F6 families of Gossypium hirsutum L. ✕ ‘Mexico Wild’ (a root‐knot tolerant primitive G. hirsutum from Mexico) were advanced through F10, with selection in greenhouse tests for resistance to root‐knot nematodes [Meloidogyne incognita acrita (Kofoid & White, 1919) Chitwood, 19491. A disinfected larval screening technique effectively classified 85% of the F6 families as intermediate to highly susceptible, even though they had been selected in F2 through F4 in the field for root‐knot resistance in highly infested soil.Two F10 lines, designated A623 and A61, having the highest resistance known to root‐knot in G. hirsutum, were developed. These lines were transgrassive segregates for resistance. Root‐knot resistance in the F1 generation from resistant A623 ✕ susceptible ‘Stoneville 213,’ ‘Coker 201,’ and ‘Dixie King II’ was incompletely dominant.Fusarium wilt [Fusarium oxysporum Schlecht. f. vasinfectum (Atk.) Snyd. ✕ Hans.] resistance in the above material was highly associated with root‐knot resistance. Therefore, it may be possible to breed for fusarium wilt resistance by breeding solely for high root‐knot resistance.

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In in vitro tests, chitosan at 1, 2, and 4% (w/v) significantly reduced the growth of Sclerotinia sclerotiorum on potato dextrose agar plates. The effect of chitosan coating on sclerotinia rot of carrots (Daucus carota L.) held at 22°C was also investigated. Carrot roots were coated with chitosan solutions (2 or 4%) and inoculated with mycelial plugs of S. sclerotiorum culture. After 5 days of storage, chitosan at both rates reduced significantly the incidence of rot (from 88 to c. 28%) and also the lesion size (from 26 to c. 12 mm) of the rot on roots. Microscope studies revealed that fungal mycelium exposed to chitosan appeared to be deformed and dead, whereas untreated mycelium was normal in appearance.

Two applications at three rates of 16 natural and commercial plant growth bioregulators were sprayed on growing cotton Gossypium hirsutum L. to evaluate their effects on levels of nutrients and allelochemicals, on any induced plant resistance to the tobacco budworm Heliothis virescens Fab., and on yield of seed cotton. In uninfested cotton, Pix, BAS-105, and V-3183 significantly decreased yield, while gibberellic acid (GA) increased yield. In infested cotton, PIX, BAS-105, BAS-109, V-2307, and V-3183 significantly decreased yield, while kinetin significantly increased yield. V-2307 and CCC decreased flavonoids by 19% each in leaves and squares, respectively, while arabinogalactan increased flavonoids by 60% in squares. BAS-109 increased leaf tannins by 27%. V-2307 decreased leaf anthocyanins by 53% while GA and V-3183 increased leaf anthocyanins by 28 and 39%, respectively. There appeared to be a trend that flavonoids generally were increased where yields were increased. Two cytokinins, Kinetin and Burst, tended to increase yield, pest resistance, and flavonoids.Flavonoids are important allelochemicals (secondary plant constituents giving either the plant or the pesian adaptive advantage) for normal plant growth, development, and defense against infection and injury by phytophagous pests. Plant flavonoids affect the behavior, development, and growth of a number of insects (Hedin and Waage, 1986). Flavonoids isolated from cotton (Gossy-

A technique was developed for evaluating cotton (Gossypium spp.) for cultivars, F 3 lines, and G. hirsutum races. These levels could not be detected resistance to the root-knot nematode (Meloidogvne incognita acrita). by rating root galling alone. Selection for resistance to root galling and egg Resistance was based on egg production (a nematode response to the plant) production was necessary to develop cotton lines with high resistance to and root galling (a plant response to the nematode). To assess root galling both processes. Cotton accessions exhibited higher levels of resistance and and egg production on test plants, individual plants were inoculated with more levels of resistance (ranging from highly resistant to highly 8,000 eggs in a greenhouse and evaluated 35-45 days later by counting egg susceptible) than has been reported previously in cotton. Selecting highly masses and rating root galling. Plants almost free of egg masses and root resistant germplasm by this technique should result in development of galls were selected and their progeny tested. Final selection for resistance agronomically desirable cotton cultivars capable of preventing economic was based on actual numbers of eggs per plant. By using this technique, loss from root-knot nematodes. levels of resistance to egg production were differentiated among upland Additional key words: Gossypium hirsutum races, G. barbadense race, breeding for resistance. 4 min with a laboratory shaker to disperse eggs on roots. This ological Society, 1979. method of dispersing eggs with NaOCI is a modification of methods Vol. 69, No. 4,1979 427 'Only galls with one egg mass were measured. YNumbers of large egg masses per plant. ' Measured while on root at fullest point on line parallel with root. 'Root-knot index is based on I = none or very light galling, 2 = light galling, ' Means with different letters are significantly different, P = 0.05, according 3 = moderate galling, 4 = heavy galling, 5 = very heavy galling, to Duncan's multiple range test.