Cytological Evaluations of Advanced Generations of Interspecific Hybrids Between Allium cepa and Allium fistulosum Showing Resistance to Stemphylium vesicarium.

Natalia Kudryavtseva,Ludmila Khrustaleva,Mikhail Divashuk,Lowell Black,Sergey Odintsov,Pavel Sokolov,Peter Hanson,Michael J Havey

doi:10.3390/genes10030195

Abstract

Interspecific crossing is a promising approach for introgression of valuable traits to develop cultivars with improved characteristics. Allium fistulosum L. possesses numerous pest resistances that are lacking in the bulb onion (Allium cepa L.), including resistance to Stemphylium leaf blight (SLB). Advanced generations were produced by selfing and backcrossing to bulb onions of interspecific hybrids between A. cepa and A. fistulosum that showed resistance to SLB. Molecular classification of the cytoplasm established that all generations possessed normal (N) male−fertile cytoplasm of bulb onions. Genomic in situ hybridization (GISH) was used to study the chromosomal composition of the advanced generations and showed that most plants were allotetraploids possessing the complete diploid sets of both parental species. Because artificial doubling of chromosomes of the interspecific hybrids was not used, spontaneous polyploidization likely resulted from restitution gametes or somatic doubling. Recombinant chromosomes between A. cepa and A. fistulosum were identified, revealing that introgression of disease resistances to bulb onion should be possible.

Highlights

Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium (Wallr.) Simmons, is a serious fungal disease of bulb onion (Allium cepa L.) occurring worldwide, which may result in 100% losses of the bulb crop [1]
In this paper we present the results of a cytological study of advanced generations derived from hybrids between A. cepa × A. fistulosum that show resistance to Stemphylium vesicarium
A. fistulosum and A. cepa were planted in the field at the World Vegetable Center (Shanhua, Taiwan) and subjected to natural disease pressure by S. vesicarium

Summary

Introduction

Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium (Wallr.) Simmons, is a serious fungal disease of bulb onion (Allium cepa L.) occurring worldwide, which may result in 100% losses of the bulb crop [1]. Research has been undertaken to identify sources of resistance to SLB in Allium species and determine its genetic basis [8]. Allium fistulosum L. is a source of desirable traits for improvement of the bulb onion [9] and shows resistance to Stemphylium vesicarium which may be conditioned by a single dominant gene [8]. In 2001, hybrids between A. cepa and A. fistulosum were produced to initiate introgression of resistance to SLB into the bulb onion [8]. The first interspecific hybrids between A. fistulosum and A. cepa were obtained in 1935 [9], hybrids are highly

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