Chandrasekharan, P ABSTRACT
Crosses were done between promising rice accessions from different parts of Kerala during 1996-97, hybrids were identified and subsequent selections continued based on height (80 -120 cm), higher productive tillers, longer panicles and high grain numbers and
matta (bold grain and red rice). Those selected were given PC numbers. PC 1 was identified
in F6, PC 2 in F7 and both were released in February 2003. Four more short duration varieties have been identified: PC 5 in F9, PC 3, PC 4 and PC 6 in F10. These were evaluated in yield trials in the second crop of 2004-05 and in the first crop 2005-06 and the superiority of their performance was confirmed. PC 3 “Sivam” and PC 6 “Sundaram” are two varieties where genes responsible for high grain number exceeding 400 grains from TKTM have been transferred in full since the latter was the donor for this trait. PC 1 and PC 2 have now spread to about 600 and 500 acres respectively during the last 4 seasons in almost all districts of Kerala.
Tamil Nadu Agricultural University, Coimbatore 641003
Introduction
Thavalakkannan is a tall indica variety and phenotypically very similar to Chenkazhama and both were very popular among Palakkad rice farmers before the introduction of high yielding dwarfs by IRRI, Philippines. Extreme palatability of their rice, the ability of cooked rice to preserve in cold water for 12 hours without losing hardness and taste and their high recovery from paddy after milling (above 60 %) were the welcome traits. Main difference between these two varieties is that Chenkazhama is a week earlier than Thavalakkannan (TK) of 135 days .To ensure maximum plant diversity, TK was collected from a farmer in Thiruvilvamala (TKTM) and Chenkazhama from another in Ottappalam (OTP), in 1995. In the first crop of 1996-97, when TKTM population was studied, it was surprising to observe one plant of height 182 cm, main panicle length of 31 cm and had 430 spikelets (potential grains), two plants had 344 and 327 and others between 188 and 282 spikelets. This population of TKTM represented grain production of a very high order when compared with the grain numbers of IR 36, IR 8, Athira and Matta Thriveni, the dwarfs then in cultivation, their maximum -grain number being
214. Other varieties, or TK (PTB 8, PTB 9) and Chenkazhama (PTB 26) and the one collected from Ottappalam (OTP) and included in the present study had the maximum of 250 grains on the main panicle. Thus TKTM is a distinctly superior variety from the point of view of the plant breeder. Since all characters are governed by genes, it should be possible to transfer this high grain number to the currently cultivated semi - tall and dwarf varieties. Crosses were done from 1996 - 97, hybrids were identified and subsequent selection continued based on height (80-120 cm) higher productive tillers, longer panicle, high grain
number and Matta (bold grain;red rice) which
farmers of Kerala prefer. Rice farmer of Palakkad gets Rs. 300 more for 500 kg paddy if it belongs to the category, Matta.
Materials and methods
Rice varieties, PTB 8, 9 (TK Matta and TK White rice), IR 8 and IR 36 were obtained from Pattambi Rice Research Station as also PTB 26 (Chenkazhama). Other varieties, Athira and Matta Thriveni (dwarfs of Kerala Agricultural University) were obtained from local farmers. Since the first crop commencing May is the most suitable for TK and Chenkazhama,
crossing work was invariably done in first crop. Farmers do not grow TK and Chenkazhama in second (II) crop since their yield performance is poor. Seeds collected from crossing, had to be sown and therefore, in the majority of cases, sowings had to be done in the second crop for the identification of hybrids. Dwarf varieties are grown in both crops (I and II) and therefore, selections in succeeding generations have been done in both the crops and better looking plants carried forward. Selection work up to II crop was done at Mannapra. From the year 2000, the work was done at Alampallam, Vandazhi and Vadakkencherry, all in Palakkad district. Since the aim of the study was to transfer the high grain-number of the tall Indica variety of Thavalakkannan from Thiruvilvamala (TKTM), four important characters,
(I) height of the plant in cm, (2) number of productive tillers, (3) length of panicle and (4) number of spikelets on the main panicle were recorded for all plants selected. Only in the final stages was the duration of the crop recorded. Those selected were initially given culture numbers and yield trials were conducted following standard procedures. Those finally selected, based on grain yield, were given PC (my initials) numbers and also named, to distinguish them from other varieties. PC 1 was identified in F6, PC 2 in F7 (in the farmers’ fields at Alampallam and Vandazhi respectively) and named” second coming of Thavalkkannan and Chenkazhama respectively “by Karshaka Sree, a monthly Publication of Malayala Manorama for Kerala farmers in its February 2003 issue. Four more short duration varieties were identified: PC 5 “Santham” in F9 and PC 3 “Sivam”, PC 4 “Sathyam”, PC 6 “Sundaram”in F10. These short duration varieties were all evaluated in the second crop of 2004-05 and their yield performance confirmed in first crop of 2005-06 before naming them. Details of these varieties were brought to the notice of the Palakkad farmers by the Malayalam daily, Mathrubhoomi on February 6th
2006 followed by Karshaka Sree, in March 2006. The Scientific aspects of the study are presented and discussed in this paper.
Results and Discussion
Table 1 gives details of these characters for I and II crops. Data for the second (II) crop clearly show reduction in height, length of panicle and number of spikeiets while the tiller number gets increased in the II crop in some (e.g., TKTM;Chenkazhama (OTP), IR 8). Excepting PC 6, Sundaram, all others showed the ability of producing more tillers, especially in the II crop (Table, 4).
Table 2 gives details of number of inter - varietal hybrids between tall Indica (TKTM) and Chenkazhama (OTP) and dwarf rice varieties IR 8, IR 72 (IRRI) matta Thriveni, Athira (Kerala Agr. Univ.varieties). Spikelet fertility or seed - fertility percentage provides an index of relationship (close or otherwise) of varieties involved in the cross.
Usually, it is the maximum fertility that should be compared and for the study to be completed a number of F1 hybrids should be available. Seed fertility of IR 8 x PTB 8 and Chenkazhama (OTP) X IR 8 are similar indicating that Thavalkkannan Matta of Pattambi research .station (PTB 8) is similar in genetic relationship to Chenkazhama of Ottappalam (OTP). Seed fertility of TKTM X IR 8, TKTM X Matta Thriveni and its reciprocal (about 30 %) showed that IR 8 and Matta Thriveni are the most diverged from TKTM. Seed fertility of IR 36, Athira with TKTM (maximum 69 %) compared with those of Chenkazhama (maximum 99 %) do indicate great divergence of TKTM and Chenkazhama (OTP). If fertility indicates close relationship, seed sterility (100- seed fertility per cent) percentage shows how far are the two varieties distant. An attempt has been made to pictorially represent these varieties, TKTM and Chenkazhama (OTP) based on sterility per cent. While Chenkazhama
(OTP) is comparatively recent in evolutionary scale, TKTM is ancient.
Table 3 gives details of the maximum grain number recorded and the number of selections
made in F2 to F10 as well as details of range of
number of spikelets in F1 generation. However, it is the responsibility of the plant Breader to select a variety if it is likely to be superior to the current variety under cultivation by the farmer. This happened in the case of the cross, IR 36 X TKTM. In this cross although the range of
number of spikelets in the 3 F1 hybrids suggested
maximum of 322, maximum of 272 was reached
in F6 in 135 days of duration; further increase
was difficult to be achieved. The figures underlined indicate those studied in II crop and the number of 272 was achieved in the II crop and since this variety had grains which are bold and 1000 grains weighed 28 g (more than the weight of TKTM) the plants of this line was harvested and seeds mixed to form a culture. After yield trials, this was named PC 1. In the case of the cross, Athira X Chenkazhama, there were eight F1 hybrids raised in the second crop. Subsequently in each generation there was rise in the maximum of spikelets if the crop was in I crop, a temporary decrease if it was in II crop and a dramatic increase in the subsequent I crop
(216,388 in I crops in F2, F3» 289 in second crop
of F4and 379 in I crop of F5). Maximum of 496
was reached in F8. By that time the panicles
started showing symptoms of disease and
selection work had to be restricted to F7
(maximum of 417 spikelets).
As can be seen in table 4 this was a semi - tall (about 120 cm). One thousand grains weighed 25.0 g. Yield trial of this culture was done at Vandazhy Village of Palakkad District. PC 1 is dwarf and capable of yielding 6.0 mt/ha in a duration of 135 days while P6 2 gives 5.6 mt/ha in 120 days (Table 5). Subsequently PC 1 and PC2 have now spread to 600 and 500 acres respectively in almost all the districts of Kerala, during the last four Seasons.
TKTM X Athira
This cross needs special mention because it has yielded two short duration varieties, one of 100 and the other of 110 days duration. This cross succeeded only when Thavalkkannan was used as mother. Three F1 hybrids were identified in the second crop (Table 3) and their maximum spikelets ranged from 127 to 184.
Thereafter it rose to 369 in F3and the maximum
number of 413 was reached in F10in the I crop
of 2004 - 05. One particular plant needed special mention. It was semi-tall (122 cm), had 6 tillers: main tiller carried 413 spikelets and 370, 345, 337, 174 and 158 in second to sixth respectively, of spikelets totaling 1797 grains per plant in the first crop. However, the progeny of the same plant showed maximum of 216 in the II crop (Table, 4). The culture emanating from the progeny of this line recorded maximum of 6.375 mt/ha in the second crop of 2004-2005, the maximum under the short-duration category (Table 5), with 110 days’ duration. Another distinct group of plants in this cross was shorter (107 cm), with 5 productive tillers and 435 spikelets in I crop of 2004-05; in the II crop, the height was reduced to 80 cm and spikelets to 181. However, the culture that emanated from this plant - progeny proved to be shortest in duration of 100 days and the grain yield recorded from the yield trial was 5.579 mt/ha. Higher yielding 110 days’ duration, PC 3 , was named “Sivam” and the shortest duration of 100 days, PC 6, “Sundaram”.