Genetic Improvement in White Clover Representing Six Decades of Plant Breeding

Abstract

Improvements in white clover (Trifolium repens L.) performance during the past 60 yr can be attributed to increased use of fertilizer, better management practices, and development of genetically superior cultivars. The rate of genetic improvement during the past six decades was evaluated in New Zealand using a world collection of 110 white clover ecotypes and cultivars. Genetic differences were assessed by evaluating all cultivars in the same environment. Field trials conducted from 1985 to 1989 were managed using rotational grazing by sheep (Ovis aries L.) with an average of nine grazings per year. Cultivars were grouped according to decade of release, the climate in which they originated (cold, cool, or warm), and plant type (small‐leaved, medium‐leaved, large‐leaved non‐ladino, and large‐leaved ladino). Regression analyses were used to determine the rate of genetic improvement. In absolute units, white clover yield has increased at an annual rate of 1.44 g m−2, whereas the percentage clover by weight in the sward has increased at an annual rate of 0.14%. This equates to a genetic gain of 6% per decade for both traits, which is higher than rates reported for other forage crops. Genetic gains for clover yield and percentage clover in the sward have been greatest in small‐leaved (7.5 and 8.7% per decade) and large‐leaved, non‐ladino types (6.6 and 8.3% per decade), whereas cultivars originating in cool climates (8.3 and 8.1% per decade) have improved at a faster rate than those originating in either cold (3.5 and 3.2% per decade) or warm climates (1.5 and 2.6% per decade).

Review: World checklist of white clover varieties II

“…Better yields than other cultivars in early spring and late autumn in Japan (Yamada et al 1987). Had lower clover DM yield, clover content, and stolon density than HUIA, whereas TRIBLA had higher clover DM yield than HUIA under rotational grazing in New Zealand (Woodfield & Caradus 1994). Very poor winter growth in New Zealand (Caradus et al 1993b).…”

“…These differences can arise because of GxE interactions, different grazing/cutting managements, or because of genetic shifts during seed multiplication. Despite this variability, genetic gain as a result of breeding white clover cultivars has averaged 6% per decade for DM yield and clover content (Woodfield & Caradus 1994). Production of HCN in cultivars reported to be A96049 Received 2 July 1996; accepted 11 November 1996 acyanogenic probably occurs because of the presence of enzyme and cyanogenic glucoside in different plants within the cultivar.…”

Doğal Meralanrdan Toplanan Ak Üçgül (Trifolium repens L.) Genotiplerinin Performanslarının Belirlenmesi

“…Sağlamtimur et al, (1986), Aygün (1998) and Bullitta (1989) pointed out that plant characteristics are important on new variety development in breeding programs. A study related to white clover breeding has long been neglected until recant 20 years and this subject is vital on novel genotype development in Turkey (Açıkgöz 2001;Connolly, 2000;Woodfield, 1994;Hallowell, 1966;Elçi, 2005;Anon., 2008). Relationship between plant characteristics in white clover is shown Table 2.…”

Attributes related to seasonal herbage growth in white clover

“…In Argentina, nearly 300.000 ha are sown annually and the land where this legume is present in the Humid Pampa region was estimated in 4.9-5.4 M ha. Many cultivars have been released all over the world and genetic improvement has been possible due to improved evaluation methods and identification of parents with superior breeding value (Woodfield & Caradus, 1994). Germplasm collections are important sources of variation for breeding programs, but they must be properly characterized to be effectively utilized.…”