Campbell and Lipps, 1998;Yang et al., 1999). Resistance expression often differs among envi-The development of wheat (Triticum aestivum L.) cultivars resis-

Inheritance of height in barley (Hordeum vulgare L.) was studied with the objective of finding genes for short stature and understanding height inheritance. Segregation for height was visually classified in F3 populations derived from crosses of 11 short‐stature genotypes to two testers, tall cultivar Robust and M62 (a Minnesota semidwarf line containing the ‘Jotun’ derived sdw gene). Populations were classified in the field from 1987 to 1991. Height in the short‐stature genotypes was hypothesized to be controlled by one, two, or three recessive genes. The seven genotypes which have only one short‐stature gene, ‘Diamant’ (‘Triumph’ and ‘Cheri’), ‘Gus’, ‘Kombar’, NK41558, and SMAI6W41428, appear to contain sdw or an alternative allele at that locus. We hypothesize that two genotypes, E295 and ‘Poco’, contain one short‐stature gene in addition to the sdw gene, and that Apam Dwarf contains two short‐stature genes as well as sdw. ‘UC476’, the only short‐stature genotype in this study that appears not to contain sdw, likely has two other short‐stature genes. Heights of the parents and F2.3 progenies fell roughly into four classes, which we hypothesized corresponded to genotypes with no, one, two, or three recessive shortstature genes. Height differences in all populations and among the parents indicated that modifying genes play an important role in determining height. This study revealed that the sdw gene is wide‐spread, occurring in 10 of the 11 short‐stature genotypes. Putative new genes for short‐stature were found in E295, UC476, Poco, and Apam Dwarf.

The introgression of exotic germplasm could increase the heterosis among maize (Zea mays L.) populations. Our objective was to assess heterotic relationships among BSSS (R) (‘Reid’ germplasm) and BS 26 (‘Lancaster’ germplasm) from the temperate USA; the southern African cultivars Salisbury White, Southern Cross, and Natal Potchefstroom Pearl Elite Selection (NPP ES); and the subtropical CIMMYT Populations 34, 42, 44, and 47. The nine cultivars and their diallel crosses were evaluated at five Mexico, Zimbabwe, and U.S. locations. Populations 34, 42, 44, and 47 and NPP ES demonstrated the highest per se grain yield with Population 44 ranking first (8.42 Mg ha−1). Low to moderate levels of high parent heterosis was observed for their crosses; nonetheless, they occurred frequently as parents of superior crosses at Mexico where Population 42 × Population 47 ranked first (8.42 Mg ha−1). BSSS (R) demonstrated the best general combining ability with variety heterosis effects averaging 1.34 Mg ha−1 Diversity among varieties was determined on the basis of “dominance‐associated” gene effects. When the diversity was resolved by principle coordinate analysis, BSSS (R) was separated from BS 26, and Salisbury White from Southern Cross along different dimensional axes, suggesting that the two pairs are sources of different genes for heterosis. The highest yielding cross (9.28 Mg ha−1) and best heterotic combination involved Population 44 and BSSS (R). BSSS (R), NPP ES, and Populations 44 and 42 performed well outside their target ecologic zones, indicating their potential benefit to breeding programs in new geographic areas.

Observed 30 selected lines were crossed to two testers: CML-320 (heterotic group “A”) and CML- 321 (heterotic group “B”). The 60 line x tester combinations were evaluated at four location in the subtropical region of Mexico. In the combined analysis across locations the variance componentsfor the GCA and SCA were significant for grain yield. Significant SCA values allowed the separation of the inbred lines into two opposite heterotic groups based on the performance of the test crosses. On the basis of this information, two synthetics were formed with 7 inbred lines each defined as heterotic groups “A” and “B”. Nine single crosses outyielded the commercial check hybrid. Across locations the top yielder hybrid produced 9.48 t/ha which was 15.6% higher than the check. Average yield by location was 7.1, 3.8, 11.1 and 9.0 t/ha at Tlaltizapán, Tlajomulco, Celaya y Pabellón, respectively. Positive and significant GCA values were observed in six inbred lines. The GCA effects ranged from 1.18 to -2.19. The inbred lines from this study can effectively be used in hybridization programs.

Single fertilizer nitrogen rate of 146 kg N ha−1 for sugarbeet is outdated. Sugarbeet–fertilizer nitrogen recommendation should consider soil characteristics. Sugarbeet yield and sugar content was optimized at 112 kg N ha−1. In‐season soil nitrogen and red‐edge normalized difference vegetative index can predict yield response to nitrogen. Economic optimum nitrogen rate varies from 0 to 405 kg N ha−1. Fertilizer N application is critical to optimize sugarbeet (Beta vulgaris L.) yield and sugar concentration. Regardless of observed yields, current fertilizer recommendations in North Dakota and Minnesota suggest a single application rate of 146 kg N ha−1 (considering both fertilizer N residual soil N of 120 cm depth) for the Red River Valley (RRV) irrespective of soil type and organic matter content. Field experiments were conducted at three sites to determine sugarbeet response to N application rates, 0, 112, 146, 179, and 213 kg N ha−1 and optimal N rate during 2015 and 2016 growing seasons. Year and site had a significant effect on yield and sugar concentration. In 2015, fertilizer‐N significantly increased yield for all three sites, but in 2016, only one site responded to N. The highest N rate (213 kg N ha−1) reduced sugar concentration in 2016. In‐season soil available N (of 0–120 cm) significantly correlated with yield (R2 = 0.35) and economic return (R2 = 0.28). In season, red edge normalized difference vegetative index (RENDVI) based on the handheld optical sensor was significantly (P < 0.05) related to fertilizer‐N application rate. Economic optimum N rate for three sites varied from 0 to 405 kg N ha−1 depending on year and site characteristics. Our results suggest a revision of current sugarbeet fertilizer N recommendation to replace the single rate with N rates based on site characteristics and profitability to N applications.