Assessment of heterosis for selected traits in hybrid HEAR
Notice bibliographique
Résumé
summer oilseed rape with canola quality is one of the most important crops grown in westem canada, with the majority of the acreage seeded to hybrid cultivars.Although the phenomenon of hybrid vigor or heterosis is not completely understood, hybrid cultivars tend to possess greater vigor, increased seed yields, improved quality and better disease resistance.Previous studies have shown that crosses of summer oilseed rape can result in 40 to r20%o high-parent heterosis for seed yield.until recently, the development of hybrids in high erucic acid rapeseed (HEAR) has not been a viable option due to the limited genetic pool available.For this study twelve genetically and geogr.aphicallydiverse HEAR cultivars/strains þarents) were selected and crossed by full hand emasculation in a top-cross design to produce 45 F1 hybrid combinations.seven of the twelve parental lines were HEAR cultivars/strains developed by the university of Manitoba (uM) and the remaining five were prop.ietaryEuropean (EU) produced HEAR strains.Adequate seed was produced to evaluate the hybrids and parents in six enviromrents in Manitoba during 2004 and 2005.six agronomic traits (vigor, days to first flower, days to maturity, pre-harvest lodging, plant height, and seed yield) and six seed quality chalacteristics (oil concentration, protein concentration, sum of oil and protein concentration, erucic acid concentration and glucosinolate concentration) were assessed in this study.Based on this assessment, mid-parent, high-parent and commercial heterosis estimates for each hybrid combination were calculated.General combining abilities of the parent cultivars/strains and specific combining abilities of the hybrid combinations for each agronomic and quality trait were also calculated.Differences between hybrids and parent cultivars/strains were easily visually distinguishable in field trials after emergence due to the higher vigor of the hybrids.superior performing hybrids produced in this study displayed high-parent heterosis estimates for seed yield of up r.o 155%o and commercial heterosis for seed yield of up to 107%.These superior performing hybrids were much taller and had considerably better lodging resistance than parental cultivars/strains.Although seed protein concentration was lower in the higher seed yield hybrids than in the parents, the oil concentration exceeded the parents.The top performing hybrids produced in this study were frorn uMx EU crosses, as predicted by pedigree and/or-geographical diversity.glucosinolate content in the seed.\n 19'74, Dr. Baldur Stephenson at the University of Manitoba was the first plarrt breeder in the world to successfully release a rapeseed cultivar named "Torver" that had the desired edible oil profile and was also low in seed glucosinolate content (stefansson and Kondra, 1975).cultivars which were low in both erucic acid and glucosinolates were termed "double low" and were described as "canola" in 1979 by the Canola Crushers of Westem Canada to clearly distinguish them fiom rapeseed (Sernyk, 1982).During the same period canola or double low oilseed rape lines were being developed, Dr. Baldur stephenson recognized the usefulness of maintaining or.improving the high emcic acid profile and began to lower the glucosinolate content ofthe seed meal while raising the e¡ucic acid content ofthe oil (>50%).These lines were refered to as high erucic acid'apeseed (HEAR).By lowering the glucosinolate content irr rapeseed, this created new uses for the meal mainly as a high protein livestock feed.with both the oil and meal being used, the economics of crushing HEAR greatly improved.New uses for erucic acid such as a slip agent in plastics and metal manufacturing have since been discovered (Katavic et a\.,2001).The world's first HEAR cultivar released was Reston in 1982 (Alberla Agricultr.rre,1982) which was then followed by Hero in 1991(Scarth et al., 1991)).several new HEAR cultivars f¡om the cross that produced Hero were released through the 1980's and early 1990's.Much of the University of Manitoba breeding efforts to develop new HEAR cultivars has used these cultivars as a source for high erucic acid content and low glucosinolate conteff.
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|---|---|---|
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