Molecular evaluation and genetic behavior of white tip nematode resistance against Aphelenchoides besseyi in artificially infected rice plants

Abstract

Genetic behavior of some morphological, yield and its related traits was studied under nematode infection condition using five rice genotypes which were crossed using complete-diallel analysis to produce 20 rice hybrids. All 25 genotypes were evaluated under both normal and white tip nematode infection conditions. Although, molecular evaluation using simple sequence repeats for characters related to resistance were done. As a result of this study, the parental varieties Giza179, Giza182 and Sakha105 were the best of all parents, since they possessed favorite general combining ability (GCA) effects for many traits. The three crosses Sakha106 × Sakha101, Sakha105 × Sakha101 and Giza182 × Giza179 recorded the desirable values of specific combining ability (SCA) for most of the studied traits. Dominance genetic variance played the most significant role in inheritance of the traits under study. The two crosses Sakha101 × Sakha106 and Sakha105 × Sakha101 were considered the best for yield and its components under affected condition by white tip nematode. RM5526 marker was the best in detecting genetic diversity among the rice accessions for the resistance-associated trait, no. Of Aphelenchoides besseyi (A. besseyi) individuals in 100 grains (NA). While, RM161 marker was the best in detecting genetic diversity among the rice accessions for the resistance-associated trait, loss rate of panicle weight (LRPW). Principal component analysis (PCA) was applied for morpho-physiological characters and molecular data analysis and showed a good separation of the genotypes which was in high agreement with phylogenetic tree clustering and also showed that SSR analysis can be recognized with the help of principal component analysis, which are accountable for the observed genotypic variations presented within each component. Two DNA fragments with molecular size of 165 bp and 146 bp may play an important role in the white tip nematode resistance in rice while they appeared only in the resistant parents and crosses. These bands should be isolated, sequenced and compared with the genes in data base which are responsible for white tip nematode resistance in rice. Both DNA fragments will be of great interest in nematode resistance programs in rice in the future. Finally, we can recommend the farmers to use the two varieties Giza 179 and Giza182 for planting in land affected with white tip nematode. The farmers could also be recommend to use the two hybrids Sakha106 × Sakha105 and Giza179 × Sakha105 when planting in land affected with white tip nematode while they proved to be resistant to white tip nematode by using morphological and molecular analyses. For researchers we can recommend by using the two specific molecular markers, RM5526 and RM161 for fast identification of white tip nematode resistant rice varieties in Egypt.