Comparative susceptibility of starch granules of double- and triple-mutants containing Amylose-extender, waxy, sugary-1, sugary-2 and dull genes of maize inbred OH43 (Zea mays L.) to amylase.

Abstract

SummaryStarch granules were prepared from 14 double-and 26 triple-mutants containing amylose-extender (ae), 14 double-and 18 triple -mutants containing waxy (wx), 15 double-and 20 triple-mutants containing sugary-1 (su1), 13 double-and 23 triple-mutants containing sugary-2 (su2), and 14 double-and 19 triple-mutants containing dull (du) of maize inbred Oh43 (Zea mays L.). The relative susceptibilities of these starch granules to fungal glucoamylase were determined and the starch granules were examined by scanning electron microscopy. A commercial normal maize starch was used as a control. Starch granules of the double -and triple-mutants containing su1 and su2 were digested two to eight times faster than normal. The ae gene reduced susceptibility and seems to be epistatic to su1 and su2. Starch granules of the double-and triple-mutants containing wx were digested about two times faster than normal and those containing shrunken-2 (she) were digested 1.2 to eight times faster than normal. Starch granules of triple-mutant combinations with opaque-2 (O2) showed digestion properties which were comparable to those of their respective nonopaque double-mutant counterpart.

Observations on the α‐Amylolysis Pattern of Some Waxy Maize Starches from Inbred Line Ia453

“…The susceptibility to fungal glucoamylase attack of a range of mutant maize starch granules from inbred line Oh43 was investigated by Fuwa et al (1979). In contrast to our results, they found that the endosperm mutations duwx and aeduwx were highly digestible.…”

“…In combination with the wx mutation, the starch does not possess amylose and the situation is thus different. The aewx granules are also of B-type crystallinity Seib 1995, Jane et al 1999) but were reported to be susceptible to amylase like most other wx combinations with A-type crystallinity (Fuwa et al 1979). In triple combination with the du and wx mutations, B-type crystallinity was reported from inbred W64A (Shi and Seib 1995).…”

“…1). Fuwa et al (1979) showed that aeduwx starch granules from inbred Oh43 were as highly susceptible to glucoamylase attack as were duwx granules. In contrast, the similar endosperm mutation of inbred Ia453 resulted in highly resistant granules (Fig.…”

“…Among a range of starches from different genotypes and inbred lines, the sugary (su) mutation, which also gives an increased amylose content, possessed the best susceptibility to enzymatic attack (Fuwa et al 1978a,b). The majority of several double-and triple-mutations, including the wx genotype (aewx, duwx, and aeduwx), within the maize inbred Oh43 also possessed granules that were better digested by glucoamylase than the nonmutant starch (Fuwa et al 1979).…”