BREEDING FOR RUST RESISTANCE AND SOME ECONOMIC CHARACTERS IN SNAP BEAN | ||||
| Egyptian Journal of Plant Breeding | ||||
| Volume 21, Issue 2, April 2017, Page 339-361 PDF (1.4 MB) | ||||
| Document Type: Original research | ||||
| DOI: 10.12816/ejpb.2017.424333 | ||||
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| Abstract | ||||
| This study was conducted to improve some new promising snap bean (Phaseolus vulgaris L.) lines by selection for some economic characters and rust [Uromyces appendiculatus (Pers.) Unger] resistance. Two F3 populations of snap bean (Concessa x Paulista and Concessa x Samantha) were used in this study as the main genetic material in addition to check cultivars (Concessa, Paulista and Samantha). Results showed that all studied trait means improved by selection. Thirty selected lines and three commercial cultivars were evaluated for rust reaction and some economic characters during two successive autumn seasons (2014 and 2015). Twenty three lines showed absolute resistance against rust in both seasons. Seven breeding lines showed variable severity (3.0-60.0%) over the two years of investigation, being more pronounced in 2015. The genotype FA 1-3 was categorized as highly resistant (hypersensitive). While, Paulista and Samantha cultivars were rated as susceptible (30.00-58.33%). It could be concluded that susceptibility of lines and climatic conditions may be primary factors in disease widespread. Epidemiological work carried out during study years revealed an intense disease severity during the sixth week after planting, though the infection was apparently taking place during the fifth week. The disease severity in second season was greater than in the first one and this was attributed to the favorable infection conditions. The lower dew point coincides with the fifth week after planting, however, it seems probable that atmospheric humidity does not influence directly the primary infection, but it may influence the progress of the pustule as related to the genetic composition of given genotypes. Estimated coefficient of variance (CV%) values indicated that most of the new selected lines had enough homogeneity in most studied characters as compared with the check cultivars. The large portion of phenotypic variance (σ2p) was due to the genetic variance (σ2g). Also, estimated broad-sense heritability showed high values (64% to 97%) in all traits, except pod weight trait, indicating that the observed significant phenotypic differences among the studied genotypes are of genetic nature and there are small environmental effects on the phenotypic variation. Therefore, yield and pod quality as well as rust resistance traits can be improved through selection based on phenotypic observations in snap bean. The promising selected lines of snap bean FA 1-16, FA 2-6, FA 2-13, FA 2-14, FA 2-15 and FA 2-17 could be considered for certification (after more evaluation). They had homogeneity, pod quality and resistant to rust disease. | ||||
| Keywords | ||||
| Phaseolus vulgaris; Snap bean; Uromyces appendiculatus; Dew point; Rust resistance; Selection; Heritability | ||||
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