Heritability and indirect selection indices of early growth in timothy (Phleum pratense L.)

Abstract

Breeding improvement of early growth in timothy (Phleum pratense L.) could help sustain high-quality vegetation in timothy-based grasslands. In this study, I investigated a useful selection method for early growth using 63 timothy genotypes, an orchard grass (Dactylis glomerata L.) cultivar (cv. Paykar), and a perennial ryegrass (Lolium perenne L.) cultivar (cv. Chinita) by field and laboratory tests in Kunneppu, Japan. This study employed the first crop dry matter yield in the established year as an early growth index. Early growth significantly differed among the genotypes and showed low to moderate narrow-sense heritability, which indicates that it is desirable to focus on line selection rather than individual selection. Multiple linear regression and canonical discriminant analyses revealed three useful indirect selection indices for early growth (plant vigor at establishment in field conditions, and thousand kernel weight and 7th day dry matter weight in Petri dishes in laboratory conditions). Predicted increases in timothy dry matter weight by multiple linear regression analyses using the above three traits also demonstrated that there is potential to achieve early growth similar to that of orchard grass, although it is difficult to secure as much early growth as perennial ryegrass.