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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 1/15/2016 Publication Date: 6/21/2016 Citation: Davis, R.F., Stetina, S.R. 2016. Resistance and tolerance to nematodes in cotton. In: Galbieri, R., Belot, J.L., editors. Nematoides fitoparasitas do algodoerio nos cerrados brasileiros: Biologia e medidas de controle. Instituto Mato-grossense do Algodao - IMAmt: Cuiaba (MT), Brazil. p. 166-241. Interpretive Summary: Meloidogyne incognita is widely known as the southern root-knot nematode or the cotton root-knot nematode and Rotylenchulus reniformis is known as the reniform nematode. Most of the cotton-producing areas of the world are at risk form one or both of these nematode species. Although other nematodes also parasitize cotton, M. incognita and R. reniformis are responsible for a large majority of the economic losses. The terms resistance and tolerance are used to differentiate the relative amounts of nematode reproduction and damage to the plant. Resistance and susceptibility to plant-parasitic nematodes represent a spectrum describing the effect of a host plant on a nematode’s ability to reproduce. Similarly, tolerance and intolerance represent a spectrum describing the degree of damage inflicted by the nematode on the host plant. Tolerance is typically measured in terms of yield suppression. Both resistance and tolerance can be useful in managing plant-parasitic nematodes. Potential mechanisms of resistance and tolerance are discussed. Sources of resistance to both M. incognita and R. reniformis are known. Examples of the effects of both moderate and high levels of resistance and tolerance on cotton yield and on nematode population levels are given. Although resistance reduces nematode population levels, tolerance in the absence of resistance does not. Repeatedly growing plants with a single source of resistance increases selection pressure on the nematode populations and may result in populations that can overcome that source of resistance. Combining sources of resistance may slow development of virulent nematode populations. If resistant cultivars become the dominant tactic for managing these nematodes, then other nematode species may emerge as previously unrecognized problems. Sources of resistance to M. incognita and R. reniformis are listed. Identifying new sources of resistance to these nematodes in cotton should be a priority. The development of cotton cultivars with resistance and tolerance to M. incognita and R. reniformis will provide farmers with a simple to use, consistently effective, and inexpensive tool for nematode management. Technical Abstract: Meloidogyne incognita is widely known as the southern root-knot nematode or the cotton root-knot nematode and Rotylenchulus reniformis is known as the reniform nematode. Most of the cotton-producing areas of the world are at risk form one or both of these nematode species. Although other nematodes also parasitize cotton, M. incognita and R. reniformis are responsible for a large majority of the economic losses. The terms resistance and tolerance are used to differentiate the relative amounts of nematode reproduction and damage to the plant. Resistance and susceptibility to plant-parasitic nematodes represent a spectrum describing the effect of a host plant on a nematode’s ability to reproduce. Similarly, tolerance and intolerance represent a spectrum describing the degree of damage inflicted by the nematode on the host plant. Tolerance is typically measured in terms of yield suppression. Both resistance and tolerance can be useful in managing plant-parasitic nematodes. Potential mechanisms of resistance and tolerance are discussed. Sources of resistance to both M. incognita and R. reniformis are known. Examples of the effects of both moderate and high levels of resistance and tolerance on cotton yield and on nematode population levels are given. Although resistance reduces nematode population levels, tolerance in the absence of resistance does not. Repeatedly growing plants with a single source of resistance increases selection pressure on the nematode populations and may result in populations that can overcome that source of resistance. Combining sources of resistance may slow development of virulent nematode populations. If resistant cultivars become the dominant tactic for managing these nematodes, then other nematode species may emerge as previously unrecognized problems. Sources of resistance to M. incognita and R. reniformis are listed. Identifying new sources of resistance to these nematodes in cotton should be a priority. The development of cotton cultivars with resistance and tolerance to M. incognita and R. reniformis will provide farmers with a simple to use, consistently effective, and inexpensive tool for nematode management. |
