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Directorate of Wheat Research, Karnal 132 001, Haryana, India

 

 

 

Effect of Chemical Hybridizing Agent on Floret Opening and Seed Set in Wheat (Triticum aestivum)

Authors: N V P R GANGA RAO, V MAHAJAN1 and S NAGARAJAN

1Coreesponding Author: Dr Vinay Mahajan, Email: vimahan@hotmail.com

Address: Directorate of Wheat Research, P O Box 158, Karnal 132 001,Haryana, India

Journal: Indian Journal of Agricultural Science

Contents

Abstract Key words Introduction
Material and Methods Results and Discussion Literature Cited

Table 1: Analysis of variance for pollination time Vs cut and uncut treatments

Table 2: Per cent seed set in cut and uncut (palea and lemma) treatments of CHA male sterilized WH 542

ABSTRACT
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A chemical hybridizing agent, CH 9832 was used to induce male sterility in WH 542 during Rabi 98-99 on female fertility and extent of cross-fertilization. Starting from 24th day after CHA spray, 6 spikes with and without cutting of palea and lemma were pollinated for 13 days in a sequence. Seed set pattern indicated that florets of male sterile wheat open twice to facilitate cross-fertilization. Maximum seed set of 95.4% was obtained and this clearly indicated that CHA was not interfering with female fertility especially stigma receptivity. Reasonable amount of seed set in uncut treatment showed non-hindrance of palea and lemma in out crossing. Relatively good seed set obtained upto six days indicate that there was extended stigma receptivity. 

Key words: chemical hybridizing agent, palea and lemma, seed set, stigma receptivity, wheat (Triticum aestivum)
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Introduction
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        The needed targets of 110mt of wheat production by 2020AD can be attained via new innovative techniques like exploitation of heterosis through hybrid wheat. The cost of hybrid seed production will play a crucial role in commercial viability of hybrid wheat technology. In this context, to optimize the hybrid wheat technology, better understanding about floral biology of chemically induced male sterile wheat is essential. The information on process of floret opening and length of stigma receptivity will throw some light on male–female time of sowing for parental synchrony and need of supplemental pollination. Very little information is available world wide on this aspect. Earlier studies on floret opening indicated the importance of lodicules, which collapsed and allowed the carpels of sterile florets continue to grow, forcing the lemma and palea apart resulting in floret opening which lasts for 2 days or more (Hoshikawa 1960, De Vries 1971). The objective of the present investigation was i) to study floret behaviour in CHA induced male sterile WH 542 and; ii) to study the effect of CH 9832 on female fertility.

Material and Methods
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Fifteen plots of two-meter length of WH 542 were sown on Dec.5th 1998. Male sterility was induced by spraying chemical hybridizing agent CH 9832 at 10-12mm spike length stage coinciding with stage 23 (Zadoks et al, 1974). At pre-emergence of spike from the boot leaf (stage 51), 20 spikes in each plot were bagged. Later from stage 53 onwards six different spikes were pollinated everyday for 13 days till stigma lost its receptivity. Among the six spikes pollinated, the palea and lemma were cut in three spikes and pollinated while the remaining spikes were pollinated without cutting. Observations were recorded for number of seeds set in cut and uncut florets as well as in untreated carefully hand emasculated cut florets as check. The data was computed for analysis of variance after Arc Sine transformation.

Results and Discussion
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The analysis of variance revealed that significant differences were found in treatments (cut and uncut) with respect to seed set over a period of 13 days (Table 1). In cut treatments, cutting of palea and lemma ensured floret opening artificially by means of expoxure of stigma and style to incoming pollen. The amount of seed set formation without cutting of palea and lemma in uncut treatment mimics natural floret opening and indicates about longevity of stigma receptivity.

The per cent seed set in cut and uncut treatments vis-a-vis pollination time (day of pollination) differ significantly. The maximum seed set of 95.4% was observed in cut treatment at Zadoks decimal growth stage 63 (Table 2). And reasonably good seed set was observed between Zadoks decimal growth stages 62–67. In uncut treatment maximum seed set (75.8%) was observed during Zadoks decimal growth stage 65 (29 day after CHA spray). Seed set pattern in uncut treatments indicating that male sterile wheat florets open twice. It was found that first cycle of floret opening continues only for shorter period because of which seed set per cent of 33.4 was observed on Zadoks decimal growth stage 62, followed by close of florets for about one day. Correspondingly, high seed set on 27 day after CHA spray in cut treatment indicates that stigma was receptive even the florets were closed (Table 2).

In our experiments, the second cycle of floret opening continues for about 6 days (64 - 67 Zadoks decimal growth stages) with seed set ranges from 24.2% to 75.8% which was normally sufficient for cross-fertilization to takes place. The second cycle of floret opening process starts after an interval of 2 days or more from first floret opening (Hoshikawa 1960). This second opening lasts for a period of several days (De Vries 1971) and is normally sufficient for cross-fertilization to take place provided viable pollen is available. Hence the results of the present investigation where CHA was used to generate male sterility was in conformity with works of Hoshikawa (1960) and De Vries (1971). Analysis of variance showed that cutting of palea and lemma was not going to make any difference in seed set in comparison to uncut treatment (Table 1). Second cycle of floret opening, in search of pollen promotes cross-fertilization. Hence, it can be inferred that palea and lemma are not a hindrance to cross-fertilization in male sterile wheat. Further, synchrony problem between male and female parents can be avoided by adjusting planting of male and female in such a way that male may reach anthesis little latter than female in order to coincide pollen shedding with the second cycle of floret opening. Seed set of about 95.4% in this CHA sprayed WH 542 indicates that CHA was not interfering with female fertility and stigma receptivity.

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ACKNOWLEDGEMENT

We thank Indian Council of Agricultural Research for funding under A P CESS fund project on “Development of Hybrid Wheat” under grant no.2(11)/96-FCI dt.5-1-98 and acknowledge the help rendered by Sh Vineet Kumar and Sh Manoj Srivastav, Research associates at various levels.

LITERATURE CITED

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De Vries A Ph 1971. Flowering biology of wheat, particularly in view of hybrid seed production - a review. Euphytica 20:152 -70.

Hoshikawa K 1960 Studies on the reopened floret in wheat. Proceedings of crop science society of Japan 29:103-6.

 Zadoks.J C, Chang  T T and Konzak C F 1974. A decimal code for the growth stages of        cereals. Weed research.14:415-21.

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