Development, Management and Utilization of a Kiwifruit (Actinidia spp.) In Vitro Collection: A New Zealand Perspective

Abstract

The New Zealand Institute for Plant and Food Research Limited (PFR) supports a large kiwifruit breeding program that includes more than twenty Actinidia species. Almost all the kiwifruit accessions are held as field collections across a range of locations, though not all plants are at multiple locations. An in vitro collection of kiwifruit in New Zealand was established upon the arrival of Pseudomonas syringae pv. Actinadiae-biovar 3 in 2010. The value of an in vitro collection has been emphasized by restrictions on importation of new plants into New Zealand and increasing awareness of the array of biotic and abiotic threats to field collections. The PFR in vitro collection currently holds about 450 genotypes from various species, mostly A. chinensis var. chinensis and A. chinensis var. deliciosa. These collections and the in vitro facilities are used for germplasm conservation, identification of disease-free plants, reference collections and making plants available to users. Management of such a diverse collection requires appropriate protocols, excellent documentation, training, sample tracking and databasing and true-to-type testing, as well as specialized facilities and resources. This review also discusses the New Zealand biosecurity and compliance regime governing kiwifruit plant movement, and how protocols employed by the facility aid the movement of pathogen-free plants within and from New Zealand.

Keywords: Actinidia spp.; Pseudomonas syringae actinidiae; biosecurity and compliance; cryopreservation; germplasm conservation; medium term in vitro storage; tissue culture.

Figure 1

(a) Plant & Food Research (PFR) locations within New Zealand. PFR kiwifruit collection is grown in orchard blocks at Kerikeri, Ruakura, Te Puke, Motueka and Clyde; (b) Map showing the boundaries and status of regions in respect of the presence of Pseudomonas syringae pv. Actinidiae-biovar 3 (Psa-3) (adapted with permission from KVH [4]). Containment region (yellow): Limited Psa-3 infections. Movement of plant material is restricted; Exclusion region (green): No orchards with Psa-3 identified, or Psa-3 has recently been identified for the first time. Material is unrestricted; Recovery region (red): Psa-3 is already widespread. Material is restricted; Controlled areas (stars): only within the South Island. Exclusion regions and movement restrictions apply.

Figure 2

The diversity of the genotypes in the PFR kiwifruit in vitro collection. (a) Number and per-centage of genotypes for each species. (b) Genotypic distribution by sex in number and percentage. * This collection includes one genotype each from A. callosa, A. chrysantha, A. chinensis var. deliciosa coloris, A. latifolia and A. valvata; two genotypes each from A. hemsleyana, A. indochinensis and A. setosa; three genotypes of A. kolomikta; and five genotypes from A. macrosperma species, respectively. ** Gap analyses are underway to confirm the species and sex of the unidentified accessions.

Figure 3

The proportions of kiwifruit genotypes (%) that could be maintained in medium term storage (MTS) for different periods without rejuvenation. MTS is in vitro storage of kiwifruit plants at 5 °C with longevity describing the length of time in days that the plants could be left before requiring rejuvenation.

Figure 4

Flow diagram summarizing steps involved in placing a plant into medium-term storage (MTS) and tracking of plants using Germplasm Management System (GMS) and Vial Management System (VMS). When a plant is received, its details are entered into the GMS database and the plant is prepared for MTS at 5 °C. GMS provides details of every plant in the laboratory with VMS used to record plants being held in vials in MTS. The activities highlighted in blue are activities recorded in VMS. Discarded accessions are also recorded in the system (indicated in pink).

Figure 5

Regeneration percentages of five kiwifruit species following cryopreservation using a protocol established at The New Zealand Institute for Plant and Food Research Limited (reproduced from Table 2 [18] with permission from Springer Nature License Number 6013930561362).

Figure 6

SSR-amplified fragments of a kiwifruit genotype. An example output of GeneMarker^® v 2.2.0 software (© SoftGenetics, LLC, State College, PA, USA) showing R = reference sample displaying identical allele/peak pattern as clone 1, 2 and 3 (C1–3) and suggest true to type.

Figure 7

Summarized workflow for preparation of in vitro plants for overseas trials and plant movement within New Zealand at the PFR in vitro facility.