Morphology,cytology and forage potential of Pennisetum americanum (L.) K. Schum. x P. Purpureum Schum. amphidiploids

Summary F₁ hybrids between short-day photoperiod- sensitive maiwa bulrush millet, Pennisetum americanum (2n=14), and elephant grass, P. purpureum (2n=28), are triploid (2n=21), sterile, and can only be propagated vegetatively. Fertile amphidiploids, (2n=42, with 21 bivalents) were produced by colchicine treatment. Good seed set was obtained upon selfing the amphidiploids and the progeny exhibited variable pollen fertility and bivalent univalent and multivalent formation.Reciprocal crosses between elephant grass and the colchicine-induced amphidiploid failed to produce seeds. The maiwa millet x amphidiploid cross resulted in poor seed set and the reciprocal failed. Maiwa x amphidiploid hybrids were pollen sterile with 2n=21, rather than the expected 2n=28, indicating chromosome elimination.Morphologically, the amphidiploids and maiwa x amphidiploid hybrids closely resembled elephant grass and the F₁ hybrid. The amphidiploids showed no superiority over the F₁ hybrid and elephant grass in either forage yield or quality but one maiwa x amphidiploid genotype surpassed a promising local elephant grass selection in forage dry matter yield and flowered for a relatively short period.     

Comparative cytological study of Solanum aethiopicum Gilo group,Solanum aethiopicum Shum group and Solanum anguivi

Summary Comparative cytological studies were carried out on Gilo and Shum cultivar groups of Solanum aethiopicum (scarlet eggplant) and their ancestor-Solanum anguivi, in order to elucidate the evolutionary relationships between them. Results indicated preferential pairing of chromosomes in S. anguivi and non-preferential pairing of chromosomes in Gilo and Shum cultivar groups of S. aethiopicum during early stages of meiosis. The low degree of pairing in Gilo and Shum cultivar groups of S. aethiopicum and higher percentage of chromosomal abnormalities (12.50 and 10.58% respectively showed cases of translocation heterozygotes and suggest that the two taxa have hybrid origin. Conversely, the high degree of pairing and very low percentage of chromosomal abnormalities (2.50%) tend to suggest that S. anguivi is more ancient than either the Gilo and Shum cultivar groups of S. aethiopicum. It had already been proved that the Gilo and Shum cultivar groups of S. aethiopicum together with the Kumba and Aculeatum groups originated from S. anguivi (Lester & Niakan, 1986). Also studies on external morphology and cytological studies have shown the Gilo cultivar group to be more complex morphologically and having higher percentage of chromosomal aberrations (12.50% as against 10.58% observed in Shum cultivar group). It is suggested that the Gilo cultivar group might have evolved from the Shum cultivar group through hybridization and selection, while the S. anguivi was already stabilized as their ancestor.     

Barriers to hybridization of Solanum bulbocastanum Dun. and S. Verrucosum Schlechtd. and structural hybridity in their F1 plants

Summary Results of reciprocal crosses between Solanum verrucosum (2n=2x=24) and S. bulbocastanum (2n=2x=24) are described in terms of pollen tube behaviour in styles, of berry and seed set, of fertility and of meiotic behaviour of the F₁ hybrids. Pollen tube growth of S. verrucosum is strongly inhibited in styles of S. bulbocastanum, whereas no inhibition is observed in the reciprocal cross. Therefore S. bulbocastanum x S. verrucosum fails to set berries or seeds, whereas the reciprocal cross produces both berries (54.4% berry set) and seeds (0.3 per berry). Only 14.6% of the seeds germinate. Both the diploid and corresponding tetraploid hybrid plants are vigorous, flower abundantly, have a rather regular meiosis (mainly rod bivalents), but show a high degree of cytoplasmic-genic male sterility. Crossability of the diploid hybrid plants is nil when used as pollen parents and near to zero when used as pistillate parents. The barriers to hybridization of the parent species (unilateral inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of the parental chromosomes) are discussed and methods are suggested to overcome these barriers.     

Segregation of isozymes in selfed progenies of a synthetic amphidiploid between Solanum integrifolium and S. melongena

Isozyme and cytogenetic analyses were performed on selfed progenies of a synthetic amphidiploid between scarlet eggplant, Solanum integrifolium (= S. aethiopicum),and eggplant, Solanum melongena `DMP', for estimating genetic uniformity. Isozymes in the 379 examined seedlings segregated into five genotypes (phenotypes) each at the four loci examined, Pgd-2 of phosphogluconate dehydrogenase (E.C.1.1.1.43), Idh-2 of isocitrate dehydrogenase (E.C.1.1.1.41), Pgm-2 of phosphoglucomutase (E.C.2.7.5.1)and Skdh-1 of shikimate dehydrogenase (E.C.1.1.1.25), indicating that the selfed seedlings were not genetically uniform. Most of the examined 15 selfed seedlings exhibited a somatic chromosome number of 48, that is the same number of the synthetic amphidiploid, whereas isozyme genotypes among them were variable. It is suggested that the segregation of isozymes was not caused by variation of chromosome number but by genetic segregation of isozyme genes. The genome of the synthetic amphidiploid was indicated to be unstable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Meiosis and fertility in interspecific hybrids of Nicotiana tabacum L. ×N. glauca Grah. and their derivatives

Nicotiana glauca is of potential interest to breeders as it carries resistance to black root rot of tobacco. Cytological investigations of sexual interspecific hybrids of N. tabacum T′T′TT (2n = 4x = 48) cv. ‘Wiślica’ × N. glauca GG (2n = 2x = 24) were carried out. The analyses of chromosome association at diakinesis and metaphase I in the PMCs of amphihaploid F₁ T′TG (2n = 3x = 36) revealed low variable pairing with 0–5 bivalents. The sterile amphihaploids F₁ were converted into partial female fertile amphidiploids T′T′TTGG by chromosome doubling. Among 36 mature plants obtained, 15 were found to have chromosome numbers (2n = 6x = 72) and were verified as amphidiploids, 9 had (2n = 6x = 70 or 71) chromosomes while the remaining 12 were haploid. True amphidiploids, in spite of quite high chromosome pairing during meiosis, were very different in pollen fertility, ranging from 0% to 85%. Male fertility disturbances did not correlate with the degree of female fertility upon pollination with N. tabacum. Sesquidiploids T′TG (2n = 5x = 60) obtained from backcrossing the amphidiploids to parental tobacco showed more than 22 bivalents, 10–12 univalents and occasional multivalents that indicated the possibility of interchange events between N. tabacum and N. glauca genomes.     

Characterization of interspecific hybrids and first backcross generations from crosses between two cultivated eggplants (Solanum melongena and S. aethiopicum Kumba group) and implications for eggplant breeding

Common (Solanum melongena L.) and scarlet (S. aethiopicum L.) eggplants are cultivated for their fruits and form part of the same genepool. We have studied plant and fruit characteristics, pollen viability and seed set, phenolics content, and fruit flesh browning in accessions of S. melongena and S. aethiopicum Kumba group, as well as interspecific hybrids between these species and first backcross generations to each parental species. Respective genotypes were also characterized with seven polymorphic SSR markers. The results demonstrate that many differences exist for plant and fruit morphology among S. melongena, S. aethiopicum and the interspecific hybrids. The latter are very vigorous and generally intermediate between the two parents, except for fruit size which is smaller (and parthenocarpic due to a high pollen sterility) than those of any of the parents. Backcross progenies also exhibited morphological variation with moderate heritability values for the attributes evaluated. Variation for fruit size was present in the backcross generations but fruits were small resulting in little variation for fruit shape. Backcross plants with moderate fertility produced seeded fruits. Primary hybrids had fruit phenolics content similar to that of S. aethiopicum, the parent with lowest phenolics concentration, and were heterotic for fruit flesh browning. Backcross progenies were quite variable for both traits. SSR markers did not reveal segregation distortion in the backcross generations for these interspecific hybrids. The results demonstrate that generations derived from sexual interspecific hybridization can be a powerful tool for S. melongena and S. aethiopicum Kumba group breeding.     

Amphidiploids between Cyclamen persicum Mill. and C. purpurascens Mill. induced by treating ovules with colchicine in vitro and sesquidiploids between the amphidiploid and the parental species induced by conventional crosses

Summary We cultured colchicine-treated hybrid ovules in vitro to produce fertile amphidiploids of C. persicum (2n=2x=48. referred to as AA) × C. purpurascens (2n=2x=34, referred to as BB). Seedlings and mature plants were obtained from the ovules without colchicine and those exposed to 50 mg/l colchicine for 5, 10 and 15 days, whereas they were not obtained from the ovules exposed to 50 mg/l colchicine for 20 days and 500 mg/l for 5, 10, 15 and 20 days. Although 8 mature hybrids derived from the ovules without colchicine produced a few fertile pollen grains, they failed to produce viable seeds by self-fertilization. The hybrids had 41 somatic chromosomes. Four and 3 mature plants were derived from ovules exposed to 50 mg/l colchicine for 10 and 15 days, respectively. One each among 4 and 3 mature plants showed a high frequency of pollen grain fertility, produced several seeds by self-fertilization, and had 82 somatic chromosomes which is twice the number of hybrid chromosomes (2n=41, AB). These findings indicated that these plants are amphidiploids (2n=82, AABB) between C. persicum and C. purpurascens. Three and 2 viable seeds were derived by the conventional crosses of diploid C. persicum × the amphidiploid and the amphidiploid × C. purpurascens, respectively. Flowering plants that developed from the seeds of diploid C. persicum × the amphidiploid were barely fertile and had 65 somatic chromosomes (2n=65, AAB), whereas those that developed from the seeds of the amphidiploid × C. purpurascens were barely fertile and had 58 somatic chromosomes (2n=58, ABB). The somatic chromosomes indicated that these plants are probably sesquidiploids between the amphidiploid and either C. persicum or C. purpurascens. The interspecific cross-breeding of cyclamen using the amphidiploids and the sesquidiploids is discussed.     

Cytogenetic studies of the F1 hybridSolanum indicum L. ×S. melongena L. and its amphidiploid

Summary The F₁ hybrid (S. indicum ×S. melongena) resembled the wild parent and exhibited hybrid vigour. In spite of normal meiosis, it was partly sterile with 48.9% stainable pollen. Its sterility is attributed to cryptic structural hybridity.The amphidiploid (S. indicum — melongena) obtained through colchicine treatment was fully fertile. It showed a low multivalent formation during meiosis and it is classified as a segmental allopolyploid. p ]The practical value of the hybrid in eggplant breeding has been indicated.Part of Ph. D. thesis accepted by Annamalai University.     

Cytogenetics of interspecific hybrids in the genus Capsicum L.

Summary Crosses between a wild species C. chacoense and three cultivated species of chili pepper viz. C. annuum, C. frutescens and C. chinense yielded hybrids when C. chacoense was the seed parent but the reciprocal crosses were unsuccessful. C. chacoense × C. annuum F₁ hybrids were partly fertile and therefore an F₂ population could be raised; the other two F₁ hybrids were totally sterile. Chromosome pairing in the F₁ plants resulted largely in bivalents and a few multivalents and univalents. The genomes of the four species share large homologies and the role of chromosome structural changes in genome differentiation is suggested. Hybrid sterility is the major reproductive isolation mechanism.     

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.     

Inheritance in Solanum aethiopicum,the scarlet eggplant

Summary Analyses of F₁ and F₂ hybrid progenies from crosses between the ancestral species Solanum anguivi and cultivars of its domesticated derivative S. aethiopicum, have proved the mode of inheritance of prickles, stellate hairs and some other morphological characters and suggested the mode for several more. Most wild-type traits were dominant: many recessive domesticated traits involved imperfect morphogenesis suggesting loss of genetic control. F₁ hybrids between cultivars show marked heterosis and are recommended for crop production.     

Cytological observations in some hybrids between the rice species Oryza sativa L. and O. glaberrima Steud.

Summary Several hybrids between Oryza sativa and O. glaberrima and their backcrosses with O. sativa were studied. Their seed sterility was very different; large differences were also observed in the level of pollen sterility and in the earliness of microspore failure. The proportion of aborted embryo sacs was much lower than the rate of sterile male gametophytes. The backcross populations were much more sterile than the corresponding F₁ hybrids. On the base of our observations and according to the literature, we may conclude that genic unbalance is the main cause of sterility of these hybrids, but that physiological factors may also be involved. Thus a restoration of fertility is generally possible by selection. On the other hand, male-sterile lines could be bred from some of these hybrids.     

The increase of seed fertility of Brassicoraphanus through cytological irregularity

Summary Amphidiploids (Brassicoraphanus) were produced by means of colchicine treatment of F₁ hybrids between Brassica japonica Sieb. and Raphanus sativus L. The cytology of the amphidiploids was studied from F₁ to F₃ generations. Some plants had the euploid chromosome number 2n=38, whereas others had the aneuploid number 2n=37. One or two of either quadrivalents or trivalents, as well as some univalents, were seen in most of the plants examined. All the plants showed a low seed fertility. In F₃ generation there arose some yellow-flowered plants, all of which showed a higher seed fertility than normal white-flowered plants. It is postulated that the change of flower colour might originate in the segmental exchange of only partially homologous chromosomes following multivalent formation. A gene causing white flower colour was perhaps closely linked to a gene causing sterility, and both genes were probably excluded together through the segmental exchange of the chromosomes. Therefore, it can be said that the increase of fertility was induced by cytological irregularity.     

Cytogenetic studies on the interspecific hybrid Capsicum baccatum L.× C. frutescens L. and its progeny

Summary Morphological and cytogenetical studies were carried out on the F₁ and F₂ hybrids and backcross derivatives of the interspecific cross Capsicum baccatum L. x C. frutescens L. The F₁ and F₂ hybrids displayed irregular meiosis with a maximum association of eight chromosomes in the former and one quadrivalent in the latter with the appropriate number of bivalents and univalents. It is inferred that C. baccatum differs from C. frutescens (yellow) by at least tow or three interchanges and from the white cultivar by a single interchange. Structural repatterning of chromosomes, erratic meiotic behaviour, genes for pollen sterility, segregational imbalances following intergenomic recombination are believed to be major factors causing sterility in the hybrids. The two species are sympatric and natural hybrids have not been realised.     

High-performance liquid chromatographic analysis of anthocyanins in induced amphidiploids of Iris laevigata Fisch. × I. ensata Thunb.

Summary Anthocyanins of colchicine-induced amphidiploids of I. laevigata × I. ensata were analyzed by the HPLC procedure and compared with those of parental species and F₁ hybrids of I. laevigata × I. ensata. The amphidiploids were characterized by seventeen anthocyanins, and exhibited all anthocyanins of the parental species and the F₁ hybrids. Malvidin 3RGac5G and petunidin 3RGac5G in anthocyanins detected were major pigments in the amphidiploids, which exhibited strongly the malvidin 3RGac5G-petunidin 3RGac5G type of I. ensata rather than the petunidin 3RGac5G-malvidin 3RGac5G type of I. laevigata. Moreover, a higher degree of anthocyanin content was observed in the amphidiploids and the F₁ hybrids. Namely, the anthocyanin content of the amphidiploids and the F₁ hybrids were 2.81 and 2.45 times as much as that of the mid-parent. This implies that there is a complementary effect on anthocyanin synthesis of parental genes in them. Finally, the utility of the amphidiploids was discussed.Contribution from the Laboratory of Plant Breeding, Faculty of Agriculture, Miyazaki Univ., No. 64.     

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.     

RAPD variation in Solanum anguivi Lam. and S. aethiopicum L. (Solanaceae) in Uganda

Variation in 39 polymorphic RAPD markerswas studied for 18 populations of Solanum anguivi, S. aethiopicum Gilogroup and S. aethiopicum Shum groupin Uganda. UPGMA and PCO analyses of thedata revealed no clear groupingscorresponding to the species and groups. AnAMOVA analysis of the genetic variationshowed that the variation among species andgroups was less than 10%, whereas thevariation within species and groups wasmore than 90%. A Mantel test showed nocorrelation between genetic distance andgeographic distance. The data gives onlyvery weak support for the separation of themore morphologically distinct S.aethiopicum and S. anguivi. TheGilo- and Shum-groups of S.aethiopicum, which were previouslyregarded as two separate species can not beseparated on the basis of RAPD data, and itis most likely that they are keptmorphologically distinct by a strongman-made selection pressure.     

Interspecific hybridization between Solanum melongena and Solanum macrocarpon: study of the F1 hybrid plants

Summary Egg plant is one of the most common vegetable crop grown in India and other parts of the world. The cultivated egg plant Solanum melongena is found to be susceptible to the shoot and fruit borer (Leucinodes orbonalis). Whereas the species Solanum macrocarpon is resistant. In order to incorporate the resistance of shoot and fruit borer to the cultivated egg plant, an interspecific hybridization between Solanum melongena and Solanum macrocarpon and reciprocals were carried out. The hybrids were found to be sterile, the investigations revealed that the failure of seed set in hybrids is due to the ovule abortion. In order to overcome the sterility, the colchicine has been applied to the interspecific hybrids.     

Interspecific hybrids between three eggplant (Solanum melongena L.) cultivars and two wild species (Solanum torvum Sw. and Solanum sisymbriifolium Lam.)

Three Greek eggplant cultivars, ‘Langada’, ‘Tsakoniki’ and ‘Emi’ (2n= 24), were crossed with two wild species (Solanum torvum Sw., 2n= 24 and Solanum sisymbriifolium Lam., 2n= 24). Ovules isolated 15-27 days after pollination were cultured in a modified MS medium at 24°C and a 16h photoperiod. Fifty days later, the ovules were dissected and the interspecific embryos were cultured in the same medium. Interspecific hybrids were achieved only from crosses between the eggplant cultivars and S. torvum. The hybridity of the putative interspecific F¹ hybrid (Solanum melongena×S. torvum) was confirmed by using morphological and biochemical (isozyme isocitrate dehydrogenase A, phosphoglucomutase A, phosphoglucose isomerase B, 6-phosphogluconate dehydrogenase A, 6-phosphogluconate dehydrogenase B) markers. The F¹ plants (‘Langada’×S. torvum) were selfpollinated and backcrossed to both parents. Fruits, however, were produced only when the F¹ hybrid was backcrossed as female with the eggplant cultivar ‘Langada’.     

Cross compatibility between Abelmoschus esculentus and A. moschatus

Interspecific cross compatibility between cultivated and wild okra (Abelmoschus esculentus and A. moschatus) and pollen tube growth behaviour in the crosses among a local cultivar of A. esculentus, A. moschatus and their F₁s were studied. Fruit set was observed in all the crosses except one and seed setting was absent in two of the crosses which set fruit. All seed produced were shrivelled but F₁ plants were obtained from two crosses where cultivated okra was used as the seed parent. The F₁ plants were perennial in nature with very low pollen viability and seed set. A high percentage of pollen germination and profuse pollen tube penetration in the style were observed in the cross A. esculentus × A. moschatus but low pollen tube penetration with abnormal pollen tubes was observed in the reciprocal cross. The number of pollen tubes was very low but they appeared to be normal in the backcross A. esculentus × F₁, but were generally abnormal in the reciprocal cross. Both pre- and postzygotic barriers seemed to occur in crosses between the two species. The present studies indicate that these barriers can be overcome and desirable characters from A. moschatus transferred to cultivated okra using conventional hybridisation techniques. This revised version was published online in July 2006 with corrections to the Cover Date.