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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #307481
Title: Physiological effects of Meloidogyne incognita infection on cotton genotypes with differing levels of resistance in the greenhouse

Author
item LU, PING - University Of Georgia
item Davis, Richard
item KEMERAIT, ROBERT - University Of Georgia
item VAN IERSEL, MARC - University Of Georgia
item SCHERM, HARALD - University Of Georgia

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2014
Publication Date: 1/19/2015
Citation: Lu, P., Davis, R.F., Kemerait, R.C., Van Iersel, M.W., Scherm, H. 2015. Physiological effects of Meloidogyne incognita infection on cotton genotypes with differing levels of resistance in the greenhouse. Journal of Nematology. 46(4):352-359.

Interpretive Summary: Greenhouse tests were conducted to evaluate 1) the effect of southern root-knot nematode infection in cotton on plant growth and physiology including the height-to-node ratio (a measure of stress), chlorophyll content, dark adapted quantum yield of photosystem II (a measure of the plant’s photosynthetic function), and leaf area, and 2) the extent to which moderate or high levels of resistance to the nematode influenced these effects. Cultivars FiberMax 960 BR (susceptible to the nematode) and Stoneville 5599 BR (moderately resistant) were tested together in three trials, and PD94042 (germplasm, susceptible) and 120R1B1 (breeding line genetically similar to PD94042, but highly resistant) were paired in two additional trials. Inoculation with the nematode generally resulted in increases in root gall ratings and egg counts per gram of root compared with the non-inoculated control, as well as reductions in plant dry weight, root weight, leaf area, boll number, and boll dry weight, thereby confirming that growth of our greenhouse-grown plants was reduced in the same ways that would be expected in field-grown plants. In all trials, nematode infection caused reductions in height-to-node ratios. Nematode infection consistently reduced the area under the height-to-node ratio curves for all genotypes, and these reductions were similar for resistant and susceptible genotypes. Our study is the first to show that infection by the southern root-knot nematode is associated with reduced chlorophyll content in cotton leaves of both resistant and susceptible genotypes. The susceptible PD94042 tended to have increased leaf temperature compared to the genetically similar but highly resistant 120R1B1, likely due to increased water stress associated with nematode infection.

Technical Abstract: Greenhouse tests were conducted to evaluate 1) the effect of Meloidogyne incognita infection in cotton on plant growth and physiology including the height-to-node ratio, chlorophyll content, dark adapted quantum yield of photosystem II, and leaf area, and 2) the extent to which moderate or high levels of resistance to M. incognita influenced these effects. Cultivars FiberMax 960 BR (susceptible to M. incognita) and Stoneville 5599 BR (moderately resistant) were tested together in three trials, and PD94042 (germplasm, susceptible) and 120R1B1 (breeding line genetically similar to PD94042, but highly resistant) were paired in two additional trials. Inoculation with M. incognita generally resulted in increases in root gall ratings and egg counts per gram of root compared with the non-inoculated control, as well as reductions in plant dry weight, root weight, leaf area, boll number, and boll dry weight, thereby confirming that growth of our greenhouse-grown plants was reduced in the same ways that would be expected in field-grown plants. In all trials, M. incognita caused reductions in height-to-node ratios. Nematode infection consistently reduced the area under the height-to-node ratio curves for all genotypes, and these reductions were similar for resistant and susceptible genotypes (no significant genotype × inoculation interaction). Our study is the first to show that infection by M. incognita is associated with reduced chlorophyll content in cotton leaves, and the reduction in the resistant genotypes was similar to that in the susceptible genotypes (no interaction). The susceptible PD94042 tended to have increased leaf temperature compared to the genetically similar but highly resistant 120R1B1 (P < 0.08), likely due to increased water stress associated with M. incognita infection.