Dinâmica populacional de nematóides patogênicos ao inhame e àmandioca no Recôncavo da Bahia

Abstract

Yam (Dioscorea rotundata) and cassava (Manihot esculenta) are susceptible to the attack of several nematode species. The objectives of this study were to evaluate the population dynamics of nematodes pathogenic to yam and cassava in four areas in Recôncavo of Bahia; to evaluate the population dynamics of Scutellonema bradys in yam tubers stored for different periods; and the survival of this nematode in different humid substrates and dry soil, subjected to different periods of storage under laboratory conditions. Mean population densities of Rotylenchulus reniformis varied from 39 to 1587 nematodes/100 cm3 of soil per month and from 0 to 33 nematodes/g roots per month; populations of Meloidogyne incognita varied from 0 to 91 nematodes/g of soil and roots; mean populations of Pratylenchus spp. varied from 0 to 6 nematodes/100 cm3 of soil and from 0 to 119 nematodes/g roots; while populations of S. bradys varied from 1 to 53 nematodes/100 cm3 soil and from 0 to 46 nematodes/g roots. Although populations of S. bradys were low in the soil and roots, the nematode is considered the most important yam nematode in the Recôncavo of Bahia State. Populations of S. bradys in infected tubers ranged from 1503 to 5858 nematodes, including eggs per gram of tuber peel and pulp. Higher absolute numbers of juveniles, followed by eggs, females and males were observed in stored tubers. Populations of S. bradys increased from 0 to 30 days of storage, when it reached its maximum and decreased from there, reaching the lowest values at 90 days of storage, when the tubers were rotten. Studies on the survival of S. bradys in soil, sand and plantmaxR showed that the nematode can survive for up to 156 days in moist substrates and for up to 24 hours in dry soil. These results demonstrate that S. bradys is more important when associated with yam tubers and has limited survival in soil.