Table 3.

Summarized morphological characteristics observed in nodules of Trifolium spp. 32 d after inoculation with a strain of R. leguminosarum bv. trifolii

Plant	Strain	NF (% of reference strain)*	Morphological characteristics
			Zones of differentiation (I–IV)†	Observed characteristics‡	Effectiveness classification§
T. subterraneum ‘Campeda’	WSM1325	100e	I, II, II–III, III	IT, b, BD, NS	E
	SRDI565	57d	I, II, II–III, III, IV	IT, b, BD, NS	S
	SRDI943	24bc	No	IT, b, BD#, NV	S
	WSM2304	–1a	No	IT, b, BD#, NS	ID
T. subterraneum ‘Clare’	WSM1325	100e	I, II, II–III, III	IT, b, BD, NS	E
	SRDI565	0a	No	IT, b, P	IV
	SRDI943	54d	I, II, II-III, III	IT, b, BD, NS	S
	WSM2304	–2a	No	IT, b, BD#, NV	ID
T. purpureum	WSM1325	83e	I, II, II–III, III	IT, b, BD, NS	E
	SRDI565	30c	I, II, II–III, III, IV	IT, b, BD, NS	S
	SRDI943	100e	I, II, II–III, III	IT, b, BD, NS	E
	WSM2304	2a	I, II¶, IV	IT, b, BD#, NV	ID
T. polymorphum	WSM1325	3a	No	IT, b, NS	IV
	SRDI565	5ab	No	IT, b, BD#, NS	ID
	SRDI943	15abc	No	IT, b, NS	IV
	WSM2304	100e	I, II, II–III, III	IT, b, BD, NS	E

* NF (Nodule function), Fixed N_shoot mg⁻¹ nodule d. wt expressed as percentage of most effective strain on that host. Different letters indicate treatments are significantly different across both plant species (P < 0·05, Duncan's multiple range test).

^† Nodule zones: I, Meristem; II, pre-fixation; II–III, inter-fixation; III, fixation; IV, senescent.

^‡ IT, Infection threads; b, bacteria; BD, bacteroids; NS, nodule shape stable; NV, nodule shape variable; P, pseudonodule.

^§ E, Effective; S, sub-optimal; ID, ineffective-differentiated; IV, ineffective-vegetative.

^¶ Presence of zone varies with sample.

^# Bacteroids only in some plant cells, intracellular density variable.