Resistance and clonal selection among Allium sativum L. germplasm resources to Delia antiqua M. and its correlation with allicin content

Abstract

Background: Garlic is the second largest allium crop after onion and is grown all over the world. The onion maggot (Delia antiqua M.) is a pest that seriously affects the yield and quality of garlic. Cultural controls and insecticides have several potential problems, including pesticide residue and development of resistance. Screening resistant varieties is an ideal alternative method.

Results: The resistance of 213 accessions of garlic clones against onion maggot was identified. The results showed that the pest index was between 5.56% and 91.11%, with classification into six groups by cluster analysis: HR (highly resistant), R (resistant), MR (moderately resistant), MS (moderately susceptible), S (susceptible) and HS (highly susceptible). Among these accessions, 9 and 30 were HR and R to onion maggot, respectively. Comparing the resistances of seven pairs of accessions between the original accessions and their progenies showed that single bulb clonal selection could be an effective way to improve allicin content, onion maggot resistance and most morphological traits. The relationship between allicin content and resistance was investigated, and a significant positive relationship was found. Accessions with a high content of allicin have great potential as resistant accessions.

Conclusion: This study showed significant differences among garlic germplasm in their response to Delia antiqua M. Some accessions were highly resistant and tolerant. Utilization of these accessions will help minimize environmental pollution, preserve agro-ecosystems and biodiversity, and make management processes more economical. Furthermore, these accessions could be used in breeding programs to develop new maggot-resistant onion cultivars. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: Allium sativum L.; Delia antiqua M.; allicin; garlic; onion maggot; resistance.

Figure 1

Reference photos for grades of resistance of individual plants to onion maggot (Delia antiqua M.): (a) grade 0; (b) grade 1; (c) grade 3; (d) grade 5; (e) grade 7; (f) grade 9.

Figure 2

Distribution and normality of pest index and allicin content among 213 accessions of garlic investigated in 2016. Distribution of (a) average values of pest index; (b) rank average values of pest index after normality test using Blom's formula; (c) allicin content; and (d) rank allicin content after normality test using Blom's formula.

Figure 3

Tree dendrogram of the pest index values of 213 accessions of garlic. HR, highly resistant to Delia antiqua M.; R, resistant to Delia antiqua M.; MR, moderately resistant to Delia antiqua M.; S, susceptible to Delia antiqua M., HS, highly susceptible to Delia antiqua M.

Figure 4

Effect of clonal selection on resistance improvement to Delia antiqua M investigated in 2016. 8N017, 8N036, 8N141, 8N167, 8N254, 8N257 and 8N261 are the original garlic germplasms; 8N017S, 8N036S, 8N141S, 8N167S, 8N254S, 8N257S and 8N261S are the corresponding offspring of the original garlic obtained by breeding activities. The bar values represent the mean ± SE.

Figure 5

Effect of clonal selection on allicin content and 21 quantity traits compared between unselected and selected versions. Allcin, allicin; PlH, plant height; PlW, plant width; LL, leaf length; LW, leaf width; LN, leaf number; PsH, pseudostem height; PsW, pseudostem diameter; BH, bulb height; BD, bulb diameter; BW, bulb weight; CH, clove height; CW, clove diameter; CN, clove number; PH, thickness of shortened stem; PD, diameter of shortened stem; BoL, bolt length; BBoD, basal diameter of bolt; MBoD, mid‐diameter of bolt; BoW, weight per bolt; BuL, spathe length; BuW, spathe width.