In-row Diploid Watermelon Pollenizer Competition with Triploid Watermelon Based on Four Planting Ratios

Diploid watermelon (Citrullus lanatus) pollenizers are planted within triploid watermelon fields to provide viable pollen for triploid fruit set. In recent years, pollenizer cultivars with desirable characteristics for planting in-row with triploid watermelons have been commercially available. The degree of plant competition from in-row pollenizers grown in the commercially common arrangement where pollenizers are placed equidistant from neighboring triploid plants has not been reported. Field experiments were conducted in 2005, 2006, and 2007 in Quincy, FL, to examine the competitive impact of in-row pollenizers grown equidistant from neighboring triploid plants. Four ratios of pollenizers-to-triploids: 1:1, 1:2, 1:3, and 1:4 were used to provide various levels of pollenizer competition. No significant difference in yield based on the weight or number of fruit per triploid plant resulted from the varied pollenizer ratios. Therefore, pollenizers grown in-row at an equidistant spacing from the neighboring triploid plants had no competitive impact on the yield of the triploid watermelon crop.

Molecular Biological Approach of Crocus sativus L. and its Allies

The hay saffron (Crocus sativus L.) is a sterile triploid plant, known in human culture only, with no fertile seeds produced. The origin of saffron is still a mist, however it is assumed to be an autopoliploid mutant or a hybrid. The recent classification and most of the former taxonomic publications define C. sativus to be derived from C. cartwrightianus, a wild species. Because of the sterility of hay saffron it seemed to be reasonable to apply molecular biological methods to complete classical taxonomic studies in examining its relations. The DNA polymorphism based AFLP method has confirmed the close relationship between these species.

Genome relationship between Thinopyrum bessarabicum and T. elongatum: revisited

New meiotic pairing data on triploids and amphidiploids derived from the diploid hybrids between Thinopyrum bessarabicum (Savul. &Rayss) A. Love (2n = 14; JJ) and T. elongatum (Host) D. R. Dewey (2n = 14; JeJe) are presented, which support the close relationship between the genomes of these two species. Three triploids having the JJJe genome constitution were analyzed. Two (both derived from backcrossing amphidiploids of T. bessarabicum × T. elongatum with T. bessarabicum) had an averaged metaphase I pairing pattern of 3.89 I + 0.96 rod II + 3.30 ring II + 2.75 III + 0.06 chain IV + 0.01 ring IV in spikes from a field-grown plant and two greenhouse-grown plants sampled in early spring. Another, which was the F1 triploid progeny of T. bessarabicum × T. elongatum as the result of fertilization of an unreduced megaspore (JJ) by a reduced microspore (Je), had 3.62 I + 2.16 rod II + 1.34 ring II + 3.28 III + 0.10 chain IV + 0.02 ring IV in spikes of a field-grown plant. The first triploid plant had an averaged metaphase I pairing of 4.60 I + 0.74 rod II + 4.03 ring II + 2.19 III + 0.06 chain IV + 0.01 V in spikes sampled in a warmer greenhouse. The amphidiploids exhibited variable pairing patterns with a wide range of multivalent frequency. It is interpreted that the J and Je genomes are essentially homologous, with difference due mainly to two translocations. A genetic mechanism for a "bivalentization" appeared to be present in most, if not all, amphidiploids and the triploids derived from them. Meiotic pairing patterns reported here for triploid hybrids T. junceiforme (Love &Love) A. Love (2n = 28; JJJeJe) × T. bessarabicum, its reciprocal, and T. bessarabicum × T. scirpeum (K. Presl) D. R. Dewey (2n = 28; JeJeJeJe) also support the conclusion that J and Je genomes are homologous. The network of meiotic data supports the conclusion that J and Je are two versions of the same basic genome.Key words: genome, meiosis, hybrid, amphiploid, bivalent formation.

Cytomorphological studies of a spontaneous triploid in Pennisetum hohenackeri Hochst. ex Steud.

During studies on the genomic relationships of the wild species of the genus Pennisetum, one spontaneous triploid (3x = 27) plant was identified among the diploid cytotypes (2n = 18) of Pennisetum hohenackeri Hochst. ex Steud. The triploid plant resembled the diploid in most morphological characters, except for the reduced number of spikelets. Chromosome associations of 9 II + 9 I were observed at diakinesis and metaphase I. The bivalents divided normally, while the univalents lagged and formed a separate nucleus, which was included in one of the daughter cells. On the basis of these studies, this plant was considered to be an allotriploid and might have originated as a spontaneous hybrid between diploid P. hohenackeri and an unknown tetraploid (amphidiploid) taxon with one of its genomes homologous to that of diploid P. hohenackeri. The possible donor of this genome could be P. orientale, which is a tetraploid with a basic chromosome number of x = 9.Key words: allotriploid, meiosis, diakinesis, univalents, micronuclei, laggards.

MORPHOLOGY AND CYTOLOGICAL BEHAVIOR OF ANEUPLOIDS OF SORGHUM BICOLOR

Ten types of single trisomics were tentatively classified within a progeny of a selfed homozygous triploid plant of Sorghum bicolor Moench using morphological characteristics. Of the 111 offspring obtained, 40 were found to be diploid, 58 trisomic, 11 double trisomic, 1 triple trisomic and 1 plant (because no heads were formed) unknown. Most of these trisomics were less vigorous than the diploids. Trisomics differed in number of tillers, plant height, panicle length, and fertility. Two types of trisomics had abnormalities apparently related to the sterility observed in these types. In Type 8, pollen grains had papilliform appendages and in Type 9 ovaries contained tumorous growths.One double trisomic was tentatively identified as Type 1–4 according to morphological appearances. Cytological analysis of pairing relationships of metaphase I of this plant indicated a close correspondance to the theoretical expectation.The trisomic types (excluding variants) arranged in order of decreasing frequency of occurrence correlated well with their order in decreasing percentage of trivalent formation. This order, therefore, might be interpreted to give an indication of the relative length of the extra chromosome found in each trisomic type.