Advanced cycle pedigree breeding in sunflower. I: Genetic variability and testcross hybrid performance for seed yield an
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Advanced cycle pedigree breeding in sunflower. I: Genetic variability and testcross hybrid performance for seed yield and other agronomic traits Godfree Chigeza • Kingston Mashingaidze Paul Shanahan
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Received: 6 July 2012 / Accepted: 3 October 2012 / Published online: 20 October 2012 Springer Science+Business Media Dordrecht 2012
Abstract As a plant breeding programme matures there is a general tendency to recycle elite inbred parents, a strategy known as advanced cycle pedigree breeding. The challenge with this approach is not only to maintain genetic variability in the base breeding populations but also their usefulness for further genetic advancement in developing experimental hybrids with better performance than the commercial hybrids on the market. To assess the genetic variability and usefulness of breeding populations in sunflower (Helianthus annuus L.), 109 new inbred lines across four breeding populations Pop1, Pop2, Pop3 and Pop4 in advanced cycle pedigree breeding scheme were testcrossed to two testers to form testcross hybrid (TCH) groups: Pop1TC, Pop2TC, Pop3TC and Pop4TC. Moderate to high genetic variability along with high heritability were obtained for seed yield and oil yield within and across all TCH groups. Heritability for oil content was low to high ranging from 0.36 (Pop2TC) to 0.81 (Pop1TC). Genetic advance (GA%) with a 10 % selection intensity ranged from 36 % (Pop2TC) to 42 % (Pop1TC) for seed yield; 38 % (Pop3TC) to 43 % G. Chigeza (&) K. Mashingaidze ARC-Grain Crops Institute, P/Bag X1251, Potchefstroom 2520, South Africa e-mail: [email protected] G. Chigeza P. Shanahan (&) Faculty of Science and Agriculture, University of KwaZulu Natal, Pietermaritzburg, South Africa e-mail: [email protected]
(Pop1TC) for oil yield; and 1.3 % (Pop2TC) to 5.1 % (Pop1TC) for oil content. To quantify the commercial potential of experimental TCHs, founder parent heterosis (FPH), mid-standard heterosis (MSH) and high standard heterosis (HSH) were calculated. Out of a total of 218 experimental TCHs evaluated, 28 had positive FPH, MPH and HSH values for oil yield representing a 13 % selection intensity as is usually applied in early generation testing. Keywords Genetic variability Helianthus annuus Heterosis Testcross hybrids
Introduction The crossing of related parental lines of commercial cultivars or obsolete cultivars to form new breeding populations followed by pedigree selection or single seed descent in breeding programmes is commonly referred to as advanced cycle pedigree breeding (Lu and Bernardo 2001). The strategy usually involves recycling elite inbred lines as way of avoiding linkage drag and thereby conserving gains already achieved in the past (Condo´n et al. 2008). While the avoidance of linkage drag is a necessity especially in mature plant breeding programmes, an undesirable feature of advanced cycle pedigree breeding is the narrowing of the genetic base (Yu and Bernardo 2004). Further challenges to this approach in crops such as sunflower
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is whether the varia
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