Previous PageTable Of Contents

Development and characterization of RILs for molecular mapping of reproductive stage moisture stress tolerance in rice

S. Robin1. R. Manimaran1, R. Pushpa1, P. Jeyaprakash2, S. Mahendran3, H.R. Lafitte4 and G.N. Atlin4

1Department of Rice, Tamil Nadu Agricultural University, Coimbatore, TN 641 003, India email srobin@eth.net
2
Agricultural Research Station, Paramakudi, TN 623707, India email agrijp@yahoo.com
3
Coastal Saline Research Centre, Ramanathapuram, TN 623721, India email profmahe@rediffmail.com
4
International Rice Research Institute, MCPO Box 7777, Metro Manila, Philippines

Abstract

Moisture stress occurring in the reproductive stage of the rice crop is often considered as the most devastating factor limiting production. Genetic analysis of reproductive stage moisture stress tolerance was the subject of this study. Results from the earlier mapping populations and germplasm screening revealed that phenology difference in the test entries can influence the performance of lines under natural moisture stress conditions. Hence, a drought tolerant landrace known for its long-term adaptation in the target drought prone ecosystem was crossed with a high yielding variety of same phenology, IR64 to develop sets of near flowering lines through recombination breeding. The population comprising 214 lines differed significantly in grain yield under stress. Three subsets of lines with three ranges of heading days viz., 59-64, 65-70 and 71-76 were constituted. Within individual subsets no correlation existed between heading days and grain yield under stress though within the range, grain yield exhibited a normal distribution. These subsets of lines similar in duration are subjected for further analysis on molecular dissection of physiology of reproductive stage stress tolerance.

Media summary

Mapping population reconstituted based on the flowering days were evaluated for grain yield under moisture stress conditions, reveals the genetic variation in drought tolerance besides differences in the heading days.

Key Words

Drought Tolerance, Reproductive phase, Near Flowering Lines, Rice

Introduction

Water deficits constitute an increasingly important constraint limiting rice production, highlighting the need for varieties with improved drought tolerance and technologies increasing water-use efficiency. Breeding varieties for sustainable production under moisture stress conditions has always been difficult because selection becomes either impossible or inefficient in the absence of a representative drought period during the testing season (Blum 1988). Drought tolerance is a complex character resulting from the interaction of many quantitative component traits. However, with the advent of DNA markers, the scope for improving such complex traits changed significantly. It is now possible to map the genes controlling the traits under study (Quantitative Trait Loci or QTL), find markers tightly linked to the QTLs, and assess the molecular marker allele variation at the QTLs rather than, or in addition to, phenotypic variation to select the appropriate genotypes throughout breeding generations (Robin, 2000). Recently several studies have been undertaken to map QTLs for many component traits which are presumably associated with drought tolerance such as constitutive root traits and adoptive leaf traits viz., osmotic adjustment, stomatal conductance, leaf rolling etc. (Zhang et al. 2000). On consideration of the influence of the heading days on grain yield under stress (natural), in this study, attempts are made to develop a mapping population comprising of lines with more identical phenology hitherto referred as near flowering lines (NFLs). Such lines will unravel the genetic difference existing among the genotypes for reproductive stage drought tolerance nullifying the effect of difference in heading days.

Methods

Population development

The contemporary mapping populations derived out of diverse parents delivered DHLs or RILs greatly differing in phenology. The reproductive stage starting with panicle initiation to grain filling has varied response to moisture stress. Hence the populations with varying flowering duration will respond differently to moisture stress occurring under field conditions. To minimize the bias, mapping population with IR64 and Norungan, a traditional landrace were made since both the parents are of almost same duration.

The population comprising of 241 F5 families were evaluated at Ramanathapuram, the target production environment during wet season, 2003-2004 (Oct-Jan) along with the parents in two replications. The experiment was conducted under natural moisture stress conditions so as to have realistic evaluation of the phenology from on-season trial. The season experienced moisture stress during the reproductive stage and grain yield apart from heading days, plant height, panicle length, number of productive tillers and panicle length were measured and analysed.

Results and Discussion

As the population significantly differed for all the traits studied, the lines also exhibited a normal distribution for grain yield (g/plot). However, since the heading days ranged from 55 to 79 days, the variation in phenology was stratified into three subsets of near flowering lines with the heading day ranges of 59-64; 65-70 and 71-76.The mean and range of the traits studied were computed for individual subset and furnished in Table 1.

Table 1. Range and mean of the subsets of NFLs of IR64 x Norungan for heading days, plant height, panicle length, number of productive tillers and grain yield (g/plot)

Parents/ subsets

Heading days

Plant Height (cm)

Panicle length (cm)

Number of productive tillers

Grain Yield (g/plot)

IR64

771.41

78.852.18

21.831.18

92.83

28563.64

Norungan

712.12

120.100.47

24.501.65

81.18

34535.46

Subset I: range mean

59-64
61.630.29

63.16-128.33
98.682.90

17.83-25.33
22.270.29

5.0-16.0
8.610.38

75.0-455.0
254.5413.15

Subset II: range mean

65-70
67.650.20

63.16-137.50
106.242.11

17.83-25.33
22.270.29

5.0-17.0
8.630.39

50.0-440.0
254.8510.58

Subset III: range mean

71-76
73.030.21

59.00-141.50
108.522.29

19.33-29.00
23.600.23

5.0-15.0
8.260.21

50.0-525.0
252.8412.55

The results revealed non significant correlation between heading days and grain yield within the subsets. However among a set of NFLs, all the traits varied significantly including grain yield (Figure 1).

Fig 1. Grain yield (g/plot) of RILs –Complete Set

Conclusion

The experiment did not experience severe drought and grain set was observed in all the entries. The entire population flowered within 80 days after sowing. However the strategy of reconstituting individual sets of NFLs is undetaken by inclusion of RILs from other population derived from the cross IR50 x Norungan. Apart from these, germplasm screening has brought out breeding lines falling within the range of the NFLs in heading days which are also included in the subsets accordingly. The study will undertake association mapping with the help of microsatellites, candidate genes and single nucleotide polymorphism(SNP) markers for mapping the genomic regions of drought tolerance in rice.

References

Blum A (1998) Drought resistance. In: Plant breeding for stress environments. CRC Press, Boca Raton, Florida, pp 43-76

Robin S, Courtois B, Pathan MS, Jeyaprakash P, Lafitte R, Atlin G, Nguyen HT (2002) Marker assisted backcross breeding for improvement of drought tolerance in indica and japonica rice. In: Abstracts of International workshop on “Progress towards developing resilient crops for drought-prone areas”, 27-30 May 2002, IRRI, , Manilla, Philippines

Zhang J, Zheng HG, Aarti A, Pantuwan G, Nguyen TT, Tripathy JN, Sarial AK, Robin S, Babu RC, Nguyen BD, Sarkarung S, Blum A, Nguyen HT (2001) Locating genomic regions associated with components of drought resistance in rice: comparative mapping within and across species. Theor Appl Genet 103:19-29

Previous PageTop Of Page