Environments

This research was conducted during the P-V 2014 cycle in five environments in the state of Morelos Jojutla (A1), Mazatepec (A2), Cuautla (A3), Cocoyoc (A4) and Zapata (A5), areas of great importance to the cultivation rice and stained with frequent outbreaks of grain. In Table 1 are described environmental conditions and geographical location of the localities in evaluation.

Genetic material used

It was established and evaluated five advanced rice lines coarse type Morelos, known as C7Za05 (T1), C14Za06 (T2), C20Za06 (T3), C21Za06 (T4) and C27Za06 (T5), additionally the variety Morelos A-2010 witness (T6).

Dates transplant

Were evaluated two date’s transplant: April 11 (F1) and May 12 (F2) of 2014.

Experimental design

Was used in each environment an experimental design completely randomized with three replications blocks, five lines were randomized within each block or pit, the size of the experimental unit was 10 m² for each line and the useful area sampled was 1 m².

For statistical analysis of the data was used a factorial design where the sources of variation were dates transplant, environments and genotypes.

Agronomic management

Two pacholes (seedlings) on various dates were set in the Campo Experimental Zacatepec, INIFAP in the state of Morelos, each 30 days before transplantation. The five advanced lines in F₆ to evaluate (C7Za05, C14Za06, C20Za06, C21Za06 and C27Za06) were seeded, plus the variety Morelos A-2010 was planted as a witness. The pachol mesh covered to prevent damage from birds during the early days of its development.

The site preparation consisted of two fallow land, one normal and the second cross. As planting was under the transplant system, the preparation of three gashes (formation of levees), 10 m wide by 40 m long, was conducted within each pit, he was subsequently addressed (activity manually to they form levees, where completely flooded the pit and levees according to the water level) are built to hold water. This was done in advance in all environments and in both planting dates. At 30 days after planting pachol for both evaluation dates, transplantation was carried out; each line seedlings were placed in sacks identified and transported to the definitive site for its development.

For weed control Propavel+Hierbester was applied to the most persistent weeds (^{Esqueda and Rosales, 2004}). The manual weeding were performed to control weeds in the streets and levees, mainly. The formula was applied fertilization 180-40-40 of N-P-K fractionated in two stages; the first 100-40-40 after the first month after transplant and the first application of herbicides, the second 80-0000 when differentiation reproductive vegetative apex in approximately 70 days after transplantation.

Variables registered

The variables recorded during physiological maturity were plant height (AP), number of productive tillers (MP) and unproductive (MI), panicle length (LP), number of grains per panicle (GP), stained grains (GM), openings per panicle (GV) and the grain weight (PG) in a square meter grains.

Statistical analysis

For statistical analysis of the data was used the ^{SAS (2002)} program ver. 9.0 with a factorial experimental design with three levels of variation transplant date (F), locations (A) and genotypes (G). For comparison of means Tukey test (α≤ 0.05) was used.

Dates transplant

The statistical analysis showed ficant differences (p≤ 0.05) between the dates of transplantation, as shown in Table 2. The mean comparison test according to Tukey (α≤ 0.05) indicated that the date 1 (F1) was statistically than date 2 (F2). In this regard, in F1, the more grains per panicle (GP), fewer stained grains per panicle (GM) and higher grain weight (PG) and a yield of 1.21 kg m^-2 compared was obtained with the second, which only got a weight of 1.04 kg m^-2. The coefficients of variation in the statistical analysis for the different variables, but are above 20% are not considered high and are within the acceptable results. Although the aim of this study was not know the stability of the materials, a low percentage was obtained in the coefficient of variation (CVi) representing greater stability (^{Francis and Kannenberg, 1978}), and the variable grain weight was a stable through varying environments therefore desirable and more stable genotype would be of higher performance and lower coefficient of variation.

The Figure 1 shows that during the first two months of crop development for the first date transplant (F1), the rooms had high temperatures and low rainfall, however, during the second day, the temperature dropped but there was an increase of cloudy days with more precipitation, these slight changes significantly affected the responses of the variables evaluated. In the second date (F2), there was a greater number of productive tillers; however, the panicles had a higher amount of stained beans, because during this phase of crop development increased cloudiness and high temperatures in the evaluated environments, conditions that could create an enabling environment for the development of fungal diseases environment was presented, the which coincides with the results of ^{Torres (2015)}, who mentions that the increased field performance is the result of improvements genetic potential, crop management and appropriate environmental conditions for cultivation.

Source: own elaboration with data from meteorological system of the state of Morelos, with data from 2014.

Figure 1 Temperature and rainfall in the evaluated environments (Jojutla, Mazatepec, Cuautla, Cocoyoc and E. Zapata) for two dates transplant in the state of Morelos.  

Other studies have reported differences in behavior evaluated in different planting dates regarding yield components varieties, variation is attributed to the reproductive stage of the crop coincides with the shorter days, less solar radiation and low temperature (^{Adames, 2014}).

Environments

Statistical analysis showed significant differences between the environments evaluated (p≤ 0.05) as shown in Table 3. The comparison of means test indicated that the environments significantly affect the response of the variables evaluated; in Jojutla town of genotypes they showed higher plant height, grains per panicle and higher yield, 1.25 kg m^-2 of grain, but a larger number of unproductive tillers. The Cocoyoc and Zapata, environments showed more stained and vain grains per panicle, representing an undesirable characteristic as it lowers grain quality and promotes greater weight loss. The variable length panicle showed no significant differences between environments.

The Figure 2 shows temperature differences in Jojutla, Mazatepec, Cuautla, Zapata Cocoyoc and locations. This difference caused differential response in the agronomic performance of the genotypes evaluated when changing an environmental condition to another.

Source: own elaboration with data from the meteorological system of the state of Morelos, climate report 2014.

Figure 2 Monthly mean temperature of Jojutla, Mazatepec, Cocoyoc, Zapata and Cuautla environments. 

According to the statistical analysis, Jojutla environment led to the best grain yield; on the contrary, the lowest values were for Zapata and Mazatepec. The temperature graph shows that Jojutla showed higher temperature throughout the crop cycle than other locations. The precipitation was higher in Cocoyoc, Zapata and Mazatepec localities (Figure 3), which could indicate that these environments had higher cloudiness and high temperatures (Figure 2), generating an environment conducive to the development of diseases like environment spotted grain, however Jojutla had lower precipitation (Figure 3), higher temperature (Figure 2) and better performance, although it is noteworthy that all experiments counted on irrigation water every third day and cultivation remained flooded during development.

Source: own elaboration with data from meteorological system of the state of Morelos, only data 2014.

Figure 3 Average monthly precipitation of Jojutla, Mazatepec, Cocoyoc, E. Zapata and Cuautla environments.  

Genotyping

Statistical analysis indicated significant differences (p≤ 0.05) for genotypes established on two dates transplant and in five locations. The test means comparison indicated that the C20Za06 line was statistically superior to others for the variable number of productive tillers and statistically lower for plant height (desirability), exceeding characters including the commercial variety Morelos A-2010; however, for the other components of performance as panicle length and grains per panicle all lines were statistically equal ^{Caicedo (2008)} obtained similar results with rice genotypes for most evaluated characteristics, except for the length of panicle. There were no significant differences for varying stained grains per panicle, for effect of genotypes, indicating that only the date of transplantation and this had an effect on environments. Spotted grain is a complex of causal agents among which are: fungi (Bipolaris oryzae, Phyllostica sp., Alternaria padwickii, Curvularia sp., Pyricularia sp., Cercospora orizae and Sarocladium sp.). In the state of Morelos, pathogens identified as causing grain discoloration are Cochliobolus miyabeanus, C. lunatus, Alternaria alternata, A. solani, Fusarium proliferatum, F. moniliforme, Curvularia spp., Cladosporium cladosporioides spp., and Aspergillus spp., and bacteria Pantoea stewartii and Xanthomonas spp. (^{Hernández et al., 2012}). This complex affects the grain to reduce weight (up to 40%), germination (between 26 and 41%) and the grain filling (30%). Also they have reported significant differences in the incidence of grain discoloration in genotypes, which means that have been detected tolerant materials (^{Palacios et al., 2008}).

For grain weight, the line C21Za06 was statistically superior to others, but failed to overcome the witness variety Morelos A-2010, since the latter obtained the same performance as shown in Table 4; however, it is less affected by the tainted grain.

Interaction planting dates (F), locations (A) and genotypes (T)

Only interactions F*A and A*T were significant for most variables assessed. Indicating that assessment environments presented different conditions in the two dates transplant and productive potential of genotypes it was influenced by the environment. The F*A*T interaction in the vast majority of the variables evaluated and even grain yield was not significant, indicating that a single line/variety could be used indifferently in any planting date and environment, and it would have a except like plant height behavior (Table 5). According to the above within assessment strategies segregating generations of improved varieties and trials referred to in the widest range of environments to assess the potential performance and phenotypic stability of varieties (^{Crossa, 1990}).

Combination planting date locality (F*A)

Under conditions in which the experiment was conducted, there was interaction between transplant dates and locations. According to the Tukey test the combination F1A1 (date 1 Jojutla) showed higher plant height with 132.5 cm, more unproductive tillers, grains per panicle (153) and higher grain weight (1.33 kg m^-2); the highest number of tillers developed in the F2A4 (date 2 Cocoyoc) with an average of 32 tillers per plant, but also obtained a greater number of stained and vain grains per panicle. The rice diseases are a major cause and barriers for maintaining high productivity and crop sustainability. On average rice diseases cause up to 15% of production losses under the current crop management. Among the most important diseases worldwide are considered Pyricularia (Pyricularia oryzae), bacterial blight (Xanthomonas oryzae pv oryzae), the sheath blight (Rhizoctonia solani), the virus Tungro in Asia and virus white sheet in some countries Latin America, and more recently the bacterial panicle blight caused by the bacterium Burkholderia glumae which has increased in incidence, severity and economic importance in many countries in Latin America and the United States of America (^{Correa, 2015}).

Combination transplant date*genotypes (F*G)

In this interaction only significant differences for the variables plant height, empty grains and grain weight. The combination F2T4 (date 2 line C14Za06) showed higher plant height, F2T6 (date 2 Morelos A-2010) obtained the highest number of grains openings per panicle and the best grain weight was obtained in the F1T4 combination (date 1 line C21Za06) with a yield of 1.29 kg m^-2.

Combination localities*genotypes (A*T)

The A5 and T2 combination (Zapata C14Za06) obtained greater plant height (141 cm); A4 and T3 (Cocoyoc C20Za06) presented greater number of productive tillers, spotted grains, as many unproductive tillers; A1 and T6 (Jojutla Morelos A-2010) obtained a greater number of grains per panicle; A4 and T6 (Cocoyoc Morelos A-2010) presented a higher number of empty grains and the best performance was obtained A1 and T3 (Jojutla C20Za06) with 1.40 kg m^-2. The results are consistent with previous studies that mention a differential response in genotypes under different conditions, indicating that there were differences between environments and their influence on the expression of genotypes in yield and the variables evaluated (^{Orona, 2013}).