In August of 2008, a disease of chrysanthemum (Dendranthema morifolium (Ramat.) Tzvel) caused losses of 70 to 80% in one of the largest chrysanthemum gardens in Yangling, Shanxi Province, China. Chrysanthemum plants in nearby areas also were affected to various degrees. Symptoms included flattened stems, shortening of internodes, yellowing of leaf margins, root death, and dwarfing of plants. Affected plants eventually collapsed. On the basis of these symptoms, a phytoplasma was suspected. Total nucleic acids were extracted from 0.5 g of phloem tissue from stems of eight symptomatic and eight asymptomatic plants by the cetyltrimethylammoniumbromide (CTAB) method (1). To amplify phytoplasma DNA, primer pairs R16mF2/R16mR1, followed by R16F2n/R16R1 (2), were used in a nested PCR. A final amplicon product (1.2 kb) was obtained from all symptomatic plants but not from asymptomatic ones. Restriction fragment length polymorphism (RFLP) analyses of R16F2n/R16R1 amplicons with MseI, AluI, HhaI, HaeIII, KpnI, RsaI, and HpaII endonucleases indicated that all symptomatic plants, but none of the asymptomatic plants, contained a phytoplasma strain of group 16SrI, subgroup B (3). A search of rDNA sequences in GenBank revealed a similarity (>99%) to aster yellow phytoplasma, 16SrI group, thereby confirming strain identity based on RFLP analysis. These results indicate the disease of chrysanthemum is associated with a phytoplasma related to the aster yellow phytoplasma group. Sequences were deposited in GenBank (Accession No. FJ543467). A vector of this phytoplasma in chrysanthemum has not been identified. References: (1) E. Angelini et al. Vitis 40:79, 2001. (2) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) I. M. Lee et al. Int. J. Syst. Evol. Microbiol. 48:1153, 1998.

Stem anatomy and modulus of elasticity (MOE) were compared between upright and trailing cultivars of periwinkle [Catharanthus roseus (G.) Don.]. The inheritance of growth habit and flower form was also studied. Internode cross sections revealed that phloem fiber was distributed at the inner cortex in upright cultivars but not in trailing cultivars. Except the youngest internode, the upright ‘Vitesse Pink’ had the highest MOE throughout the 1st–13th internodes above the cotyledon. The more trailing ‘Cora Cascade Strawberry’ had consistently lower MOE than a less trailing ‘Cora Cascade Polka Dot’. All F1 plants between upright and trailing cultivars were upright, and the F2 generation derived from self-pollinating F1 fit a 3 upright : 1 trailing segregation ratio. All F1 plants between upright/double-flower and trailing/single-flower exhibited upright and single-flowers, whereas plants in the F2 generation fitted a 9 upright/single-flower : 3 trailing/single-flower : 3 upright/double-flower : 1 trailing/double-flower ratio. New double-flowered periwinkle selections with trailing growth habit were successfully developed from the F2 population.

A double-flowered periwinkle [Catharanthus roseus (L.) G. Don.] mutant TYV1 was identified and the morphology and inheritance of the double-flowered phenotype was studied. TYV1 has an outer salverform whorl of petals and an additional inner funnel-shaped whorl of petals originating from the apex of the corolla. The apex of corolla tube forms a narrow opening. There are hairs under the opening at the apex. The stigma in this mutant is set below the anthers. The overlap between the top end of the pistil and bottom ends of anthers in TYV1 flowers at 1 to 2 days after anthesis is 0.56 ± 0.01 mm. TYV1 could be used as either the male or female parent in crossing. Self-pollinated TYV1 produced all double-flowered progeny compared with self-pollinated single-flowered cultivars Little Pinkie and Titan Burgundy, which produced all single-flowered progeny. F1 plants between TYV1 and ‘Little Pinkie’ or ‘Titan Burgundy’ were all single. Three F2 populations segregated into 3 single: 1 double ratio. Backcrossing F1 to seed parents also indicated that a double-flowered form was controlled by a recessive allele. A single dominant gene expressed in the homozygous or heterozygous state resulted in the single-flowered phenotype. All the young seedlings of self-pollinated TYV1 and double-flowered progeny had distorted leaves before the sixth pair of leaves emerged.

Neoregelia cultivars have been used in many areas for landscaping and indoors in a variety of creative ways, but scientific reports of their pollination and hybridization are presently limited. Cross-combinations of Neoregelia cultivars were created to define conditions for pollination timing and to evaluate cross-compatibility. Neoregelia cultivars have short-lived flowers. Hybrid seeds were obtained only when cross-pollination was performed before 1200 hr. Results of 19 cross-combinations including six reciprocal crosses revealed that hybrid seeds were obtained in the female parents with a 1.9- to 2.0-cm style length, but not in those with a 2.6- to 3.0-cm style length. The pollen tube penetrated the ovule as early as 1 day after pollination in the compatible cross, whereas swollen pollen tubes were observed at half and two-thirds of the style in the incompatible cross. Removal of 50% of the style length of the female parents could overcome the fertilization barrier for those incompatible crosses and hybrid seeds could be successfully obtained.