Components of partial resistance to Leptosphaeria nodorum among seven soft red winter wheats

Summary Seven soft red winter wheat cultivars were evaluated for partial resistance to Leptosphaeria nodorum under field conditions. The results demonstrate that resistance is available among cultivars that are adapted to the southeastern U.S. and that resistance is long lasting. Resistant cultivars had longer incubation and latent periods, slower rates of lesion development, and reduced the level of sporulation of L. nodorum. Seedlings of susceptible cultivars sustained severe disease with dew periods as short as 48 hr in greenhouse tests. One resistant cultivar sustained little damage with dew period as long as 144 hr.Latent period was shortest on the second leaf below the flag leaf (F-2 leaf) of all cultivars and longest on the flag leaf which reflected the effect of microclimate and leaf age. The range in length of latent period on the flag, F-1, and F-2 leaves of resistant cultivars was less than that for susceptible cultivars. Differences between cultivars were greatest (up to 6.8 days) for the F-2 leaf. A delay in production of inoculum on the F-2 and lower leaves of resistant cultivars should delay infection of the flag leaf and spike.The greatest differentiation among cultivars for sporulation of L. nodorum was on upper leaves at Feekes growth stage 11.2. Oasis consistently had less sporulation than other cultivars at all sampling dates and leaf positions. The rate of disease progress up the plant (disease severity) and area under the disease progress curve were also least on Oasis.There were significant correlations among components of resistance and associated components suggesting that a single or interrelated mechanisms control expression of resistance. Overall, Oasis was the most resistant cultivar followed by Coker 762 and Coker 747. There cultivars have remained resistant for ten or more years. Stacy was intermediate in resistance and was the most variable of the seven cultivars for the components tested. Holley, Omega 78, and Florida 301 were highly susceptible by all criteria tested. Plant height was not a factor in resistance. The resistant cultivars are mostly later in maturity than the susceptible cultivars. In this study, crop maturity was similar under existing environmental conditions during the two seasons when most data were collected.     

Resistance in Cucumis sativus L. to Tetranychus urticae Koch. 3. Search for sources of resistance

Summary After a first screening of 800 cucumber varieties, a laboratory test and a practical test, the following nine varieties have been selected for their distinguishable level of resistance to the twospotted spider mite: PI 220860, Hybrid Long Green Pickle, PI 178885, Ohio MR 200, Taipei no 1, Robin 50, Aodai, PI 163222 and PI 218036. Besides resistance tolerance for the twospotted spider mite also appears to occur. Related Cucumis species do not seem to possess higher levels of resistance than the most resistant C. sativus varieties. The resistance-parameters acceptance and reproduction appear to be positively correlated. On resistant varieties the metabolism of the spider mites is clearly disturbed, but this seems not to be caused mainly by bitter principles.     

α-Tomatine and other steroidal glycoalkaloids in fruits of tomato lines resistant to the glasshouse whitefly (Trialeurodes vaporariorum Westw.)

Summary The total steroidal alkaloid compositions of the mature-harvested fruits of the tomato cultivar Allround (Lycopersicon esculentum), of the species L. hirsutum glabratum, resistant to the glasshouse whitefly (Trialeurodes vaporariorum), and of four resistant lines were determined by capillary gas chromatography. The contents of -tomatine in the red-ripe fruits of Allround and in those of the lines were low (5 mg/kg fresh weight). The green-mature fruits of the wild species had a high content (3390 mg/kg fresh weight) of -tomatine. The total alkaloid profiles of Allround and of the lines were similar. Comparison of flame ionisation detector response with thermoionic detector response indicated that in addition to tomatidine, the aglycone of -tomatine, a small amount of one other steroidal alkaloid might be present in Allround and in the lines. The wild species contained five compounds which possibly are steroidal alkaloids.The safety level of -tomatine in tomatoes is discussed. It was concluded that, in respect of the glycoalkaloids of the mature-harvested fruits, the resistant tomato breeding lines are as safe for human cosumption as the standard cultivar.     

Genetics and histology of powdery mildew resistance in apple

Summary Eight scab-resistant cultivars and selections along with eight commercial apple cultivars were evaluated for powdery mildew resistance in greenhouse and nursery tests. Dayton, Liberty, Delicious and Tolman Sweet were rated moderately resistant to infection in both greenhouse and nursery tests. Segregation of seedlings among 14 progenies for mildew reaction indicated that mildew resistance is polygenically controlled in this material with additive gene effects. Recovery of mildew resistant seedlings from crosses involving a scab-resistant parent(s) suggested that this material can be useful in developing scab- and mildew-resistant apple cultivars. Histological investigations were conducted to describe mildew symptoms of infected leaves.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary The stripe rust resistant spring wheat (Triticum aestivum L.) varieties Anza, Glennson 81, Ollanta, and Yecora Rojo gave 1,2,2, and 2-gene segregations, respectively, in hybrids with susceptible Jupateco 73 when inoculated in field conditions at Davis, California USA with Puccinia striiformis West. pathotype CDL-6 and rated at post-heading stage. Intercrosses of these varieties, Anza/Yecora Rojo was not studied, permitted the following conclusions about the genes expressed in adult plants: Anza, one recessive gene; Glennson 81, two dominant genes; Ollanta, two genes, at least one is dominant; and Yecora Rojo; one dominant and one recessive gene, one of which is common with Ollanta. The resistance genes in these varieties, which expressed resistance in the seedling stage, were believed to be effective at the adult stage. Thus, seven resistance genes were identified in the four varieties. The genotypes were designated for the purposes of this study as follows: Anza, YrA YrH; Glennson 81, Yr9, YrJ, Ollanta YrL YrD; and Yecora Rojo, YrC YrD. It was recommended that these and other Yr genes be used as multiple gene complexes to increase durability of resistance to P. striiformis, an organism known to evolve virulence rapidly in field conditions. The demonstrated durability of Anza in California may be a result of its combination of resistance alleles at two loci.     

Genetics of resistance to five strains of turnip mosaic virus in Chinese cabbage

Summary Inheritance of resistance to turnip mosaic virus (TuMV) strains C1, C2, C3, C4, and C5 in Chinese cabbage (Brassica campestris subsp. pekinensis) was evaluated using monoclonal antibodies. Crosses were made between a resistant line, 0–2, and four susceptible line. Seoul (SE),SSD31 (SS), Cheongbang (CH), and Yaki 1 ho (YA), to determine the inheritance of resistance of 0–2 in different genetic backgrounds. Resistance to TuMV was controlled by a single dominant gene or double dominant genes depending on the strain and cross. The resistance genes of 0–2 were modified by susceptible parents such that a single dominant gene was involved in the SS×0–2 combination, but double dominant genes in the SE×0–2 against TuMV-C3 or TuMV-C5. ELISA tests using inoculated and noninoculated leaves in the same plant suggested that the dominant resistance genes inhibit virus movement rather than virus multiplication.     

Resistance to the glasshouse whitefly (Trialeurodes vaporariorum Westw.) in sweet pepper (Capsicum annuum L.)

Summary Fourteen cultivars, one F₁-hybrid and one half-wild type (Cind) of sweet pepper were tested on resistance to glasshouse whitefly. Several mutually significant levels of resistance were found. Most resistant appeared to be California Wonder, Severka M, Korál and Yolo Wonder. During the test sweet pepper plants were infested both with whiteflies and their parasite — Encarsia formosa, which caused the blackening of whitefly puparia. The blackened puparia are easily seen, enabling an easier and more rapid evaluation of the number of puparia present.     

A comparative study on anther development in male-fertile and male-sterile plants of Pelargonium crispumL'Her. ex Ait.

Summary Anther development of male-fertile and male-sterile plants in Pelargonium crispum was anatomically examined. Three cultivars, i.e., Lemon crispum, Crispum minor and Prince Rupert, were used. Lemon crispum and Crispum minor are male-fertile, whereas Prince Rupert is male-sterile. The tapetum in every cultivar examined behaved like an amoeba. The tapetal cells of the anther form plasmodial masses. Then, the plasmodial masses fuse producing a periplasmodium. The periplasmodium degenerates and finally disappears. There are no differences in tapetal behaviour between fertile and sterile anthers. In the sterile anthers the endothecium and lip cells do not develop sufficiently. Young microspores show normal growth at early stages. After the completion of their cell wall formation, however, the microspores in the sterile anthers lose their cytoplasm and become empty. On the other hand, the microspores in the fertile anthers increase the volume of their cytoplasm and become fertile pollen grains.     

On the chimeral nature of the Shamouti orange

Summary Evidence that Shamouti orange is a periclinal chimera has been obtained as all nucellar seedlings from two Shamouti trees, yielded only Beledi type fruit. All nucellars from another Shamouti tree bore only Shamouti type fruit, thus indicating a homohistont condition in another tree source.     

Inheritance of resistance to powdery mildew (Erysiphe graminis f. sp. hordei) in eleven primitive barley varieties

The inheritance of the powdery mildew resistance of eleven primitive barley varieties was investigated. crosses with varieties with identified resistance genes revealed that at least three different genes are present in a group of six genotypes from Greece (Hor736, Hor847, Hor878, Hor1159, Hor1379 and Hor1873) and one from Turkey (Hor1188). One dominant gene is common to these seve genotypes and in the Greek accessions a second gene is present. The expression of this second gene was respectively dominant in the crosses with Hor736 and Hor1159, recessive in the crosses with Hor878 and Hor1873, and depended on the employed powdery mildew isolate in the crosses with Hor847 and Hor1379. The detected genes differ from the resistance genes of the crossing partners, viz. Ml-al2, Ml-(Ab), Ml-(CP) and Ml-(1402). The accessions from China (Hor824 and Hor4021) each possess two resistance genes which differ from Ml-a12, Ml-(La) and Ml-(CP). The major gene is common to both accessions and is either identical, allelic or closely linked to a gene in the variety Nigrate. The Columbian accession Hor1894 possesses one resistance gene linked to a resistance gene in Nigrate but this gene differs from the Ml-a locus. The variety Palestine (Hor3997) possesses two resistance genes of which one is allelic or closely linked to Ml-(at).     

Pollen and pollination experiments. VII. The effect of pollen treatment and application method on incompatibility and incongruity in Lilium

Summary Four methods were investigated for their capacity to overcome incompatibility and incongruity in Lilium longiflorum and the Lilium hybrid Enchantment. Temperature treatments of pollen at 40° to 60°C for one hour had no effect on germination capacity. None of the temperature treatments influenced incompatibility or incongruity. Application of cut-style pollination had a positive effect on self-pollination of Enchantment, but did not overcome self-incompatibility in L. longiflorum. With the aid of genetically inactivated (by irradiation) compatible mentor or pioneer pollen self-incompatibility of L. longiflorum could be largely overcome. Both methods also gave promising results in realizing interspecific crosses.     

Influence of race and post infection temperature on two components of partial resistance to wheat leaf rust in seedlings of wheat

Summary Components of partial resistance, infection frequency and latency period, were determined in 71 winter and spring wheat genotypes in the seedling stage, after infection with three races of leaf rust (Felix 3B, Clement B and Betuwe 85C) at three different day/night temperature regimes (24/18°C, 18/12°C and 12/6°C). The genotypes were split into two groups and two separate experiments were carried out. Five genotypes, SVP 84039, Akabozu, Banco, BH 1146 and Orso, conferred a low infection frequency and a long latency period and Westphal 12A a long latency period, indicating a relatively high level of partial resistance. The correlation coefficient between infection frequency and latency period was low. Race-specificity was not found. There was a significant temperature effect on the latency period. In the second experiment the temperature x genotype interaction was significant. Temperature-response functions of transformed data demonstrated that the latency periods of four relatively resistant genotypes, Westphal 12A, Banco, BH 1146 and Orso and of Sarno and Mirela were most sensitive to temperature. The range between the genotypes with the longest and the shortest latency period was highest at 12°C. Therefore, low temperature regimes are preferred to distinguish differences in level of partial resistance.     

Accumulating polygenes for partial resistance in barley to barley leaf rust,Puccinia hordei. II. Field evaluation

Summary Eight lines from the cross between Vada and Cebada Capa with long to very long latent periods and four barley cultivars representing the known range of partial resistance to barley leaf rust, caused by Puccinia hordei, were evaluated in the field for partial resistance and in the greenhouse for the latent period (LP) in the young flag leaf.Each of the 12 entries was sown (15-4-1983) on a plot of 1.0 m². There were four replicates. To reduce interplot interference the plots were separated from each other by 4.0 m of spring rye. The number of urediosori per tiller was evaluated at 27-6, 4-7, 12-7 and ten days after heading. The LP was measured on 10 to 15 plants per entry in 1982 and on 10 plants in 1983.The levels of partial resistance varied greatly. The difference in number of sori per tiller between the most susceptible cultivar, Akka, and the most resistant cultivar, Vada, was about 50 times. Between Akka and the most resistant line this was approximately 5000 times. The LP's varied similarly. Vada had a LP 64% longer than that of Akka, the LP of line 26-6-11 was 15% longer. The range of partial resistance has been extended more than twofold.The correlation coefficients between LP and the level of barley leaf rust, expressed in transformed scale units, varied from -0.99 for the first sampling date to -0.97 for the third sampling date. Sampling the same development stage, ten days after heading, did not improve the r-value (r=–0.98). The LP evaluated in the young flag leaf is shown to be a very reliable criterion for partial resistance in the barley-Puccinia hordei pathosystem.Earliness tends to be associated with susceptibility. The correlation of days to heading with LP was 0.63, and with the level of barley leaf rust in the field 0.64.     

Chromosome location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L.) 1. Mlk and other alleles at the Pm3 locus

Summary Several wheat cultivars/lines were inoculated with isolates of Erysiphe graminis tritici to identify new genes/alleles for resistance. The wheats were tested with 13 isolates that had been characterized from responses on differential lines with known resistance genes. Gene Mlk which occurs in cultivars Kolibri, Syros, Ralle and several other European common wheats was found to be an allele at the Pm3 locus and is now designated Pm3d. The mildew resistance in an old Australian wheat, W150, is conferred by a single gene also allelic to Pm3 and now designated Pm3e. The near-isogenic line Michigan Amber/8^*Cc possesses another allele now designated Pm3f. A Syrian land variety of common wheat shows mildew resistance that is conditioned by the combination of genes Pm1 and Pm3a. Finally, two accessions of Triticum aestivum ssp. sphaerococcum appeared to possess the Pm3c allele.     

Genetic nature of low capsaicin content in the variant strains induced by grafting in Capsicum annuum L.

Summary The genetic nature of low capsaicin content in variant strains induced by grafting was elucidated by crossing the G₅S₂₃ strain with the two cultivars, Yatsubusa (Capsicum annuum L. var. fasciculatum Ilish) and Spanish Paprika (C. annuum L. grossum Sendt) originally used for grafting. Decreased capsaicin synthesis was a stable characteristic for at least several generations from G₅S₁₆ to G₅S₂₃ and was transmitted to the progenies of crosses. This fact shows that the decreased capsaicin synthesis is a genetic trait in the graft-induced variant strains. The genetically dependent characteristic of pungency of the G₅S₂₃, Yatsubusa and Spanish Paprika were analysed by High Perfomance Liquid Chromatography measurement and tasting assay.Cross experiment between the G₅S₂₃ strain, hot parent Yatsubusa and sweet parent Spanish Paprika showed that pungent and sweet for pungency chracteristics are generally controlled by at least two pairs of genes. Although segregation of capsaicin content and pungency was clearly demonstrated in F₂ progenies from reciprocal crosses between the G₅S₂₃ strain and Spanish Paprika, F₂ progenies from reciprocal crosses between G₅S₂₃ and Yatsubusa were all hot and did not develop low capsaicin plants.     

Effect of the black sigatoka resistance locus bs 1 and ploidy level on fruit and bunch traits of plantain-banana hybrids.

Summary Plantain (Musa spp., AAB group) cultivation is threatened by black sigatoka, an airborne fungal (Mycosphaerella fijiensis Morelet) leaf spot disease. Several traits in plantains and bananas are mainly affected by major genes. The host resistance response to black sigatoka is under the control of at least three different genes, one major recessive gene bs ₁ and two other independent additive alleles. Diploid and tetraploid plantain hybrids were evaluated for bunch weight, fruit weight, fruit length and fruit circumference. The F₁ euploid hybrids were derived from interspecific crosses between the resistant diploid wild banana Calcutta 4 and the susceptible triploid plantain cultivars Obino l'Ewai and Bobby Tannap. Linear and multiple regression models, coefficients of determination, and Durbin-Watson statistics were used to determine the single and combined effects of the major locus for black sigatoka resistance and ploidy on the different traits in the progenies. Differences in yield were mainly due to changes in weight and girth of fruit, which are affected by black sigatoka disease. The combined effect of ploidy and resistance to black sigatoka was partially responsible for the quantitative trait variation in yield. As a result of the gene interaction in the black sigatoka resistance locus bs ₁, the partially resistant and less susceptible phenotypes showed higher yield than their more susceptible full sibs.     

Embryo development in two barley genotypes after self pollination and pollination with Hordeum bulbosum L.

Summary Embryo development in vivo was compared in the two barley genotypes VK 16032 and Vogelsanger Gold after self pollination and after pollination with H. bulbosum. Embryo growth in VK 16032 after crossing with H. bulbosum showed a similar growth pattern to that of the self pollinated embryos, although the size increase was smaller. The hybrid embryos continued to grow until day 18 after pollination. The embryos from the cross between Vogelsanger Gold and H. bulbosum ceased to grow 8 days after pollination. Arrested embryo growth with subsequent abortion in Vogelsanger Gold was associated with a very early depletion and break down of the endosperm. Use of barley genotypes less sensitive to the genomic disturbances after crossing with H. bulbosum in combination with genotypes like Vogelsanger Gold is recommended in haploid breeding work.     

Chromosome locations of genes controlling ‘purple leaf base’ in rye and wheat

Summary Purple leaf base is expressed only if there is anthocyanin pigmentation in coleoptiles either in rye or in rye-wheat-additions. Genes controlling purple leaf base were found to be located on chromosomes 5R (An5), 4B (Ra2) and 6B (Ra3) using the trisomic set of rye cv. Esto and autoplasmic rye-wheat-additions, respectively.     

Lilium x ‘Black Beauty’—a potential bridging hybrid in Lilium

Summary Lilium Black Beauty, a rare intersectional hybrid previously reported sterile, was re-examined for pollen and ovule fertility. No pollen tubes were detected following incubation of styles pollinated with Black Beauty pollen. However, embryos varying in size from small globular to long boat-shaped and only rarely associated with endosperm, were found in 0.1–1.0% of the ovules in Black Beauty pistils pollinated with Oriental or Aurelian division lilies. Aseptic extraction and culture of these embryos on a nutritive medium resulted in growth, germination, and plantlets. It is apparent that with embryo culture, Black Beauty has unique value as a species bridge in that it accepts pollen of both Oriental and Aurelian lilies, two of the major commercial lily divisions.Scientific Journal Series Paper Number 9197 of the Minnesota Agricultural Experimental Station.     

Inheritance of resistance to Russian wheat aphid in barley

Summary The inheritance of resistance to Russian wheat aphid Diuraphis noxia (Mordvilko), in two resistant barleys, Hordeum vulgare L., ASE/2CM//B76BB and Gloria/Come, was studied in the field and in the greenhouse. The resistant genotypes were crossed with susceptible genotypes Esperanza and Shyri. Resistance reactions of F1, BC1, and F2 plants, and individual F2 plant derived F3 families indicated that resistance in each genotype was controlled by the same single dominant gene.