TOMATO BREEDING FOR NEMATODE RESISTANCE: SURVEY OF RESISTANT VARIETIES FOR HORTICULTURAL CHARACTERISTICS AND GENOTYPE OF ACID PHOSPHATES
Root-knot nematodes (Meloidogynespp) are important plant parasites. Among the thirty-seven recognized species of Meloidogyne, seven are know to attack tomatoes. M. incognita, M. javanica, M. arenaria and M. hapla are economically the most important. The former three species are widespread between 35°S and 35°N latitudes whereas M. hapla is a more temperate regions species, fequently occuring north of 35°S latitude (Taylor, A.L., Sasser, J.N., 1978). In California, M. incognita and M. javanica are often found in the Sacramento and San Joaquin Valleys where the bulk of the processing tomato crop is grown (Siddiqui, I.A. et al. 1973). Heavily interested plants have a very shallow and knotted root system. Normal development is impaired and distribution of hormones, minerals and photosynthates is altered. As a consquence, top growth is reduced, yields are low and plants wilt during the hot periods of the day even through soil water is plentiful. Symptoms of mineral deficiency are common and often additional fertilizer is applied increasing further the costs of producing a poor crop. The extent of economic losses due to nematode infestation is difficult to evaluate. However, in some regions like Hawaii and Morelos (Mexico) decreases in yield as high as 75% have been reported (Macfarlane, J.S., 1974; Palacios A.A., 1972 and Moss, C.S., 1972). In addition to the losses caused by the direct effect of nematode infestation, predisposition or even breakdown of resistance to other root diseases is common. For example, nematode susceptible lines resistant to bacterial wilt (Pseudomnassolanace a r u m) do not survive well if in addition to nematodes, conditions for the bacterial disease are present (Gilbert, J.C., et al., 1974). Chemical control is feasible but it is costly and represents only a temporary solution. Recently, largely used nematicides like DBCP have been banned from the market because of their adverse effects to human health. The need for nematode resistant varieties has spurred establishment of a project aimed at the incorporation of nematode resistance in California adapted varieties. As far as we know, there are no acceptable California processing varieties with nematode resistance. This paper describes the initial efforts in pursuit of that goal.
Medina Filho, H.P. and Stevens, M.A. (1980). TOMATO BREEDING FOR NEMATODE RESISTANCE: SURVEY OF RESISTANT VARIETIES FOR HORTICULTURAL CHARACTERISTICS AND GENOTYPE OF ACID PHOSPHATES. Acta Hortic. 100, 383-394