An intersubgeneric hybrid between Glycine tomentella Hayata and the soybean,G. max (L.) Merr.

Summary The objective of the present paper is to provide information on the morphology and cytology of an intersub-generic hybrid (2n=59) between Glycine tomentella Hayata (2n=78) and G. max (L.) Merr. (2n=40) obtained through in vitro immature seed culture. The hybrid plant was slow in vegetative growth and twinning like the female parent but morphologically was intermediate between both parents for several traits. At metaphase I, the average chromosome associations and ranges for 25 cells were 44.0 I (37–51)+7.5 II (3–11). The plant was completely pollen and seed sterile. The present investigation suggests that wild perennial Glycine species can be exploited as either the male or female parent in wide hybridization programs with the soybean, G. max.     

Nutrient culture medium components affecting plant recovery from immature embryos of three Glycine genotypes and an interspecific hybrid grown in vitro

Summary Immature embryos of Glycine max (L.) Merr. cv. Bay, G. tabacina (Labill.) Benth. and G. tomentella Hayata were cultured on 72 media combinations to identify a nutrient medium which would allow a greater percentage of interspecific plants to be recovered from cultured embryos of G. max × various perennial Glycine species. The highest mean plant recovery rate of 79% was from a medium containing B5 nutrient salts as reported by Gamborg et al. (1968), vitamin components according to Williams (1978) and 30 g/l sucrose. This is as compared with 25% from a medium used previously. In an additional test, 67% of hybrid embryos of G. max × G. tomentella were recovered from the same medium, from which G. tomentella was most effectively recovered in all testing.Contribution No. 89-276-J of the Kansas Agric. Exp. Stn., Manhattan.     

A partially male-sterile mutant line of soybeans,Glycine max (L.) Merr.: inheritance

Summary A partial male sterility system in the soybean (Glycine max (L.) Merr.) germplasm population AP6(SI)CI was found to be controlled monogenically by a recessive allele, msp. Observations of msp msp plants in different environments suggested that environmental conditions significantly affect expressivity of the msp allele with respect to male sterility. We obtained no experimental evidence of cytoplasmic effects on msp expression. Background genotypes, however, seem to affect msp expressivity through their determination of flowering dates and resultant interactions with varying environmental conditions.Homogeneous populations of partially male-sterile plants can be generated by increasing families of msp msp plants in fertility-inducing environments, if measures are implemented to prevent the introduction and/or build-up of fertile genotypes that arise from natural cross-pollinations.Joint contribution: North Central Region, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-9596 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

A partially male-sterile mutant line of soybeans,Glycine max (L.) Merr.: Characterization of the msp phenotype variation

Summary Investigations of variable expression of msp partial male sterility in soybeans (Glycine max (L.) Merr.) showed that higher temperatures promote male fertility in msp homozygotes and showed that infectious agents are not intrinsic to the sterility system. Exchange grafts failed to modify fertility levels of msp msp rootstocks, Msp Msp scions, and their self-progeny. Tests for soybean mosaic virus and tobacco ringspot virus were negative in partially male-sterile plants, in control fertile plants, and in self-progeny of grafted plants. Growth-chamber experiments and field observations manifested that male fertility of msp msp plants is higher in hot environments than in cooler ones. The unexpected aberrant ratios of fertile to partially male-sterile plants observed in 1977 (Stelly & Palmer, 1980) are explainable on the basis of msp temperature sensitivity.Our observations suggest that homogeneous msp msp populations may be increased in hot environments.Research Geneticist, SEA-AR, USDA, Iowa State University, Ames, Iowa 50011, USA.     

Wide crosses in soybeans: Prospects and limitations

Summary It was attempted, though in vain, to cross soybean with Glycine species of the subgenus Glycine.     

The effect of pre- and post-inoculation temperature on resistance in certain cultivars of poplar to races of Melampsora larici-populina kleb.

Summary Four cultivars of Populus spp., compatible to varying degrees with four races of M. larici-populina Kleb., were raised in a controlled environment on a high (28°/20°C, day/night) and low (20°/10°C) temperature regime. Leaf discs cut from the plants were inoculated separately with four individual races of M. laricipopulina and subsequently incubated at either low (20°C) or high (25°C) temperature for 14 days when disease development on the discs was assessed using three parameters (Incubation period to flecking, uredia per leaf disc and uredospores per mm²). The degree of resistance in all cultivar/race combinations was high on cultivars cultured at a high temperature regime compared to those cultured on a low temperature regime. Analysis of variance demonstrated that the major components: pre-inoculation temperature regime, post-inoculation temperature regime, race and cultivar, and most second and third order interactions between these were highly significant (P<0.001) for most disease parameters. The variance of the temperature components and all interactions involving these were usually higher than those for the cultivar and race components and those interactions lacking temperature components.These results emphasize the importance of the temperature regime at which plants are raised and the temperature of incubation, following the inoculation in determining the relative degree of resistance of these cultivars of poplar to races of M. larici-populina. The implications of these results in the epidemiology of leaf rust and the stability of the host-parasite relationship are discussed.     

Reactions of poplar clones to physiologic races of Melampsora larici-populina Kleb.

Summary Four mono-uredospore isolates of Melampsora larici-populina Kleb. produced qualitatively distinct reactions on four half-sib clones of Populus deltoides Marsh. and thus were recognisable as races. Two of the races could be distinguished equally readily by the distinctness of their reactions (three quantitative parameters) on four compatible clones of Populus spp. The pronounced race specific reactions of the clones of P. deltoides, allied to the less distinct, but nevertheless race specific reactions, of the compatible clones are consistent with an integrated rather than a disjunctive concept of resistance in Populus spp. to M. larici-populina.     

Identification and cataloguing of genetic information for resistance to wheat leaf rust

Summary Specific host-pathogen relationship is used to derive genetic information for resistance in commercial cultivars. Twenty-two cultivars were classified into 12 groups based on their reactions to 13 leaf rust (Puccinia recondita) races of India. The cultivars in each group were matched with the Lr gene carrying lines to see which genes they might possess. Confirmation of this information was sought through pedigree analyses.(1) Agra local and NP4 do not seem to have any resistance genes. (2) C306 has gene Lr14a, and NP824 one of the genes Lr12, Lr13, Lr14a or Lr22. (3) kalyansona carries Lr13 and another additional gene not in study. (4) Chhoti Lerma, NP852, Pusa Lerma, Sharbati Sonora, Shera, UP301 form one group and carry Lr1. (5) Sonalika seems to have Lr2a, Lr11 and additional genes. (6) Hy.65 has Lr10. (7) HS1076-2 and HW135 have the genes Lr2a and Lr3do. (8) HW124 carries the genes Lr1 and Lr3do. (9) Safed Lerma has Lr1 and Lr17. (10) NP846 has the genes Lr1 and Lr15. (11) HB117-107, Janak, UP215 form one group and possess the genes Lr3do and Lr15. (12) Girija possesses the genes Lr10 and Lr15.Based on such grouping of commercial cultivars for resistance genes a Catalogue system is advocated for the design of wheat breeding programmes like the development of multiline and multigene cultivars.     

Inheritance of long juvenile period under short day conditions for the BR80-6778 soybean (Glycine max (L.) Merrill) line

The long juvenile period characteristic (LJP), which delays flowering under short day conditions, has been identified in soybean cultivars (Glycine max L. Merrill). This characteristic may be especially important as it increases the range of adaptation of soybean in low latitudes and gives greater flexibility for sowing periods within the same latitude. The inheritance of the long juvenile period was studied in the BR80-6778 soybean line to provide knowledge to support the development of cultivars adapted to short day conditions. Cultivars with classic flowering, Paraná, Bossier, Bragg and Davis, which flower early under short day conditions, were also used as parents in single crosses. They were crossed among themselves and with the genotypes with LJP, BR80-6778 and MG/BR 22 (Garimpo). The study was carried out under short day conditions (early sowings) in greenhouses and in the field at Embrapa National Soybean Research Center, Londrina, PR. Flowering was assessed daily. The results indicated that the BR89-6778 line shares a pair of alleles with the Paraná cultivar, and when associated with the cc allele retards flowering under short day conditions. The following genotype constitutions were attributed to the cultivars: Paraná (aaBBCC), Bossier (AabbCC), and BR80-6778 (aaBBcc). The combination of the genes aabb and aabbcc has a pronounced effect on the manifestation of the trait. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A of soybean [Glycine max (L) Merr.]

At present, no report on inheritance of male fertility restoration has been released, yet more than 10 cytoplasmic-nuclear male-sterile soybean lines as well as their maintainers and restorers have been developed. Based on our previous work, 25 restorers for the male-sterile line NJCMS1A were identified and the inheritance of male fertility restoration for these restorers was studied. The results showed that F₁s between NJCMS1A and its restorers were completely male-fertile. The numbers of fertile and sterile plants in the F₂ population of Cross I (NJCMS1A × N23601) and Cross II (NJCMS1A × N23683) corresponded to a segregation ratio of 15:1, and the numbers of non-segregation lines, 3:1 segregation lines and 15:1 segregation lines in F_2:3 of the same two crosses fitted a 7:4:4 genotypic segregation ratio. The testcross BC₁F₁s between the F₁s of the above two crosses and NJCMS1A, NJCMS1B showed a 3:1 segregation ratio. Accordingly, it was inferred that two pairs of duplicate dominant genes controlled the male fertility restoration of NJCMS1A in both crosses. Meanwhile, F₂ of other 23 crosses between NJCMS1A and its 23 restorers showed a fertility segregation ratio of 3:1 or 15:1. The F₁s of the five testcrosses between NJCMS1A and the F₁s of five crosses selected from the above 23 crosses showed that fertility segregation was 3:1 in BC₁F₁s between NJCMS1A and F₁s of the crosses of which fertility segregation fitted 15:1 in F₂ population, while fertility segregation in BC₁F₁s was 1:1 for those fertility segregation fitted 3:1 in F₂ population. Allelism tests showed that restore genes of all restorers in the experiment were allelic to two pairs of dominant genes. All results showed that some restorers bore one pair of dominant restore gene and the others bore two pairs of duplicate dominant gene. The mechanism of F₁ male sterility of the cross N8855 × N2899 was discussed.     

Field screening of soya bean (Glycine max (L.) Merrill) germplasm for aluminium tolerance by the use of augmented design

Summary Selection for aluminium tolerance is necessary to adapt the soya bean crop to vast areas of acid soil in the tropics such as the Brazilian Savannas (Cerrados). The breeding programmes include field testing of large numbers of varieties. The tests are laborious, time consuming and need to be repeated to minimize effects of uncontrolled environmental factors. The present results show that augmented designs are efficient in the identification of Al-tolerant genotypes. These designs (i) allow elimination of soil differences as common causes for error in comparison of entries, and (ii) can be successfully employed in genetic studies and breeding programmes for crop improvement, being more cost effective than fully replicated trials.     

Identification of genes for resistance to Puccinia striiformis f. sp. hordei in 18 barley genotypes

Barley genotypes Hor 1428, Hor 2926, Hor 3209, BBA 2890, Abyssinian 14, Grannelose Zweizeilige, and Stauffers Obersulzer are resistant to all races of Puccinia striiformis f. sp. hordei so far detected in the U.S.A. Heils Franken, Cambrinus, Astrix, Emir, Hiproly, Varunda, Trumpf,Mazurka, Bigo, BBA 2890, and I 5 are resistant to some races and susceptible to others. Previous studies showed that Hor 1428, Hor 2926, Hor 3209, Abyssinian 14, Stauffers Obersulzer, I 5, Heils Franken, Emir, Astrix, Hiproly, Varunda, and Trumpf each have two genes, and BBA 2890, Grannelose Zweizeilige, Cambrinus, Mazurka, Bigo, and BBA 809 each have a single genefor resistance. To determine the genes in specific genotypes and their relationships, all possible crosses were made among the 18 genotypes. Seedlings of parents and F₂ progeny were tested under controlledconditions for resistance to selected races that were avirulent on both parents. Based on segregation within the individual crosses to selected races, at least 26 of 30 genes detected in the 18 genotypes were different. Allelic and linkage relationships of some of the genes were determined. The genetic information should be useful for understanding the host-pathogen interactions and for control of stripe rust using resistance.     

Partial resistance in lettuce to downy mildew (Bremia lactucae). 2. Differential interactions between plant genotypes and fungus races and the relationship of latent period,infection frequency and number of infected leaves with the level of partial resistance

Summary In three experiments differential interactions between lettuce genotypes and Bremia lactucae races were investigated and also the influence of latent period, infection frequency and number of infected leaves on the level of resistance.In experiment 1 very significant differential interactions were observed mainly caused by two plant genotypes (PIVT 82 and PIVT 315) and race NL 7. In experiments 2 and 3 differential interactions were absent or of minor importance. Results suggest that partial resistance often was of a race-non-specific character. Latent period appeared to be a major component of resistance in the lettuce-Bremia lactucae relationship. It determines the onset of the next cycle of spore production and is also indicative of fungus growth in host tissue. Compared with infection frequency and number of infected leaves, latent period shows a small error variation and can efficiently be measured. The closeness of the relationship of the number of primary infections and the number of infected leaves with resistance level varied, depending on the experiment. The above three components appeared to be associated but the degree of the association varied. The variable behaviour of the three components suggests that they are governed by different genes.For the level as well as for the complexity and durability of the resistance, accumulation of as many components of resistance as possible is desirable. Therefore, in parents all such components should be analysed before crosses are carried out to improve resistance level. In the final products of crossing and selection the relative importance of components should also be investigated to determine whether an increased resistance level results from additional effects of the parents on one component (e.g. latent period) or from accumulation of different components in a plant genotype.Students at the Agricultural University Wageningen     

Induced mutagenesis for the development of multiline cultivars in bread wheat

Summary Variation for resistance toPuccinia graminis f.sp.tritici, P. recondita f.sp.tritici andP. striiformis was induced in theTriticum aestivum cultivar Lalbahadur using nitrosomethyl urea. Variations were isolated from the M₂ population in the post-seedling stage in the field when infected with a mixture of races of each of the three rusts. Plants exhibiting simultaneous resistance to stem rust, leaf rust and yellow rust were indentified. Repeated screening in the subsequent generations confirmed the resistance of the mutant lines that are morphologically similar to the parental cultivar. The rust resistance of 20 mutant lines was also confirmed at the seedling stage using individual races of stem rust and leaf rust. The different patterns observed in the mutant lines tested against a wide range of races show that these lines can be used as components of a multiline. The patterns of variation compared with those of the known genes for resistance against the Indian races of the pathogens suggest that the mutations for rust resistance are due to factor different from those already known in bread wheat, providing a broadened genetic base for future breeding programmes.     

Genetic analysis of partial resistance to coffee leaf rust ( Hemileia vastatrix Berk & Br.) introgressed into the cultivated Coffea arabica L. from the diploid C. canephora species

The objective of this study was to identify polymorphic molecular markers associated with partial resistance to coffee leaf rust, Hemileia vastarix. A segregating F ₂ population derived from a cross between the susceptible Coffea arabica cv. Caturra and a C. canephora-introgressed Arabica line exhibiting high partial resistance was analyzed. Rust resistance measured as rust incidence (RI) and defoliation (DEF) was evaluated in field conditions in three consecutive years (2003–2005). During the 2003 season, which was characterized by favorable conditions for a rust epidemic, the F ₂ plants exhibited different levels of resistance ranging from very susceptible (50.1% for DEF and 49.5% for RI) to highly partial resistance (9.1% for DEF and 3.7% for RI). Molecular analysis enabled identification of seven polymorphic markers (5 AFLP and 2 SSR) exhibiting significant association with partial resistance. Coexistence of resistance homozygous alleles (RR) at codominant SSR loci was correlated with high resistance. This study is the first attempt to develop PCR-based sequence specific markers linked to partial rust resistance in coffee.     

Development of barley leaf rust,Puccinia hordei,infections in barley. II. Importance of early events at the site of penetration for partial resistance

Summary The investigation involved three barley genotypes that varied from extremely susceptible (Akka) to an extreme level of partial resistance (17-6-16). The barley leaf rust colony size was measured in primary leaves 3, 6, 12 and 18 days after inoculation and in flag leaves 6, 12, 18, 24 and 30 days after inoculation with race 1-2-1. Akka always had the largest colonies, 17-5-16 the smallest, with Vada at an intermediate position. The genotypic differences were proportionally largest at the second sampling day and smallest at the last sampling day. The rate of colony growth decreased rapidly over time for all genotypes and in both plant stages. Measured at the same time (colony age the same) the rate of colony growth was largest for 17-5-16 and smallest for Akka in most periods. The time needed to reach a given colony size showed already large differences in the very early states especially in the flag leaves. Akka took 3.9 days to reach a size of 17 × 10^-3 mm² (only 5 to 10% of the colony size at the start of sporulation), Vada needed 8.3 days and 17-5-16 even 12.0 days. To reach a size of 320 × 10^-3 mm² the three genotypes needed 12.7, 18.0 and 22.8 days respectively, differences that are only slightly larger than those at the very small colony size.It was concluded that the partial resistance of barley to barley leaf rust is not primarily due to a reduced fungal growth in the partially resistant host tissue but predominantly so to an initial and temporary stagnation at the site of penetration. The longer this stagnation lasts, the longer the latent period and the higher the partial resistance are. Once this stagnation has been overcome the fungal growth rates do not vary much between genotypes with different levels of partial resistance.     

Partial resistance of barley to leaf rust,Puccinia hordei. III. The inheritance of the host plant effect on latent period in four cultivars

Summary The latent period (LP) in the barley-leaf rust relationship is an important component of the partial resistance complex. The inheritance of the host plant effect on LP was studied in five crosses between four cultivars. The LP, effectuated by the susceptible cultivars L94 and L92, were 8.0 and 8.6 days resp., those of the resistant cultivars Minerva (Mi) and Vada (Va) 16.9 and 17.1 days resp. The mean F₁ and F₂ values of the crosses L92×L94 and Mi x Va were intermediate between the parental ones. The variances of the F₂'s were slightly larger than those of the parents and the F₁'s indicating some segregation. In the crosses between a susceptible and a resistant cultivar the F₁ value was half way between the mid-parent and susceptible parent value. The F₂ mean lay approximately half way between the mid-parent and F₁ value, with a distribution positively skewed and slightly bimodal. There was no transgression, in fact not even the parental values were recovered among nearly 500 F₂ plants. The F₃-lines of the crosses between susceptible and resistant cultivars showed within line variances from as low as the parental values to as high as or higher than those of the F₂. In hte F₃'s the parental values could be recovered although no transgression occurred.L94 is supposed to carry no genes effecting a longer LP. The long LP of Mi and Va, assuming no linkage, is thought to be effectuated by the cumulative action of a recessive gene with a fairly large effect and some four to five minor genes with additive inheritance. One of these minor genes is supposed to be carried by L92, while Mi and Va are thought to differ for one minor gene only. In case linkage exists, the number of minor genes involved could be higher.     

Breeding for resistance to yellow disease of hyacinths. II. Influence of flowering time,leaf characters,stomata and chromosome number on the degree of resistance

Summary Analysis of an incomplete diallel design with 14 hyacinth cultivars and 4 wild accessions of Hyacinthus orientalis showed a significant GCA component for resistance to yellow disease. The late flowering hyacinth cultivars King of the Blues and Marconi and the early flowering Hyacinthus orientalis 70129 were found to be the best combiners for yellow disease resistance. Within a cultivar, the degree of earliness itself was not associated with the degree of resistance. Correlation coefficients of leaf characters and degree of resistance showed that hyacinths with short and/or narrow leaves are generally more resistant than those with long and/or broad leaves. Tetraploid cultivars with few, large stomata tend to be susceptible, diploid ones with many small stomata tend to be the more resistant.     

The inheritance and association of resistance to rust,common bacterial blight,plant habit and foliar abnormalities in Phaseolus vulgaris L.

Summary No antagonistic or synergistic interaction was found between isolates of Uromyces appendiculatus var. appendiculatus and Xanthomonas campestris pv. phaseoli when inoculated to the same plant. A single dominant gene was suggested to control resistance to three isolates of rust in the crosses Pompadour Checa × Chichara and Pompadour Checa × NE W-4. A two-gene model was confirmed for the reaction to the three rust isolates for the crosses Pompadour Checa × GN Tara and Pompadour Checa × San Cristobal; a dominant (Ur _p) gene determined resistance and was epistastic to a dominant gene (Ur _t) for susceptibility. (Ur _t) was expressed only in the presence of recessive (ur _p) alleles. The reaction to common bacterial blight was quantitatively inherited and an association was detected with plant habit but not with rust reaction and leaf variegation. Plants with leaf variegation and crippled growth, were detected in the progeny of the cross Pompadour Checa × GN Tara and were controlled by duplicate recessive genes (mutatorunstable genes) and three genes, acting additively, respectively. The developmental expression of the latter trait varied considerably. Linkage was detected between genes controlling the variegated and the crippling traits.Published as Paper No. 7839, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under project No. 20-036.     

Comparison of the sensitivity of the mean and the mode in screening coffee seedlings for resistance to coffee berry disease Colletotrichum coffeanum Noack sensu Hindorf (A short communication)

Summary The utility of the modal grade as an alternative to the mean grade in the pre-selection test for screening seedlings of Coffea arabica L. for resistance to coffee berry disease (CBD) caused by Colletotrichum coffeanum NOACK sensu HINDORF was examined. Three criteria were used to compare the sensitivity of the modal grade with that of the mean grade when partitioning 6 weeks old seedlings into different resistance classes. The criteria were: the sensitivity of the two statistics as estimators of central tendency, the sensitivity of the modal grade and the mean grade as selection criteria and the correlation between the two statistics.The modal grade was neither more sensitive in detecting genotypes that fell in diffent resistance classes nor more severe than the mean grade in screening for genotypes susceptible to CBD. In the cases studied, the modal grad was highly correlated with the mean grade (r_s ranged from 0.55^**–0.82^**). Hence, it is concluded that there are practically no gains in adopting the modal grade as a pre-selection criterion in preference to the mean grade.