Quantitative and Microscopic Assessment of Compatible and Incompatible Interactions between Chickpea Cultivars and Fusarium oxysporum f. sp. ciceris Races

Abstract

BackgroundFusarium wilt caused by Fusarium oxysporum f. sp. ciceris, a main threat to global chickpea production, is managed mainly by resistant cultivars whose efficiency is curtailed by Fusarium oxysporum f. sp. ciceris races.MethodologyWe characterized compatible and incompatible interactions by assessing the spatial-temporal pattern of infection and colonization of chickpea cvs. P-2245, JG-62 and WR-315 by Fusarium oxysporum f. sp. ciceris races 0 and 5 labeled with ZsGreen fluorescent protein using confocal laser scanning microscopy.FindingsThe two races colonized the host root surface in both interactions with preferential colonization of the root apex and subapical root zone. In compatible interactions, the pathogen grew intercellularly in the root cortex, reached the xylem, and progressed upwards in the stem xylem, being the rate and intensity of stem colonization directly related with the degree of compatibility among Fusarium oxysporum f. sp. ciceris races and chickpea cultivars. In incompatible interactions, race 0 invaded and colonized ‘JG-62’ xylem vessels of root and stem but in ‘WR-315’, it remained in the intercellular spaces of the root cortex failing to reach the xylem, whereas race 5 progressed up to the hypocotyl. However, all incompatible interactions were asymptomatic.ConclusionsThe differential patterns of colonization of chickpea cultivars by Fusarium oxysporum f. sp. ciceris races may be related to the operation of multiple resistance mechanisms.

Fusarium Wilt Affecting Chickpea Crop

“…The yellowing pathotype induces progressive foliar yellowing with vascular discoloration and late plant death, while the wilting pathotype causes fast and severe chlorosis, flaccidity, vascular discoloration and early plant death [44].…”

“…Races 0, 1B/C, 5, and 6 are found mainly in the Mediterranean Basin and California (USA) [23,40,44,46,47]. Race 1A has been reported in India, United States and the Mediterranean regions [20], whereas races 2 and 3 have been reported in Ethiopia, India, and Turkey [44,48,49] and race 4 has been reported in Ethiopia, India and Iraq [24,44,49].…”

“…Plants infected with races causing wilting syndrome within three to four weeks of inoculation with no visible yellowing of leaves. On the other hand, infection with races 0 and 1B/C leads to progressive foliar yellowing of plant leaves coupled with vascular discoloration [43,44]. In addition, some susceptible chickpea lines exhibit a phenomenon known as a late wilting, which is characterized by a prolonged latent period that eventually leads to 100% wilt [12,23,45,50].…”

Fusarium wilt of chickpeas: Biology, ecology and management

“…Invasion takes place mainly through the cotyledons and zones of the epicotyl and hypocotyl at the junction of or close to cotyledons, and to a lesser extent in the zone of root elongation and maturation (Jim enez-Díaz et al, 1989a;Stevenson et al, 1997). Later studies in infested hydroponic cultures showed that races 0 and 5 of the pathogen colonize the surface of the tap and lateral roots in both susceptible and resistant cultivars, and preferentially penetrate the meristematic cells of the root apex (Jim enez- Díaz et al, 1989a;Jim enez-Fern andez et al, 2013). Then, the fungus grows in the intercellular spaces of the root cortex to reach the central root cylinder and enter into the xylem vessels.…”

“…Further colonization by the pathogen takes place by means of hyphal growth and microconidia carried in the vessels by transpiration stream, as well as by lateral mycelia spread to adjacent vessels from infected ones. The systemic colonization along the plant axis (i.e., the determinative phase of pathogenesis) is then followed by development of symptoms (i.e., the expressive phase) once intense colonization of xylem vessels in root and lower stem has occurred by 10e20 days after inoculation (Jim enez-Díaz et al, 1989a;Jim enez-Fern andez et al, 2013).…”