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Reports of a grain yield improvement of single cross (SCSH) vs. three-way (TWSH) sorghum (Sorghum bicolor L. Moench) hybrids are scarce. The objective of this study was to compare midparent heterosis, high parent heterosis, and general and specific combining ability for yield traits (panicle length and width, grain yield/panicle, grains/panicle and 100-grains weight) of SCSH, TWSH and its parental lines. Irrigated and rainfed field trials were established in the Mexican Highlands (2100 m altitude; 8 °C mean early morning temperature during the growing season). Both trials included five groups of genotypes (three or four pairs of 'A'/'B' lines, four 'R' lines, 11 SCSH and 41 TWSH). Significant differences (p0.05) were found for groups of genotypes (G) and environments (E) for most traits, but the GE interaction was not significant (p0.05). The TWSH group did not show significant differences (p0.05) with that of the SCSH group for any trait. None significant differences (p0.05) were found for grain yield/panicle and grains/panicle between the group of 'R' lines, and those of SCSH and TWSH. High parent heterosis estimates were low due to the high expression of the 'R' lines. Estimates of general combining ability of female and male parents were significantly different (p0.05), but not for specific combining ability in both hybrid types. Our 'R' lines can be sown as open pollinated varieties in the Mexican Highlands instead of sorghum hybrids. [ABSTRACT FROM AUTHOR]

The redbay ambrosia beetle, Xyleborus glabratus Eichoff, (Coleoptera: Curculionidae: Scolytinae) is a severe pest of North American trees and shrubs in the family Lauraceae. Supercooling point (SCP) is an important physiological baseline for cold tolerance studies and could provide useful insights into the invasive potential of X. glabratus in northern latitudes of North America. The supercooling point (SCP) of X. glabratus was experimentally determined on field-collected and artificially cold hardened specimens. Field-collected beetles were captured in Jackson County, Mississippi using Lindgren funnel traps baited with manuka oil lures. Testing was conducted from June through August 2011. The mean SCP for field-collected X. glabratus was -21.7 ± 0.5 °C (± SE). A significant negative trend in the SCPs of field-collected beetles occurred over the summer testing period. Xyleborus glabratus specimens were reared from redbay (Persea borbonia (L.) Sprengel bolts in June 2012 and artificially cold hardened in a low temperature incubator at a thermo-photoperiod of 7 °C:2 °C (10:14 h L:D) for 31 days. Artificially cold hardened X. glabratus supercooled to a mean temperature of -23.9 ± 0.4 °C (± SE), which was significantly lower than that of field-collected beetles. Biometric indices of beetles (size, weight, and size x weight interaction) had no effect on the mean supercooling SCPs of either field-collected or artificially cold hardened beetles. Results from environmentally conditioned beetles suggest that X. glabratus has a high degree of thermal plasticity. Based on the artificially cold hardened mean SCP, X. glabratus and laurel wilt disease have the possibility to impact sassafras and northern spicebush throughout eastern North America. The data, although preliminary, suggests that a previous spatio-temporal model based on climate match data may have substantially underestimated the geographical area that may be affected by X. glabratus. This study will help form the basis of building and validating models to better predict the North American invasion potential of X. glabratus. [ABSTRACT FROM AUTHOR]

The work was carried out in "Los Palacios" Rice Research Station, where the behavior of rice genotypes selected for cold tolerance under field conditions in early cold seeding was studied. A group of morphologic and agronomic traits previous to crop harvest was evaluated. Data were statistically processed by multivariate techniques of Principal Components and Cluster. Genotypes were grouped in 15 classes and there was a differentiated answer of genotypes to cold conditions. [ABSTRACT FROM AUTHOR]

The work was carried out at "Los Palacios" Rice Research Station under controlled conditions in 2002 to ±18°C and relative humidity of 85 %; the behavior of rice lines and varieties selected for cold tolerance was studied. Seed germination, plant height and root length were evaluated at 5, 10 and 15 days. Data were statistically processed by means of multivariate cluster analysis. Genotypes were collected in five classes and the best ones are in the classes I, IV and III. [ABSTRACT FROM AUTHOR]

In "Los Palacios" Rice Research Station areas, belonging to the National Institute of Agricultural Sciences, the present work was developed, with the objective of carrying out an association analysis of 12 characters evaluated in early cold sowing to a group of genotypes selected for cold tolerance. For statistical data analysis, multivariate statistical techniques of Principal Components and Cluster were used. The best associations were given by panicle length, full grains per panicle and yield, and between height 20 and 30 days after germination. Also, along with the previous variables, empty grains and shoot number 60 days after germination were the most important characters for the analysis, such associations constituting an essential information for cold tolerant material selection in rice breeding programs. [ABSTRACT FROM AUTHOR]