Evaluation of Heterosis and Combining Ability of Yield Components in Chillies

Nine F1 hybrids were obtained from crossing between three maintainer lines, CA1445, CA1449 and CA1450 and three restorer lines, CA683, CA1447 and CA1448. The hybrids were significantly different in yield and agronomic performance by using DMRT. The F1 hybrids CA1450 × CA1447 and CA1450 × CA1448 gave the highest yield while different statistically significant from each other in terms of yield levels differed at statistically significant level in this productivity performance when compared with their female parents, male parents and YokSiam variety but not differ statistically significant when compared with JomThong 2 and Jakkrapat varieties. The F1 hybrid CA1450 × CA1448 showed positive heterosis in terms of fruit weight per plant, the number of fruit per plant, fruit weight, fruit width, fruit length and pericarp thickness while F1 hybrid CA1450 × CA1447 expressed positive heterosis in fruit weight per plant, the number of fruits per plant, fruit weight, fruit length and pericarp thickness. The general combining ability of the female parent, CA1450, was good for five characteristics. The male parent, CA1447 was good for five characteristics.


Introduction
Cytoplasmic male sterile (CMS) is a unique attribute important for breeding programs of many crops as this trait impairs the production of viable pollen or male gamete (Kim et al., 2006;Lee et al., 2008).CMS system was applied for producing F 1 chilli hybrid (Duvick, 1959;Min et al., 2009) as this approach could help reduce production cost by 47% compare to the conventional method (Yang et al., 2008).While assuring the hybrid seeds will be free from self-pollination action contamination (Mulyantoro et al., 2009;Wang et al., 2006).The farmers using hybrid seed chilli is consistent and higher output, especially expressive heterosis in chilli hybrid seed that result from heterozygosity (Bosland & Votava, 2000;Kuroda et al., 1998).

Materials and Methods
The three maintainer varieties, CA1445, CA1449 and CA1450 were crossed with three restorer cultivars, CA683, CA1447, CA1448 in a testcross method (Kempthorne, 1957;Singh & Chaudhary, 1979).When the fruit matured the seeds were extracted from the fruit and dried.The nine hybrids were compared with the parents and commercial cultivars as checks.A randomized block design with three replications was used.Ten plants were used in each treatment.They were planted in a double row bed, at a spacing of 50 × 50 cm with a plot size of 4.5 m 2 .Fertilizer was applied at the rate 200 kg of 15N-15P-15K/ha.Liquid fertilizer contained 150 g of 15N-0P-0K, 65 g of 13N-0P-42K, 75 g of 0N-52P-34K and 5 g of trace element which consisted of Mg 9.0%, Fe 4.0%, Mn 4.0%, Cu 1.5%, Co 0.05%, Zn 1.5% , B 0.5% and Mo 0.1% were mixed in 100 liters of water.Insecticide such as imidacloprid, fipronil sulfur and methomyl were used at recommended rates once a week.Horticultural characteristics were evaluated at harvesting time.Heterobeltiosis over the better parent for some horticultural characteristics; yield, fruit number per plant, fruit weight and fruit length were calculated (Chen et al., 2003).General and specific combining abilities of three female parents and three male parents were calculated for yield, fruit weight, fruit number per plant, fruit weight, fruit length and fruit width were evaluated (Kempthorne, 1957;Singh & Chaudhary, 1979).Analysis of combining ability was carried out by using R software.

Fruit Yield
The fruit yield of all line × tester F 1 hybrids, parental and commercial varieties of green chilli were grown for yield and horticultural characteristics comparison.The line × tester F 1 hybrid CA 1450 × CA1448 was the highest yielding among the line × tester F 1 hybrid, followed by F 1 hybrid CA1450 × CA1447, higher than output levels of the parental and commercial varieties.They showed a range from 2.346 to 6.794 t/rai (Table 1).The results indicated among the various lines tested, the yield per rai, the number of fruits per plant, fruit weight, fruit width and fruit length differed at statistically significant levels.F 1 hybrid CA1450 × CA1448 produced the highest yield at 6.794 t/rai, followed by F 1 hybrid CA1450 × CA1447 with 5.913 t/rai (Figure 1a -1b), higher than output levels of the parental and commercial varieties namely JomThong 2, Jakkrapat and YokSiam which yielded 5.413, 5.026 and 4.169 t/rai, respectively.Specifically, F 1 hybrid CA1449 × CA1448 obtained the lowest yield at 2.346 t/rai; F 1 hybrids CA1445 × CA1448 and CA1449 × CA683 produced the longest fruit length of 19.91 and 19.70 cm respectively; F 1 hybrid CA1450 × CA1448 got the widest fruit width of 3.27 cm; F 1 hybrids CA1450 × CA1447 and CA1450 × CA1448 obtained maximum fruit weights of 51.17 and 50.20 gram, respectively.The levels of yield components of all these hybrid lines were differed from those of commercial varieties at statistically significant level.(b) Female variety CA1450 and male varieties CA1447, CA1448.

Heterosis of F 1 Hybrids
The analysis of F 1 heterosis over parent (% Hp) revealed F 1 hybrid CA1445 × CA683 and CA1450 × CA1448 had positive heterosis over their male and female parents in terms of fruit length, fruit width, fruit weight, fruit weight per plant and the number of fruits per plant, except, however, the F 1 hybrid CA1450 × CA1448 which showed the heterosis in fruit length over its female parent only (Table 2).The F 1 hybrid CA1449 × CA683 hybrid showed positive heterosis over the male and female parents in the aspects of fruit length and fruit weight while its fruit width indicated the positive heterosis over the male parent only.The F 1 hybrid CA1450 × CA1447 expressed its positive heterosis over its male and female parents in terms of fruit length, fruit weight, fruit weight per plant and the number of fruits per plant.It can be concluded that a number of F 1 hybrids from crossing CA1445, CA1449 and CA1450 (B line) with male parents (C line) exhibited positive heterosis in some horticultural characteristic such as number of fruits per plant, fruit weight per plant, fruit weight and fruit length.

Heterobeltiosis of F 1 Hybrids
Heterobeltiosis of the line × tester, the F 1 hybrids compared with the better parents (%Hb) showed that there were three F 1 hybrids, CA1445 × CA683, CA1449 × CA683 and CA1450 × CA1448, which showed significant heterobeltiosis of some characteristics (Table 2).The F 1 hybrid CA1445 × CA683 showed heterobeltiosis in fruit length, fruit width, fruit weight and the number of fruits per plant, 11.55%, 1.88%, 16.73% and 47.06%, respectively.The F 1 hybrid CA1450 × CA1447 showed heterobeltiosis in fruit weight per plant, fruit weight and the number of fruits per plant, 29.85%, 7.72% and 2.27%, respectively.The F 1 hybrid CA1450 × CA1448 showed heterobeltiosis in the number of fruits per plant and fruit weight per plant, 6.59 and 49.25%, respectively.All these horticultural characteristics were different at statistically significant level (Table 2) and were major contributing factors for the highest yields of these three F 1 hybrids among all hybrids tested.*, ** significant difference at P ≤ 0.05 and P ≤ 0.01 levels, respectively.

General Combining Ability and Specific Combining Ability
The general combining ability effects calculated for each parent are present in Table 3.Among the 6 parents, the highest and significant general combining ability effect for green fruit yield per plant was observed in CA1450 followed by CA1447.The female parent CA1450 was found to be good general combiner for the characteristics fruit weight per plant, yield, fruit weight, fruit width and pericarp thickness.The female parent CA1445 showed significant positive general combining ability effects for the number of fruits per plant.The male parent CA1447 showed significant positive combining ability for fruit weight per plant, yield, fruit weight, fruit width and fruit length.The female parent CA1449 and male parent CA683 exhibited significant positive general combining ability effects for plant height.The cross having desired significant specific combining ability effects are present in Table 3.The F 1 hybrid CA1445 × CA683 showed significant specific combining ability effect for the number of fruits per plant.This cross involved the parent of positive general combiners.The F 1 hybrid CA1449 × CA683 exhibited significant specific combining ability effect for fruit weight per plant, yield, fruit weight, fruit width, fruit length and pericarp thickness.The F 1 hybrid CA1450 × CA1448 showed significant specific combining ability effect for fruit weight per plant, yield, the number of fruits per plant, fruit weight, fruit width, fruit length and pericarp thickness.The F 1 hybrid CA1449 × CA1447 showed significant specific combining ability effect for fruit weight per plant, yield and fruit width.The F 1 hybrid CA1450 × CA1448 had maximum specific combining ability effect for yield and fruit weight per plant.Two F 1 hybrid, CA1449 × CA683 and CA1450 × CA1448, exhibited high specific combining ability effects for fruit weight per plant, yield, fruit weight, fruit width, fruit length and pericarp thickness.Analysis of variance of horticultural characteristics is shown in Table 4.

Discussion and Conclusion
The F 1 hybrids CA1450 × CA1448 and CA1450 × CA1447 obtained maximum yield at 6.794 and 5.913 t/rai levels, respectively, higher than the performance of other hybrid, male parent, female parent and commercial varieties at statistically significant different levels.The F 1 hybrid CA1450 × CA1448 showed positive heterosis in terms of fruit weight per plant, the number of fruit per plant, fruit weight, fruit width, fruit length and pericarp thickness while F 1 hybrid CA1450 × CA1447 expressed positive heterosis in fruit weight per plant, the number of fruits per plant, fruit weight, fruit length and pericarp thickness.The line x tester F 1 hybrids, CA1445 × CA683, showed significant heterobeltiosis for fruit weight per plant, the number of fruits per plant, fruit weight, fruit width, fruit length and pericarp thickness, respectively, in consonance with the trials of Geleta & Labuschagne, 2004;Shrestha et al., 2011;Sousa & Maluf, 2003;Patel et al., 2010, as high heterosis hybrids are associated with parents having good characteristics (Pérez-Grajales et al., 2009).Although there was no parental varieties which showed a good appearance in all but some parents varieties show a high general combining ability value in some characteristics.These are useful in breeding program to improve the fruit yield and qualities of commercial varieties.Zou et al. (2007) for example used combining ability concept for the analysis in breed improvement program to obtain high yield Chilli varieties.The female parent, CA1450 showed positive general combining abilities in fruit weight per plant, yield, fruit weight, fruit width, and pericarp thickness, while that of CA1447 appeared positive in fruit weight per plant, yield, fruit weight, fruit width and fruit length.The F 1 hybrid CA1450 × CA1448 showed significant specific combining ability effect for fruit weight per plant, yield, the number of fruits per plant, fruit weight, fruit width, fruit length and pericarp thickness indicating the relationship with additive and non-additive effect which have influence on the horticultural expression of the hybrids (Rego et al., 2009;Haung et al., 2009;Zewdie et al., 2001;Legesse, 2000).

Table 1 .
Yield components and horticultural characteristics of F 1 hybrids, male parents, female parents and commercial varieties, winter 2010

Table 3 .
General combining abilities and specific combining abilities in horticultural characteristics of male parents, female parents and F 1 hybrids chillies, winter 2010 *, ** significant difference at P ≤ 0.05 and P ≤ 0.01 levels, respectively.

Table 3 .
General combining abilities and specific combining abilities in horticultural characteristics of male parents, female parents and F 1 hybrids chillies, winter 2010 (continue) *, ** significant difference at P ≤ 0.05 and P ≤ 0.01 levels, respectively.

Table 4 .
Analysis of variance of horticultural characteristics of chillies , ** significant difference at P ≤ 0.05 and P ≤ 0.01 levels, respectively. *

Table 4 .
Analysis of variance of horticultural characteristics of chillies (continue) *, ** significant difference at P ≤ 0.05 and P ≤ 0.01 levels, respectively.