Fasciation in chickpea: genetics and evaluation

Summary A spontaneous fasciated mutant was detected in the chickpea cv. Amethyst. It was characterised by broad, strap-like stems, irregular leaf arrangement and clustering of pods towards the stem apices. F₂ and F₃ segregations showed that fasciation was controlled by a single, recessive gene for which the symbol fas is proposed. Field trials comparing the fasciated mutant with its non-fasciated isoline showed that fasciation was associated with lower yield, larger seeds, delayed flowering and increased lodging.     

Allelic relationship between spontaneous and induced mutant genes for stem fasciation in chickpea

Stem fasciation is a morphological abnormality observed in plants where the stem is widened and leaves and flowers or pods are clustered at the apex. Several spontaneous mutants and one induced mutant for stem fasciation are found in chickpea (Cicer arietinum L.). This study was aimed at determining allelic relationship between spontaneous and induced mutant genes controlling stem fasciation and effects of stem fasciation on grain yield. Two spontaneous (ICC 2042 and ICC 5645) and one induced (JGM 2) stem fasciation mutants were crossed in all combinations, excluding reciprocals. The F₁ and F₂ plants from a cross between the two spontaneous mutants had fasciated stem. This indicated the presence of a common gene (designated fas1) for stem fasciation in the two spontaneous mutants. The F₁s of the crosses of the induced mutant JGM 2 with both spontaneous mutants had normal plants and segregated in a ratio of 9 normal : 7 fasciated plants in F₂. Thus, the gene for stem fasciation in the induced mutant JGM 2 (designated fas2) is not allelic to the common gene for stem fasciation in spontaneous mutants. The two genes in dominant condition produced normal non‐fasciated stem. The fasciated and the non‐fasciated F₂ plants did not differ significantly for number of pods per plant, number of seeds per plant, grain yield per plant and seed size, suggesting that it is possible to exploit the fasciated trait in chickpea breeding without compromising on yield.     

Genetic analysis of male sterility in rice mutants with environmentally influenced levels of fertility

Summary Twenty-six male sterile plants grown in the field were recovered in the M7 generation from ethyl methane sulfonate-treated material of the rice cultivar M-201. Fertility increased five-fold when ratooned plants from the field were grown in a growth chamber with a 12 hour daylength. Crosses between mutant and normal fertile cultivars produced fertile F₁ plants. Female fertility was normal as judged by percent seed set from unbagged panicles of parental and recombinant lines. Transgressive segregation for fertility was observed for all crosses in the F₂ and F₃ generations. Five of 37 F₃ male sterile plants showed moderate levels of seed fertility under winter greenhouse conditions and reduced seed set when transplanted to summer field plots. Fertility data from reciprocal crosses suggested cytoplasmic factors had little or no effect on levels of male sterility in the mutant lines. Chi-squared analyses of F₂ and F₃ generation results indicated male sterility of the mutants is conditioned by two nuclear genes with epistatic effects.     

Identification of alleles at two loci controlling resistance to Phomopsis stem blight in narrow-leafed lupin (Lupinus angustifolius L.)

The genetics of resistance to Phomopsis stem blight caused by Diaporthe toxica Will., Highet, Gams & Sivasith. in narrow-leafed lupin (Lupinus angustifolius L.) was studied in crosses between resistant cv. Merrit, very resistant breeding line 75A:258 and susceptible cv. Unicrop. A non-destructive glasshouse infection test was developed to assess resistance in the F₁, F₂, selected F₂-derived F₃ (F_2:3) families, and in selfed parent plants. The F₁ of Unicrop × 75A:258 (and reciprocal cross) was very resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible), which suggested the presence of a single dominant allele for resistance in 75A:258. In Merrit × Unicrop (and reciprocal), the F₁ was moderately resistant, and the F₂ segregated in a ratio of 3:1 (resistant: susceptible). Thus Merrit appeared to carry an incompletely dominant resistance allele for resistance. The F₁ of Merrit × 75A:258 (and reciprocal) was very resistant and the F₂ segregated in a ratio of 15:1 (resistant: susceptible), which supported the existence of independently segregating resistance alleles for resistance in 75A:258 and Merrit. Alleles at loci for early flowering (Ku) and speckled seeds (for which we propose the symbol Spk) segregated normally and independently of the resistance alleles. Resistant F₂ plants gave rise to uniformly resistant or segregating F_2:3 families, whereas susceptible F₂ plants gave rise only to susceptible F_2:3 families. However, the variation in resistance in the F₂ and some F_2:3 families of crosses involving 75A:258, from moderately to extremely resistant, was greater than that expected by chance or environmental variation. We propose the symbols Phr1 to describe the dominant resistance allele in 75A:258, and Phr2 for the incompletely dominant resistance allele in Merrit. Phr1 appears to be epistatic to Phr2, and expression of Phr1 may be altered by independently segregating modifier allele(s). This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of resistance genes,heat tolerance genes and cytoplasms on expression of resistance to Pseudomonas solanacearum (E.F. Smith) in potato

Summary Effects of resistance genes and heat tolerance genes on expression of resistance to bacterial wilt caused by Pseudomonas solanacearum were investigated in 30 F₁ progenies from parents with different levels of bacterial wilt resistance and heat tolerance. A race 1 and a race 3 isolate of the bacterium were used for inoculation under screenhouse conditions at two locations. Results obtained indicated that with reduction in levels of parental resistance, resistance in the F₁ progenies was also reduced. Under hot conditions, a reduced heat tolerance in the genetic background also resulted in lower levels of resistance expression. The effect of heat tolerance tended to diminish at lower temperatures leaving the effect of resistance genes more consistent. There existed a strong interaction between resistance genes and genes for heat tolerance. The nature of resistance to bacterial wilt in potato and implications for breeding for resistance are discussed.Effects of reciprocal crosses on expression of resistance to a race 1 isolate under hot screenhouse conditions, were studied in 5 sets of reciprocal F₁ progenies involving different resistant and susceptible parents. The reciprocal differences observed were not significant suggesting absence of cytoplasmic effects on expression of resistance.     

A genetic study of growth characters and yield characters of oilseed rape

Summary Analysis of single plants in parental, F₁ and F₂ populations of three crosses of oilseed rape indicated cytoplasmic effects in F₁ or F₂ generations for most of the observed characters. There was evidence of dominance for early flowering and early maturity. Heterosis was exhibited for yield and yield components. The heritabilities for the characters under study were generally very low.     

Variation of harvest index in several wheat crosses

Summary Harvest index was studied in F₁ and F₂ generations of eight wheat (Triticum aestivum L.) crosses and their reciprocals. The parental varieties involved in the crosses represented a fairly wide range of character expression for plant height, tillering potential, grain yield per plant and harvest index. Differences between reciprocal crosses were not evident for the expression of harvest index of the crosses under study. Means and degrees of dominance of F₁ and F₂ populations suggested partial dominance of high harvest index over low harvest index. The pattern of variation among F₂ segregates was quantitative and the distribution was normal. The gene action governing the expression of harvest index was largely additive. Evidence was obtained for non-additive gene action in some crosses. There was complete absence of high parent heterosis for harvest index in the F₁'s but midparent heterosis was found to be present in all crosses. Estimates of heritability and genetic advance were moderate to high. Usefulness of selecting for harvest index as a measure of yield efficiency particularly in early generations is discussed.     

The inheritance of resistance to beet necrotic yellow vein virus (BNYVV) in B. vulgaris subsp. maritima, accession WB42: Statistical comparisons with Holly-1-4

In this study, the inheritance of resistance to Beet necrotic yellow vein virus (BNYVV) in accessions Holly-1-4and WB42 was investigated. Crosses between both resistant sources and susceptible parents were carried out and F₁F₂ and BC₁ populations were obtained. Virus concentrations in WB42and its F₁ populations were lower than in Holly-1-4. Observed ratios of susceptible and resistant plants in segregating populations of Holly-1-4 as well as WB42 were in agreement with hypothesis of one dominant major gene. Segregation of plants in F₂ populations obtained from crosses betweenHolly-1-4 and WB42 revealed that the resistance genes in Holly-1-4 and WB42 were nonallelic and linked loci. This revised version was published online in July 2006 with corrections to the Cover Date.     

The inheritance of nitrate content in lettuce (Lactuca sativa L.)

Summary The inheritance of nitrate content in lettuce was analysed using 16 F₂ populations and three F₃ populations. Frequency distributions of nitrate content in F₂ and F₃ populations were unimodal and symmetrical, indicating a quantitative inheritance. Both significant positive and negative deviations of the F₂ mean from the mid-parent value were found, indicating dominance or epistasis. Deviations towards low nitrate content were more frequent than deviations in the other direction. Estimates of heritabilities for nitrate content in the F₂ populations ranged from 18% to 69% and were in most cases above 50%. Crosses between low nitrate cultivars did not have lower estimates of heritability in the F₂ than crosses between cultivars with larger differences in nitrate content. In one case a genotype x experiment interaction for nitrate content of parental cultivars was found.Three F₃ populations of crosses between cultivars with low nitrate content were analysed. Estimates of heritabilities for F₃ line means ranged from 78% to 91% and estimates of the genetic standard deviation of nitrate content in unselected advanced generations ranged from 0.24–0.33 g kg^–1. The estimates of heritabilities and of genetic variation in advanced generations offer good prospects of selection of low nitrate genotypes in lettuce. A comparison of efficiency of selection in the F₂ generation and F₃ line selection is made.     

Evaluation of cytoplasmic effects on agronomic and seed quality traits in two doubled haploid populations of Brassica napus L.

Cytoplasmic effects have been occasionally implicated in the inheritance of several traits in oilseed rape (Brassica napus L.), including linolenic acid concentration (18:3) in the oil. It is important that these be considered when choosing the direction of cross for producing new breeding populations. To study this phenomenon, a reciprocal cross was made between two genotypes of oilseed rape, Reston and LL09, which differed for their erucic and linolenic acid concentrations in the seed oil. Two DH populations, which were produced by microspore culture from reciprocal F₁ plants, were evaluated in the growth room for one generation and in the field at two locations in Southern Ontario in 1993and 1994. Field notes were taken on days to flower, days to maturity,plant lodging, plant height and, seed quality traits. In the growth room study, the phenotypic distribution of 18:3 differed significantly between the two reciprocal DH populations. In the field, significant reciprocal differences between the population means were detected for 18:3,flowering date and protein content in both years and for days to maturity and oil content in 1993 only. To further study the parental lines,chloroplast (cp) and mitochondrial (mt) DNA from parental lines were isolated and subjected to RFLP and RAPD analysis. Several random primers revealed reproducible DNA polymorphism (RAPD) between the parental mt DNA. It is concluded that the direction of cross should be taken into consideration by oilseed rape breeders relying solely on doubled haploids for developing genotypes with modified seed quality traits in Brassica napus L. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Analysis of genic male sterility in Brassica oleracea

Summary The male sterility system MS-1 of Brassica oleracea was studied in order to elucidate if nucleo-cytoplasmic interactions determine this system. Crosses of male sterile MS-1 genotypes with heterozygous MS-5 genotypes gave fully fertile F₁ progenies. Selfing of seven F₁ plants resulted in five F₂ populations showing a 9:7 segregation ratio and two a 3:1 ratio for fertile and male sterile plants. Two F₂ progenies deviated from the expected 9:7 or 3:1 segregation ratios for fertile and male sterile plants. Thermosensitivity and distortion of the meiosis are suggested as the causal factors underlying the deviation of the segregation ratios. It was concluded that nuclear factors determine the male sterility in the MS-1 system, because the presence of a nucleocytoplasmic interaction in this system should have given only a 3:1 segregation ratio for fertile and male sterile plants in the F₂ generation.     

Resistance to the cabbage root fly, Delia radicum, within Brassica fruticulosa

Two transgenic Bt rice lines, KMD1 and KMD2, both containing a synthetic cry1Ab gene from Bt, were crossed with conventional rice varieties. The inheritance of resistance to SSB of KMD1 and KMD2was investigated through LSB and field examination of their progenies, e.g. F₁, BC₁ and F₂ populations. In LSBs, 100.0% of newly hatched SSB larvae died on the second day after feeding on leaf tissues of F₁ and GUS positive BC₁ plants, of which the area of leaf tissues consumed by SSB is also similar to that of transgenic parents. These results imply that the resistance of Bt rice to SSB is dominantly controlled and could be easily exploited in hybrid rice production. Field evaluation showed that segregation ratios for SSB resistance to susceptibility in BC₁ populations fit the ratio of 1:1, which was also confirmed by LSBs. However, in F₂ populations, the ratio was significantly smaller than 3:1 for resistant to susceptible plants in all 6 indica × japonica (KMD1 and KMD2) crosses, though it fitted 3:1 in all 4 japonica × japonica crosses. The results implied that the resistance of Bt rice to SSB was controlled by a dominant gene which was present in a homozygous condition in both KMD1 and KMD2, but the inheritance could be affected by other factors. Assays for Cry1Ab protein showed that, in most crosses, the content of Cry1Ab is significantly higher in leaves of GUS positive F₁, BC₁ and F₂ plants than that in transgenic Bt parent plants, which accounts for the high resistance observed in these plants to SSB. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tolerance to paraquat is correlated with the traits associated with water stress tolerance in segregating F2 populations of barley and wheat

To identify scorable marker traits that can be used in cereal breeding programs for selecting drought tolerant individuals, we investigated the correlation among the drought-associated traits in two F₂ populations derived from the crosses made between drought tolerant and sensitive barley and wheat parental genotypes. The parental genotypes of these crosses also differed by at least three other traits – paraquat tolerance, leaf size, and the relative water content. These three traits were scored in two F₂populations of 80 individuals for each barley and wheat cross. Analysis of results indicated that the enhanced tolerance to paraquat was correlated with reduced leaf size and increased relative water content, two traits associated with water stress phenotypes of the drought tolerant barley and wheat parents. Our results suggested that the selection based on paraquat tolerance istechnically less demanding and thus useful for rapid screening of individuals for enhanced drought tolerance in segregating populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Restoration of meiotic regularity and fertility among derivatives of Lens culinaris x L. Nigricans hybrids

Summary The wild lentil, L. nigricans is cross compatible with the cultivated species. Chromosome pairing in their F₁ hybrids is highly irregular due to a difference of three translocations between the parental species. However, the hybrids are partially fertile and in the F₂ populations there is a marked improvement in fertility. About 19% of the F₂ plants were meiotically stable, fully fertile and their chromosome arrangement was similar to that of the cultivated species. All these are clear indications for the possibility of rapid introgression between the two species and hence systematic screening of L. nigricans for traits of economic value is fully justifiable.     

Chromosome associations and crossability with Iris ensata Thunb. in induced amphidiploids of I. laevigata Fisch. × I. ensata

Summary The chromosome associations of amphidiploids of I. laevigata × I. ensata were analysed and compared with those of the parental species and F₁ hybrids of I. laevigata × I. ensata. The F₁ hybrids showed partial chromosome associations. Their mean chromosome association per cell was 20.73I+3.63II, although the mean chromosome association per cell in the parental species was 0.09I+15.96II for I. laevigata and 0.03I+11.98II for I. ensata, respecively. In contrast, the normal association (28II) was partially restored in the amphidiploids. Their mean chromosome association per cell was 1.93I+26.48II+0.28III+0.03IV+0.03V. In this study, moreover, the crossability between I. ensata (2X and 4X) and the amphidiploids and between I. laevigata and the amphiliploids was examined. No hybrid plants were obtained from both reciprocal crosses between I. ensata (2X) and the amphidiploids and between I. laevigata and the amphidiploids. Only the cross of I. ensata (4X) × the amphidiploids in the reciprocal crosses produced hybrid plants. The observation of their somatic chromosome numbers indicates that these are true hybrid plants between autotetraploid I. ensata and the amphidiploids, and such plants can be called autoallotetraploids between I. ensata and I. laevigata. The interspecific cross-breeding of I. ensata using the autoallotetraploids is discussed.     

Segregation distortion of Brassica carinata derived black rot resistance in Brassica oleracea

Three segregating F₂ populations were developed by self-pollinating 3 black rot resistant F₁ plants, derived from across between black rot resistant parent line 11B-1-12 and the susceptible cauliflower cultivar ‘Snow Ball’. Plants were wound inoculated using 4 isolates ofXanthomonas campestris pv. campestris (Xcc) race 4, and disease severity ratings of F₂ plants from the three populations were scored. A total of 860 arbitrary oligonucleotide primers were used to amplify DNA from black rot resistant and susceptible F₂ plants and bulks. Eight RAPD markers amplified fragments associated with completely disease free plants following black rot inoculation,which segregated in frequencies far lower than expected. Segregation of markers with black rot resistance indicates that a single, dominant major gene controls black rot resistance in these plants. Stability of this black rot resistance gene in populations derived from 11B-1-12 may complicate introgression into B. oleracea genotypes for hybrid production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dominance of bush growth habit in spaghetti squash (Cucurbita pepo)

Summary Bush and vine habit accessions and their reciprocal F₁s of spaghetti squash (Cucurbita pepo) were compared for various vegetative and reproductive characteristics. Bush habit was dominant to vine. Vine plants produced more leaves, longer internodes, and more male flowers than did bush and F₁ plants. Pistillate flowers developed at lower nodes in bush and F₁ plants than in vine plants. Vine plants produced as much or more vegetative matter than did bush and F₁ plants, but bush and F₁ plants produced more fruits and greater yields than did vine plants.     

Trisomic genetic analysis of aroma in three Japanese native rice varieties (Oryza sativa L.)

Information on the genetics of aroma in rice facilitates breeding and selection of new aromatic varieties with high yield and good quality. Objective of the present study was to make clear the number of genes controlling aroma, and the allelism of aroma genes and the location of aroma gene(s) on the chromosome in three Japanese native aromatic rice varieties (Kabashiko, Shiroikichi and Henroyori). Lack of leaf aroma in all F₁ plants of non-aromatic/aromatic crosses indicated the recessive nature of aroma, and the segregation ratios (3:1) of non-aromatic to aromatic plants in its F₂ populations from Nipponbare/aromatic varieties crosses revealed that each of the three aromatic varieties contains a single recessive gene for aroma. Through trisomic analysis, the segregation of non-aromatic and aromatic plants in all F₂ populations from the crosses between trisomics lines NT8, with an extra chromosome 8, and aromatic varieties deviated significantly from disomic segregation of 3:1 ratios, and fitted to trisomic segregation, however, in other F₂ populations derived from other 7 types of trisomic F₁ plants, the segregation ratios of non-aromatic to aromatic were 3:1, indicating that the single recessive aroma gene was located on chromosome 8 in three aromatic varieties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chloroplast-DNA variation in the wild and cultivated olives (Olea europaea L.) of Morocco

The male sterile plants that segregated in a BC₅F₂ of `C. sericeus × C. cajan var. TT-5' population were maintained by sib mating. The male sterile plants were crossed with ICPL-85012.Approximately 50% of the F₁ plants were sterile. F₂ plants derived from the fertile F₁ plants did not segregate for male sterility. The reciprocal hybrid i.e. ICPL-85012 × Fertile derivatives from C. sericeus × TT-5, did not express male sterility. However, among the 12 F₂ plant to row progenies, two segregated 25% male sterile plants and remaining 10 did not segregate. The segregation pattern in subsequent progenies revealed that the sterility was under control of a single recessive allele. Studies on the backcross and their BC₁F₂ and BC₁F₃progenies revealed another sterility gene which was found to be dominant in inheritance. This paper shows that what was thought to be cytoplasmic male sterility from C. sericeus cytoplasm is actually a single dominant gene possibly acting in concert with a single recessive gene to mimic cytoplasmic male sterility. This revised version was published online in July 2006 with corrections to the Cover Date.