Potential of Nicotiana glauca (Grah.) as a source of resistance to black root rot Thielaviopsis basicola (Berk. and Broome) Ferr. in tobacco improvement

Nicotiana glauca, a wild relative of Nicotiana tabacum, is an attractive potential source of black root rot (Thielaviopsis basicola)‐resistant germplasm. Moreover, it shows a resistance or tolerance to PVY, TEV, anthracnose and powdery mildew. In this study its potential as a source of resistance to black root rot caused by Th. basicola was investigated. Nicotiana glauca GG (2n = 2x = 24) was crossed as male with two N. tabacum TT (2n = 4x = 48) flue‐cured cultivars: ‘BY103’ and ‘K 326’, both of which are susceptible to black root rot. Amphihaploid F₁ TG (2n = 3x = 36), amphidiploid TTGG (2n = 6x = 72) and sesquidiploid TTG (2n = 5x = 60) hybrids were obtained. The resultant sesquidiploid hybrids were used as maternal components in backcrossing to N. tabacum and a segregating post‐sesquidiploid TTg (2n = 5x = 52–54) offspring was obtained. Amphihaploids exhibited a level of resistance to black root rot characteristic of N. glauca. The expression of resistance varied in the sesquidiploid generation, possibly reflecting cytological instabilities in that progeny. A wide variation in response to black root rot was found for post‐sesquidiploids a clear reflection of extensive chromosome segregation in that hybrid generation.     

Nitrogen Accumulation and Translocation for Winter Wheat under Different Irrigation Regimes

The translocation of pre‐anthesis nitrogen to the grain is an important source for winter wheat. The relation between the nitrogen translocation and irrigation regime was studied in the field under a rain‐proof trough shelter. Nitrogen (N) translocation amount, N translocation efficiency decreased with a decline in irrigation amount or by excessive irrigation. Compared with different organs, the leaf and stem had higher N translocation amounts, and contributions to grain for both cultivars – Jinan 17 and Lumai 21, indicating that stem also is a major N source for grain development. The contribution of pre‐anthesis total above ground N to grain N ranged from 57 to 76 %, indicating the importance of pre‐anthesis storage of N for achieving high grain N concentrations. Grain nitrogen and yield (kg ha^?1) were positively and significantly correlated with the N translocation amounts and contributions, respectively, suggesting that the sink strength may be involved in the translocation of N from a vegetative organ to the grain. N harvest index (NHI) was significantly correlated with N translocation efficiency, suggesting that the latter is a prerequisite for increasing grain N and improving grain quality. The experiment showed that N translocation status is enhanced by better irrigation practices, but limited by severely deficient or excessive irrigation.     

Geographical distribution of allozyme patterns in shallot (Allium cepa var. ascalonicum Backer) and wakegi onion (A. × wakegi Araki)

Summary Shallot and wakegi were collected in the main islands of Indonesia, and in Japan, Korea, Taiwan, Malaysia, Thailand and Bangladesh. Five isozyme resolutions, phosphoglucomutase (PGM), glutamate oxaloacetate (GOT), glutamate dehydrogenase (GDH), esterase (EST) and peroxidase (POX) were employed for demonstrating inter-and intraspecific differences. A dendrogram separated 189 collected accessions into 25 types of wakegi onion and 18 types of shallot. All accessions of Japan, Korea and Taiwan were determined to be wakegi onion, whereas those of Bangladesh, Malaysia and Thailand were shallot. Twenty-six out of 165 Indonesian accessions indicated wakegi onion distribution in Sumatra, West Java province and in Sulawesi Island. This confirmed that there is mixed-cultivation of the two Allium species with no distinction made between them. Japan and Indonesia had respectively 12 and eight unique types of wakegi onion, while Korea had only one type. West Java showed the most various type of wakegi onion, whereas East Java had many types of shallot. Shallots collected from Bangladesh were distinetly different from those of South East Asian types.     

Isolation of wheat mutants with increased resistance to powdery mildew from small induced variant populations

Small variant wheat populations created by induced mutagenesis (n = 69) or adventitious regeneration (n = 66) were intensively screened for an altered response (compared to the parent variety ‘Guardian’) to the causal pathogen of powdery mildew in wheat, Blumeria graminis f. sp. tritici. Intensive field screening following natural infection of replicated plots of wheat lines over two years revealed a total of 13 mutants exhibiting significantly greater resistance than ‘Guardian’: eight from induced mutagenesis (11.6%) of the M2 population and five from adventitious regeneration (7.6%). Complete resistance was identified in two lines, (one (M66) developed following induced mutagenesis, and the other (SC240) by adventitious regeneration). The complete resistance in the induced mutant was stable over two generations and was associated with a high frequency of leaf flecking, and consequently a low grain yield. Resistance in SC240 proved to be unstable; SC240 exhibited complete resistance to powdery mildew in the SC₂ and SC₃ generations, but only 20% of the SC₄ plants were completely resistant, while the remainder were indistinguishable in mildew response to ‘Guardian’. The mildew response of all the SC₅ generation of SC240 was not significantly different from ‘Guardian’. Yield analysis of the thirteen mutants with increased resistance in the presence of powdery mildew indicated that eleven exhibitedgrain yields at least as high as that of ‘Guardian’, while the mutant M19 exhibited a yield significantly higher than that of ‘Guardian’. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genotypic variability in vegetable amaranth (Amaranthus tricolor L for foliage yield and its contributing traits over successive cuttings and years

Summary Twenty nine strains of vegetable amaranth (Amaranthus tricolor were grown for two successive seasons to study different selection parameters for foliage yield and its nine contributing morphological and quality traits. The strains AV-38 (5.06 kg/plot) and AV-31 (5.04 kg/plot) recorded highest foliage yield, followed by AV-30 (4.78 kg/plot) and AV-23 (4.70 kg/plot). The protein and carotenoid content averaged 1.24 ± 0.03 mg/100 mg and 0.83 ± 0.02 mg/g respectively. The leaves of A. tricolor also have considerable quantities of ascorbic acid (112.33 ± 5.00 mg/100 g) and fibre (8.39 ± 0.10%). The mean of individual cuttings for plant height, leaf size, stem diameter, foliage yield, protein, ascorbic acid and fibre content increased with successive cuttings till third cutting and thereafter showed a decline. Genotypic coefficient of variation (GCV) values ranged from 6.80 to 28.25%. However, the fibre content, branches/plant, leaves/plant, plant height and stem diameter showed lowest values of GCV. The values of heritability estimates were high for all the traits in all the cuttings as well as on pooled basis and ranged from 0.89 for branches/plant to 0.98 for foliage yield. Highest expected genetic advance was noticed for ascorbic acid (57.48%), followed by foliage yield (48.30%) and leaf size (29.51%).     

Genetic Analysis of Some Chemotypes in Ocimum basilicum var. glabratum

Screening of a population of Ocimum basilicum var. glabratum Benth., raised from seeds collected from France, West Africa and Kerala (India) was carried out for chemical composition of its essential oils. In all three collections, plants were found to be comprised of 3 chemotypes which were morphologically indistinguishable, but each chemotype was found to be capable of intercrossing freely with the other two. Selfing was carried out during 4 consecutive generations, after which three pure lines were established. Study of the selfed progeny of each collection exhibited an interesting segregation in S₂ and S₃ generations. Along with segregation in F₂ and F₃ generations of various hybrids the results can be explained by assuming a gene ‘M’ existing in 3 (or more) allelic forms: The allele M₀ for biosynthesis of estragole (methyl chavicol) is dominant to allelcs M₁ , for eugenol and M₂ for camphor. Also, allele M₁ is dominant to allele M₂ . The assumption was further confirmed by testcrosses of F₁ hybrids of each cross with their recessive parent.     

Potential for Selection in the Progeny of an Interspecific Hybrid in Foxtail Millet

Genetic variation for morphology and grain yield components was studied in the F₂ and 14 F₃ families of an interspecific cross of Setaria italica (foxtail millet) with S. viridis s. s. (green foxtail). It appeared possible to recover the cultivated type using a simple selection procedure in F₂ and F₃. Comparison with a cross involving S. viridis var. major (giant green foxtail) is discussed.     

Correlation of isoenzyme polymorphism and Bayoud-disease resistance in date palm cultivars and progeny

Summary Seedlings of date palm (Phoenix dactylifera L.), obtained from seven cultivars crossed with two males, were analyzed by polyacrylamide gel electrophoresis for esterase (EST), glutamate oxaloacetate transaminase (GOT), endopeptidase (ENP) and alcohol dehydrogenase (ADH) polymorphisms. Eleven, eight, five and two phenotypes were revealed for the enzymes tested, respectively. Seedlings of F₁ populations derived from Bayoud (Fusarium)-resistant and low fruit quality cultivars were characterized by a high electrophoretic polymorphism, when compared with progenies of Bayoud-susceptible and high fruit quality cultivars. In almost all cases, the most frequent electrophoretic phenotypes scored for each enzyme in different F₁ populations, were similar to those of the corresponding parent cultivars. Heterozygous phenotypes have been found for, at least, 3 loci; Got-2, Est-1 and Enp, indicating that such loci could be used to screen for hybrid seedlings. The expected Mendelian segregation of allozymes has been observed for these 3 loci, in many F₁ populations. It seems that progenies of Bayoud-resistant cultivars are characterized by a high level of electrophoretic polymorphism. The estimation of this index and the search for genetic linkage with segregating allozymes, may be biochemical criteria useful as an aid in distinguishing date palm seedling populations derived from Bayoud-resistant cultivars and suitable for breeding programs.     

Intersubgeneric Crossability in the Genus Glycine Willd.

In intersubgeneric crosses between wild perennial Glycine species of submenus Glycine and soybeans, Glycine max (L.) Merr., of subgenus Soja, all the putative hybrid pods aborted from 9 to 30 days after pollination (DAP). Spraying of 70 ppm gibberellic acid on hybridized gynoecia facilitated pod retention. Fluorescence microscopy revealed normal pollen germination and pollen tube growth in all the intersubgeneric crosses except in the G. cyrtoloba × G. max cross.     

Combining ability between lines of Cucumis sativus L. and Cucumis sativus var. hardwickii (R.) Alef

Summary Three Cucumis sativus L. (CS) lines adapted to USA growing conditions were used as female parents in crosses to one line each of seven Cucumis sativus var. hardwickii (R.) Alef. (CH) accessions used as male parents to determine the relative combining ability of the CH accessions for six horticultural characters. The 21 F₁ progenies were grown in a randomized complete block design in two locations and evaluated for fruit number, lateral branch number, fruit length, fruit length/diameter ratio, number of female flowering nodes, and days to anthesis. General combining ability (GCA) was significant for all characters in each location. Specific combining ability (SCA) was significant for all characters except days to anthesis in one location and lateral branch number in both locations. Significant location × combining ability interactions were also evident for several characters. Results suggest that CH may be useful for improving fruit yield in commercial cucumber, but that limitations may lie in the attainment of acceptable fruit.Research supported by the College of Agric. and Life Sci., Univ. of Wisconsin, Madison; USDA, ARS, and by funds from Pickle Packers Intl., Inc. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee of warranty of the product by the USDA and does not imply its improval to the exclusion of the other products or vendors that may also be suitable.