Resistance of green beans to aphid-borne viruses in New Zealand.
The viruses that have been found to attack green bean (Phaseolus vulgaris) in New Zealand are bean common mosaic (BCMV) (transmitted by Aphis craccivora Koch), bean yellow mosaic virus (BYMV) (by Myzus persicae (Sulz.), Macrosiphum euphorbiae (Thos.) and A. craccivora) subterranean clover red leaf virus (SCRLV) (by Aulacorthum solani (Kalt.)), pea leaf roll virus (PELRV) (by Myzus persicae) and (identified for the first time on green beans in New Zealand this season) lucerne mosaic virus (AMV) (transmitted by Acyrthosiphon pisum (Harris), M. persicae and Aulacorthum solani. The importance of these viruses in New Zealand is discussed, sources of resistance are described, and the results are presented of experiments on breeding cultivars resistant to SCRLV. It was not possible to screen plants in the greenhouse, because transferring aphids from infected subterranean clover (Trifolium subterraneum) does not consistently produce the disease.<new para>ADDITIONAL ABSTRACT:<new para>Resistance of Phaseolus vulgaris cv. to aphid-borne viruses was studied in New Zealand. It was found that cv. C44 had the highest pod yield relative to the standard cv. Gallatin 50 in 1977-8.<new para>ADDITIONAL ABSTRACT:<new para>Under epidemic conditions in 1975-76, tolerance of subterranean clover red leaf virus (SCRLV) was found in the Phaseolus vulgaris garden cultivars Canadian Wonder, Masterpiece and Topnotch Golden Wax; the processing cultivars Prelude, 27, Tempo and Fortune had no observable infection. Among resistant progenies selected from crosses between tolerant cultivars and susceptible cultivars with good processing quality in trials, the most promising line was C44 from Gallatin 50 X Masterpiece, which has a good upright habit although its pods are stringy at maturity. The line OSU190 X Prelude may be suitable for garden or fresh use. The resistant cultivar Long John is a New Zealand selection of the released line OSU58. It has good pod colour and quality but is highly susceptible to Pseudomonas phaseolicola. Line OSU10183-B appears to be immune to SCRLV.