Nicotiana Repanda Research Articles

Overcoming hybrid inviability in interspecific cross between Nicotiana repanda WILLD. and N. tabacum L.

The combination of 2 techniques, i, e., pollination after the destruction of chromosomes in pollen grains with ionizing radiations and in vitro culture of crossed ovules, was applied to interspecific hybridization between N.repanda and N. tabacum in order to investigate the possibility of overcoming hybrid inviability in the cross-combinations. By using these techniques, it became possible to obtain aneuploid hybrids, which had never been reported previously.

CYTOPLASMIC MALE STERILITY IN NICOTIANA, RESTORATION OF FERTILITY, AND THE NUCLEOLUS. II. N. DEBNEYI CYTOPLASM

Previously, it was shown that a fragment chromosome, apparently derived from the Nicotiana repanda chromosomal complement, restores to normal the morphology and fertility of the abortive and feminized anthers produced by plants that possess the N. tabacum genome in cytoplasm from N. repanda. Furthermore, that restorer chromosome organizes the nucleolus and inhibits the nucleolus-forming activity of the nucleolar organizers of N. tabacum chromosomes present in the same cells, particularly in pollen mother cells. To determine whether these relations are basic or only coincidental, restorer chromosomes for other cytoplasms are now being investigated. The present paper describes a study of a chromosome, presumably derived from N. debneyi, with partial restoring power. Acting in the cytoplasm of N. debneyi, it directs formation of morphologically normal anthers, without, however, restoring pollen fertility. We find that this chromosome also has a functioning nucleolar organizer, but only slightly inhibits the nucleolus-forming capacity of N. tabacum chromosomes. The suggestion of a relationship between the nucleolar apparatus and restoration of normal anthers is thus strengthened by the observation that restorers are found on nucleolus-forming chromosomes from two very distinct Nicotiana species, as well as in several comparable cases cited from the Triticinae. The manner in which the nucleolus, or its organizer, may direct defeminization and restoration of anther morphology is not known; suggestions were offered in the preceding paper in this series (Gerstel, Burns and Burk 1978).

CYTOPLASMIC MALE STERILITY IN NICOTIANA, RESTORATION OF FERTILITY, AND THE NUCLEOLUS

Plants with the cytoplasm of Nicotiana repanda and the chromosomes of N. tabacum produce nonfunctional and feminized anthers. Introduction of a satellited fragment chromosome, apparently derived from N. repanda, restores normal anthers and pollen fertility. The fragment is somatically stable and addition-homozygotes transmit it to the great majority of their offspring. Cells with the fragment exhibit amphiplasty, i.e. , in plants having one or two fragments, nucleolar organizers of N. tabacum are suppressed and the nucleoli are entirely or largely produced by the fragments. Formation of nucleoli by organizers from N. repanda in N. repanda cytoplasm may thus be a condition for male fertility. The manner in which nucleoli may influence the development of originally indeterminate sex primordia is discussed. Further cytological studies of cytoplasmically male-sterile plants and restorer chromosomes are needed to decide whether the observed relationship is of functional significance or merely accidental.

Nicotiana repanda as a potential source for disease resistance in N. tabacum.

Nicotiana repanda as a potential source for disease resistance in N. tabacum.

The Role of Host Plants in the Dynamics of Populations of Heliothis Spp. 1 , 2

When host plants of Heliothis zea (Boddie) and H. virescens (F.) were studied in a 2500-acre area near Brownsville, Texas in 1970, H. zea was found primarily on grain sorghum during the spring and on cotton during June–August. Cotton was the primary cultivated host of H. virescens , but in the spring and fall, it was also common on such uncultivated bosts as Nicotiana repanda Willd., Verbena neomexicana (Gray) Small, and Ruellia runyonii Tharp & Barkley; in addition, H. virescens was found on Aubtilon trisulcatum (Jacq.) Urban in tbe fall.

Host Plants of Heliothis virescens and H. zea (Lepidoptera: Noctuidae) in the Lower Rio Grande Valley, Texas1

Plants of the lower Rio Grande Valley, Texas were surveyed for eggs and larvae of the tobacco budworm, Heliothis virescens (F.), and the bollworm, H. zea (Boddie). H. virescens was common on 5 of the hosts studied and H. zea on 9. The earliest hosts of each species were a wild tobacco, Nicotiana repanda Willd., and alfalfa. During the crop-growing season, H. virescens was most abundant on tomato and cotton.

Interference between cucumber mosaic virus and tobacco mosaic virus on different hosts

Interference between tobacco mosaic virus (TMV) and a strain of cucumber mosaic virus, causing local lesions on Zinnia elegans, (CMV-LL), is described. Interference was observed on Nicotiana repanda and N. glutinosa when CMV-LL functioned as protecting virus, as well as on Z. elegans when the protecting virus was TMV. Simultaneous inoculations of N. repanda or N. glutinosa with the two viruses prevented the establishment or the multiplication of CMV-LL. Increasing concentrations of TMV in the challenge inocula resulted in an increased percentage of protection. This supports the hypothesis that the protecting virus occupies some cellular structures or exhausts some precursors needed for the establishment or multiplication of the challenge virus. No interference was observed among the common strains of cucumber mosaic virus, potato virus X, potato virus Y, and TMV.

Nota sobre a molestia de virus do fumo denominada faixa das nervuras

The present paper deals with the virus disease of the tobacco plant recently described by Kramer & Silberschmidt (12) under the name faixa das nervuras (veinbanding). New host plants are added to the list of suscepts, as follows : Nicotiana repanda Willd., JV. angustifolia (*), N. Gossey Domin, N. Sanderae Hort. ex. W. Watson, N. glutinosa L., N. longiflora Cav., N. paniculata L., Lycopersicon esculentum Mill., L. pimpinellifolium Mill., and Cyphomandra betacea Sendt. Datura stramonium L., already studied by Kramer & Silberschmidt (12) and Nicotiana glauca Grah., Nicandra physaloides Gaertn., Solanum nodiflorum (**), S. nigrum L., Lactuca sativa L., Brassica oleracea L., Vigna sinensis Endl. var. Black., and Dolichos lablab L., var. purpurens were found not to be susceptible to the virus. (*) This species was received with this name from the Division of Tobacco and Plant Nutrition, U.S.D.A. (**) One plant of S. nodiflorum out of 22 which were inoculated gave symptoms of veinbanding. However as no backinoculation was made it can not be stated with certainty if it was truly affected by this virus. The symptomatology on tobacco described by the above mentioned authors agrees as a whole with which has been observed that is : clearing of the veins, chlorotic spotting and veinbanding. In addition it is stated that the white necrotic spotting found associated with the disease on certain tobacco varieties, v. g. Sumatra and Turkish must be attributed to the same virus. On potato plants of the varieties President and Green Mountain the virus causes local streak-like symptoms followed by chlorotic mottling of young leaves. Late symptoms take the form of leaf-drop streak. The virus of faixa das nervuras is easily transmissible through the sap giving practically 100% of success. The physical properties of the virus are : tolerance to dilution 1:10.000, thermal death point 54°C. and logevity in vitro 72 hours. No vector of the virus is known. The statement of Kramer & Silberschmidt (12) that the virus of faixa das nervuras belongs to the group of the potato virus Y is confirmed. A discussion is given about the position of the virus within the group. Our results do not permit to state that the virus is more related to the veinbanding virus as claimed by these authors. It is also pointed out that the differences found in the litterature between the Y and veinbanding viruses are slight, justifying in the maximum the separation of both, but as strains of the same virus.