F1 Rice Research Articles

Root development of F1rice hybrid and parents as affected by nitrogen concentration of culture solution

Abstract Nitrogen (N) nutrition is the major factor involved in attaining high yield in rice (Oryza sativa L.). This study was conducted to elucidate the relationship between the ammonium-N concentration of the culture solution and the root system development of F1 rice hybrid and parents. The rice plants were grown in culture solutions at 0.2, 2, and 20 mg L-1 of N for 30 d. Two and 20 mg L-1 N of culture solutions suppressed the elongation of both nodal root axes and lateral roots, whereas 20 mg L-1 N promoted the proliferation of the lateral roots. As a result, total root length was greatest in the 0.2 mg L-1 N-fed plants. On the contrary, the dry matter partitioned to the root systems of the 0.2 mg L-1 N-fed plants was the same as or smaller than that of the 2 and 20 mg L-1 N-fed plants. The ratio of total length to dry weight of the root system (specific root length) showed a trend similar to the total root length. The trend of root system development was similar in both F1 hybrid and parents. Moreov...

Heterozygous diploid plants regenerated from anther culture of F1 rice plants

Plants derived from anther culture are theoretically haploid, but diploid plants are also known to arise. Anther culture-derived diploid plants are usually homozygous and are believed to be due to spontaneous doubling of chromosomes in either microsporocytes or callus cells during the culture process. However, heterozygous diploid regenerants may also arise from a) regeneration from cultured somatic cells, b) mutation occurring during or after a spontaneous doubling event, c) fusion of unlike haploid cells in chimeric callus, and d) regeneration from diploid microsporocytes resulting from aberrant meioses. This study was designed to elucidate the frequency and origin of diploid regenerants from rice anther culture. Regenerants were obtained from 11 F1 genotypes. Progeny testing detected heterozygosity in 7 out of 211 regenerants. Each of the heterozygous regenerants were from ‘Calrose 76’/waxy ‘M-101’, Half of the diploid regenerants from this cross were heterozygous. No heterozygous regenerants arose from the other 10 F1 genotypes. Progeny testing indicated that two of the heterozygous regenerants were as heterozygous as the F1 plants for three parental characters. The other five regenerants exhibited decreased levels of heterozygosity. One of the heterozygous regenerants exhibited evidence of mutation for a non-parental character. However, mutation is an unlikely cause of the observed high levels of parental-type heterozygosity. No evidence for the occurrence of chimeric callus was detected, making this an unlikely cause as well. The most likely origin of the observed partial heterozygosity is regeneration from diploid microspores, which could also produce plants exhibiting complete parental-type heterozygosity.

Grain Quality of F1 Rice Hybrids

Grain Quality of F1 Rice Hybrids

Effect of Low Light on F1 Rice Hybrids

Effect of Low Light on F1 Rice Hybrids

Heterosis in Japonica/Indica F1 Rice Hybrids with Special Reference to Nodal Root Function.

Although root system of japonica/indica F1 hybrids of rice (Oryza sativa L.) must play an important role for expression of heterosis, few studies have been conducted. This study was carried out to evaluate how the function of root system in japonica/indica F1 rice hybrids is related to heterosis for shoot growth. Two F1 hybrids grown in culture solution for 45 days after sowing and F1 hybrid cultured in soil-filled pots till full ripening were compared with parents. Shoot dry weight of F1 hybrids was greater than that of parents when their stem and nodal root numbers were similar to those of parents. Heterobeltiosis for shoot dry weight reached the maximum 180 when the F1 hybrid surpassed parents in the stem and nodal root numbers. F1 hybrids were the same as one or both parents in S/R ratio, but dry weight of a single nodal root of F1 hybrids exceeded that of parents in most cases. Moreover, nitrogen uptake rate of a single nodal root (Nno) as well as leaf area and shoot dry weight of a single nodal root in F1 hybrids was greater than those in parents during vegetative growth. Nitrogen uptake rate per root system dry weight (Ndw), however, was much the same. These results strongly suggest that in japonica/indica F1 hybrids, more photosynthate is partitioned to each nodal root, so that this enhances its function and consequently, the entire root system.

Biomass, Grain Yield, and Harvest Index of F1 Rice Hybrids and Inbreds

Biomass, Grain Yield, and Harvest Index of F1 Rice Hybrids and Inbreds

Physiological mechanism of heterosis in seedling growth of indica F1 rice hybrids.

To determine the possible cause of higher seedling vigor in F1 rice (Oryza sativa L.) hybrids, embryo weight, endosperm weight, leaf area, and seedling growth performance of 16 F1 indica crosses and their parental lines were evaluated. The embryos of 16 F1 rice hybrids showed midparent heterosis and those of 11 F1 rice hybrids showed better parent heterosis (heterobeltiosis). Lower heterosis in the F2 embryos was also observed. Midparent heterosis in endosperm weight did not always appear. Seedling growth of F1 rice hybrids grown in standard nutrient solution for 16 days showed midparent heterosis and relative growth rate in each four-day interval had little heterosis. Heterosis in embryo weight and leaf area were closely related with that in seedling weight. Higher leaf area expansion related with bigger embryo was considered the primary factor for heterosis in seedling growth of indica-indica F1 rice hybrids.

Heterosis for nutrient uptake in F1 rice hybrid-seedlings.

Nutrient uptake and morphological features in 12 rice hybrids were compared with the corresponding parental values. The uptakes of ammonium-N, nitrate-N, phosphorus and potassium (in nutrient mg·plant wt g-1·h-1) were determined by using 25-day-old seedlings. The results revealed that: (l) Nutrient uptake showed desirable heterosis, unlike morphological features. (2) Nutrient uptake was larger in the order of potassium, ammonium-N, nitrate-N and phosphorus. Potassium was five times as uptake as phosphorus. These facts also were observed in the F1 hyrbrids and their parents. (3) The degree of heterosis for nutrient uptake was higher in the order of nitrate-N, phosphorus, ammonium-N and potassium. The degrees for nitrate-N and potassium were 80% and 30%, respectively. (4) Plant weight and its heterosis did not show significant correlations to heterosis for nutrient uptake. (5) Correlations between nitrate-N and potassium uptake, and between the heterosis for their uptakes were highly positive significant. (6) It can be concluded that heterosis for physiological characters such as nutrient uptake appears before that for mophological characters, and that the higher nutrient uptake of the F1 rice hybrid was presumably not dependent on their larger weight, but on the higher rate of physiological ability.

Evaluation of Some F1 Rice Hybrids Developed Using MR365A As CMS Line

Evaluation of Some F1 Rice Hybrids Developed Using MR365A As CMS Line

Heterosis for rate of nitrogen uptake in F1rice hybrids

Abstract Rate of nitrogen uptake and dry or fresh weight in 8 F1 rice hybrids at the vegetative stage were compared with the corresponding parental values. Dry and fresh weight, amount and rate of nitrogen uptake per plant showed heterosis (ratio of F1 hybrid to mean parental value), unlike the rate of nitrogen uptake per unit weight. Heterosis for dry weight was not correlated with that for the 15N uptake rate per unit plant weight. Thus, the higher nitrogen uptake of the F1 hybrids was presumably not due to the higher rate of nitrogen uptake, but to their larger weight.

Survival of Some F1 Rice Hybrids and Their Parents in Saline Soil

Survival of Some F1 Rice Hybrids and Their Parents in Saline Soil

Heterosis for Root Pulling Resistance in F1 Rice Hybrids

Heterosis for Root Pulling Resistance in F1 Rice Hybrids

Harvest index and straw weight of some experimental f1 rice hybrids

Harvest index and straw weight of some experimental f1 rice hybrids

Heterosis breeding in rice (Oryza sativa L.)

Studies conducted at the International Rice Research Institute (IRRI) during 1980 and 1981 have shown up to 73% heterosis, 59% heterobeltiosis and 34% standard heterosis for yield in rice. The latter was estimated in comparison to commercial varieties: IR36 and IR42 (yield 4-5 t/ha in wet season trials and 7-8 t/ha in dry season trials). Generally speaking, absolute yield was lower and extent of standard heterosis was higher in wet season than in dry season with some exception. Yields up to 5.9 t/ha (22% standard heterosis) in the wet season and 10.4 t/ha (34% standard heterosis) in the dry season were obtained. Most of the hybrids performed better in some season while some performed better in both seasons. Hybrids showed better lodging resistance although they were 5-10 cm taller. F1 hybrids had significant positive correlations with the parental traits viz., yield (r = 0.446), tillering (r = 0.746), height (r = 0.810) and flowering (r = 0.843). Selection of parents among elite breeding lines on the basis of their per se yield performance, diverse origin and resistance to insects and diseases should give heterotic combination. Yield advantage of hybrids was due primarily to increase in number of spikelets per unit area even though tiller number was reduced. Grain weight was either the same or slightly higher. High yielding hybrids also showed significant heterosis and heterobeltiosis for total dry matter and harvest index. For commercial utilization of heterosis in rice, effective male sterility and fertility restoration systems are available and up to 45% natural outcrossing on male sterile lines has been observed. Consequently, F1 rice hybrid have been successfully developed and used in China. Prospects of developing hybrid rice varieties elsewhere appear bright especially in countries that have organized seed production, certification and distribution programs and where hybrid seed can be produced at a reasonable cost.

Heterosis for Yield and Yield Components in Rice

It is important to know the degree and direction of hybrid vigor for its commercial exploitation. Heterobeltiosis and standard heterosis were studied in 14 crosses between rice (Oryza sativa L.) cultivars (improved and landraces) and three wild aborted male sterile parents. These crosses showed marked variations in the expression of heterobeltiosis and standard heterosis for yield and yield components. Grain yield manifested highly significant heterobeltiosis and standard heterosis in five crosses. Heterobeltiosis ranging from –55 to 139% and standard heterosis from –11 to 369% were observed. Highest heterotic effect among the yield components was for panicle number plant-1 followed by spikelet number and panicle length. With appropriate choice of parental lines, it is possible to develop F1 rice hybrid possessing distinct yield superiority over the best-inbred lines.Key words: F1; Heterobeltiosis; Hybrid vigor; Oryza sativa; Standard heterosisDOI: http://dx.doi.org/10.3126/narj.v4i0.4857Nepal Agriculture Research Journal Vol. 4&5, 2001/2002Page: 6-12Uploaded date: 8 June, 2011