Pollen germination,pollen tube growth and fertilization following self and interspecific pollination of Paspalum species

Summary Crossability between most Paspalum species is very low. This study was undertaken to identify the impediments to hybridization. Accessions of P. intermedium Munro. ex Morong, P. jurgensii Hackel and P. dilatatum Poir were self-pollinated and crossed with one anther. Paspalum intermedium is essentially self-sterile but P. jurgensii and P. dilatatum are highly self-fertile. Following pollination, pollen germination and tube growth were studied by observing the pollinated pistils with fluorescent microscopy. Examination of self-pollinated pistils revealed that the pollen germinated shortly after contacting the stigmas. Germination was over 80% for the P. intermedium and P. dilatatum accessions but only 57% for P. jurgensii. Pollen tubes grew to the micropyle within 45 minutes after pollination in P. dilatatum and 1 hour and 15 minutes in P. jurgensii. However, in the P. intermedium accessions most tubes did not grow beyond the stigma and very few penetrated the style and ovary. Apparently stylar-incompatibility is the reason for the low selfed seed set. In the cross-pollinations, pollen germinated shortly after pollination and germination ranged from 57 to 88% for the different crosses. In all crosses the pollen tubes grew to the micropyle within 30 minutes to 2 hours after pollination indicating that a cross-incompatibility system is not the cause for low crossability among these species. By examining embryo sacs from P. intermedium × P. dilatatum, its reciprocal and P. intermedium × P. urvillei crosses, it was determined that gametes failed to unite in some crosses and this is a major reason for low crossability.     

Testing for resistance to fungal leaf diseases in an inexpensive growth chamber

Summary A simple walk in growth chamber was constructed for testing resistance to fungal leaf diseases. It consisted of a small tent of transparent plastic, provided with heat insulation and fluorescent tubes, and was placed in a refrigerated unit. A day-night effect was produced in the tent by switching on the lights and turning them off again.This set-up was used to incubate small plants and leaf discs of lettuce, inoculated with Bremia lactucae Regel, and small spinach plants inoculated with Peronospora spinaciae Laub.The method proved to be reliable and practical; its use is recommended for other diseases as well.Samenvatting Een eenvoudige groeikamer werd gebouwd voor toetsen op resistentie tegen bladschimmelziekten. Het apparaat bestond uit een kleine tent van transparant plastic, voorzien van warmte isolatie en TL verlichting. Het geheel bevond zich in een koelcel. Door de lampen in en uit te schakelen werd een dag en nacht wisseling in de tent verkegen.Deze apparatuur werd gebruikt gedurende de incubatieperiode van kleine slaplantjes en bladschijfjes, besmet met Bremia lactucae Regel en van kleine spinazieplantjes, besmet met Peronospora spinaciae Laub. De methode bleek betrouwbaar en praktisch te zijn en is ook bruikbaar te maken voor andere ziekten.     

Pollen grain germination and pollen tube growth following in vivo and in vitro self and interspecific pollinations in annual Cicer species

Summary Germination of pollen grains and growth of pollen tubes were studied to determine the cause of barreness in crosses among annual Cicer species. In vivo and in vitro time-course studies and fluorescent microscopy revealed no pollination incompatibility among the selfs, crosses and reciprocals of C. arietinum L., C. reticulatum Lad. and C. cuneatum Rich. In general, Cicer pollen grains germinated and grew on styles of Cicer species. Pollen tube growth was characterized by irregularly spaced and intermittent callose deposits. Failure of seed formation in interspecific pollinations may be attributed to the slowness of pollen tube growth or collapse of fertilized ovules. In addition to these causes, shortness of stamens and sparsity of pollen grains were responsible for flower drop in natural selfs. Although the number of pollen tubes entering the micropyle in interspecific pollinations was low, it may be possible to grow the fertilized ovules on an artificial medium to obtain F₁ plants.     

Cytology and leafspot resistance in Arachis hypogaea x wild species hybrids

Summary Introgression of germplasm from diploid wild Arachis species to A. hypogaea has great potential for improving pest resistance in cultivated peanuts. This investigation evaluated methods for incorporating exotic germplasm into cultivated peanuts, especially for Cercospora arachidicola Hori resistance. Interspecific hybrids between A. hypogaea (cvs. NC 2 and NC 5) and the wild species A. cardenasii Krap. et Greg. nom. nud. and A. chacoense Krap. et Greg. nom. nud. were analyzed cytologically and for leafspot resistance. All F₁ hybrids were sterile, had irregular meiosis, and very few multivalents. They were highly resistant to C. arachidicola in field tests and had a 10-fold reduction of conidia per lesion in the greenhouse as compared to A. hypogaea cultivars. After colchicine treatments of F₁ hybrids, hexaploids (2n=60) and aneuploids (2n=54, 56, 63) were observed. The hexaploids had up to 18 univalents per pollen mother cell and very few multivalents, indicating a low frequency of intergenomic chromosome pairing. For C. arachidicola resistance, significant differences were not found among wild species parents, F₁ hybrids and two generations of hexaploids. Most hexaploids were stable at 2n=60 and embryos aborted when backcrosses with the respective wild species were attempted. However, when hexaploids were backcrossed to A. hypogaea, several fertile pentaploid (2n=50) offspring were obtained. Use of self-pollinating pentaploids is believed to be the quickest method to recover 40-chromosome hybrid derivatives in these hybrids.     

Pollen germination and pollen tube growth following self-pollination and intra- and interspecific pollination of Medicago species

Summary Pollen germination and pollen tube growth after self- and intra- and interspecific pollinations of annual [M. scutellata (L.) Mill., M. disciformis DC., and M. rigidula (L.) All.] and perennial (M. sativa L.) Medicago species were studied using a Carl Zeiss microscope with a fluorescence filter attachment.Self-pollination of self-fertile annual and intraspecific pollination of cross-fertile perennials were characterized by high pollen germination and rapid normal pollen tube growth. In contrast pollen germination percentages were very low and many pollen tube growth abnormalities occurred following interspecific pollination and self-pollination of self-sterile plants. The time period from pollination to fertilization for interspecific crosses was about double that following self-pollination of the annual species. However, fertilization occurred frequently following interspecific pollinations. Much of the sterility was due to factor(s) operating after fertilization.Cooperative investigations of the Kansas Agricultural Experiment Station, Dept. of Agronomy and the U.S. Department of Agriculture, Agricultural Research Service. Contribution No. 82-582-J- Mention of a trademark name or proprietary product does not constitute a guarantee or warranty by the U.S. Department of Agriculture, and does not imply its approval over other products that also may be suitable.     

The nature of the Bolivian weed potato species Solanum sucrense Hawkes

Summary Two theories for the origin of the Bolivian weed potato species Solanum sucrense Hawkes have been tested. The first was that it had an allopolyploid origin as a hybrid of the cultivated tetraploid S. tuberosum ssp. andigena (Juz. et Buk.) Hawkes with the wild/weed tetraploid cytotype of S. oplocense Hawkes. The second hypothesis postulated that it was a cross of the weed diploid species S. sparsipilum (Bitt.) Juz. et Buk. with S. oplocense.Synthetic hybrids of S. tuberosum ssp. andigena x S. oplocense and of S. sparsipilum x S. oplocense have been compared morphologically with S. sucrense accessions. Their crossability has also been investigated.The crossability and morphological studies strongly suggested that the former hypothesis was the more likely. This was borne out by observations made on the 1974 University of Birmingham Expedition when segregating populations of S. sucrense and S. oplocense were collected growing with feral S. tuberosum ssp. andigena.The evidence from this study indicates that the S. tuberosum ssp. andigena x S. oplocense hybrid has formed the basis of the S. sucrense gene pool. It is suggested that this hybridogenic taxon be maintained under the name Solanum x sucrense.The clarification of the taxonomic relationships of these three species will be of interest to Globodera resistance breeders, in view of the fact that these taxa are resistant to various pathotypes of the golden nematode.     

Resistance to Sappaphis devecta (Wlk.) in apple

Summary Simple methods of selection for resistance to Sappaphis devecta (Wlk.), the rosy leaf-curling aphid, are described. Cox's Orange Pippin was shown to carry a single dominant resistance gene, for which the symbol Sd is suggested. There was clear evidence that the apple varieties James Grieve, Northern Spy and Ashmead's Kernel also provide monogenic sources of resistance, and there were similar indications for Gascoyne's Scarlet and ST 14/20.     

The classification of varieties of groundnut (Arachis hypogaea L.)

Summary An expanded scheme of groundnut variety classification is presented which is revised in the light of recently collected West African material and is designed in concordance with the most recent taxonomic treatment of the species Arachis hypogaea L. This species consists of two subspecies ssp. hypogaea and ssp. fastigiata Waldron. Each subspecies contains two botanical varieties. Those of ssp. hypogaea are var. hypogaea and var. hirsuta Kohler and those of ssp. fastigiata Waldron are var. fastigiata and var. vulgaris Harz. Each infraspecific taxon contains a morphologically distinct group of cultivated varieties.Grain Legume Research Laboratory, Agricultural Research Council of Malawi, POB215, Lilongwe, Malawi.Department of Agricultural Botany, University of Reading, Reading, England.     

Cytological and geographical characterizations of Hemarthria

Summary Chromosme numbers were determined for 56 Hemarthria altissima (Poir.) Stapf et C. E. Hubb. introduction, forty of these were diploid (2n=18) and 16 were tetraploid (2n=36). These results, combined with previous findings, show that all but three of the tetraploids in the USDA Hemarthria altissima collection originated north of 20 S latitude. All other introductions collected throughout southern Africa were diploid. Meiosis was regular in a hexaploid, 6 tetraploid and 32 diploid introductions but a low frequency of quadrivalents was found in the teraploids. H. uncinata R. Br. and H. uncinata var. spathacea (Domin) Vickery were found to have 2n=36 chromosomes H. compressa (L.f.) R. Br., introduced from Japan, had 2n=54 chromosomes. No major cytological abnormalities exist in these Hemarthria species. Significant variation exists among the ploidy levels for cold tolerance and in vitro organic matter digestion to provide the basis for a forage improvement program.Joint contribution from the Department of agronomy. Institute of food and Agric. Sciences (IFAS), Univ. of Florida. Gainesville, Fl and, Plant Genetics and Germplasm Institute, USDA, Beltsville, MD Published as IFAS Journal Series No. 2849.     

On bacterial wilt of alfalfa (Medicago sativa L.) caused by Corynebacterium insidiosum (McCull.) Jensen,in Italy

Bacterial wilt of alfalfa (Medicago sativa L.) caused by Corynebacterium insidiosum (McCull) Jensen was unknown in Italy until 1957. The authors established in that year in the province of Bologna this dangerous disease in 2–3 year-old stands of alfalfa which appeared uniformly and extensively thinned.They started a breeding programme with the use of bacterial wilt resistant material from the U.S.A., while also studies on methods of testing for resistance under Italian conditions are in progress.     

Natural hybridization between Solanum acaule Bitt. and S. megistacrolobum Bitt. in the province of jujuy,Argentina

Summary Evidence is provided that hybridization of the tetraploid (2n=4x=48), self-fertile tuber-bearing species Solanum acaule Bitt. with the diploid (2n=2x=24), self-incompatible, tuber-bearing S. megistacrolobum Bitt. takes place in several localities of the province of Jujuy in the high, cold plateaux of the Argentine Puna. The triploid hybrids (2n=3x=36) closely resemble S. acaule in growth habit, leaf morphology and floral structures and for this reason they can be easily overlooked for that species in the field. Experimental data show that S. acaule can be crossed with S. megistacrolobum though the crossability is rather low and variable according to the particular cross considered. The artificial hybrid obtained compares well with the natural hybrid in morphology and chromosome number. The hybrids, though almost completely male sterile, are successful colonizers of disturbed areas around farmers' dwellings, cattle enclosures and other areas where the soil is rich in organic matter.There is some evidence that the Tilcara material of S. acaule subsp. aemulans and the hybrids of S. acaule x S. megistacrolobum have some characters in common, which can be interpreted as having a similar origin.It is postulated that S. acaule subsp. aemulans, in Jujuy at any rate, is not a primitive form of S. acaule as thought by Hawkes and Hjerting, but rather a fertile hybrid derivative of S. acaule x S. megistacrolobum through the functioning of 2n gametes.We also provide evidence that S. bruecheri Correll should not be considered a hybrid of S. acaulle x S. megistacrolobum but a synonym for S. gourlayi Hawkes. The new name, S. x indunii Okada et Clausen, is proposed to designate this hybrid.     

Notes on species delimination,species relationships and polyploidy in Avena L.

Summary On the combined evidence from morphology, ecology, and cytogenetics, seven species are recognized in the genus Avena L. 1. A. clauda Dur., 2. A. ventricosa Bal. 3. A. longiglumis Dur, 4. A. strigosa Schreb., 5. A. magna Murphy et Terr., 6. A. murphyi Ladiz. and 7. A. sativa L. The first three species are wild diploids. The fourth is a diploid-tetraploid complex of wild forms, weeds and cultivars. The fifth and sixth are wild tetraploids and the seventh constitutes a hexaploid aggregate of wild forms, weeds and cultivated forms. A short morphological and ecological characterization is given to each species.The cytogenetic, ecological and morphological evidence available on the evolutionary divergence and on the genetic affinities between the seven species is reviewed and discussed. The conclusion in drawn that in Avena there are two independent developments of polyploidy: 1. strigosa tetraploids, where the diploid background is well known; 2. the tetraploid-hexaploid of A. magna, A. murphyi and A. sativa (series Denticulatae). Here the first two species apparently represent the general tetraploid background from which hexaploid A. sativa evolved. It is also argued that it is impossible to explain the morphology, ecology and cytology of series Denticulatae in terms of the known diploid species of Avena, and a yet missing hypothetical diploid ancestor was extrapolated.     

Problems in breeding and cytology of sugar cane

Occasion for writing this article was the appearance of two papers of Price, one concerning the occurrence of apomixis in sugar cane, the other dealing with cytological results of intra-and interspecific crosses of Saccharum. Especially in the latter he criticized Bremer's discovery of endo-duplication during megasporogenesis in Saccharum forms.The present author formulates his stand-point by an ample discussion of endoduplication as cause of chromosome increase in Saccharum crosses. The phenomenon of parthenogenesis is treated in relation to hybridization and speciation. The author concludes that Price gives evidence of insufficient understanding of endo-duplication while also about the occurrence of parthenogenesis he cannot agree with him.     

Chromosome behavior and sterility of hybrids between the common onion,Allium cepa,and the related wild A. oschaninii

Summary Four hybrid plants were obtained when cytoplasmic male-sterile onion inbreds, Allium cepa L., were pollinated with a wild cepa-like allium introduced from northeastern Iran and identified as A. oschaninii O. Fedtsch. It has been proposed on morphological grounds that A. oschaninii is wild A. cepa or the ancestor of A. cepa. Nevertheless, chromosome irregularities and complete sterility in the hybrids suggest that there may be a greater sterility barrier between A. cepa and A. oschaninii than between A. cepa and 3 other species reported to cross with A. cepa, namely A. fistulosum L., A. galanthum Kar. et Kir., and A. pskemense B. Fedtsch.Cooperative investigation of the U.S. Department of Agriculture and the Idaho Agricultura Experiment Station, Parma Branch Station.     

Hybridization of Desmodium species

Summary Under different light regimes, Desmodium canum (Gmel.) Schin. & Thell. responded as a long-day plant, D. intortum (Mill.) Urb. and D. uncinatum (Jacq.) dc. as short-day plants, and D. sandwicense E. Mey. as photoperiod-insensitive. Tripping method with anther removal, washing of stigmas and pollen transfer was simple and less time-consuming, gave an equal number of hybrids but more selfed progenies than the tedious method of emasculating prior to anthesis. A high percentage of selfing indicated that the four species are self-compatable and that foreign pollen did not show advantage over that from the same plant. Silver marking of the leaflet midrib of D. sandwicense and D. uncinatum in crosses with D. intortum was a useful dominant marker, but did not appear in the cross D. canum × D. uncinatum. Brown flecking of D. intortum leaflet was a dominant characteristic and occurred on the progenies from crosses with D. sandwicense and D. uncinatum along with the silver marking. Stem growth habit, leaflet form, and pubescence were helpful but less reliable for identifying hybrids. F₁ hybrids were readily verified by isozyme patterns of esterase and peroxidase, the zymograms having common and different bands of the parents.Plant Breeding Paper No 639.     

A possible gene source for early,day-length neutral pigeon peas,Cajanus cajan (L.) Millsp.

Summary Atylosia scarabaeoides Benth. and A. platycarpa Benth., close relatives of the species Cajanus cajan (L.) Millsp., were screened for photoperiodic response. Four photoperiods ranging from 12 h 45 min to 19 h were studied in three environments. A. scarabaeoides flowered freely only in the first photoperiod. A. platycarpa not only flowered early (39 to 63 days after planting) in all four photoperiods, but also exhibited a relatively constant vegetative phase up to 16 h of illumination. Cajanus cajan, in which most cultivars-if not all-exhibit a response to photoperiod, was successfully hybridized with the two Atylosia species. It is suggested that genes for earliness and insensitivity to day-length could be transferred from A. platycarpa to C. cajan.     

Flax scorch

Summary Scorch is a soilborne disease of flax which as far as known only occurs in the Netherlands, Belgium and Northern France. Due to the publication of Marchal (1900) the fungus Asterocystis radicis de Wild had for a long time been considered as the causal organism. In later years, however, Dutch investigators (v. d. Meer, 1928, and Diddens, 1931) proved that the disease is caused by the fungus Pythium megalacanthum de Bary and that Asterocystis is quite harmless to flax.The only way of controlling the disease has been the breeding of resistant varieties. As early as 1888 Prof. L. Broekema established that resistance occurs and attempted to raise scorch-resistant varieties. In later years also other investigators and breeders worked on the same problem.The breeding for flax scorch resistance forms part of the working programme of the S.V.P. (Foundation for Agricultural Plant Breeding). Though different isolates of the scorch-fungus were tested by the author, no physiological specialization was found. He evolved a laboratory method for investigating flax scorch resistance and studies the heredity of the resistance. On page 204 the resistance of some varieties is expressed n relative figures.It is attempted to promote breeding work of Dutch private breeders by providing them with resistant populations and lines.Vlasbrand is een bodemziekte welke, voor zoverre bekend, alleen voorkomt in Nederland, België en Noord-Frankrijk. Op grond van de publicatie van Marchal (1900) werd de schimmel Asterocystis radicis de Wild lange tijd als de veroorzaker van deze ziekte beschouwd. In latere jaren bewezen Nederlandse onderzoeksters (v. d. Meer, 1928 en Diddens, 1931) echter dat de ziekte door de schimmel Pythium megalacanthum de Bary veroorzaakt wordt en dat Asterocystis ongevaarlijk is voor vlas.Het kweken van resistente rassen vormt de enige mogelijkheid de ziekte te bestrijden. Prof. L. Broekema stelde reeds in 1888 vast, dat resistentie voorkomt en trachtte vlasbrand resistente rassen te kweken. In latere jaren legden ook anderen zich hierop toe.Het kweken op vlasbrand resistentie vormt een onderdeel van het werkprogramma van de S.V.P. Hoewel verschillende isolaties door de schrijver onderzocht zijn, werd geen physiologische specialisatie aangetroffen. Hij werkte een laboratoriummethode uit voor onderzoek op vlasbrandresistentie en bestudeert de erfelijkheid van de resistentie. Op blz. 204 is de resistentie van enige rassen in verhoudingscijfets uitgedrukt.Door de Nederlandse kwekers te voorzien met resistente populaties wordt getracht de kweekarbeid te bevorderen.     

Cytogenetic studies and the occurrence of triploidy in the wild potato species Solanum commersonii Dun.

Summary The South American wild potato species Solanum commersonii Dun. exists as two subspecies, subsp. commersonii and subsp. malmeanum (Bitter) Hawkes and Hjerting, and as both diploid and triploid cytotypes. The two subspecies were completely cross fertile but there were reciprocal differences in the number of seeds set per berry and the mean seed weight. Crosses between diploids and colchicine-induced autotetraploids yielded only a few seeds per berry, but 16 of the 18 germinated seeds were triploid or nearly so. Such a high proportion of triploids is unusual for such crosses in potatoes. Some triploids has a high percentage of stainable pollen. The origin of naturally occurring triploids is discussed in the context of 2n gametes, a triploid block, and endosperm balance numbers.     

Resistance to Heterodera schachtii in patellares section of the genus Beta

Summary Fifty-two accessions of the section Patellares wild beet (including 26 Beta patellaris Moq., 13 B. procumbens Chr. Sm and 13 B. webbiana Moq.) and 14 progeny families were selected and tested against sugarbeet cyst nematode, Heterodera schachtii Schm. All Patellares species tested were highly resistant, but not immune, to the development of H. schachtii, after infection. This is the first report that mature female nematodes developed in the roots of B. webbiana plants. The occasional development of nematode cysts in roots of juvenile wild beets was, however, not a heritable genetic factor.Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

On the inheritance of the dwarf character in Polyantha × Rosa chinensis minima (Sims) Voss F1-populations

Summary The inheritance of the dwarf character was studied in F1-seedling populations arisen from crosses between diploid Polyantha cultivars and the diploid dwarf species R. chinensis minima (Sims) Voss. Dwarfness is controlled by a single dominant gene D. R. chinensis minima and its dwarf descendants are heterozygous for D, while polyanthas are homozygous for d. The origin of R. chinensis minima and its potential for breeding new pot roses are discussed.