text: user8792: I cannot seem to find a way to query nucleotide database (https://www.ncbi.nlm.nih.gov/nuccore) by a specific qualifier of the feature. For example, by /host under the feature "source".
  For example, below is a part of one record, where the qualifier /host contains "Bemisia tabaci B".
  How could I search for all sequences that contain the word "Bemisia" in the qualifier \host?
  FEATURES             Location/Qualifiers
   source          1..351658
                   /organism="Candidatus Portiera aleyrodidarum BT-B-HRs"
                   /mol_type="genomic DNA"
                   /strain="BT-B"
                   /host="Bemisia tabaci B"
                   /db_xref="taxon:1206109"
   gene            1..1926
                   /gene="dnaK"
                   /locus_tag="C530_RS00005"
                   /old_locus_tag="C530_001"
   CDS             1..1926
                   /gene="dnaK"
                   /locus_tag="C530_RS00005"
                   /old_locus_tag="C530_001"
                   /inference="COORDINATES: similar to AA
                   sequence:RefSeq:WP_014894920.1"
                   /note="Derived by automated computational analysis using
                   gene prediction method: Protein Homology."
                   /codon_start=1
                   /transl_table=11
                   /product="molecular chaperone DnaK"
                   /protein_id="WP_014894920.1"
                   /translation="MIRIIGIDLGTTNSCVAVLENGKSRVIENSEGARTTPSIIAYTD
                   DNEILIGQTAKRQAVTNPSNTLYAIKRLIGRKFNDDIVQKDIKMVPYKIVSAENGDAW
                   VQVKNRKLAPPQISAEILKKMKKTAEDYLGEKITEAVITVPAYFNDSQRQATKDAGRI
                   AGLNVKRIINEPTAAALAYGMDKNRGDKKIAVYDLGGGTFDISIIEIADVDGETQFEV
                   MATNGDTFLGGEDFDLKLINYIVKQFKLESGVDLSGDSLAMQRLKEAAEKGKIELSSS
                   QQTDINLPYITADKTGPKHLTLKITRAKLESLVEDLIKRSLLPCKKAIDDAKLTTKEI
                   DDIILVGGQTRMPLVQKKVAEFFGKEARKDVNPDEAVAMGAAIQGGVLGGDVKDVLLL
                   DVTPLTLGIETMGGIMTPLIEKNTTIPTKKTQIFSTAEDNQTAVTIHALQGERKKALQ
                   NKSLGRFDLTDIPPAPRGTPQIEVAFDLDANGILNITAKDKATGKEQSIIIKSSGGLS
                   EEEINKMIQDAETNKEEDKKFEELVQTRNQADGMIHTIRKTLKEIKNEDEKNKLESLI
                   NNLEQTLKSDDIKTIKEDLNKLTEEYSTIYQKIYSEKKPQNHNSEPAQKNAEKSSSKK
                   EGDVVDAEYEEVNNKTK"
                   ...
  
  Best,
  Milan
  
  user9608: For this particular query, try host=Bemisia tabaci B[WORD].  However, you may also be interested in related queries like host=Bemisia tabaci B biotype[WORD].
  But, I am not sure a general solution exists, as I do not believe all qualifiers are indexed.
  
  Also, you can see how your query is interpreted on the right side under "Search details".  For the original attempt ([host]"Bemisia tabaci B"), it is interpreted as:
  host[All Fields] AND "Bemisia tabaci B"[All Fields]
  
  while the goal is to produce
  host=Bemisia tabaci B biotype[WORD]
  
  
original_text: 8792: <p>I cannot seem to find a way to query nucleotide database (<a href="https://www.ncbi.nlm.nih.gov/nuccore" rel="nofollow noreferrer">https://www.ncbi.nlm.nih.gov/nuccore</a>) by a specific qualifier of the feature. For example, by /host under the feature "source".
  For example, below is a part of one record, where the qualifier /host contains "Bemisia tabaci B".
  How could I search for all sequences that contain the word "Bemisia" in the qualifier \host?</p>
  
  <pre><code>FEATURES             Location/Qualifiers
   source          1..351658
                   /organism="Candidatus Portiera aleyrodidarum BT-B-HRs"
                   /mol_type="genomic DNA"
                   /strain="BT-B"
                   /host="Bemisia tabaci B"
                   /db_xref="taxon:1206109"
   gene            1..1926
                   /gene="dnaK"
                   /locus_tag="C530_RS00005"
                   /old_locus_tag="C530_001"
   CDS             1..1926
                   /gene="dnaK"
                   /locus_tag="C530_RS00005"
                   /old_locus_tag="C530_001"
                   /inference="COORDINATES: similar to AA
                   sequence:RefSeq:WP_014894920.1"
                   /note="Derived by automated computational analysis using
                   gene prediction method: Protein Homology."
                   /codon_start=1
                   /transl_table=11
                   /product="molecular chaperone DnaK"
                   /protein_id="WP_014894920.1"
                   /translation="MIRIIGIDLGTTNSCVAVLENGKSRVIENSEGARTTPSIIAYTD
                   DNEILIGQTAKRQAVTNPSNTLYAIKRLIGRKFNDDIVQKDIKMVPYKIVSAENGDAW
                   VQVKNRKLAPPQISAEILKKMKKTAEDYLGEKITEAVITVPAYFNDSQRQATKDAGRI
                   AGLNVKRIINEPTAAALAYGMDKNRGDKKIAVYDLGGGTFDISIIEIADVDGETQFEV
                   MATNGDTFLGGEDFDLKLINYIVKQFKLESGVDLSGDSLAMQRLKEAAEKGKIELSSS
                   QQTDINLPYITADKTGPKHLTLKITRAKLESLVEDLIKRSLLPCKKAIDDAKLTTKEI
                   DDIILVGGQTRMPLVQKKVAEFFGKEARKDVNPDEAVAMGAAIQGGVLGGDVKDVLLL
                   DVTPLTLGIETMGGIMTPLIEKNTTIPTKKTQIFSTAEDNQTAVTIHALQGERKKALQ
                   NKSLGRFDLTDIPPAPRGTPQIEVAFDLDANGILNITAKDKATGKEQSIIIKSSGGLS
                   EEEINKMIQDAETNKEEDKKFEELVQTRNQADGMIHTIRKTLKEIKNEDEKNKLESLI
                   NNLEQTLKSDDIKTIKEDLNKLTEEYSTIYQKIYSEKKPQNHNSEPAQKNAEKSSSKK
                   EGDVVDAEYEEVNNKTK"
                   ...
  </code></pre>
  
  <p>Best,
  Milan</p>
   9608: <p>For this particular query, try <a href="https://www.ncbi.nlm.nih.gov/nuccore/?term=host%3DBemisia%20tabaci%20B%5BWORD%5D" rel="nofollow noreferrer">host=Bemisia tabaci B[WORD]</a>.  However, you may also be interested in related queries like <a href="https://www.ncbi.nlm.nih.gov/nuccore/?term=host%3DBemisia%20tabaci%20B%20biotype%5BWORD%5D" rel="nofollow noreferrer">host=Bemisia tabaci B biotype[WORD]</a>.</p>
  <p>But, I am not sure a general solution exists, as I do not believe all qualifiers are indexed.</p>
  <hr />
  <p>Also, you can see how your query is interpreted on the right side under &quot;Search details&quot;.  For the original attempt (<code>[host]&quot;Bemisia tabaci B&quot;</code>), it is interpreted as:</p>
  <pre><code>host[All Fields] AND &quot;Bemisia tabaci B&quot;[All Fields]
  </code></pre>
  <p>while the goal is to produce</p>
  <pre><code>host=Bemisia tabaci B biotype[WORD]
  </code></pre>
  