Breeding Sesame for Mechanized Harvest in Turkey

M. Ilhan Çagirgan 1

ABSTRACT

Non-shattering sesame is the key to mechanized harvest of sesame and its expanded cultivation. To obtain different types of non-shattering mutants, seeds of five sesame genotypes were irradiated in the range of 150-750 Gy doses of gamma rays in different experiments. Three different harvesting procedures were applied to the M1 populations, i.e., plant harvesting, branch harvesting and bulk harvesting. Mutants were generally selected in M2 and confirmed in M3 and further generations, resulting eleven closed capsule mutants. Despite their poor agronomic performance, modification should be possible in the changed genetic backgrounds and through forced recombination by irradiation in the on-going project. It was finally concluded that selecting unique induced mutants such as closed capsule is not a matter of “lucky chance” but growing quite large M2 populations, preferably in plant progeny rows, and careful screening.

Introduction

            Sesame (Sesamum indicum L.) is one of the important oilseed crops in the world. It’s grown annually about 7 million hectares in the warmer areas of Africa, Asia and Latin America. It is suitable to different crop management systems and is also grown as second crop after wheat in Turkey. Despite of its attributes in crop rotation, main problem in its cultivation is to shatter at maturity. Because sesame fruits called capsule split along its sutures when mature and shatter the seeds to the ground. This wild plant character makes it difficult its harvest by combine. Because of this problem, it is grown and harvested manually by small holders, only in the countries where hand labour is inexpensive. Therefore the development of productive non-shattering cultivars is critical to the extended successful cultivation of sesame in more intensive agriculture with mechanized  harvesting. Although one natural non-shattering sesame plant was found in Venezuela in early 1940s, since then, it was useless for variety development because of many undesirable pleiotropic side effects on agronomic performance. Since there were no other useful natural gene sources in the world, the only solution is to induce mutations. Consequently, several programs aimed at inducing mutants for non-shattering sesame (Ashr,1982; Cagirgan, 1997; Maneekao et al, 1997; Wongyai et al, 1997).  Our sesame breeding program started in 1994. Eight independent gamma rays induced closed capsule mutants were selected in locally adapted genetic backgrounds. Their agronomic evaluations were also done (Cagirgan, 2001; Cagirgan et al., unpublished) which were poor in fertility and thus in yield in comparison to parental normal cultivars. In this study we communicate our all story of selecting closed capsule mutants including recently selected ones.

 

 1 Department of Field Crops, Faculty of Agriculture, Akdeniz University, Antalya, Turkey

  Email: cagirgan@akdeniz.edu.tr

Materials and Methods

Seeds of five genotypes (Table 1) were irradiated in the range of 150-750 Gy doses of gamma rays in different experiments. Irradiated seeds with their controls were sown to raise M1. Three different harvesting procedures were applied to the M1 populations, i.e., plant harvesting, branch harvesting and bulk harvesting. The M2 generations, therefore, were grown either as progeny rows or bulk populations. Potential mutants suitable for the breeding objectives were selected after a careful screening during the vegetation period, carrying mutations for closed capsule, determinate growth habit, wilting tolerance, etc.

Table 1 Sesame material used for mutagenesis

 Cultivars

Branching

Carpels/

per capsule

Capsules/

per axil

Seed color

Registered as variety in

Muganli-57

Multi

2

1

Yellow-brown

1986

Özberk-82

Multi

2

1

brown

1986

Çamdibi

Multi

2

3, or irregulare

brown

Pure line

Gölmarmara

Multi

2

1

white

1986

6159

Multi

2

1

white

Improved line

Results and Discussion

Reduction of seed loss at maturity and harvest is the key to a successful cultivation of sesame by developing cultivars with closed capsules suitable for mechanised harvesting. As known, only available natural recessive gene for indehiscent capsules was found in Venezuelan gene pool in 1943 but, since then, it was useless for variety development because of many negative pleiotropic effects on agronomic performance of the progenies developed up-to-now (Ashri, 1985). In the first two experiments, 8 independent mutants with closed capsules (Table 2) were successfully selected and confirmed (Cagirgan, 1996, 2001). In a recently mutated material which is growing in the field as M2, we distinguished 3 new independent mutational events for closed capsule, which needs confirmation and further characterization. However, all the story of closed capsule mutants selected in our program is summarised here. The highest number of mutants was obtained in Muganli-57, which may show a tendency to mutate for this character. Three of them derived from Experiment I, and one mutant from Experiment II. The mutant, cc-?-4, has problem of high sterility and hard capsule, difficult to open. Another mutant, cc-?-2, has closed capsules with slight opening on the tip, which is typical to this mutant .It is interesting to note here that the mutant selected in Experiment II, cc-?-6, was as similar as the cc-?-2 selected in Experiment I, suggesting that it is possible to repeat to induce similar type of unique mutants. The cc-?-5 was of another interesting one to notice, which was selected secondly for closed capsule among the plants in M3 of a multicarpel mutant. The cc-?-9 is the source family for this selection, which opens its multi carpel capsules and shatter the seed but there are conjuctions among the carpels in the tips of capsules, so it was grouped in this group but not counted as a success. Çamdibi yielded two similar looking mutants selected in the two different irradiated seed lots. Only one closed capsule mutant was selected in Özberk-82 in Experiment I and Gölmarmara in Experiment II. As we concluded before, 300 and 400 Gy dose range was efficient to induce closed capsule mutants. Finally we could select at least one mutant from all five genotypes, which we focused on. Despite of the pessimism in the literature, our results clearly shows that selecting such unique mutants as closed capsule is not a matter of “lucky chance” but just growing big enough populations to select for and a serious screening. We observed lower percentage of recessive closed capsule mutant segregants in the progeny rows than expected because of their lower vigour and competition ability with normal open capsule types. Although we could select our first closed capsule mutant, cc-?-1 in the bulked M2 population of Çamdibi, it is advisable to arrange M2 populations to screen for closed capsule in the plant progenies instead of bulking M1. If bulking M1 is preferable for any reason, then the M2 must be grown in a very good prepared seed bed with spaced planted, preferably every seed should be placed in a different hole. Ashri (1982) grew several bigger M2 bulk populations of 4 hectares of No.45, Israeli sesame variety, irradiated with gamma rays and EMS, but there was no any closed capsule mutants selected. These intensive efforts with sesame have been very insightful to us while planning the management of our M2 populations. Therefore the negative results should be also published to improve selection techniques in mutant populations.

            Plant yield, yield components and fertility level of closed capsule mutants were given in Table 3. All mutants were of lower seed yield than their parent cultivars. However cc-?-3 and cc-?-6 had the plant yields better than the rest of the mutants. Plant yields of similar looking independent mutants, i.e., cc-?-2 vs cc-?-6 and cc-?-1 vs cc-?-7, were different, which was an unexpected result due to the heterogenic experimental field and lack of replication. The replicated performance trials also indicated poor performance of closed capsule mutants grown in 1998-2000 (unpublished data). Number of capsules per plant was generally higher in the closed capsule mutants then their respective parent cultivars. But we counted all the capsules having seed as potential fruits, although their size not comparable to the parent cultivars’. Lowest capsule number per plant was obtained in cc-?-5, which was multicarpellated. Since Çamdibi has more than one capsule per leaf axil, its mutants were of low number of capsules. Number of seeds was lower than their respective parent cultivars. The lowest value for this trait was noticed in cc-?-5, multi carpel mutant. The highest fertility (%) was obtained in cc-?-6 (62.0 %) compared to Muganli-57 (88.8%).  The cc-?-4 was of the lowest value, 8.6 %, which has also high threshability problem. The cc-?-3 was of the best threshability because of partial membrane development in the capsules. Thousand seed weight was also lower in the closed capsule mutants than their respective parents. However their seed sizes were in the acceptable range (Table 3). New mutants such as cc-?-11, cc-?-12 and cc-?-13 need characterization and confirmation in M3. Some induced closed capsule mutants were found to be allelic to the known id gene (Çagirgan et al, 2000, unpublished), however this study needs to be repeated because of incomplete cross series and sign of out-crossing in the studied crosses.

            Despite their poor agronomic performance at the moment, we expect that these induced closed capsule mutants selected repeatedly will be very useful to make sesame a modern crop suited to intensive management conditions with mechanised harvesting. We believe that changing the genetic background of the closed capsule mutants with the forced recombination by irradiation may be the key component of the success targeted. We hope that some preliminary data will be available to present at the workshop from the material already is being grown in the field as M2/F3.

 

Table 2 Closed capsule mutants of sesame selected in different experiments

Mutant

Parent

cultivar

Dose

(Gy, 60Co)

Characteristics

cc-?-1

Çamdibi

150-750*

Closed capsule, partial sterility

cc-?-2

Muganli-57

450

Closed capsule, slight opening in the capsule tip

cc-?-3

Özberk-82

300

Closed capsule, good fertility and threshability

cc-?-4

Muganli-57

450

Closed capsule, partial sterility

cc-?-5

Muganli-57

750

Closed capsule, 2nd sel. from multi carpel

cc-?-6

Muganli-57

300

Closed capsule, similar to cc-?-2

cc-?-7

Çamdibi

300

Closed capsule, similar to cc-?-1

cc-?-8

Gölmarmara

400

Closed capsule, partial sterility

cc-?-9

Muganli-57

750

Semi closed capsule, multi carpel, source of and isogenic to cc-?-5

cc-?-11

Muganli-57

400

Closed capsule (needs further characterization)

cc-?-12

Muganlı-57

400

Closed capsule (needs further characterization)

cc-?-13

6159

400

Closed capsule (needs further characterization)

* bulked over doses

Table 3 Plant Yield, yield components and fertility levels of closed capsule mutants of sesame.

Parent culti./

Mutant

Dose

(60Co)

Yield/

plant (g)

Capsules/ plant

Seeds/

capsule

Fertility

(%)

1000

seed w.

Muganli-57

0

17.8

85

59.4

88.8

4.6

         cc-?-2

450

1.2

138

27.7

35.0

3.6

         cc-?-4

450

<1

181

38.7

8.6

*

         cc-?-6

300

4.9

105

40.8

62.0

3.8

         cc-?-5

750

<1

27

10.3

26.8

3.3

         cc-?-11

400

*M2 plants in the field

         cc-?-12

400

Özberk-82

0

17.5

82

64.9

95.0

3.5

          cc-?-3

300

4.0

89

36.5

54.3

3.2

Çamdibi

0

23.8

136

65.2

90.5

4.1

          cc-?-1

bulk

1.1

91

17.1

30.1

3.0

          cc-?-7

300

2.3

121

36.1

32.8

3.0

Golmarmara

0

*

*

*

*

*

          cc-?-8

400

*

*

*

*

*

6159

0

*M2 plants in the field

         cc-?-13

400

* Data not available

Acknowledgements

My sincere thanks are to International Atomic Energy Agency for funding the main project with the Research Contracts No: 7855, 10964 and 13001; and to Drs Helmut Brunner and Rownak Afza for seed irradiation and last but not least to my students at every level for their voluntarily contributions. The travelling support from the Turkish Research Council is gratefully acknowledged.

References

Ashri, A. 1982. Status of breeding and prospects for mutation breeding in peanuts, sesame and      castor beans. pp 65-80. In: Improvement of oil-seed and industrial crops by induced   mutations. IAEA,Vienna.

Cagirgan, M. I. 1996. A Preliminary report on the first induced indehiscent capsule mutants in sesame. p. 248. In: EUCARPIA Meeting on Tropical Plants, Communications and Posters, CIRAD, Montpellier, France.

Cagirgan, M.I., 2001. Mutation techniques in sesame (Sesamum indicum L.) for intensive management: Confirmed mutants. pp. 31-40. In: Sesame Improvement by Induced Mutations, IAEA-TECDOC-1195, IAEA, Vienna,

Maneekao, S., N. Srikul, B. Poo-sri, and S. Kumphai. 1997. Sesame improvement through mutation induction for reduction of seed loss at harvest. pp 69-75. In: Proc. 2nd FAO/IAEA Res. Coord. Mtg. held in Antalya,Turkey, Induced Mutations for Sesame Improvement, IAEA,Vienna.

Wongyai, W., W. Sengkaewsook, and J. Verawudh, 1997. Sesame mutation breeding: Improvement of non-shattering capsule by using gamma rays and EMS. pp 76-84. In: Proc. 2nd FAO/IAEA Res. Coord. Mtg. held in Antalya,Turkey, Induced Mutations for Sesame Improvement, IAEA,Vienna.