Resistance to white rot disease and enhancement of yield and its components by selection in mutants of two garlic cultivars

The study was conducted during the winter seasons of 2015 to 2019 to select garlic clones superior in yield, quality and tolerant or resistant to white rot disease. Fourteen mutants from Balady and five mutants from Egassed-1 garlic cvs. were isolated in stable form and selected after 4 successive generations (M1V4) from previous breeding program using mutagens viz., di-ethyel sulphate (DES), di (2-chloro ethyel) amine (DEA) and gamma ray. Cloves of two local garlic cultivars (Balady and Egassed-1) were irradiated with gamma ray doses i.e. 1, 3, 5,10 and 15 Gy or treated with previous mutagens. Out of Balady selected clones, Mut 6-1 and Mut 6 had the heaviest cloves compared to the original cultivar with values of 3.8 and 3.6 g/cloves, in 2015/2016 and 2016/2017 seasons, respectively. Likewise, Mut 6-2 and Mut 7 which resulted from Eggaseed-1 cv. had the heaviest cloves compared to the original cultivar with values of 7.6 and 7.2 g/cloves, in the first and second seasons, respectively. Significant positive correlations were found between the most of the desirable traits. Artificial infestation with Sclerotium cepivorum was carried out under greenhouse conditions during two successive seasons of 2017/2018 and 2018/2019 and under natural infestation in the open field to evaluate the resistance in the two cultivars and their mutants. In case of Balady cv., Mut 6-1 (10 GY) and Mut 2 (0.1 % DEA) were highly tolerant in the two tested seasons with infection percentage of 11.33 and 12.33 % in the first season and 13.33 and 15.33 % in the second one with efficacy 80.4, 78.74 and 78.15, 74.87 %, respectively, compared to Balady (58 and 61 % infection). Regarding, Eggaseed-1 cv., Mut 6-2 and Mut 6-1 resulted from γ irridiation (10 GY) were highly tolerant mutants in the two tested seasons with infection percentage of 8.33 and 10.67 % in the first season and 9 and 10.67 % in the second one with efficacy 81.21, 75.93 % and 81.38, 79.99 %, respectively as compared to original cultivar (44.33 and 48.33 % infection). Results of employed QRT-PCR technique showed that Mut 6-1 (10 GY) which had significantly high tolerance to garlic white rot disease showed great regulation-up of detective defense genes (PR1, PR5, PAL and HQT) with high relative expression values compared to original cultivar, Balady. Similar results were obtained in case of Eggaseed-1 cv. Results showed that respective encoded PR and polyphenol synthase genes might have played important role in defense reaction of obtained mutants of two tested garlic cultivars against S. cepivorum infection. Mutants with high tolerance to garlic white rot disease could be used by growers in the infested areas.