Abstract:
Maize is a dynamic cereal of world's agriculture community. It is grown in spring and autumn seasons in Pakistan and both pistillate and staminate flowers experience severe temperature stress during spring sowing (February sowing) at reproductive phase, which ultimately results in poor seed setting because of increased silk dryness and pollen desiccation. In-vivo haploid induction was performed by using 2nd generation tropically adapted maize haploid inducer allocated from CIMMYT. Indigenously developed maize double haploid (DH) lines using local segregating population as source were screened out against high temperature stress. DH lines were evaluated and selected by using various indicators cell membrane thermostability (CMT), leaf temperature (LT), pollen production potential (PPP), pollen germination %age (PG%), pollen tube length (PTL), grain yield per plant (GY/P), plant height (PH), ear height (EH), days to tasseling (DT), days to silking (DS), number of grains per row (NGPR) and number of rows per cob (NRPC). Significant differences were noted at allelic level among the DH lines for high temperature tolerance related indicators, which provided wide range of option for selection, opportunity to improve tolerance level against high temperature stress and usage of these DH lines in different future maize breeding programs. Correlation coefficient analysis depicted PH, NGPR, HGW, PPP, PTL, and PG as suitable selection criteria for GY/P. The most effective physiological benchmarks for evaluating germplasm resistance to high temperature stress are CMT, PG%, and PTL. According to principal component analysis (PCA) DH lines viz. 5 (PBG-5), 11 (PBG-11), 15 (PBG-15), 19 (PBG-19), 24(PBG-24), 30(PBG-30), 33(PBG-33), 39 (PBG-39), 46 (PBG-46) and 52 (PBG-52) showed high level of diversity and performed well under the normal and high temperature stress conditions and DH lines viz. 10 (PBG-10), 13 (PBG-13), 26 (PBG-26), 37 (PBG-37) and 51 (PBG-51) performed poor under the normal and high temperature stress conditions. To develop maize varieties that can thrive in high-temperature conditions, it is necessary to cultivate DH lines that exhibit strong adaptability when exposed to induced stress. These lines could serve as a valuable genetic resource, as they likely contain a diverse array of genes that contribute to high temperature tolerance.
Keywords:
Maize DH lines
,
high temperature stress
,
pollen germination
,
pollen tube length and cell membrane thermostability