Characterization of graft-induced change in capsaicin content of Capsicum annuum L.

Summary Capsaicin contents were measured in the progenies from the test crosses between the strain, G₅S₁₇ derived from fruit with the graft-induced change in fruit shape and the original two cultivars, Yatsubusa (Capsicum annuum L. var fasciculatum Ilish) and Spanish Paprika (C. annuum L. var. grossum Sendt) used for grafting.The strain, G₅S₁₇ contained a lower amount of capsaicin than the original pungent cultivar Yatsubusa used as scion. The characteristic of the lowered capsaicin content in the strain has been stably inherited through seed propagation, and has also been transmitted to the progenies from the crosses with the original two cultivars used for scion or stock. These features in the capsaicin content agreed with those in fruit shape in the graft-induced change.     

Some notes on the association between fruit dimensions and fruit weight in Capsicum annuum L.

Summary Previous reports on the inheritance of fruit dimensions in Capsicum suggested two contradictory views: independent inheritance of individual dimensions vs inheritance of a shape index, i.e., length/width ratio.The F₂ of a cross between parent lines that differed in fruit size and weight but had similar shape indices exhibited intermediate dominance in fruit weight and in fruit width for small size. The correlation between fruit shape (as measured by the length to width ratio) and fruit weight in the F₂ was small and not significantly different from zero. The two variables, fruit width and fruit length, accounted for 90% of the variation in fruit weight. Apparently one can select for fruit weight in the F₂ independently of fruit shape.     

Inheritance studies with nine characters in Capsicum annuum L.

Summary Information obtained from breeding work with relatively small F₂ populations suggests independent segregation in 12 pairs of characters. Anthocyanin pigmentation in the cotyledon is either recessive or dominant, showing either single gene or polygenic inheritance, depending on parental genotypes. When single gene inheritance was observed, pigmentation was independent of resistance to potato virus-y, of the male sterile-1 (ms1) gene and of male sterile-2 (ms2) gene. However, additional observation suggests that one of the genes involved in pigmentation is linked with the male sterile-1 gene.     

Effect of donor plant age and inflorescence age on microspore culture of Brassica napus L.

Summary Effect of age of donor plants and age of inflorescence on embryogenesis in microspore culture of B. napus was examined. Microspores isolated from buds of older plants had a higher embryo yield than those of younger ones. The effect of the age of inflorescence showed a different pattern. In older plants, a higher embryogenesis response was observed in microspores isolated from buds of new inflorescences, while in young plants, microspores isolated from buds of old inflorescences showed high embryo yield. These different responses were considered to be attributable to a difference in the developmental stage of pollen at the time of microspore isolation. Our results indicated that microspores collected from older inflorescences and older plants have sufficient embryogenic potential when the optimum developmental stage of pollen was used. Frequency of embryo to plant conversion was influenced by the size of embryos subcultured, but not by donor plant age or the age of the inflorescence.     

Genetic nature of bushy plant type in the variant strain induced by grafting in Capsicum annuum L.

Summary To elucidate the genetic nature of bushy plant type in the variant strains derived from grafting, testcrosses were made on the one hand between one of the variant strains, G₅S₁₇, and both Yatsubusa and Spanish Paprika, and on the other hand between the two cultivars.The bushy strain has more nodes and branches on the main stem than the two cultivars.This bushy plant character was recessive to cv. Yatsubusa used as a scion and over-recessive to cv. Spanish Paprika used as a root stock.Such graft-induced change from recessive to over-recessive as bushy plant type was quite different from other varied characters such as, fruit shape, capsaicin content and guard cell size, which were generally intermediate between the two cultivars.     

Natural male sterile mutant in hot chilli (Capsicum annuum L.)

Summary A natural male sterile mutant was recovered from the normal population of chilli cv. CA 452-1. The male sterility in the mutant was governed by a single recessive gene ms. The excessive vegetative growth provided easy identification of male sterile plants in the seedling stage. The plant was found to be promising for hybrid seed production.     

Digenic nature of male sterility in pepper (Capsicum annuum L.)

Summary A cross was made between two nearly isogenic lines differing for male sterility genes, viz. ms₁ms₁Ms₂Ms₂ s Ms₁Ms₁Ms₂ms₂. F₁ plants yielded F₂ populations which segregated either in 3:1 or 9:7 ratios of fertile vs male sterile individuals. Test crosses between male sterile and male fertile sibs in the 9:7 segregating populations provided a few lines in which most of the progenies were male sterile. A 3:1 ratio model of male steriles vs fertiles is suggested and the value of the system is discussed.Contribution A.R.O. Agricultural Research Organization, The Volcani Center, Bet Dagan 50 250, Israel No. 3703-E, 1992 series.     

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.     

Somaclonal variation of regenerated plants in chili pepper (Capsicum annuum L.)

The morphological and genetic variations in somaclones of chili pepper (Capsicumannuum L.) derived from tissue culture were evaluated. Cotyledonary node explants of cultivars, Shishitou and Takanotsume, were cultured on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA)5 mg/l for shoots regeneration and regenerated shoots were rooted on MS medium supplemented with naphthalene acetic acid(NAA) 0.1 mg/l and indol-3-butyric acid(IBA) 0.05 mg/l. The regenerated plants(R₀) were selfed to obtain seeds for next generation (R₁ lines). Qualitative characters were studied in R₀generation and both qualitative and quantitative characters were studied in R₁ generation. In R₀ generation, variations were noticed in plant growth habit, stem color, flower color and color of unripe fruits, and expression of anthocyanin in unripe fruits. Comparison among the R₁ lines and their parents were made for morphological and agronomic characters. Significant variation among R₁ lines and differences between R₁ lines and their parents were observed. Genetic variations among three somaclones were revealed by random amplified polymorphic DNA (RAPD) analysis. Variation, such as early flowering and increase of yield components, is an indication of the response to selection for any specific character. Occurrence of productive variants among somaclones of established cultivars, like Shishitou and Takanotsume, indicates the possibility of their improvement through somaclonal variation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance and transfer of multiple-flower character from Capsicum chinense into Capsicum annuum

Summary Capsicum annuum L. produces a single flower and thus a single fruit per branching node. In contrast, Capsicum chinense Jacq. yields two or more flowers per node. If genes for multiple-flowers per node could be transferred from C. chinese to C. annuum, it might be possible to breed C. annuum varieties with a more concentrated fruit set and potentially higher yield. Using progeny from an interspecific cross between C. annuum cv. NM 6-4 and C. chinense CA4, it has been determined that a minimum of five independently segregating chromosomal regions control the difference in flowering behavior between these two accessions. One of the segments is located on a translocated chromosome. Epistatic interactions among independent chromosomal regions appear to play a major role in the determination of this trait.Although it is unlikely that the multiple-flower character can be transferred to C. annuum in its full intensity while maintaining a horticulturally-acceptable phenotype, it may be possible to breed varieties which produce an average of more than 1.5 flowers per node, a value 50% higher than existing C. annuum varieties.     

Inheritance of resistance to potato virus Y in garden pepper (Capsicum annuum L.)

Summary Bell pepper suffers considerable losses from a strain of potato virus Y (PVY^o-sbp). Crosses were attempted between two resistant lines Perennial and S41-1 and two highly susceptible bell pepper commercial cultivars California Wonder and Yolo Wonder. Studies of F₁'s, F₂'s, back crosses and F₃'s indicated that Perennial and S41-1 carry a recessive gene imparting resistance to potato virus Y.     

Nuclear RFLP between pepper cultivars (Capsicum annuum L.)

Summary Forty one nuclear probes, distributed across the different linkage groups of the previously published map, were used to examine restrition fragment length polymorphism between cultivated peppers. Total DNA from thirteen accessions of Capsicum annuum var. annuum and one accession of C. baccatum var. pendulum was separately cut with ten restriction enzymes. The analyses were restricted to only one enzyme per probe to reduce the polymorphism redundancy. Nei & Li's genetic distances between accessions were calculated from the 141 resultant nuclear DNA restriction fragments. The genetic variation was larger between C. annuum and C. baccatum than between C. annuum cultivars. Large fruited related accessions closely clustered together. Distances between the small fruited cultivars were larger than within the bell pepper group. A correspondence analysis performed on differences between the global RFLP patterns of each accessions of C. annuum revealed the particular genomic structure of four small fruited cultivars: Criollo de Morelos 334, H3, Perennial and Doux Long des Landes. The percentage of probes revealing at least one RFLP with at least one enzyme ranged from zero to fifty percent for all the pairwise comparisons of C. annuum accessions. 82 presumptive loci were detected with a mean number of 1.46 alleles per locus within C. annuum and 1.83 within all the accessions. This result indicates that molecular markers will be more usable in intraspecific study of C. annuum than isozyme markers.     

Graft-induced change in fruit shape in Capsicum annuum L. I. genetic analysis by crossing

Summary Characteristics of fruit shape in the progeny from a graft-induced change were analysed. Non-pointed, typically inverted-blunt (two-lobed) fruit apex was observed in chimeric state within a scion of Yatsubusa grafted onto Spanish Paprika (inverted-blunt, three-or four-lobed fruit). This frequency of change in fruit shape was unstable in an early generation on the graft.     

Evidence for salt tolerance in pepper varieties (Capsicum annuum L.) in Tunisia

Summary Salt tolerance in pepper (Capsicum annuum L.) is described in terms of yield, mortality and root weight. Significant differences in absolute and in relative salt tolerance were demonstrated between Tunisian varieties. Relative salt tolerance of Beldi was found to be due to its root system which remained unreduced under stress condition; local adaptation could be involved. D'hirat showed interesting levels of absolute salt tolerance and low mortality. An EC_w-value \s-> 7.63 dS/m was critical for almost all characters observed, with reductions of approximately 50%. Fruit weight and shoot-root ratio were not significantly affected by high salt concentrations of the irrigation water.     

Genetic analysis of broad spectrum resistance to potyviruses using doubled haploid lines of pepper (Capsicum annuum L.)

Summary Genetic analysis of resistance to PVY in androgenetic doubled haploid lines, F1, F2 and backcross progenies of the Mexican pepper line, CM 334 (Capsicum annuum L.), was performed. Three reaction types were observed when seedlings were inoculated with several PVY strains of different pathotypes and with an American PeMV strain. Resistant genotypes never showed systemic symptoms although some individuals sporadically developed necrotic local lesions on inoculated cotyledons. Susceptible genotypes exhibited either a typical systemic mosaic or a systemic necrosis that caused the death of the inoculated seedlings. Segregation analyses indicated that resistance to pepper potyviruses in CM 334 is conferred by two genes. The first one, tentatively named Pr4, is dominant and confers the resistance to all now known pathotypes of PVY and to PeMV. The second one, tentatively named pr5, is recessive; it confers only the resistance to common strains of PVY. The systemic necrotic response is conferred by an independent dominant gene, tentatively named Pn1.     

Segregation for prebifurcation shooting,stem length and leaf number of main stem in two crosses of Capsicum annuum L.

Summary Extensive prebifurcation shooting which terminates in fruits is present in certain cultivars (e.g. Santaka) of Capsicum annuum L. Plants with such architecture setting their fruits along the periphery may therefore be expected to be suitable for mechanical harvesting. From inheritance studies (parents. F₁ 's and two different F₂ populations) it was found that prebifurcation shooting, though a quantitative character, is controlled by relatively few genes. Few genes control main stem length and also leaf number of main stem. Correlations between the above three traits were not significant.     

Inheritance of resistance to fruit rot (Phytophthora capsici Leon.) and induction of resistance in bell pepper (Capsicum annuum L.)

Summary Fruit rot in bell pepper caused by Phytopthora capsici Leon. is a limiting factor in its commercial production. Crosses were made between Waxy Globe, a small fruited hot type, resistant to fruit rot and four highly susceptible bell pepper commercial cultivars (Chinese Giant, California Wonder, Osh, Kosh and Yolo Wonder). Studies of the F₁'s, F₂'s and backcrosses indicated that Waxy Globe carries a dominant gene imparting resistance to fruit rot. After three backcrosses with California Wonder, lines were obtained combining the resistance gene of Waxy Globe with the large fruit size and low capsaicin of California Wonder.     

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.     

Heritability and gain from selection for quantitative resistance to Xanthomonas campestris pv. vesicatoria in Capsicum annuum L.

Summary Breeding for disease resistance in peppers (Capsicum spp.) to the bacterial spot pathogen (Xanthomonas campestris pv. vesicatoria (Doidge) Dye) has been based on either qualitative or quantitative evaluation methods. Quantitative evaluation of components of resistance, lesion number and lesion diameter, has been useful for determining quantitative resistance, but few breeders have applied these methods in routine selection programs. This study was aimed at determining the heritability and gain from selection for resistance to the bacterial spot pathogen based on three components of resistance. Random selections from a diverse intermated population of Capsicum annuum L. were self-pollinated for two generations to create S₁ and S₂ families. Thirty S₁ families, corresponding S₂ families and four homozygous check lines were evaluated. At forty-two days after seeding, two different leaves of each plant were inoculated by leaf infiltration with low concentrations (5×10³ colony forming units) of Group 2 (XCV PT, race 1) and 4 (XCV P, race 1) of the bacterium, respectively. After 15 days, lesion number cm^-2 and lesion diameter were measured. Total lesion area was calculated. Narrow-sense heritabilities for lesion number, lesion diameter, and total lesion area were 0, 43, and 31%, respectively, with Group 2, and 26, 43, and 33%, respectively, with Group 4. Actual S₂ gain from 20% selection pressure in the S₁ was approximately 50%, when selection towards resistance was based on total lesion area.     

Gene action in the resistance of peppers (Capsicum annuum) to Phytophthora stem blight (Phytophthora capsici L.)

Summary The variation among single and three-way crosses derived from seven lines of pepper (Capsicum annuum) selected for resistance to Phytophthora capsici was analyzed into statistical-genetic components due to general and specific combining abilities and additive-by-additive epistasis. Indirect evidence of higher order epistasis was also estimated. Epistasis was a principal source of variation. It was correlated with the level of aggressiveness of the pathogen. A breeding method such as recurrent selection seems to be the most appropriate to improve resistance to the fungus.