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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #329866
Title: Meloidogyne incognita emigration from cotton roots may be induced by the resistance QTL qMi-C11

Author
item BATISTA DA SILVA, MYCHELE - University Of Georgia
item KUMAR, PAWAN - University Of Georgia
item NICHOLS, ROBERT - Cotton, Inc
item CHEE, PENG - University Of Georgia
item Davis, Richard

Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2016
Publication Date: 12/1/2016
Citation: Batista Da Silva, M., Kumar, P., Nichols, R.L., Chee, P.W., Davis, R.F. 2016. Meloidogyne incognita emigration from cotton roots may be induced by the resistance QTL qMi-C11. Journal of Nematology. 48:302.

Interpretive Summary:

Technical Abstract: Upland cotton (Gossypium hirsutum) is one of the most widely grown crops in the southern US, and Meloidogyne incognita is the most significant pathogen of cotton in the US. Two QTLs, qMi-C11 and qMi-C14, conferring resistance to M. incognita have been identified in cotton. Previous research documented resistance expressed at two stages of nematode development, and later research documented an epistatic interaction between the two QTLs, both of which suggest the QTLs have different modes of action. Our objective was to document the effects of qMi-C11 and qMi-C14 on M. incognita penetration, development, and reproduction in cotton. We developed near-isogenic lines (NIL) carrying only a single QTL and observed M. incognita development in NILs containing both QTLs (M-120), only one QTL (NIL-C11 with qMI-C11 or NIL-C14 with qMi-C14), or neither QTL (Coker 201). Compared to the susceptible Coker 201, NIL-C11 stopped many nematodes from developing beyond the SJ2 stage whereas NIL-C14 limited the development of J4 into females, and both consequently reduced egg production. Approximately 50 % of the nematodes in NIL-C11 and M-120 plants remained in stage J2 or SJ2 25 days after inoculation (DAI) compared to 12% of Coker 201. The number of nematodes in the roots did not differ among genotypes 4 and 8 DAI, but were lower in NIL C11 and M-120 after 8 DAI, which may indicate M. incognita emigration. For additional studies, we hypothesized that on resistant lines 1) J2s are failing to establish a feeding site and leaving the roots, and 2) M. incognita is producing fewer eggs/egg mass. To test our hypotheses, two-week-old seedlings were inoculated; two days later, roots were rinsed and seedlings were transplanted into small cones. On each of five sampling dates (4, 6, 8, 10, and 12 DAI), nematodes that had left the roots were extracted from vermiculite and roots were stained to count nematodes inside the roots. NIL-C11 had more nematodes leaving the roots on 6 and 12 DAI and M-120 had more on 4, 8, and 10 DAI than Coker 201. By the end of the experiment, more than 50% of the nematodes were in vermiculite rather than in the roots for NIL-C11, while about 10% were in vermiculite for Coker 201. To measure eggs/egg mass, two-week-old seedlings were inoculated, and 30 DAI, eggs from 10 egg masses from each genotype in each replicate were counted. Eggs/egg mass did not differ among genotypes. We conclude that low levels of nematode emigration occur on susceptible plants, but qMi-C11 causes many J2s to leave the roots or fail to develop beyond the SJ2 stage. In contrast, qMi-C14 does not stimulate significantly more nematode emigration but causes many nematodes to fail to develop beyond the J4 stage.