Hybrid Breeding for MLN Resistance: Heterosis, Combining Ability, and Hybrid Prediction

Abstract

Prior knowledge on heterosis and quantitative genetic parameters on maize lethal necrosis (MLN) can help the breeders to develop numerous resistant or tolerant hybrids with optimum resources. Our objectives were to (1) estimate the quantitative genetic parameters for MLN disease severity, (2) investigate the efficiency of the prediction of hybrid performance based on parental per se and general combining ability (GCA) effects, and (3) examine the potential of hybrid prediction for MLN resistance or tolerance based on markers. Fifty elite maize inbred lines were selected based on their response to MLN under artificial inoculation. Crosses were made in a half diallel mating design to produce 307 F1 hybrids. All hybrids were evaluated in MLN quarantine facility in Naivasha, Kenya for two seasons under artificial inoculation. All 50 inbreds were genotyped with genotyping-by-sequencing (GBS) SNPs. The phenotypic variation was significant for all traits and the heritability was moderate to high. We observed that hybrids were superior to the mean performance of the parents for disease severity (−14.57%) and area under disease progress curve (AUDPC) (14.9%). Correlations were significant and moderate between line per se and GCA; and mean of parental value with hybrid performance for both disease severity and AUDPC value. Very low and negative correlation was observed between parental lines marker based genetic distance and heterosis. Nevertheless, the correlation of GCA effects was very high with hybrid performance which can suggests as a good predictor of MLN resistance. Genomic prediction of hybrid performance for MLN is high for both traits. We therefore conclude that there is potential for prediction of hybrid performance for MLN. Overall, the estimated quantitative genetic parameters suggest that through targeted approach, it is possible to develop outstanding lines and hybrids for MLN resistance.

Identification of Genomic Regions Associated with Agronomic and Disease Resistance Traits in a Large Set of Multiple DH Populations

“…A significant genotype, genotype by environment interaction variances, and moderate to high broad-sense heritability were observed for GY and other related traits AD, ASI, PH, EH, TLB, MOI, and GLS measured under WW and WS conditions similar with the results reported by Yuan et al [ 24 ]. MLN-DS and AUDPC were highly heritable with 0.67 and 0.74, respectively, which is consistent with earlier reported studies [ 31 , 37 , 53 , 54 ]. Several genotypes have been evaluated by CIMMYT against MLN disease in search for resistant materials [ 12 , 24 , 31 , 32 , 38 , 55 ]; with the current study, we identified about 52 MLN disease resistant/tolerant genotypes while most of other genotypes were susceptible.…”

“…CIMMYT in collaboration with national research institutions has developed resistance breeding strategies against MLN. A large number of maize genotypes were screened, and MLN disease-resistant source materials and resistance QTLs were identified to develop resistant varieties by integrating both conventional and molecular breeding techniques [ 12 , 31 , 37 , 38 ]. Nevertheless, searching additional MLN disease-resistant lines, evaluation of the genotype’s performance, identification and validation of QTLs associated with the target disease, GY, and other related traits play a vital role in the development of MLN disease-resistant varieties.…”

“…The detailed protocol on the preparation of inoculum is explained in earlier studies [ 12 , 13 , 37 ]. In brief, the stock isolates of MCMV and SCMV pathogens were mass-produced in separately managed greenhouses.…”

Assessment of Heterosis Based on Parental Genetic Distance Estimated With SSR and SNP Markers in Upland Cotton (Gossypium Hirsutum L.)

“…In eggplant, GD assessed through SNPs showed a diminutive correlation with the hybrid means, heterosis, and SCA values [27]. In a previous study of maize lethal necrosis, a very low and negative correlation was observed between parental lines marker-based genetic distance and heterosis [31].…”

Estimation of the Resistance of Maize Lines to Sphacelotheca Reiliana in the Northern Steppe of Ukraine

“…Натепер особливості збудників вірусних, бактеріальних та грибкових захворювань, механізм взаємодії з організмом-хазяїном та стійкість до хвороб у кукурудзи інтенсивно вивчаються на молекулярному рівні (Wu et al, 2017;Ge et al, 2020;Nyaga et al, 2020;Ali et al, 2021). Серед них значна увага приділяється сажковим хворобам (Schirawski et al, 2010;Di et al, 2017;Zuo et al, 2019).…”