Evaluation of Brassica genotypes for resistance to shatter. I. Development of a laboratory test

Abstract

INDEX WORDSBrassica spp ., shatter-resistance, siliqua strength, field shatter . SUMMARY A new test procedure for measuring shatter-resistance of siliquae of Brassica s pp . i s described . A siliqua with its proximal end clamped is loaded as a cantilever in a testing machine . The maximum bending moment, the corresponding stiffness and the energy to cause the siliqua to rupture were taken as measures of the resistance of the siliqua to shatter . Studies showed that ranking of accessions based on either bending moment or energy closely approximated the rankings based on observations of field shatter . A reasonably high significant negative correlation was found between percentage of shattered siliquae and both bending moment and energy (r = -0 .595 and -0 .531 respecitvely, P = 0 .001). The above results indicated that bending moment and energy could be used as criteria in evaluating rapeseed genotypes for shatter-resistance in breeding programmes .

Breeding Brassica napus for Shatter Resistance

“…Peng-Fei et al (2011) evaluated 220 lines of B. napus for shatter resistance using 'ripping' method (Tan et al 2007) and showed that ripping force ranged from 1.46N to 4.23N. The levels of pod strength reported in this study appear to be in general agreement with studies in Australia (Kadkol et al, 1984;Raman et al, 2011) indicating limited genetic variation in B. napus. Raman et al (2011) evaluated 181 accessions of Brassica napus, one B. rapa, three B. juncea and two accessions of B. carinata, using a pendulum test (Kadkol, 2009) in two separate experiments.…”

“…These tests are somewhat subjective and are often not necessarily comparable due to the difference in maturity and moisture status of siliquae or differences in environmental conditions (Morgan et al, 1998 Table 2. Early tests used to identify shatter resistance in Brassica species Kadkol et al (1984) suggested that the methodology used to test siliqua shatter resistance should simulate shattering as it occurs in the field and during harvesting. They further suggested that it would be most appropriate to test the siliqua as a cantilever because most external forces acting on the siliqua would load it at the distal end whilst it is attached to the plant at the proximal end.…”

“…Liu et al (1994) developed a pendulum-based test (Fig 3) that was a further development from the quasi-static cantilever test developed by Kadkol et al (1984). The use of a pendulum provided a dynamic cantilever test of the siliquae that simulates the natural process in the field and achieves rates of loading comparable to those in the field.…”

“…These levels of RE are associated with intermediate shatter resistance which could prevent pod shatter in standing crops but insufficient to prevent harvest shatter (Kadkol, 2009). Genetic variation for higher levels of siliqua strength necessary for resistance to harvest shatter is present in B. rapa vars Yellow Sarson and Brown Sarson (Kadkol et al, 1984;Liu et al, 1994;Mongkolporn et al, 2003;Kadkol, 2009). Shatter resistance could be improved by introgressing the trait from these types and B. juncea (Kadkol 2009;Raman et al, 2011).…”

“…It may even encompass biotic and abiotic stress factors (Kadkol et al, 1986a;Morgan et al, 1998;Morgan et al, 2003;Summers et al, 2003). A summary of siliqua and plant characters as well as other factors reported to be involved in siliqua shatter are presented in Table 1 Morphological Kadkol et al, 1984Morphological Morgan et al, 1998Kadkol et al, 1984Anatomical Kadkol et al, 1986aAnatomical Morgan et al, 1998Anatomical Child et al, 2003Kadkol et al, 1989;Morgan et al, 1998Anatomical Child et al, 2003Biochemical Morgan et al, 1998Biochemical Chauvaux et al, 1997Child et al 1998;Morgan et al, 1998 Canopy structure…”