W. H. White

An assessment of the genetic diversity within a collection ofSaccharum spontaneum L. with RAPD-PCR

A local collection of 33Saccharum spontaneum L. clones and two sugarcane cultivars (LCP 82-89 and LCP 85-384) were assessed for genetic variability using random amplified polymorphic DNA (RAPD)-PCR. A total of 157 polymorphic RAPD-PCR bands were scored with 17 primers. The number of RAPD-PCR products per primer ranged from four to 16. The data were analyzed with two multivariate analysis software programs, NTSYSpc and DNAMAN®. Although these two programs yielded similar results, a bootstrapped phylogenetic tree could only be generated with the DNAMAN® software. A substantial degree of genetic diversity was found within the localS. spontaneum collection. Pairwise genetic homology coefficients ranged from 65% (SES, 196/Tainan 2n = 96) to 88.5% (IND 81-80/IND 81-144). LCP 82-89 and LCP 85-384 shared a greater similarity (82%) than either was to any clone ofS. spontaneum (ranging from 60.5 to 75.2%). The 33S. spontaneum clones were assigned to eight groups independent of their geographic origin or morphology, while the two sugarcane cultivars were assigned to the ninth group. All but two pairs ofS. spontaneum clones could be distinguished by a single RAPD primer OPBB-02. The use of a second primer, either OPBE-04 or Primer 262, separated allS. spontaneum clones. One amplification product from the RAPD primer OPA-11, OPA-11-336, proved to be cultivar-specific and has been adopted for use in our breeding program. Information from this study would help conserve the genetic diversity ofS. spontaneum.

Conventional Resistance of Experimental Maize Lines to Corn Earworm (Lepidoptera: Noctuidae), Fall Armyworm (Lepidoptera: Noctuidae), Southwestern Corn Borer (Lepidoptera: Crambidae), and Sugarcane Borer (Lepidoptera: Crambidae)

Abstract Plant resistance is a useful component of integrated pest management for several insects that are economically damaging to maize, Zea mays L. In this study, 15 experimental lines of maize derived from a backcross breeding program were evaluated for resistance to corn earworm, Helicoverpa zea (Boddie); fall armyworm, Spodoptera frugiperda (J. E. Smith); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.). Experimental line 100-R-3 was resistant in the field to leaf feeding by fall armyworm and line 116-B-10 was resistant in the field to leaf feeding by fall armyworm and leaf and stalk feeding by southwestern corn borer. When corn earworm larvae were fed field harvested silks from experimental line 81-9-B in the laboratory, their pupal weights were significantly lower than the pupal weights of larvae that were fed silks from the resistant control, Zapalote Chico. Maysin levels lower than those commonly associated with corn earworm resistance were present in the resistant experimental line, 107-8-7, indicating a new basis confers resistance to corn earworm in this line. These resistant experimental lines will provide plant breeders with new sources of resistance to lepidopterous insects for the development of improved maize breeding populations.

Monitoring and First Discovery of the Mexican Rice Borer Eoreuma loftini (Lepidoptera: Crambidae) in Louisiana

The Mexican rice borer, Eoreuma loftini (Dyar), is native to Mexico, and has been reported in the Mexican states of Baja California, Colima, Hustecas, Jalisco, Michoacan, Nayarit, Nuevo Leon, Oaxaca, San Luis Potosi, Sinaloa, Sonora, Tamaulipas, Veracruz, and Yucatan (Morill 1925; Van Zwaluwenburg 1926; Riess 1981; Johnson 1984; Rodriguez-del-Bosque et al. 1989; ReayJones et al. 2007). Eoreuma. loftini was originally described by Dyar (1917) as a member of the genus Chilo Zincken from a specimen collected in Arizona, U.S.A. The species was transferred to Eoreuma Ely by Klots (1970). It has been collected from sugarcane (Saccharum officinarum L.), corn (Zea mays L.), rice (Oryza sativa L.), sorghum (Sorghum bicolor (L.) Moench), and lemongrass (Cymbopogon citrates I flexuosus L.) (Johnson 1984). Weedy grasses including johnsongrass (Sorghum halepense (L.) Pers.), vaseygrass (Paspalum urvillei Steud.), Amazon sprangletop (Leptochloa panicoides (J. Presi) Hitchc), and barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) also have been reported as hosts (Reagan et al. 2007). It was first reported in the Lower Rio Grande Valley (LRGV) of Texas, U.S.A. during 1959 when a single larva was detected in sugarcane shipped from Mexico (Johnson 1984). By 1980, E. loftini had established itself as a serious pest in the LRGV and populations subsequently spread into the rice production region of Texas along the Gulf Coast (Johnson & van Leerdam 1981, Browning et al. 1989). From 2000 to 2002, female sex pheromone traps captured E. loftini moths in seven new southeast Texas counties (Reagan et al. 2005; Reay-Jones et al. 2007). During 2002, moths were captured within 100 km of sugarcane in east Texas and within 200 km of sugarcane in Louisiana. By 2004, E. loftini was present in over 75% of the Texas rice growing area and had spread into sugarcane plantings in Chambers County, Texas (Reagan et al. 2005, Reay-Jones et al. 2007). In an attempt to slow the spread of E. loftini into Louisiana, in 1999, the Louisiana Department of Agriculture and Forestry (LDAF) entered into a compliance agreement with the Texas Department of Agriculture which placed restrictions on the entry oiE. loftini infested Texas sugarcane into Louisiana for processing. This agreement required that east Texas sugarcane fields be monitored for E. loftini using pheromone traps. The agreements conditions also stipulated that a positive E. loftini finding in east Texas sugarcane would automatically trigger the establishment of a one-mile-radius quarantine around that field and sugarcane within that quarantined area could not be shipped into Louisiana. All truckloads of sugarcane destined for Louisiana were required to be tagged and certified as E. loftini free (Reagan et al. 2005). In a proactive effort to monitor the natural spread of E. loftini, LDAF initiated deployment of 12 pheromone traps during fall 1999 at selected sugarcane fields and adjacent to sugarcane processing facilities in Louisiana. The number of traps deployed annually increased from 12 to 40 through 2005. During this timeframe, traps also were placed near rice fields. Beginning in 2005, 35 to 40 traps have been deployed annually. Traps remained in the field from planting of rice (Mar) through harvest of sugarcane (DecJan), and until processing facilities finished milling sugarcane. The detection of E. loftini in 2 east Texas pheromone traps adjacent to sugarcane in 2004 (2-IX2004, 20-IX-2004, 2-X-2004) triggered a one-mileradius quarantine (Reagan et al. 2005). By 2005, E. loftini was widespread in east Texas and all sugarcane from that area was prohibited from entry into Louisiana due to the risk of accidental introduction of E. loftini (Reagan et al. 2007). This prohibition helped to slow the spread of E. loftini movement into Louisiana (Reay-Jones et al. 2008). The pheromone trap monitoring program determined that E. loftini was expanding its range 16.5 km/yr through the Texas rice belt toward Louisiana (Reay-Jones et al. 2007). Based on natural movement, Reay-Jones et al. (2007) predicted that E. loftini would establish in Louisiana during 2008. On 12-XII-2008 one E. loftini adult was detected in each of 2 pheromone traps in Calcasieu Parish (Louisiana, U.S.A.) located approximately 8 km from the Texas border. These traps were adjacent to harvested rice fields approximately 8 km apart. C. Carlton confirmed identifications by examination of male genitalia and com-

Cluster analysis for assessing sugarcane borer resistance in sugarcane line trials

Abstract Sugarcane borer, Diatraea saccharalis (F.), damage is complex and can be measured by multiple variables, i.e. visual damage and percentage of internodes bored. Cluster analysis is a statistical technique to summarize similarities among many objects that have multiple measured variables and was used to assess early sugarcane, Saccharum interspecific hybrids, line trials for resistance to sugarcane borer. A selection series of 44 varieties was evaluated by their response to sugarcane borer; four times under artificial infestation and once under natural infestation. The composition of varieties partially changed from year-to-year as low-yielding or poor-performing varieties were dropped from the program and as new varieties were added. Visual injury estimates and percentage of bored internodes at harvest were subjected to traditional analysis of variance with subsequent multiple comparisons and to hierachical cluster analysis. Classification of varieties by analysis of variance was made difficult by the multivariate data collected and multiple comparison test assigning variety means to overlapping groups. With cluster analysis, information from multiple variables can be used to assign varieties to discrete classes. Labels (resistant, susceptible) were placed on these discrete classes with the aid of commercial varieties of known to reaction sugarcane borer included as industry standards. The four-cluster analysis explained more variation among the varieties than the three-cluster and including an additional cluster group provided insight into the mechanisms of resistance to sugarcane borer. Groups with high visual injury ratings and low percent internodes bored may lack tolerance to sugarcane borer feeding. Conversely, groups with low ratings and high percent internodes bored may possess tolerance to sugarcane borer.

Techniques to quantify the effect of Diatraea saccharalis (Lepidoptera: Pyralidae) on sugarcane quality

Abstract The effect of sugarcane borer feeding damage on subsequent sugarcane ( Saccharum interspecific hybrid) quality has often been difficult to quantify due to errors arising from different milling techniques and sampling procedures. An experiment was conducted on cane badly damaged by the sugarcane borer to compare values of commercially recoverable sugar (CRS) from the traditional roller-mill method and a simulated form of the core-sample method. In the roller-mill method, a 15-stalk sample is crushed in a 3-roller mill, the juice is analyzed, and CRS is calculated using a cultivar correction factor which adjusts for fiber using the fiber content of clean, unbored sugarcane. In the simulated core-sample method, a 50-stalk sample plus associated trash is chopped in a pre-breaker, the crusher juice from the shredded cane samples is analyzed, and CRS is calculated using a correction for the actual fiber of the sample; thus, the detrimental effects of the sugarcane borer as reflected in water sprouts, secondary tillers, lateral shoots, and associated tops of cane are accurately taken into account. In a split-plot field experiment comparing undamaged to badly damaged cane, the sugarcane borer significantly reduced stalk weight while significantly increasing the number of water sprouts and late-season tillers. Although both the roller-mill and the core-sample method detected significant differences in CRS among cultivars when averaged over sugarcane borer-damaged and undamaged plots, only the core-sample method exhibited the precision to detect a significant cultivar × treatment interaction. The data presented in this paper show conclusively that the core-sampling method of determining CRS provides a more accurate and reliable estimate of sugarcane borer-related sugar loss under commercial conditions; however, differences between techniques are not nearly so pronounced when sugarcane-borer damage is expressed as a loss of sugar/ha. This results from the complex nature of sugarcane-borer damage and the inclusion of other yield and damage factors independent of CRS determinations.

Geographic Population Structure of the Sugarcane Borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), in the Southern United States

The sugarcane borer moth, Diatraea saccharalis, is widespread throughout the Western Hemisphere, and is considered an introduced species in the southern United States. Although this moth has a wide distribution and is a pest of many crop plants including sugarcane, corn, sorghum and rice, it is considered one species. The objective was to investigate whether more than one introduction of D. saccharalis had occurred in the southern United States and whether any cryptic species were present. We field collected D. saccharalis in Texas, Louisiana and Florida in the southern United States. Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD. We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species. Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.

A Relative Resistance Ratio for Evaluation of Mexican Rice Borer (Lepidoptera: Crambidae) Susceptibility Among Sugarcane Cultivars

ABSTRACT The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane (hybrids of Saccharum spp.) in Louisiana and Texas. Resistance to E. loftini was evaluated in 51 commercial and experimental cultivars of sugarcane, energycane (hybrids of Saccharum spp.), and sorghum [Sorghum bicolor (L.) Moench and hybrids of Sorghum spp.] in four replicated small plot field experiments from 2009 to 2012. A relative resistance ratio was developed to compare levels of susceptibility among cultivars based on the percentage of bored internodes and survival to adulthood. This index was able to separate cultivars into five resistance categories and provides a new method for comparing levels of resistance among cultivars. E. loftini pest pressure in 2009 was among the highest recorded with injury ranging from 55 to 88% bored internodes. Commercial sugarcane cultivar HoCP 85–845 was identified as resistant in three of four experiments, whereas HoCP 04-838 was identified as susceptible in all experiments. Of the five sugarcane cultivars in commercial production in the Rio Grande Valley of Texas, only TCP 87-3388 was categorized as resistant. Of the cultivars with potential for bioenergy production, all of the energycane cultivars demonstrated higher levels of resistance than high-biomass and sweet sorghum cultivars. Continued evaluation of cultivar resistance to E. loftini is important to development of effective integrated pest management strategies for this pest.

Microsatellite DNA marker-assisted selection ofSaccharum spontaneum cytoplasm-derived germplasm

New lines of Saccharum hybrids with an array of S. spontaneum cytoplasm backgrounds are reported. To expand the genetic base of sugarcane, we made eleven bi-parental crosses between ten S. spontaneum (S) and six commercial-type sugarcane (C) clones during the 2001 crossing season. Prior to crossing, all the maternal S. spontaneum inflorescences were emasculated by immersion in a 50°C circulating water bath for 5 minutes. Analysis of microsatellite fingerprints between parents and progeny allowed us to classify 1,952 progeny grown out from these crosses into four genotypic classes. Class H progeny inherited microsatellite alleles from both the S. spontaneum and the commercial-type parents and were, therefore, considered being F1 hybrids. Class S and Class C progeny inherited microsatellite alleles only from one parent and were considered to be either selfs of either parent or F1 hybrids that only inherited allele(s) from one parent. Class X progeny inherited non-parental microsatellite allele(s) in addition to the allele(s) from the maternal S. spontaneum parent and were considered to be contaminants. With the exception of one cross, eight to ten Class H progeny were pre-selected from each cross while still in seedling greenhouse and were backcrossed with commercial-type sugarcane clones. The remaining progeny were transplanted into a breeding nursery for phenotypic evaluation that concurred with the molecular classification. Pearson Correlation Coefficients between molecular and phenotypic classifications were inconsistent that justified the need of molecular markers in the selection process. This study demonstrated that the molecular approach of fingerprinting progeny to confirm parentage prior to field planting even with only one microsatellite marker might substantially increase selection efficiency.

Host plants impact courtship vibration transmission and mating success of a parasitoid wasp, Cotesia flavipes (Hymenoptera: Braconidae)

Abstract Host plants provide food, shelter, and mating habitats for herbivorous and parasitoid insects. Yet each plant species is a microhabitat with distinct chemical and physical attributes that may drive selection and diversification of insects. This study examines differences in courtship vibration signal transmission through leaves of three host plant species that vary in physical characteristics (leaf tissue density, leaf width and percent moisture) and how signal transmission relates to mating success for a parasitoid wasp. The vibration signals transmit with a longer duration and a higher relative amplitude in the host plant leaves of the species with the lowest leaf tissue density, which was also the plant type with the highest mating frequency. Host plants may be a selective force on courtship vibration signals and may contribute to the behavioral or genetic divergence of populations on different host plant species.

Sugarcane recovery from spring stand losses associated with simulated insect feeding as influenced by soil-applied herbicides

Abstract The influence of stand losses of sugarcane (a complex hybrid of Saccharum spp.) shoots in the spring associated with simulated insect feeding was investigated by removing 0, 25, 50, and 75% of the emerged sugarcane shoots 2–5 cm below the soil surface in mid-March, mid-April, and mid-May in plant-cane and first-ratoon fields of sugarcane. The effects of spring stand reductions on sugar yield and its components were determined at the end of the growing season and in the subsequent ratoon crops that remained in a conventional, Louisiana 3-year crop cycle. Sugar yields were affected by a 25% removal of shoots only when the removal occurred in mid-May during the first-ratoon crop. Reductions in sugar yield ranged from 6 to 10% when 50% of the shoots were removed in mid-April or mid-May, to 8–18% when 75% of the shoots were removed. Reductions in sugar yield associated with the April and May removal dates were generally higher when shoots were removed during the first-ratoon than the plant-cane crop. Although reductions in sugar yield were obtained in the subsequent ratoon crops, reductions in cumulative sugar yields were not as great as the reductions in the affected crop. Yearly and cumulative sugar yields were higher when metribuzin was applied each spring than when fenac or terbacil was applied; however, none of these herbicides appeared to influence how quickly the cane crop recovered from shoot loss. Reductions in yearly, tennant grower profits were greater than the reductions in sugar yield following shoot loss when averaged over an 8-year, two crop cycle, payback period. Due to high planting costs, the premature destruction of the crop prior to the completion of its 3-year crop cycle was not warranted despite the significant reduction in profit.