Abstract
The Iranian collection of Medicago sativa (alfalfa, 502 accessions) was evaluated under field conditions to identify variation in resistance to the alfalfa weevil (Hypera postica Gyllenhal) between accessions over 4 years. Twenty-one accessions were identified as resistant (score 3) to semi-resistant (score 5) based on K-means cluster analysis. These materials were grouped into 10 groups by means of Duncan's Multiple Range Test. Susceptibility to alfalfa weevil was significantly correlated with some of the agro-morphological traits such as plant height (r = 0.314, P<0.01), regrowth rate (r = 0.435, P<0.01) and fall dormancy score (r = 0.284, P<0.01). In general, the resistant germplasm originated from elevated regions at high latitudes, where a co-evolution between the plant and the pest may have taken place. Multiple regression analysis showed a positive linear relationship between susceptibility to the alfalfa weevil and traits such as growth habit, plant height, length and width of the central leaflet and regrowth rate. The resulting bi-plot based on factor analysis ranked accessions for susceptibility to the pest. The identified germplasm should prove useful in alfalfa breeding programs to develop accessions resistant to the alfalfa weevil.
Highlights
Alfalfa (Medicago sativa L.) is one of the most important forage legumes in the world, and is adapted to a wide range of environments
Studies have shown that the probability of accessing traits, such as resistance to alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), is much higher in material collected from the centers of genetic diversity than other parts of the world (Jolivet 1998; Thompson and Cunningham 2002)
Twenty-one accessions were identified as resistant to semi-resistant based on K-means cluster analysis and are suggested for use in breeding studies as sources of genes for resistance to alfalfa weevil [called resistant collection (RC), Table 2, Appendix 2]
Summary
Alfalfa (Medicago sativa L.) is one of the most important forage legumes in the world, and is adapted to a wide range of environments. It is the main forage legume in Iran, being cultivated in about 600,000 ha of mostly irrigated lands (Ahmadi et al 2015). Some parts of Iran are known as the center of diversity for diploid and tetraploid forms of M. sativa (Lesins 1976). Studies have shown that the probability of accessing traits, such as resistance to alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), is much higher in material collected from the centers of genetic diversity than other parts of the world (Jolivet 1998; Thompson and Cunningham 2002)
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