Biomass production is important in increasing yield not only for food but also for bio-fuel production that depends on high dry matter. Due to climate change, occurrence of drought may be prevalent and this affects both grain and biomass yields in crops including rice. The objectives of this study were to determine the performance of selected high biomass breeding rice lines to different levels of drought and use several drought tolerance indices to identify best genotypes that could be grown in unfavorable water stressed areas. A rainfed and flooded trial was conducted to evaluate 20 selected breeding lines for biomass production and ten entries from the same set were grown in the greenhouse at three different field capacities (FC, 50%, 75%, 100%). Most of the genotypes performed well under non-stressed conditions (flooded and 100% FC) but some genotypes performed well in water stressed condition. The plants had lower plant height, tiller plant -1, and total biomass at maturity under rainfed conditions and their flowering was delayed compared to flooded conditions. In the greenhouse, water stress slowed the rate of increase in height, and produced lower shoot and root weight, percent dry matter (% DM) and total biomass. However, drought enhanced the rate of tiller production. Two genotypes were found to more tolerant to drought stress and could be used for cultivation under water stress condition to get optimum biomass yields. These genotypes can be identified using drought tolerance indices, particularly stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP) and harmonic mean (HARM), as these have a similar ability to separate drought sensitive and tolerant genotypes. Genetic and molecular analyses, and detailed characterization of these genotypes will help understand their inheritance pattern and the number of genes controlling the traits and determine specific leaves and root traits important in developing high biomass rice.
Rice (Oryza sativa) is the staple food for a large part of the world’s human population, which is the most consumed cereal after wheat. Javanica known also as “tropical japonica” [
Different environments have different effects on the production of rice grain and biomass. Rice which is grown in humid tropics in rainfed (dry land) areas covers 19% of the total rice production areas and the 15 million hectares of rain dependent rice fields contribute about 4% of total world rice production [
The rise in concerns about the environment and price of volatile oils has diverted the attention of the world to using alternative energy resources [
One of the objectives of this study was to determine the response of selected high biomass rice genotypes to drought and rainfed growing condition. Specifically, the study aimed to determine growth and biomass yield of selected O. sativa lines under two levels of drought and their agronomic response in rainfed and flooded conditions. Six selection indices were used to identify best genotypes that could be grown in unfavorable areas. Drought tolerance indices provide a measure of drought based on yield loss under drought conditions as compared to normal conditions and hence they are used to screen drought tolerant genotypes [
The materials for evaluation were obtained from high biomass rice project of Texas A&M AgriLife Research and Extension Center, Beaumont, Texas which was aimed to identify high biomass rice as alternative source of feedstock for bioenergy generation. These breeding lines were generally late maturing, with large tiller or with many tillers, leafy and taller than conventional rice. These were derived from breeding populations developed for breeding high grain yield thus these were undesirable for high grain yield but has potential for high biomass production.
Ten selected genotypes were used in pot experiments aimed to evaluate biomass production in water-limited environment. Five seeds of each genotype were seeded in six inches in diameter and six inches deep plastic pots with equal amount of soil arranged in a completely randomized design with three replications. Equal amount of water was used until germination. At 20 days after sowing (DAS), thinning to one plant was done and the following treatments were used; 50%, 75% and 100% FC. These water levels were maintained throughout the experiment by weighing the pots every other day while the evaporated water was compensated by adding extra water. One extra pot without plant for 75% and 50% FC was maintained and the water evaporated from those pots was used to add water in the experimental pots at the same FC. Nitrogen fertilizer was applied in two splits; first at planting at the rate of 57 kg∙ha−1 and second at tillering at the rate of 91.2 kg∙ha−1. The final data gathering was done 85 DAS.
The data collected were the days to first tiller emergence, weekly tiller count, weekly increase in plant height, shoot fresh weight (FW) and dry weight (DW), root FW and DW, total fresh and dry biomass. Tiller emergence was the day when the first tiller with one fully expanded leaf appeared at the base of the plant. Tiller count was gathered by counting the tillers including the newly emerged tillers with one fully expanded leaf while plant height was gathered by measuring the length of the plant from soil surface to the tip of the longest leaf. The shoot and root weights were collected by weighing the upper part of the plant and root including the node where the upper most roots originated after carefully removing soil at the end of the experiment (85 DAS). These samples were air dried for 30 days to obtain the shoot and root dry weights. Rate of tiller production, rate of leaf production and rate of increase in plant height were computed by finding the slope of number of tillers and leaves, and plant height at weekly intervals.
This experiment was conducted in the field of Texas A&M AgriLife Research and Extension Center at Beaumont, Texas (30.06˚N, 94.29˚W). Twenty selected high biomass rice genotypes were field planted to evaluate their biomass production in rainfed and flooded environment. Ten of these were included in the pot experiment on field capacity. The soil for direct seeding was prepared using disc harrow and rotavator to pulverize the soil, and was laser leveled. Before planting, levees were made to facilitate water control. Urea was applied in three splits; 57 kg∙ha−1 at planting, 91 kg∙ha−1 at flooding and at panicle differentiation at the rate of 80 kg∙ha−1. The P2O5 fertilizer was applied at planting at the rate of 34 kg∙ha−1. A split-plot design with two replications was used, with the flooded and rainfed environments as the main plot, and high biomass rice genotype as sub-plot. Each sub-plot had three rows that were 3 m long and 25 cm apart. Seeds were sown using a planter at the rate of 2 - 3 grams row−1. The flooded treatment had permanent flood starting from 30 days after seedling emergence while rainfed treatment was flush flooded when rain water was not enough to avoid severe soil cracking and wilting of the plants. In most cases, flushing of irrigation water was done when high noon leaf rolling was observed in some of the test entries. The rainfall received during emergence to harvest was 11.57 inches.
The data collected were average height, tillers plant−1 at 105 DAS, days to 50% heading and total fresh biomass yield (kg∙ha−1) at maturity. The plant height at maturity was measured from the soil level to the tip of the tallest panicle. The number of tillers plant−1 at 105 DAS was computed by dividing the total number of tillers/ 750 cm2 by number of plants/750 cm2. Flowering date was gathered when 50% of the panicles of plants in a plot had opened florets. The total fresh weight of above ground biomass of all the plants in a plot at maturity was gathered along with the date at which the crop was harvested.
All the data gathered were statistically analyzed using analysis of variance (ANOVA; SAS software). The means were separated using Duncan’s t test at an alpha level of 0.05.
Drought tolerance indices were calculated using the following equations:
where Ys and Yp are yield under stress and non-stress yield of a given genotype, respectively.
The analysis of variance showed that the differences in the number of days to first tiller, rates at which tillers were produced, shoot and root fresh and dry weight as well as the total fresh and dry biomass in three levels of FC and in genotypes was significantly different. The variations in plant heights at 43 DAS and 85 DAS and the rates of height increase in three levels of FCs and 10 genotypes, however, were highly significant. The number of tillers at 43 and 85 DAS varied significantly among genotypes but it varied only with FC at 43 DAS but not at 85 DAS. The interaction of genotype x FC for these parameters was non-significant except for the plant height at 85 DAS.
The genotypes grown at 100% FC had significantly faster tiller emergence and the rate of increase in plant height than those grown at 75% and 50% FC but plant grown at 50% FC had fastest rate of tiller production (
Among the ten genotypes studied, genotype 12 had the lowest number of days to first tiller emergence (early tiller production) but it was statistically comparable to genotype 10 and 11 (
% Field capacity | Days to first tiller emergence | Rate of tiller production | Rate of increase in plant height | Shoot weight (g) | Root weight (g) | Total biomass (g) | % Dry matter | |||
---|---|---|---|---|---|---|---|---|---|---|
Fresh | Dry | Fresh | Dry | Fresh | Dry | |||||
50 | 45.59a | 0.1117a | 0.3044a | 15.01c | 3.99c | 2.08c | 0.44c | 17.08c | 4.44c | 26.52b |
75 | 41.32b | 0.0785b | 0.4518a | 27.37b | 7.94b | 5.05b | 1.25b | 32.41b | 9.19b | 29.27a |
100 | 36.67c | 0.0731b | 0.4564b | 41.26a | 10.90a | 8.15a | 1.48a | 49.41a | 12.39a | 25.14b |
Means in each column followed by the same letter are not significantly different at 5% level of significance.
Genotypes | Days to first tiller emergence | Rate of tiller production | Rate of increase in plant height | Shoot weight (g) | Root weight (g) | Total biomass (g) | % Dry matter | |||
---|---|---|---|---|---|---|---|---|---|---|
Fresh | Dry | Fresh | Dry | Fresh | Dry | |||||
4 | 42.56abc | 0.0408e | 0.3160b | 24.77c | 6.27d | 5.67abc | 1.02abcd | 30.44bcd | 7.28d | 24.17cd |
5 | 42.88abc | 0.0605de | 0.3721b | 24.06c | 7.28bcd | 4.45bc | 0.95bcd | 28.51cd | 8.23bcd | 28.89ab |
6 | 41.33bc | 0.0419e | 0.3704b | 31.71ab | 8.58bc | 5.26abc | 1.19abc | 36.97abc | 9.78abc | 26.27bcd |
7 | 40.67cd | 0.0941cd | 0.3894b | 24.23c | 6.94cd | 5.11bc | 0.94bcd | 29.33cd | 7.88cd | 26.83bcd |
10 | 38.89cde | 0.1247bc | 0.3653b | 33.66ab | 9.25ab | 5.63abc | 1.31a | 39.29ab | 10.56ab | 26.56bcd |
11 | 36.89de | 0.1757a | 0.6216a | 33.99a | 8.32bcd | 7.74a | 1.46a | 41.73a | 9.78abc | 23.52d |
12 | 36.11e | 0.1439ab | 0.2942b | 37.80a | 10.64a | 5.91ab | 1.30ab | 43.71a | 11.94a | 27.43abc |
14 | 42.00abc | 0.0623de | 0.4569b | 21.72c | 6.34d | 3.14c | 0.80cd | 24.86d | 7.14d | 30.60a |
16 | 45.22ab | 0.0674de | 0.4240b | 21.99c | 6.54d | 3.18c | 0.66d | 24.18d | 7.20d | 31.09a |
Banks | 46.14a | 0.0553de | 0.4398b | 26.83bc | 6.22d | 5.61abc | 1.02abcd | 32.44bcd | 7.24d | 23.12d |
Means in each column followed by the same letter are not significantly different at 5% level of significance.
when compared to the check. The % DM was highest in genotype 16 having 34.4% more than Banks and genotype 11. Being best in all the parameters measured, genotype 12 has the best potential for higher biomass production in any FCs. For high % DM, however, genotypes 5, 14 and 16 are the best together with genotype 12. Genotype 6, 10 and 11 showed similar pattern but all were included in the group with lower % DM.
The amount of available water affected the growth and development of the ten high biomass rice lines. The observed reduction in tiller production under stress could be due to limited assimilates produced from inhibited photosynthesis which is directly caused by drought [
Limited water availability can cause cascade of signals mediated by phytohormone ABA [
Analysis of variance indicated significant differences between the two environments and 20 genotypes. The genotype x environment interaction was highly significant for average height, tillers plant−1 at 105 DAS and days to 50% heading but not for biomass yield (
Among the genotypes, there were significant differences for tiller plant−1 at 105 DAS, days to 50% heading and biomass yield (kg∙ha−1) but not for plant height (
Genotype | Average height (cm) | Tillers plant−1 at 105 DAS | Days to 50% heading | Fresh biomass yield (kg∙ha−1) | ||||
---|---|---|---|---|---|---|---|---|
Environment | Environment | Environment | Environment | |||||
Rainfed | Flooded | Rainfed | Flooded | Rainfed | Flooded | Rainfed | Flooded | |
1 | 102.25abc | 125.17abc | 14.67abcde | 15.42abcde | 109.50defgh | 92.50lmno | 25,178.72 | 30,148.16 |
2 | 93.67c | 135.00a | 8.48de | 12.79abcde | 111.00def | 96.50jklmn | 26,147.52 | 23,175.60 |
3 | 108.00abc | 118.17abc | 11.38bcde | 22.50ab | 121.50ab | 95.50jklmno | 26,209.68 | 43,963.92 |
4 | 95.50bc | 106.17abc | 18.46abcde | 17.67abcde | 110.00defg | 93.00lmno | 27,890.24 | 36,733.76 |
5 | 98.67bc | 114.33abc | 10.13cde | 13.83abcde | 122.50ab | 101.00ghijkl | 17,171.84 | 24,788.96 |
6 | 103.50abc | 120.33abc | 13.88abcde | 10.13cde | 109.50defgh | 96.50jklmn | 31,699.92 | 42,868.56 |
7 | 103.50abc | 122.67abc | 15.58abcde | 17.67abcde | 112.00cde | 90.00mno | 28,985.04 | 22,402.24 |
8 | 110.83abc | 111.50abc | 14.00abcde | 9.70cde | 102.50fghijk | 88.00no | 20,786.08 | 31,052.56 |
9 | 110.33abc | 111.75abc | 13.40abcde | 16.13abcde | 114.50abcd | 97.50ijklm | 23,046.80 | 26,469.52 |
10 | 119.92abc | 110.67abc | 12.95abcde | 15.08abcde | 97.00ijklmn | 89.00mno | 13,297.76 | 20,530.72 |
11 | 111.33abc | 105.83abc | 20.17abcd | 24.00a | 122.00ab | 101.00ghijkl | 45,065.44 | 45,193.68 |
12 | 99.92bc | 127.17abc | 15.00abcde | 18.33abcde | 123.50a | 102.50fghijk | 18,592.56 | 39,513.04 |
13 | 108.00abc | 101.33abc | 6.60e | 17.00abcde | 114.00bcd | 93.50klmno | 26,663.28 | 37,767.52 |
14 | 97.67bc | 118.42abc | 8.28de | 13.50abcde | 106.00defghi | 93.00lmno | 27,436.08 | 23,046.80 |
15 | 109.33abc | 111.67abc | 12.38abcde | 19.50abcd | 111.00def | 96.50jklmn | 19,107.76 | 25,114.32 |
16 | 103.50abc | 112.33abc | 15.13abcde | 18.58abcde | 104.00efghij | 89.50mno | 35,378.00 | 23,758.56 |
17 | 100.50bc | 107.42abc | 8.60cde | 10.50bcde | 100.50hijkl | 89.00mno | 14,460.32 | 29,503.60 |
18 | 96.00bc | 128.33ab | 8.75cde | 13.88abcde | 101.00ghijkl | 86.50o | 15,497.44 | 13,880.72 |
19 | 95.50bc | 125.17abc | 17.33abcde | 20.75abc | 120.50abc | 94.00klmno | 31,117.52 | 26,988.08 |
Banks | 108.08abc | 102.33abc | 18.50abcde | 15.67abcde | 110.50def | 93.50klmno | 24,984.96 | 30,405.20 |
Means in each column followed by the same letter are not significantly different at 5% level of significance.
flower (113 days) and this heading was comparable to genotype 3, 5, 11 and 19. The highest fresh biomass yield was from genotype 11 (45,129.56 kg∙ha−1) followed by genotype 6 (37,284.24 kg∙ha−1) and these were not significantly different from yields obtained from seven genotypes including Banks. The lowest biomass was obtained from genotype 18. Late heading produce more tiller and higher biomass. Genotypes having more tillers had higher biomass.
Evaluation of plant agronomic traits in stressed and non-stressed environment, can give an insight on how that genotype performs under stress. Previous studies have showed that plants grow taller in flooded condition than non-flooded condition [
Simple correlations indicated that biomass yield was significantly and positively correlated with tillers meter−1 at 56 DAS, 105 DAS and number of tillers plant−1 at 105 DAS (
Genotype | Plant height (cm) | Tillers plant−1 at 105 DAS | Days to 50% heading | Fresh biomass yield (kg∙ha−1) |
---|---|---|---|---|
1 | 113.71 | 15.04abcd | 101.00efgh | 27,663.44abc |
2 | 114.33 | 10.63cd | 103.75cdef | 24,661.56bc |
3 | 113.08 | 16.94abcd | 108.50abc | 35,086.80ab |
4 | 100.83 | 18.06abc | 101.50defg | 32,312.00abc |
5 | 106.50 | 11.98bcd | 111.75ab | 20,980.40bc |
6 | 111.92 | 12.00bcd | 103.00cdef | 37,284.24ab |
7 | 113.08 | 16.62abcd | 101.00efgh | 25,693.64bc |
8 | 111.17 | 11.85bcd | 95.25hij | 25,919.32bc |
9 | 111.04 | 14.76abcd | 106.00bcde | 24,758.16bc |
10 | 115.29 | 14.01bcd | 93.00j | 16,914.24c |
11 | 108.58 | 22.08a | 111.50ab | 45,129.56a |
12 | 113.54 | 16.67abcd | 113.00a | 29,052.80abc |
13 | 104.67 | 11.80bcd | 103.75cdef | 32,215.40abc |
14 | 108.04 | 10.89cd | 99.50fghi | 25,241.44bc |
15 | 110.50 | 15.94abcd | 103.75cdef | 22,111.04bc |
16 | 107.92 | 16.85abcd | 96.75ghij | 29,568.28abc |
17 | 103.96 | 9.55d | 94.75ij | 21,981.96bc |
18 | 112.17 | 11.31cd | 93.75ij | 14,689.08c |
19 | 110.33 | 19.04ab | 107.25abcd | 29,052.80abc |
Banks | 105.21 | 17.08abcd | 102.00defg | 27,695.08abc |
Means in each column followed by the same letter are not significantly different at 5% level of significance.
significantly and positively correlated with tillers meter−1 at 105 DAS, number of tillers plant−1 at 105 DAS and days to 50% heading. Average height was significantly and negatively correlated with days to 50% heading. These results suggest the importance of tiller number in biomass production and it can be taken earlier (56 DAS) or later (105 DAS) to estimate biomass yield.
Different drought tolerance indices were calculated for total fresh and total dry weight at a mild drought stress (75% FC), severe drought stress (50%) and for total fresh biomass in rainfed condition. The three superior and inferior genotypes for each of the drought indices are shown in
In the green house and field experiments, the availability of water affected the agronomic traits and biomass pro- duction. Most of the genotypes performed better under non stressed conditions. The best performing genotypes were impressive as these genotypes had the best traits measured in this study that could be the determinants
Trait | Average height | Tiller meter−1 at 56 DAS | Tiller meter−1 at 105 DAS | Rate of tiller production | Tillers plant−1 at 105 DAS | Days to 50% heading | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Average height | ||||||||||||
Tiller meter−1 at 56 DAS | −0.01 | |||||||||||
Tiller meter−1 at 105 DAS | −0.06 | 0.80** | ||||||||||
Rate of tiller production | −0.09 | 0.02 | 0.60** | |||||||||
Tillers plant−1 at 105 DAS | 0.14 | 0.46** | 0.57** | 0.34** | ||||||||
Days to 50% heading | −0.43** | 0.24* | 0.24* | 0.09 | −0.11 | |||||||
Biomass yield (kg∙ha−1) | 0.04 | 0.32** | 0.27* | 0.04 | 0.45** | 0.01 | ||||||
*Significance at p ≤ 0.05; **Significance at p ≤ 0.01; DAS, days after sowing.
Indices | Genotypic group | Drought condition | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Mild drought stress (75% FC) | Severe drought stress (50%) | Rainfed | ||||||||
Total FW | Total DW | % DM | Total FW | Total DW | % DM | Total fresh biomass | ||||
YP | Superior | 12, 10, 11 | 12, 10, 11 | 5, 14, 12 | 12,10,11 | 12, 10, 6 | 5, 14, 12 | 11, 3, 6 | ||
Inferior | 4, 5, 7 | 4, Banks, 7 | Banks, 11, 4 | 4, 5, 7 | 4, Banks, 7 | Banks, 11, 4 | 18, 10, 7 | |||
YS | Superior | 12, 6, 10 | 12, 6, 10 | 16, 14, 5 | 11, 12, 10 | 12, 11, 10 | 14, 5, 16 | 11, 16, 6 | ||
Inferior | 16, Banks, 14 | Banks, 16, 14 | 4, Banks, 11 | Banks, 4, 14 | 4, banks, 7 | 11, 4, Banks | 10, 17, 18 | |||
SSI | Superior | 7, 4, 12 | 7, 6, 12 | 16, 14, 6 | 11, 12, 6 | 11, 12, 6 | 14, Banks, 16 | 16, 7, 14 | ||
Inferior | 16, Banks, 14 | Banks, 16, 14 | 4, 5, 12 | Banks, 14, 4 | 16, 14, 7 | 10, 4, 6 | 12, 17, 3 | |||
STI | Superior | 12, 10, 11 | 12, 10, 6 | 16, 14, 5 | 11, 12,10 | 12, 11, 10 | 14, 5, 12 | 11, 6, 3 | ||
Inferior | 16, 5, 14 | Banks, 16, 4 | Banks, 11, 4 | 4, Banks, 14 | 4, Banks, 7 | 11, Banks, 4 | 18, 10, 5 | |||
TOL | Superior | 7, 4, 6 | 7, 6, 4 | 16, 14, 6 | 5, 7, 11 | 11, 4, Banks | 14, Banks, 16 | 16, 7, 14 | ||
Inferior | 16, Banks, 14 | 16, Banks, 14 | 4, 5,12 | Banks, 10, 12 | 10, 16, 12 | 10, 4, 6 | 12, 3, 17 | |||
GMP | Superior | 12, 10, 11 | 12, 10, 6 | 16, 14, 5 | 11, 12, 10 | 12, 11, 10 | 14, 5, 12 | 11, 6, 3 | ||
Inferior | 16, 5, 14 | Banks ,16, 4 | Banks, 11, 4 | 4, Banks, 14 | 4, Banks, 7 | 11, Banks, 4 | 18,10, 5 | |||
MP | Superior | 12, 10, 11 | 12, 10, 6 | 16, 14, 5 | 11, 12, 10 | 12, 10, 11 | 14, 5, 12 | 11, 6, 3 | ||
Inferior | 5, 16, 14 | Banks, 4, 5 | Banks, 11, 4 | 4, 7, 5 | 4, Banks, 7 | 11, Banks, 4 | 18, 10, 5 | |||
HARM | Superior | 12, 10, 11 | 12, 10, 6 | 16, 14, 5 | 11, 12, 10 | 12, 11, 10 | 14, 5, 12 | 11, 6, 3 | ||
Inferior | 16, Banks, 14 | Banks, 16, 5 | Banks, 11, 4 | Banks, 4, 14 | 4, Banks, 7 | 11, Banks, 4 | 18, 10, 17 | |||
YP: Potential yield; YS: Stress yield; SSI: Stress susceptibility index; STI: Stress tolerance index; TOL: Tolerance index; GMP: Geometric mean productivity; MP: Mean productivity; HARM: Harmonic mean.
of biomass yield. The high biomass genotypes like conventional rice were affected by drought and performed better under flooded field conditions. However, some genotypes had comparable response under stress environment. These genotypes can be identified using STI, GMP, MP and HARM drought tolerance indices as they have a similar ability to separate drought sensitive and tolerant genotypes. These genotypes can be used for cultivation under stress condition to get optimum biomass yields. In conclusion, genotype 11 and genotype 12 are more tolerant to drought stress. Genetic analysis and detailed characterization of both shoot and root rates of such genotypes will help us understand the inheritance pattern and the number of genes controlling the traits and determine specific leaves and root traits important in developing high biomass rice.
Partial support for this study was generously provided by the Texas AgriLife Research and Texas Rice Research Foundation. We would also like to thank Chersty Harper and Patrick Frank for their help.
AditiKondhia,RodanteEscleto Tabien,AmirIbrahim, (2015) Evaluation and Selection of High Biomass Rice (Oryza sativa L.) for Drought Tolerance. American Journal of Plant Sciences,06,1962-1972. doi: 10.4236/ajps.2015.612197