Heterosis for yield and yield components in diallel crosses of Brassica napus L.

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1 Tom XXVII ROŚLINY OLEISTE OILSEED CROPS 2006 Farhat Farhatullah, N.A. Khan, S.J. Abbas Department of Plant Breeding and Genetics NWFP Agricultural University Peshawar, Pakistan Heterosis for yield and yield components in diallel crosses of Brassica napus L. Heterozja dla plonu i jego składników w krzyżowaniu diallelicznym rzepaku (Brassica napus L.) Key words: Heterosis, heterobeltiosis, Brassica napus, L., F 1 hybrids Four Brassica napus varieties, Rainbow and Oscar (canola type) and Maluka and Koral (noncanola type), were crossed in a full diallel fashion to study heterosis (mid parent) and heterobeltiosis (best parent) for various parameters. Means of parents and hybrids were significantly different for all parameters except number of plants per m -2. The highest heterosis value was recorded for seed yield and number of branches plant -1. Almost all the crosses surpassed even their better parents for seed yield plant -1. The heterosis in the number of branches plant -1 was responsible for the heterosis in yield. Significantly positive heterosis was recorded in 50% crosses for days to flowering whereas only one of the crosses could exceed the better parent. Seventy five percent of the crosses were positive and significant for 1000-seed weight over better parent. The least heterosis and heterobeltiosis were computed for plant height where 7 out of 12 crosses manifested negative values. The best heterosis and heterobeltiosis were recorded for hybrids Oscar Rainbow (seed yield -1 ), Oscar Maluka (number of plants m -2 ), Maluka Rainbow (1000 seed weight) and Koral Maluka (days to podding and maturity). These crosses are recommended for commercial utilization of heterosis in future breeding programs. Słowa kluczowe: heterozja w odniesieniu do średniej rodziców i do lepszego rodzica (heterobeltioza), Brassca napus L., rzepak, mieszańce pokolenia F 1 Cztery odmiany rzepaku, Rainbow i Oskar (typu canola) oraz Maluka i Koral (typu nie canola) zostały skrzyżowane w układzie pełnego allelu dla przeprowadzenia badań nad heterozją w odniesieniu do średniej rodziców i lepszego rodzica (heterobeltioza) pod względem różnych cech. Średnie rodziców i mieszańców różniły się istotnie dla wszystkich cech z wyjątkiem ilości roślin na m 2. Najwyższa wartość heterozji była oznaczona dla plonu nasion i liczby rozgałęzień na roślinie. Prawie wszystkie mieszańce przewyższały w plonie nasion z rośliny nawet lepszego rodzica. Efekt heterozji w liczbie rozgałęzień przypadających na roślinę był skorelowany z efektem heterozji plonu. 50% mieszańców charakteryzowało się istotnie dodatnim efektem heterozji pod względem ilości dni do kwitnienia, ale tylko jeden mieszaniec przewyższał lepszego rodzica. 75% procent mieszańców było istotnie dodatnio lepsze pod względem masy tysiąca nasion od lepszego rodzica. Najmniejszą heterozję i heterobeltiozę wyliczono dla wysokości roślin, gdzie 7 mieszańców z 12 wykazało wartości ujemne. Najlepszą heterozję i heterobeltiozę zanotowano dla mieszańców: Oskar Rainbow (plon nasion), Oskar Maluka (liczba roślin na m 2 ), Maluka Rainbow (masa 1000 nasion) i Koral Maluka (liczba dni do zawiązania łuszczyn i do dojrzałości). Takie mieszańce są zalecane do zastosowania w przyszłych programach hodowlanych.

2 10 Farhatullah... Introduction Pakistan has made an improvement in the development of the agricultural sector, but the chronic shortage of edible oil has persisted unabated for the past 15 years. Local varieties of rapeseed are traditionally old and poorly yielded. In spite of economic importance of oilseed crops, no major breakthrough has been made in the improvement of this crop. The yield unit -1 area in Pakistan is low as compared to that of developed countries. Therefore, it is felt that providing farmers with new canola varieties is the only promising option for increasing per acre yield. Simple selection in this self-pollinated crop has not been fruitful. Thus the choice of diverse parents for hybridization must be based upon the combining ability of the parental lines. For the synthesis of genetically superior rapeseed, variety/hybrids possessing harmonious combination of desirable parameters and increased adaptability to a wide range of climatic conditions is prerequisite. The estimation of the value of heterosis and heterobeltiosis for understanding the genetic control of these parameters in different cross combinations under the prevailing conditions is very important. The ultimate goal would be the development of hybrid cultivars of winter rape that can potentially use the total amount of heterosis available. Therefore, the studies reported here were undertaken to quantify the contribution of various high yielding parental lines in the production of hybrid cultivars, having high seed yield. The selected hybrids will be recommended to be included in national oilseed breeding program in Pakistan. Materials and methods The experiment was conducted at Pakistan Oil Seed Development Board (PODB), Agricultural Research Institute (ARI) Tarnab, Peshawar, Pakistan. Four varieties of Brassica napus viz. Oscar, Rainbow (canola type), and Maluka and Koral (non-canola type) were crossed in a full diallel fashion and F 1 seed along with their parents were sown in rabi season in a Randomized Complete Block Design with three replications. The data was recorded on randomly selected plants in two central rows on seed yield plant -1 (g), number of branches plant -1, days to 50% flowering, podding and physiological maturity, number of plants m -2, plant height (cm), and 1000 seed weight (g). The data was statistically analyzed, using analysis of variance techniques (Steel and Torrie 1980). The heterosis (mid-parent) and heterobeltiosis (bestparent) for various crosses were calculated for all parameters (Walter 1987). The t-test was used as a significance test for positive heterotic and heterobeltiotic values of various F 1 hybrids (Wynne et al. 1970).

3 Heterosis for yield and yield components in diallel crosses Results and discussion The genotypes were significantly different for seed yield plant -1, days to flowering, podding, and physiological maturity, plant height, number of branches plant -1, and 1000-seed weight in rapeseed canola. Significant variations for various traits in brown sarsoon have also been reported (Yadava et al. 1985). However, in radish, the variations between crosses and their reciprocals were nonsignificant (Vahidy and Hartmann 1972). Mean performance of the parents and their F 1 s are presented in Table 1. Among canola type parents, Rainbow produced the maximum number of plants m -2 (10.20) and took maximum days to maturity (208). Oscar produced the highest plants (228 cm) having maximum seed yield (19.63 g) with more branches plant -1 (8.67) and took maximum days to flowering (141.67). In non-canola type parents, Maluka maintained superiority in all characters except for number of plants m -2. On average, canola type parents were better in number of plants m -2, 1000 seed weight, and days to flowering, podding, and maturity. The non-canola type parents produced plants with higher number of branches plant -1. In F 1 crosses, the hybrid Koral Oscar was almost intermediate to both parents and took and 205 days to 50% flowering and physiological maturity, respectively. This hybrid also produced the shortest plants (183 cm) as compared to the parents. The reciprocal of the same combination was the earliest in maturity (191.33). The intermediate values for reciprocal crosses of radish have been reported (Vahidy and Hartmann 1972). The cross combination of non-canola type Maluka Koral gave maximum seed yield plant -1 (42.81 g), produced the tallest plants ( cm). Manner (1959) also observed higher F 1 plants as compared to their parents in a cross made between summer and winter mustard. The hybrid Maluka Rainbow gave the maximum 1000 seed weight (4.6 g). The hybrid Koral Maluka took the maximum days to 50% podding (175.33) and the minimum days to flowering (128). On average the canola type parents (Rainbow and Oscar) were late while non-canola types (Maluka and Koral) were early in maturity. Interestingly, the F 1 s of canola canola were early, while non-canola noncanola were late in maturity as compared to their respective parents, which might be due to the additive gene effect. Similarly in turnip rape, Manner (1959) reported late maturing F 1 hybrids as compared to summer cultivar in cross between summer and winter mustard. Two F 1 hybrids of canola non-canola types (Rainbow Maluka and Oscar Koral) had early, while one hybrid (Koral Oscar) had late maturity. In rapeseed, Ahmadi (1993) obtained early maturing F 1 hybrids from a cross of re-synthesized lines and improved varieties.

4 Table 1 Means of Parents and their F1 hybrids for various traits in Brassica napus Średnie dla rodziców i ich mieszańców dla różnych cech Lines hybrids Odmiana mieszaniec to flowering do kwitnienia to podding do zawiązania łuszczyn to maturity do dojrzałości Plants m -2 Liczba roślin na m 2 Plant height Wysokość roślin [cm] Branches plant -1 Ilość rozgałęzień na roślinie Seed weight Masa 1000 nasion [g] Seed yield plant -1 Plon nasion z rośliny [g] Rainbow (R) ± ± ± ± ± ± ± ± Oscar (O) ± ± ± ± ± ± ± ± Maluka (M) ± ± ± ± ± ± ± ± Koral (K) ± ± ± ± ± ± ± ± R x O ± ± ± ± ± ± ± ± R x M ± ± ± ± ± ± ± ± R x K ± ± ± ± ± ± ± ± O x R ± ± ± ± ± ± ± ± O x M ± ± ± ± ± ± ± ± O x K ± ± ± ± ± ± ± ± M x R ± ± ± ± ± ± ± ± M x O ± ± ± ± ± ± ± ± M x K ± ± ± ± ± ± ± ± K x R ± ± ± ± ± ± ± ± K x O ± ± ± ± ± ± ± ± K x M ± ± ± ± ± ± ± ± 3.642

5 Heterosis for yield and yield components in diallel crosses The maximum number of branches plant -1 (13) were recorded for F 1 hybrid crossed between canola (Oscar) and non-canola (Koral) rapeseed which was also early in maturity. The hybrids between Rainbow and Oscar or Koral produced the maximum number of plants m -2. Heterosis The performance of single-cross hybrids can only be enhanced by adding favorable alleles from donor inbred lines. The heterosis and heterobeltiosis results are presented in Table 2. All F 1 hybrids exhibited significant (p < 0.01) heterosis (except Rainbow Maluka) and heterobeltiosis (except Rainbow Maluka, Koral Oscar, and Oscar Maluka) for seed yield plant -1. The hybrid Oscar Rainbow was the best for seed yield plant -1, which exhibited the highest significant heterosis (116.9%) and heterobeltiosis (76%). Significant heterobeltiosis for single plant yield in Indian mustard (Pradhan et al. 1993), oilseed rape (Grant and Beversdorf 1985) and mustard (Pental et al. 1995) has been reported. Significant heterosis for seed yield has also been reported in winter oilseed rape (Krzymanski et al and Sernyk and Stefansson 1983), rape seed (Srivastava and Rai, 1993) and Indian mustard (Baisakh et al. 1994). Only four hybrids Oscar Maluka, Maluka Rainbow, Maluka Koral (and its reciprocal) exhibited significantly (p < 0.01) positive heterosis and heterobeltiosis for 1000 seed weight. Habetinek (1993) and Pszczola (1993) reported positive heterotic and heterobeltiotic effects for 1000 seed weight in Brassica napus in their respective studies. However, Grant and Bevrsdorf (1985) found non-significant heterosis for 1000 seed weight in oilseed rape. Half of the hybrids exhibited positive and significant heterosis for days to 50% flowering. The Rainbow Maluka, was the only hybrid that exhibited both heterosis (p < 0.01) and heterobeltiosis (p < 0.05) for days to flowering. However, Schuler et al. (1992) and Virk and Pooni (1994) found no heterosis for days to flowering in Brassica rapa and sunflower, respectively. The positive heterosis for this character in the group of crosses (canola noncanola) signifying the role of genetic divergence in the expression of heterosis. The hybrids Maluka Koral (and its reciprocal), and Koral Oscar produced significant (p < 0.01) and positive heterosis and heterobeltiosis for days to maturity. Hirve and Tiwari (1991) and Virk and Pooni (1994) also found significant heterosis for days to maturity in Indian mustard and sunflower, respectively. However, in summer turnip rape Schuler et al. (1992) got negative heterosis for days to maturity. All crosses (except Oscar Maluka and its reciprocal) produced significant (p < 0.05) and positive heterosis for branching plant -1. Four crosses Rainbow Koral (and its reciprocal), Rainbow Oscar, and Oscar Koral showed positive and significant heterobeltiosis in which the hybrid Oscar Koral exhibited the highest value of 100% for number of branches -1. It is clear from the results that

6 Heterosis (Mid parent) and heterobeltiosis (High parent) for various traits in Brassica napus Heterozja (w odniesieniu do średniej rodziców) i heterobellioza (w odniesieniu do lepszego rodzica) dla różnych cech rzepaku Table 2 Hybrids Mieszaniec to flowering do kwitnienia to podding do zawiązania łuszczyn to maturity do dojrzałości Plants m -2 Liczba roślin na m 2 Plant height Wysokość roślin [cm] Branches plant -1 Ilość rozgałęzień na roślinie Seed weight Masa 1000 nasion [g] Seed yield plant -1 Plon nasion z rośliny [g] Het Hetb Het Hetb Het Hetb Het Hetb Het Hetb Het Hetb Het Hetb Het Hetb R O ** ** 29.3 ** O R 2.8** ** ** 76.0 ** M K ** 3.6 ** ** ** ** 13.1 ** 78.7 ** 73.9 ** K M ** 15.9 ** 4.9 ** 4.6 ** ** ** 11.3 ** 23.6 ** 20.3 ** R M 4.7** 2.1* ** M R ** ** 14.0 ** 77.7 ** 33.0 ** R K 4.4** ** * ** 50.0 ** ** 19.3 ** K R 2.9** ** ** 25.0 ** ** 19.7 ** K O 5.8** ** ** 0.8 O K ** 44.4 ** ** 13.3 ** O M 3.2** ** ** 4.0 * ** 5.1 ** 10.8 ** 0.4 M O ** 23.1 ** * significant at 5% level (p < 0.05) istotne na poziomie 5% (p < 0,05) ** significant at 1% level (p < 0.01) istotne na poziomie 1% (p < 0,01) R = Rainbow O = Oscar M = Maluka K = Koral

7 Heterosis for yield and yield components in diallel crosses high seed yielding genotypes had positive heterosis both for seed yield and number of branches. Panday and Zehr (1999) reported that higher seed yielding hybrids have a greater number of productive branches. Kumar et al. (1990) concluded that crosses possessing positive heterosis for seed yield also had positive heterosis for primary and secondary branches in Indian mustard. Only two hybrids Rainbow Koral and Maluka Koral exhibited significant and positive heterosis at p < 0.01 and p < 0.05 levels, respectively, for plant height. None of the hybrids manifested heterobeltiosis for this parameter. Rao (1977) experienced variable estimates of heterosis for plant height. The only hybrid Oscar Maluka showed significant positive heterotic values over midparent (p < 0.05) and better parent (p < 0.01) for plants m -2. These results suggest that hybrid vigour should be exploited by the production of a hybrid variety. The hybrid variety may be based on transgressive segregantes expected in the segregating generations of these crosses for selection. Conclusions The results suggest that bright prospects exist for development of F 1 hybrid cultivars in rapeseed canola breeding programs. The F 1 derivatives Oscar Rainbow (seed yield), Oscar Maluka (plants m -2 ), Maluka Rainbow (1000 seed weight) and Koral Maluka (days to podding and maturity) may be included in the future rapeseed breeding programs. References Ahmadi M.R Study of agronomic value of resynthesized rapeseed lines and early generation of crosses resyn-line improved varieties. Iranian J. Agric. Sci., 24: 3-4. Baisakh B., Panda S., Nayak B.K Heterosis for yield in Indian mustard. Envi. and Ecol., 12: Grant I., Beversdorf W.D Heterosis and combining ability estimates in spring oilseed rape (Brassica napus L.). Can. J. Genet. Cytol., 27: Habetinek J Heterosis and combining ability in a diallel cross of five varieties of winter swede rape (Brassica napus L.). Sbornic Vysoke Skoly Zemedelske v Praze, Faculta Agronomicka. Rada-A, Rostlinna Vyroba., 55: Hirve C.D., Tiwari A.S Heterosis and inbreeding depression in Indian mustard. Ind. J. Gen. Plant Breed., 51: Krzymański J., Piętka T., Krótka K Combining ability and heterosis in diallel crosses of doublezero winter swede rape. 1. F 1 generation. Postępy Nauk Rolniczych, 5: Kumar P.R., Arora R.K., Singh N.P., Yadav R.C. Kumar P A study of heterosis in Indian mustard (Brassica juncea L. Coss. and Czen.). Acta Agron. Hung., 39: 1-2.

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