XA0100279 SESAME MUTATION INDUCTION: IMPROVEMENT OF NON- SHATTERING CAPSULE BY USING GAMMA RAYS AND EMS W. WONGYAI, W. SAENGKAEWSOOK, J.VEERAWUDH Department of Agronomy, Kasetsart University, Bangkok, Thailand Abstract Improvement of non-shattering capsule by using gamma rays and EMS in the Kasetsart University Sesame Breeding Project has been carried out since November 1994. Seed treatments with gamma rays (500 Gy) and EMS (0.5 and 1.0%, 4 hrs) were used. Growth characteristics, delayed shattering and shatter resistance of capsule were investigated in M2 through M8 lines. The seed yield of thirty promising M7 lines was evaluated in April 1997 at Suwan Farm, Pakchong , Nakorn Ratchasima. Most of the tested lines gave higher seed yields than the check variety, MK 60. M 6026 gave the highest seed yield (1,477 kg/ha). All the tested mutant lines had a longer period of growth during flowering (GF). However, three promising lines had a shorter flowering period (FP) and a degree of stem termination (DST) when they were planted both in April and August 1997. Based on the criteria of determinate growth studied, these mutant lines would be classified as having a determinate growth habit. Delayed shattering and shatter resistant capsule were obtained. It is noted that the promising mutant lines were obtained from EMS treatment. Thus, the study of these mutant lines revealed that the improvement of sesame by mutation breeding for reduced seed losses before or during the harvest can be successful. 1. INTRODUCTION Yield potential in sesame can be substantially reduced due to capsule shattering or uneven capsules' ripening. Thus, breeding sesame varieties for shatter resistance is considered important in improving seed yield of sesame. It has been generally agreed and recommended by FAO Expert Consultations that it is very important to develop sesame varieties which retain their seeds. The types of capsules with better seed retention are those that have indehiscence, strong placentation, limited tip opening, pinched capsule tips, delayed shattering, and upright capsules [1]. Also, development of uniform capsule maturation is required [2]. At present the commercial sesame cultivars have indeterminate growth habit with capsule shattering. The Sesame Breeding Project of Kasetsart University has developed determinate sesame since 1988 by using determinate sesame lines which were developed by Ashri in 1981 [3]. Some promising determinate lines of our project gave a shorter flowering period of approximately 17 days. But these lines have shattering capsules. The project has been trying to improve sesame varieties for resistance to shattering since 1991 by using the indehiscent lines (id/id) of Yermanos. Sesame lines with delayed shattering were obtained from this program [4]. However, these delayed shattering lines have only black seed, single stem and low seed yield. In November 1994, the Kasetsart University Sesame Breeding Project has proposed to use gamma rays and EMS induce capsule non-shattering. In addition, since October 1995, the project has included gamma rays treatment of Fi seeds of the promising crosses from the experiment of breeding for delayed shattering and two indehiscent lines for improving non-shattering and high seed yield. Due to the infection by bacterial leaf spot, Pseudomonas syringae pv. sesami and Xanthomonas phaseolina pv. sesami of the sesame lines in our project since 1995, the work of the project has been focused on this problem in 1997. 71 2. MATERIALS AND METHODS 2.1. Experiment 1: Improvement of non-shattering capsule by using gamma rays and EMS Thirty M7 lines lines were selected for testing their yielding ability and investigated for growth characteristics in April 1997. MK 60, the recommended variety of the Department of Agriculture was used as standard check. Based on shatter resistance and the plant having 1, 2 or 3 capsules at the top of stem, nineteen M8 lines were selected for yield trial in August 1997. MK 60 and KU 18 were used as check varieties. M7 and M8 lines were grown in 4 rows of 4m with spacing of 50 x 10 cm in a randomized complete block design with four replications, at Suwan Farm, Pakchong, Nakorn Ratchasima. Streptomycin at 50 ppm was used for control bacterial leaf spot. The seeds of these lines were soaked with streptomycin for 30 minutes before planting and the plants were sprayed with it at the flowering stage and subsequently at 14 days intervals until maturity [5]. The growth characters studied were modified from Foley et al. [6] and Lin and Nelson [7] are listed in Table I. TABLE I. DEFINITION OF GROWTH CHARACTERS STUDIED BF - Date of beginning flowering. When 50% of the plants have at least one flower. FP - Flowering period. The number of days from beginning of flowering to the terminal flowering. HTBF - Height at beginning flower. Height, in cm, to the terminal node. NOBF - Number of nodes on the main stem at beginning of flowering. TF - Date of terminal flowering. When 50% of the plants have at least one flower on the main stem. HTTF - Height at terminal flowering. Height, in cm, to the terminal node. NOTF - Number of nodes on the main stem at terminal flowering. DST - Degree of stem termination. The increase in number of observable nodes on the main stem after beginning flower, (NOTF-NOBF). GF - Growth during flowering. (HTTF-HTBF). HTM - Height at harvest. Height, in cm, to the terminal node. In classifying stem termination the GF values were used as follows: GF <20 cm = determinate growth habit GF ranged from 21-40 cm = semi-determinate growth habit GF >40 cm = indeterminate growth habit. The shatter characteristics investigated were delayed shattering and shatter resistance. Measurement of delayed shattering was done after all the capsules of the plant were ripe. Delayed shatter is assessed by the number of days that elapse from the first capsule's maturation until it splits. The shatter resistance is classified by using the concept of D.R. Langham (personal communication). The method for measuring shatter resistance on a 0-8 scale is as follows: TI = 0-8 scale the amount of the seed in the capsule when it is upright KE = 0-8 scale the amount of seed in the capsule when it is inverted TO = on 0-8 scale the extent of opening of the capsule. 2.2. Experiment 2. Use of gamma ray to induce mutation in F, seeds and indebiscent lines to improve shatter resistance F, seed of the four crosses of KKU1 x KUns 7018, KKU1 x KUns 7005, KUur 8012 x KUns 7014 and RS 6054 x KUns 7014 and two indehiscent lines (UCR 5010 and KU# 4) were treated with gamma rays at doses of 300 and 400 Gy. 72 Mi seeds of these materials were grown in March 1996 at the greenhouse of Agronomy Department, Kasetsart University. 12 M2 populations were sown in plots of 10 4m long rows, in spacings of 50 x 10 cm, in December 13, 1996. Each M2 population consisted of approximately 400 plants. Selection has been done in M2 and in successive generations. Pedigree selection was employed. Selection criteria were based on shatter resistance, resistance to bacterial leaf spot and good agronomic characteristics. Streptomycin was used to control bacterial leaf spot with the same procedure as in Experiment 1, in the M3 and M4 lines. 302 M3 lines and one hundred and fifty M4 lines were planted in April 21, and August 21, 1997 respectively. The M2 through M4 generations were grown at Suwan Farm, Pakchorg, Nakorn Ratchasima Province. 3. RESULTS AND DISCUSSION 3.1. Experiment 1 3.1.1. Seed yield The data of seed yield reported in this paper were obtained from the April 1997 growing season. There was much damage from diseases in August 1997, so it was not possible to harvest seed yield. However, the growth characteristics of the plants in this experiment were recorded. Seed yield of the tested M7 lines ranged from 915 to 1,477 kg/ha. Most of mutant lines had higher yields than the check variety. Most of tested lines had larger seeds than MK 60. Days to flowering of these lines were similar except M 6027 and M 6045 which had longer flowering periods of 45 and 48 days, respectively. Mean seed yield and some agronomic characters of fifteen promising M7 lines are shown in Table II. TABLE II. MEAN SEED YIELDS AND SOME AGRONOMIC CHARACTERS OF FIFTEEN PROMISING MUTANT LINES (M7) GROWN AT SUWAN FARM IN APRIL 1997 Line Pedigree Yield No. capsules/ No. days to No. nodes/ Plant Wt. 1000 (kg/ha) plant flower maturity plant height (cm) seeds (g) M6026 RS 6032-6-1 1,477 55 39 109 31.0 164 2.80 M6045 KUur 7014-1-1 1,370 59 48 116 39.1 165 3.35 M6017 RS 80001-4-1 1,362 56 33 116 30.4 134 3.20 M6020 RS 6032-1-1 1,352 56 30 112 35.3 140 3.00 M6039 RS 6028-5-2 1,352 54 32 108 30.3 126 3.20 M 6001-1 RS 8001-1-1-2 1,337 55 32 96 37.2 147 3.08 M6027 RS 6032-6-2 1,327 63 45 110 32.9 174 2.50 M6015 RS 8001-3-6 1,277 62 32 108 31.2 132 3.23 M 6006-1 RS 8001-1-6-1 1,243 52 32 102 33.6 142 3.15 M 6006-2 RS 8001-1-6-2 1,205 55 33 98 33.6 141 2.55 M6041 RS 6028-5-3-2 1,202 56 33 103 35.5 142 3.03 M6005 RS 8001-1-1-5 1,160 54 34 96 33.2 154 2.98 M6010 RS 8001-2-6 1,157 57 33 109 28.8 127 3.05 M6011 RS 8001-2-7 1,125 61 37 106 29.2 137 3.40 M6013 RS 8001-3-1-1 1,115 57 32 108 32.8 134 3.43 MK60 Check 1,031 56 32 110 32.4 123 2.82 LSD (0.05) 321 NS NS NS NS 10.2 - LSD (0.01) - 13.6 - C.V.