Principal component analysis of interrelations in stored-wheat ecosystems infested with multiple species of insects |
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Authors: | N D G White and R N Sinha |
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Institution: | (1) Research Station, Agriculture Canada, 195 Dafoe Road, R3T 2M9 Winnipeg, Manitoba |
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Abstract: | Summary Principal component analysis (PCA) was used to determine the effects of infestation of bulk stored wheat by multiple species
of insects at 30±2°C for 60 wk. Eight 204-liter drums containing wheat at 15.5% moisture content were used as three distinct
man-made ecosystems: (a) Control system (2 drums), insect-free; (b) RST system (3 drums), artificially infested withRhyzopertha dominica (F.),Sitophilus oryzae (L.), andTribolium castaneum (Herbst); and (c) COT system (3 drums), infested withCryptolestes ferrugineus (Stephens),Oryzaephilus surinamensis (L.), andTribolium castaneum. The variables measured tri-weekly within each system included carbon dioxide, oxygen, temperature, grain moisture, seed
damage, grain weight and volume, dust weight and volume, fat acidity values (FAV) of the wheat, seed germination, microflora
includingAlternaria alternata
(Fr.) Keissler,Aspergillus glaucus group,Aspergillus candidus
Link, and bacteria, insects and the miteTarsonemus granarius
Lindquist. PCA provided multivariate synopsis of the data quantifying several important relationships among the variables monitored.
Tri-weekly and cumulative 60-wk analyses of each system showed that high bacterial counts were associated with high FAV levels;Tarsonemus numbers were positively related toAspergillus; Alternaria and seed germination were negatively related to FAV, bacteria and grain damage; and that the number of insects was related
to the presence ofAspergillus and negatively related to the presence of bacteria. Seed germination andAlternaria infection often decrease rapidly presumably because of infection by fungi of theAspergillus glaucus group. The combined action ofR. dominica andAspergillus spp. enhanced seed damage and increased grain moisture content thus promoting bacterial growth which in turn inhibited insect
and mold growth. Fat acidity values increased with time unless seed damage and bacterial infection were extensive as in the
RST system.
Contribution No. 903, Agriculture Canada, Research Station, 195 Dafoe Road, Winnipeg, Manitoba, R3T 2M9. |
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