Cold Tolerance In Maize Research Articles

Identification of quantitative trait loci involved in the response to cold stress in maize (Zea mays L.)

The effect of low temperature on the physiology of maize has been well studied, but the genetics behind cold tolerance is poorly understood. To better understand the genetics of cold tolerance we conducted a quantitative trait locus (QTL) analysis on a segregating population from the cross of a cold-tolerant (EP42) and a cold-susceptible (A661) inbred line. The experiments were carried under cold (15 °C) and control (25 °C) conditions in a phytotron. Cold temperature reduced the shoot dry weight, number of survival plants and quantum yield of electron transport at photosystem II (ΦPSII) and increased the anthocyanin content in maize seedlings. Low correlations were found between characteristics under low and optimum temperature. Ten QTLs were identified, six of them at control temperatures and four under cold temperatures. Through a meta-QTL analysis we identified three genomic regions in chromosomes 2, 4 and 8 that regulate the development of maize seedlings under cold conditions and are the most promising regions to be the target of future marker-assisted selection breeding programs or to perform fine mapping to identify genes involved in cold tolerance in maize.

Divergent selection in a maize population for germination at low temperature in controlled environment: study of the direct response, of the trait inheritance and of correlated responses in the field

Improving cold tolerance in maize (Zea mays L.) is an important breeding objective, allowing early sowings which result in many agronomic advantages. Using as source the F(2) population of B73×IABO78 single cross, we previously conducted four cycles of divergent recurrent selection for high (H) and low (L) cold tolerance level, evaluated as the difference (DG) between germination at 9.5°C and at 25°C in the germinator. Then, we pursued the divergent selection in inbreeding from S(1) to S(4). This research was conducted to study (1) the direct response to selection (by testing ten S(4) L and ten S(4) H lines), (2) the trait inheritance (in a complete diallel scheme involving four L and four H lines), (3) the associated responses for cold tolerance in the field (at early and delayed sowings) and (4) the responses for other traits, by testing the ten L and the ten H lines at usual sowing. Selection was effective, leading to appreciable and symmetric responses for DG. Variation among crosses was mainly due to additive effects and the ability to predict hybrid DG based on parental lines DG was appreciable. Associated responses for cold tolerance traits in the field were noticeable, though the relationship between DG and these traits was not outstanding. High tolerance was also associated with early flowering, short plants, less leaves, low kernel moisture, red and thin cob, and flint kernels. These divergently selected lines can represent valuable materials for undertaking basic studies and breeding works concerning cold tolerance.

Association of polyamines in governing the chilling sensitivity of maize genotypes

Chilling stress is an important constraint of global production of maize. This study was undertaken to compare the chilling responses of different maize seedling tissues and to analyze changes in polyamines as a result of chilling stress. Reponses to chilling were characterized in two maize (Zea mays L.) inbred lines, ‘HuangC’ and ‘Mo17’, that putatively differ in chilling sensitivity. Seedlings were exposed to low temperature (5°C) and chilling injury was estimated by electrical conductivity (EC), malonaldehyde (MDA) concentration, and by changes in putrescine (Put), spermidine (Spd) and spermine (Spm) concentrations in root, mesocotyl, and coleoptile tissues. Membrane permeability (as measured by EC), MDA concentrations and Put concentrations in the three tissue of maize seedlings increased after chilling stress, except for the Put concentration in roots. Spd and Spm concentrations in the three tissues of seedlings decreased after chilling stress. The EC for cold stressed tissues were lower in HuangC than Mo17. Also, the EC of coleoptile tissues were lower than for mesocotyl in both inbred lines. We suggest that mesocotyl tissue can be used to evaluate cold tolerance in maize. Stepwise regression analyses showed that chilling injury in roots was generally correlated with Spd concentration while in the mesocotyl injury was mainly correlated with Put and Spd concentrations. Spermidine and Spm concentrations in the coleoptile were correlated with chilling injury. Characteristics changes of polyamines in chill-tolerant maize seedling combined with regression analysis are a reliable method for evaluating chill tolerance in maize lines.

Combining Maize Base Germplasm for Cold Tolerance Breeding

Early planting can contribute to increased grain yield of maize (Zea mays L.), but it requires cold tolerance. A limited number of cold‐tolerant maize genotypes have been reported. The objectives of this study were to test a new strategy to improve cold tolerance in maize searching for broad × narrow genetic combinations that may be useful as base populations for breeding programs, to compare genotype performance under cold‐controlled and field conditions, and to establish the major genetic effects involved in crosses between cold‐tolerant inbred lines and populations. Nine cold‐tolerant populations were crossed to five inbred lines and evaluated in a cold chamber and in the field. Most inbred line × population crosses performed better than populations per se or hybrids used as checks, both in the cold chamber and in the field, suggesting that broad × narrow genetic combination could be a suitable start point for further breeding programs for cold tolerance. The crosses between the inbred line EP80 and northwestern Spanish populations are the most promising base germplasm. In particular, EP80 × Puenteareas showed the greatest yield and good performance at the first stages of development under cold conditions. In addition, EP80 and Puenteareas showed favorable general combining ability for most traits. Early vigor rating would be the most suitable trait to select maize genotypes with superior cold tolerance during emergence and postemergence stages, because it was the only trait for which differences among genotypes were observed in both the cold chamber and the field. Although evaluation under controlled conditions is essential to test cold tolerance, field evaluations are complementary because no association was found between traits evaluated in both conditions.

Genetic Variation in Physiological Discriminators for Cold Tolerance—Early Autotrophic Phase of Maize Development

ABSTRACTEarlier spring planting to maximize the duration of the growing season has increased the importance of early‐season cold tolerance in maize (Zea mays L.). The objectives of this study were to assess the response of several physiological parameters associated with cold tolerance in maize during early autotrophic development and to quantify variability in the response to cold stress among 49 maize inbred lines. At the 7‐leaf tip stage, maize inbred lines were subjected to two day/night temperature regime treatments, 25/15°C (control) and 15/3°C (cold). Carbon exchange rate (CER), leaf chlorophyll content, quantum efficiency of Photosystem II, leaf conductance, dry weight, root/shoot ratio, and rate of development were measured at the 8‐leaf tip stage for genotypes under both treatments. The cold treatment effects were significant for all parameters except root/shoot ratio. Genetic diversity for most traits investigated was observed for the response of the inbred lines to cold stress. Results of this study show that leaf CER and rate of development are good discriminators of cold tolerance during early phases of development.

The use of chlorophyll fluorescence as a screening method for cold tolerance in maize

Chlorosis in maize (Zea mays L.) is a common phenomenon in the 12 to 17°C temperature range. A newly developed chlorophyll-fluorescence technique was used to elucidate the underlying subcellular processes of resistance to chlorosis. Four populations were used that were developed by divergent mass selection for contrasting resistance to chlorosis in a cold-tolerant dent and a cold-tolerant flint population. Young plants from the four populations were kept for six days at 17/10, 15/10 and 13/10°C (day/night). After 1, 3 and 6 days various chlorophyll-fluorescence parameters were determined. The measurements were done on leaf 4. Differences were not uniform for all fluorescence properties. The resistant and susceptible populations of the two sets differed for the Q-quenching which is related to the electron transport rate in the chloroplast. For the E-quenching which is related to the Calvin cycle activity, the resistant dent differed significantly from the other three populations. The ratio Fm/Fo (related to the transfer of absorbed light-energy from antennae pigments to reaction centers in the chloroplast) was higher for the resistant dent population than for the susceptible one. The flint types did not differ for this property.Apparently, divergent mass selection for chlorosis resistance resulted in various changes at the subcellular level that are not necessarily comparable for flint and dent types.When after 6 days the temperature was raised from 13°C to 17°C, the fluorescence signals led to the conclusion that there was a full recovery of various processes after two days, except for the metabolic activity of the susceptible flint.

Recurrent Selection for Cold Tolerance in Maize1

We conducted experiments in 1973 and 1974 (planted each year as early as possible in the spring) to evaluate effectiveness of recurrent selection for cold tolerance in two Iowa maize (Zea mays L.) breeding populations, BSSS2(SCT) and BSSS13(SCT). Progress from selection for cold tolerance was measured by changes in percentage emergence, emergence index (based on emergence rate), and seedling dry weight. Changes in other agronomic traits were studied also.Relatively more progress for improved cold tolerance was realized from two cycles of recurrent selection in BSSS13(SCT) than from three cycles of recurrent selection in BSSS2(SCT). Percentage emergence and seedling dry weight of BSSS13(SCT) were improved 8.4%/cycle and 0.6 dg/cycle, respectively. These traits did not respond consistently to selection within BSSS2(SCT). Emergence index was not changed by selection in either population. Also, one cycle of selection based on data collected from growth‐chamber plantings of both populations did not choose significantly different genotypes from those chosen by selection based on data collected from field plantings.The C2 cycle of BSSS13(SCT) was characterized by more vigorous seedling and juvenile plant growth, an earlier flowering date, and a lower harvest moisture than the C0 cycle. The C3 cycle of BSSS2(SCT) showed an earlier flowering date, shorter mature plant height, and lower harvest moisture than the C0 cycle.Grain yields of advanced selection cycles of BSSS2(SCT) were lower than, and those of BSSS13(SCT) were equal to, that of the highest‐yielding hybrid check.

Genetics of cold tolerance in maize and sweet corn seed

Genetics of cold tolerance in maize and sweet corn seed