Page 230 - Breeding and regulatory opportunities, Renaud

Chapter 6

Category 3: Traits of greater importance for organic growers.

There is also category of traits that are not necessary diferent from traits of

importance for conventional growers, but have a higher priority for organic

growers compared to conventional growers such as resistance to biotic and

abiotic stress. This is because organic growers refrain from chemical crop

protectants and therefore need more emphasis on varietal characteristics

related to abiotic and biotic stress tolerance. For some diseases, resistance is

available such as for club root (Piao et al., 2009), downy mildew (Farnham et al.,

2002; Vicente et al., 2012), and black rot (Tonguc and Griiths, 2004). However, in

the case where breeding has not yet been conducted for the release of resistant

cultivars other options can be applied. For example, hot water treatments are

used for control of the seed borne diseases black leg and black rot in cultivars

that are not resistant (Lammerts van Bueren et al., 2003). Where disease resistant

cultivars are not available, certain morphological traits can reduce disease or

pest incidence and compensate for use of chemical crop protectants. Examples

are small beads and domed head shape that shed water more easily to prevent

head rot (Myers et al., 2012). Osman et al. (2008) reported that for onions

more erect leaves can shed water more easily reducing incidence of disease

development. Another example of a morphological trait reducing ear disease

incidence in cereals is in the length of the peduncle of wheat by selecting for

cultivars that the ear rise above the leaf canopy and dries more rapidly after rain

or morning dew (Löschenberger et al., 2008). Speciic to Brassicas, epicuticular

wax is another trait that can be manipulated to afect pest resistance where

glossy leaves have shown less damage from lepidopteran pests, reduced

tissue damage from thrips and but may contribute to more potential damage

by lea beetles (Lammerts van Bueren et al., 2011). Also with respect to weed

suppression certain morphological traits can replace the use of herbicides by

choosing for more planophile and large leaf types that provide more shade to

the soil and therefore better suppress weeds.

With respect to abiotic stress tolerance, traits are related to adaptation to low-

inputs of water and nutrients are of importance for organic growers. These traits

relate to a reduced dependence on irrigation and an extensive root system to

explore large soil volumes and improve capacity of nutrient uptake and use

under cold spring conditions (see e.g. Messmer et al., 2012). As organic growers

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