Page 122 - Breeding and regulatory opportunities, Renaud

Chapter 4

Broccoli producers in the USA need cultivars that exhibit heat tolerance,

head stability, and uniform maturation in the ield, while others are seeking

extended harvest from side-shoot development (Heather et al., 1992; Farnham

et al., 2011a,b; Myers et al., 2012). Some desired traits in organic management

are shared with conventional producers, such as drought tolerance, insect

and disease resistance and high yield. Other cultivar characteristics that are

more important to organic producers include vigorous early growth, waxy

leaves, ability to perform in soils with potentially low or luctuating nutrient

mineralization rates, and the ability to compete with weeds (Lammerts van

Bueren et al., 2002; Lammerts van Bueren and Myers, 2012; Lammerts van

Bueren et al., 2012). This is particularly important in broccoli due to its relatively

high nitrogen requirement and shallow ine root system, which limits its ability

to take up water and nutrients (Pasakdee et al., 2005; Sajeemas et al., 2006;

Myers et al., 2012). Most studies investigating traits needed for organic farming

systems have focussed on ield crops such as cereals (e.g. Murphy et al., 2007;

Löschenberger et al., 2008; Prsystalski, 2008; Wolfe et al., 2008; Annicchiarico

et al., 2010; Reid et al., 2009, 2011; Kirk et al., 2012; Koutis et al., 2012), with few

conducted on vegetable crops (Osman et al., 2008; Lammerts van Bueren et

al., 2012; Myers et al., 2012). None of these studies have evaluated commercial

cultivars of broccoli across multiple regions or seasons for agronomic

performance under organic conditions.

Some studies comparing performance of genotypes in organic and conventional

management systems have shown that for certain traits, cultivar rank varies

between the two management systems (e.g. for winter wheat: Murphy et

al., 2007; Baresel et al., 2008; Kirk et al., 2012; for lentils: Vlachostergios and

Roupakias, 2008; for maize: Goldstein et al., 2012), while others have shown

no diferences in ranking performance (for maize: Lorenzana & Bernardo, 2008;

for cereals: Prsystalski, 2008; for onions: Lammerts van Bueren et al., 2012). The

results of these studies have profound implications for organic variety selection

and breeding strategies and raise questions as to the need for cultivars to be

bred with broad adaptability or speciic adaptation for the requirements of

regional organic management. Two diferent outcomes have been identiied.

First, some studies showed cultivar performance varies between management

systems with signiicant diferences in ranking, and in some cases low genetic

correlations for lower heritability traits (e.g. Kirk et al., 2012; Murphy et al., 2007),

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