Interaction of Fusarium oxysporum f. sp. gladioli and Meloidogyne incognita on gladiolus cultivars and its management through corm treatment with biopesticides and pesticides

Effects of single and concomitant (simultaneous) inoculations with Fusarium oxysporum f. sp. gladioli (Fog) and Meloidogyne incognita (Mi) were examined on the plant growth and flowering of five cultivars of gladiolus viz., King Lear, Her Majesty, Friendship, White Prosperity and American Beauty in earthen pots. In addition, the effectiveness of corm dressing with Trichoderma harzianum, Pseudomonas fluorescens, carbendazim and nemacur against corm rot and yellows, root-knot and Fog + Mi disease complex was tested. All cultivars were found susceptible to F. oxysporum f. sp. gladioli and M. incognita. However, the cvs. White Prosperity and American Beauty expressed moderate tolerance to Fog and Mi, respectively. The cvs. Her Majesty and American Beauty scored highest corm rot and yellows indices (2.9-3.2 on 0-5 scale), and exhibited 28-32% decrease in the number of florets per spike due to Fog infection. Corm dressing with T. harzianum or carbendazim checked the corm rot and yellows (P ≤ 0.05) and increased the plant growth and flowering of gladioli (P ≤ 0.05). The Mi inoculation caused maximum galling on the cv. White Prosperity (40 galls/root system) and lowest on cv. American Beauty (11 galls) and significantly reduced flowering of gladiolus cultivars (11-23%, P ≤ 0.05) except cv. American Beauty. A treatment with nemacur or P. fluorescens suppressed the galling and egg mass production of M. incognita, and improved the plant growth and flowering variables (7-38%) compared with the inoculated control (P ≤ 0.05). In concomitantly inoculated plants, severity of corm rot and yellows increased (P ≤ 0.05), and significantly greater decrease in the plant growth and flowering variables occurred in all cultivars, but gall formation and egg mass production were decreased. Treatment with carbendazim-nemacur mixture or P. fluorescens effectively controlled the Fog + Mi disease complex leading to significant (P ≤ 0.05) decrease in the corm rot and yellows (4-43% and 5-21%) and root-knot indices (9-33% and 4-40%). The two treatments increased in the spike length (11-15% and 9-16%), spike number (13-43% and 13-57%) and florets per spike (40-55% and 30-46%), respectively, compared with the inoculated control.