RA 00015.pdf - OAR@ICRISAT

Figure 6. An ICRISAT breeding nursery.
of the Striga haustorium and of the anatomy of
the roots of sorghum cultivars showing mechanical
resistance.
After the Striga seed germinates, the haustorium
makes contact with the sorghum root and
penetrates its cortex, distorting or rupturing the
cortical cells. The haustorium pierces the endodermis
and pericycle. The elongated cells of
the haustorium rupture and the differentiating
protoxylem strands establish vascular connection
with the vascular bundle of the host root
(Fig 7).
Resistance to Striga is correlated with the
presence of thick-walled endodermal cells (and
associated sclerenchyma tissue) in the pericycle
and also the presence of silica crystals in these
cells. Haustoria were observed to penetrate the
cortex of resistant cultivars, but failed to advance
past the endodermis into the vascular bundles,
suggesting that the combined endodermis/
pericycle formed a mechanical barrier (Fig 8).
We are carrying out more-detailed studies in
collaboration with the sorghum breeders and
hope to further examine the role of the mechanical
barrier in resistance, and to investigate its
inheritance.
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