in areas where hybrid production is not yet feasible.

Resistance of Pines to the Pine Reproduction Weevil, Cylindrocopturus eatoni

The pine reproduction weevil causes serious losses in young plantations of Pinus jeffreyi Grev. & Balf and P. ponderosa Laws. Crossing P. Jeffreyi with P. coulteri D. Don. produces resistant progenies. A three-way hybrid of these two and P. ponderosa is also resistant. The mode of action of resistance is not known though nonpreference, antibiosis, and tolerance all are indicated. Within-species variation in resistance appears to be heritable. Both within- and between-species resistance may be imparted by either parent, though indications are that it may be more attributable to the female parent. Progenies from selfpollination of recognized hosts are less resistant than progenies from non-selfing. Hany pine species and hybrids have been classified as resistant or non-resistant from data of forced attacks and natural infestations. A large-scalc pollination project is underway to produce weevil-resistant pines for tree planting in California.