Comparative Assessment of Genetic Variability Realised in Doubled Haploids Induced from F1 and F2 Plants for Response to Fusarium Stalk Rot and Yield Traits in Maize (Zea mays L.)

Doubled-haploid lines (DHs) are normally produced from F1 plants in maize (Zea mays L.). Several studies have found a low frequency of recombinants in doubled haploids produced from F1 plants that could limit the selection response. Hence, an attempt was made to produce doubled haploids from the F2 generation to verify whether one more round of meiotic recombination could lead to increased genetic variability and assess the response to selection. The F1 and F2 plants of two cross-combinations, VL1043 &times: CM212 and VL121096 &times: CM202, were subjected to doubled-haploid production and evaluated in terms of their reaction to Fusarium stalk rot and yield traits along with F2 individuals of the same two crosses. There was significant variation in the number of DHs produced when F1 and F2 plants were subjected to DH production in the cross VL121096 &times: CM202. Furthermore, substantial genetic variability was observed among the DHs produced from the F1 generation (DHF1s), F2 generation (DHF2s), and F2s for Fusarium stalk rot (FSR) resistance. The genetic variance was more extensive in DHF2 compared to DHF1 plants in the cross VL1043 &times: CM212. Extreme candidate plants (highly resistant, resistant, and highly susceptible) were found in the F2 generation with a more standardized range than in the DHs. In the DH populations, the close correspondence between the phenotypic coefficient of variability (PCV) and the genotypic coefficient of variability (GCV) indicated less influence from the environment compared to the F2 plants. The heritability estimates in the DHs were greater than in the F2 plants of the VL1043 &times: CM212 cross, while in the VL121096 &times: CM202 cross, the heritability was almost the same between the DHs and F2 plants due to the relatively small population size of the DHs. The positively skewed leptokurtic distribution of the DH populations indicated the role of fewer genes, with the majority of them exhibiting complementary epistasis with decreasing effects in response to FSR. The mean estimated yield and genotypic variance in the top crosses produced from randomly chosen DHF1 and DHF2 plants of the cross VL1043 &times: CM212 were similar in magnitude.